Interleave Scanning and LiftMode

Transcription

1 Interleave Scanning and LiftMde Interleave is an advanced feature f NanScpe sftware that allws the simultaneus acquisitin f tw data types. Enabling Interleave alters the scan pattern f the piez: after the trace and retrace f each main scan line (in which tpgraphy is typically measured), a secnd trace and retrace is inserted t btain nntpgraphical infrmatin. The Interleave cmmands use a set f Interleave cntrls that allw several scan cntrls (Drive Amplitude, { HYPERLINK "javascript:vid(0);" }, and varius { HYPERLINK "javascript:vid(0);" }) t be set independently f thse in the main scan cntrls. Typical applicatins f interleave scanning include { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\magnetic%20frce%2 0Micrscpy%20(MFM).htm" \ "Link t Magnetic Frce Micrscpy (MFM)" } and { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\electric%20frce%20 Micrscpy%20(EFM).htm" \ "Link t Electric Frce Micrscpy (EFM)" } measurements. There are tw frms f Interleave scanning available: LiftMde Enabling Interleave with the mde set t Lift enacts LiftMde. During the interleave scan, the feedback is turned ff and the tip is lifted t a user-selected height abve the surface t perfrm far field measurements such as magnetic r electric frces. By recrding the cantilever deflectin r resnance shifts caused by the magnetic r electric frces n the tip, an image map f frce changes can be prduced. LiftMde was develped t islate purely MFM and EFM data frm tpgraphic data. Interleave Mde Interleave can als be used in Interleave Mde. In this mde, the feedback is kept n while additinal tpgraphy, phase lateral frce, r data is acquired. Hw Interleave Mde Wrks Enabling Interleave changes the scan pattern f the tip relative t the imaged area. With Interleave mde disabled, the tip scans back and frth in the fast scan directin while slwly mving in the rthgnal directin as shwn n the left f figure 1, belw. This is the standard scan pattern f NanScpe systems.

2 Figure 1: Cmparisn f standard (left) and Interleave (right) raster scan patterns. With Interleave mde enabled, the system first perfrms a standard trace and retrace with the main Feedback cntrls in effect. The tip mves at half the nrmal rate in the slw scan directin. An additinal trace and retrace are then perfrmed with the Interleave feedback cntrls enacted. The frame rate halves because twice as many scan lines are perfrmed fr the same scan rate. This mdificatin f the scan pattern is illustrated t the right in figure 1, abve. Tw mdes are pssible fr Interleave scan: Interleave and Lift. With Interleave selected, the feedback remains n during the interleave pass with the values under Interleave feedback cntrls ({ HYPERLINK "javascript:vid(0);" }, { HYPERLINK "javascript:vid(0);" }, etc.) in effect. In Lift mde the feedback is turned ff and the tip is lifted ff the surface and scanned at a user-selected height fr the interleave trace and retrace. Tpgraphy data recrded during the main pass is used t keep the tip a cnstant distance frm the surface during the Interleave trace and retrace: The tip first mves t the Lift Start Height, then t the Lift Scan Height. A large Lift Start Height can be used t pull the tip frm the surface and eliminate sticking. The Lift Scan Height is the distance maintained between the sample tpgraphy and the tip during the scan. This value is added pint-by-pint t the height data btained during the Main tpgraphy trace and retrace. Values can be psitive r negative. NOTE: A new feature in NanScpe 8.15 allws the user t run a lifted scan at a set distance frm the sample surface, ignring the sample tpgraphy during the lifted, interleaved, scan lines. T enable this parameter, set Interleave Mde t Linear in the Interleave parameter list. Operatin f Interleave Scanning and LiftMde These instructins apply t { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\stm\\scanning%20tunneling%2 0Micrscpy%20(STM).htm" \ "Link t Scanning Tunneling Micrscpy (STM)" }, { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\cntact%20afm\\cntact%20af M.htm" \ "Link t Cntact AFM" }, r { HYPERLINK

3 "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\tappingmde%20afm\\tapping Mde%20AFM.htm" \ "Link t TappingMde AFM" }. Yu must be familiar with TappingMde r Cntact AFM t btain gd images f surface tpgraphy. The interleave scanning prcedure is described belw; further detail is given fr specific mdes elsewhere: see { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\magneti c%20frce%20micrscpy%20(mfm).htm" \ "Link t Magnetic Frce Micrscpy (MFM)" } and { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\electric %20Frce%20Micrscpy%20(EFM).htm" \ "Link t Electric Frce Micrscpy (EFM)" }. 1. Obtain a tpgraphy scan using the apprpriate methd (usually Cntact r TappingMde). When using LiftMde, it is imprtant that the { HYPERLINK "javascript:vid(0);" } and { HYPERLINK "javascript:vid(0);" } under Feedback cntrls be adjusted t give a faithful image f the surface. Because the height data is used in the lift pass t trace the tpgraphy, a pr measurement f surface height may give inaccurate measurement during the lift pass r cause the tip t strike the surface. Typically, the height data is displayed n Channel Chse the Interleave Mde (Interleave, Lift, r Linear) apprpriate fr the measurements t be perfrmed. 3. Adjust the Interleave cntrls panel t the desired settings. When using TappingMde, the { HYPERLINK "javascript:vid(0);" }, { HYPERLINK "javascript:vid(0);" }, gains, and Amplitude Setpint can be set differently in the Interleave panel than in the main Feedback panel. Hwever, it is ften cnvenient t begin with the main and interleave cntrls set t the same values. D this by tggling the parameters f the apprpriate Interleave parameters t an ff (grayed) cnditin. The values can be changed nce the prbe is engaged. If yu are using LiftMde r Linear Lift Mde, set the Lift Scan height. If yu are using Interleave mde, set the Gains and Amplitude Setpint. Fr mre infrmatin, refer t { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\use%20f%20 LiftMde%20with%20TappingMde.htm" \ "Link t Use f LiftMde with TappingMde" }. NOTE: Certain cnstraints are impsed: scan sizes, ffsets, angles, rates and numbers f samples per scan line are the same fr the main and interleave data, and the imaging mde (Cntact, TappingMde, r frce mdulatin) must als match. 3. Chse the Interleave Data Type. Depending n the type f micrscpe, Interleave mde allws the ptins f amplitude, phase, frequency, ptential, input ptential, r data types fr ding far-field (MFM r EFM) imaging. Auxiliary channels are als available fr sme applicatins.

4 Once the Interleave Scan Line is chsen, Interleave mde is autmatically enabled, triggering interleave scanning. Interleave data typically displays as the secnd image. Ntice that the scan rate in the slw directin is halved. 4. Display the interleave data by switching Scan Line (in the Channel panels) t Interleave. Final Cnsideratins Lift Scan Height: The lateral and vertical reslutins f the Lift data depend n the distance between tip and sample: the lwer the tip, the higher the reslutin. Hwever, the Lift Scan Height must be high enugh that the tip des nt cntact the sample during the Lift trace and retrace. Tip Shape: As shwn belw, the tip separatin in the LiftMde is defined in terms f the Z directin nly. The Lift Scan Height is added t the height values taken frm previus scan lines pint-by-pint. Hwever, the tip may be clser t the sample than the Z separatin indicates. On features with steep edges, the tip may get very clse t the sample even thugh the Z separatin is cnstant. Line Directin: The Line Directin shuld be set t Retrace fr bth the main and interleaved scans. If it is set instead t Trace, a band may appear alng the left side f the images due t the ramp between the surface and the Lift Scan Height. Use f LiftMde with TappingMde Additinal cnsideratins when using LiftMde with { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\tappingmde%20afm\\tapping Mde%20AFM.htm" \ "Link t TappingMde AFM" } are discussed belw. Main Drive Amplitude and Frequency selectin As usual, these parameters are set when yu tune the cantilever prir t engaging. It is helpful t keep in mind the measurements t be dne in LiftMde when setting these values. Fr example, if Amplitude data will be mnitred during the Lift scan fr { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\magneti c%20frce%20micrscpy%20%28mfm%29.htm" \ "Link t Magnetic Frce Micrscpy (MFM)" }, the Drive Frequency shuld be set t the side f the resnance (hwever, certain parameters can be set independently fr the interleave scan; see belw.) Setpint Selectin When the main and interleave { HYPERLINK "javascript:vid(0);" } and { HYPERLINK "javascript:vid(0);" } are set t the same value (i.e., when these parameters in the Interleave panel are grayed ut), the cantilever scillatin amplitude increases t the free scillatin amplitude when the tip is lifted ff the surface in LiftMde. If a small { HYPERLINK "javascript:vid(0);" } value frces

5 a large decrease in scillatin amplitude while the feedback is running, the amplitude can grw cnsiderably when the tip is lifted free f the sample surface. The change can als be large if the main Drive Amplitude was increased r the main Drive Frequency altered after the tip was engaged. The vibratin amplitude remains at the setpint during the main scan even if these parameters are changed. This culd result in the tip hitting the surface in the lift scan fr small Lift Scan Heights. Interleave Drive Amplitude and Frequency Selectin The cantilever Drive Amplitude fr the Lift scan can be set independently f the main Drive Amplitude. Click n the parameter in the Interleave panel t enable it (turns green) and adjust the value. This allws the tuning f a measurement in the Lift scan lines withut disturbing the tpgraphy data acquired during the Main scan lines. The Interleave Drive Amplitude must be set lw enugh that the tip des nt strike the surface during the Lift pass. Cautin/Attentin/Vrsicht: Befre enabling the Interleave Drive Amplitude, check that its value is nt much larger than the main Drive Amplitude value t prevent pssible damage t the tip. The Interleave Drive Frequency can als be adjusted, which may be useful if acquiring amplitude data in LiftMde. Amplitude Data Interpretatin When mnitring amplitude data in LiftMde, brighter regins crrespnd t larger amplitude, and darker regins t smaller amplitude. Cantilever Oscillatin Amplitude The selectin f the scillatin amplitude in LiftMde depends n the quantity t be measured. Fr frce gradients that are small in magnitude but ccur ver relatively large distances (smetimes hundreds f nanmeters, as with magnetic r electric frces), the scillatin amplitude can be large, which fr sme applicatins may be beneficial. The Lift Scan Height must be crrespndingly large s that the tip des nt strike the surface. Hwever, the lateral reslutin f far field (MFM r EFM) measurements decreases with distance frm the surface. Typically, the reslutin is limited t a value (in nm) rughly equal t the Lift scan height. Small amplitudes must be used t sense frce gradients, such as Van der Waals frces, which ccur ver shrt distances (typically a few nm). As much f the cantilever travel as pssible shuld be within the range f the frce gradient. Electric Techniques The tw mst cmmn electric techniques used with the Dimensin Icn micrscpe are Electric Frce Micrscpy (EFM) and Surface Ptential Detectin. Bth mdes make use f Interleave and LiftMde prcedures. Ensure yu are familiar with befre attempting electric measurements.

6 Electric techniques are similar t. The tw-pass LiftMde measurement allws the imaging f relatively weak but lng-range electrstatic interactins while minimizing the influence f tpgraphy. In the case f MFM, the system is measuring lng-range magnetic fields. LiftMde recrds measurements in tw passes, each cnsisting f ne trace and ne retrace, acrss each scan line. First, LiftMde recrds tpgraphical data in TappingMde n ne trace and retrace. Then, the tip raises t the Lift Scan Height, and perfrms a secnd trace and retrace while maintaining a cnstant separatin between the tip and lcal surface tpgraphy. 1. Cantilever measures surface tpgraphy n first (main) scan (trace and retrace). 2. Cantilever ascends t lift scan height. 3. Cantilever fllws stred surface tpgraphy at the lift height abve the sample while respnding t electric influences n secnd (interleave) scan (trace and retrace). Electric Frce Micrscpy Overview measures variatins in the electric field gradient abve a sample. The sample may be cnducting, nncnducting, r mixed. Because the surface tpgraphy shapes the electric field gradient, large differences in tpgraphy make it difficult t distinguish electric field variatins due t tpgraphy r due t a true variatin in the field surce. The best samples fr EFM are samples with fairly smth surface tpgraphy. The field surce culd be trapped charges, applied vltage, and s n. Samples with insulating layers (passivatin) n tp f cnducting regins are als gd candidates fr EFM. Surface Ptential Imaging Overview Bruker prvides several methds fr surface ptential imaging: { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptent ial%20detectin.htm" \ "Link t Surface Ptential Detectin" } (aka AM-KPFM) measures the effective surface vltage f the sample by adjusting the vltage n the tip s that it feels a minimum electric frce frm the sample. { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" } cmbines the { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptent ial%20detectin.htm" } mde with Bruker's prprietary { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\operatingprin ciples.htm" \l "Peak" }.

7 { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" } uses a frequency mdulatin technique t measure surface ptential. FM-KPFM is generally mre accurate and has higher spatial reslutin than AM-KPFM. { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- FM- KPFM.htm" } cmbines { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" } with Bruker's prprietary { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\operatingprin ciples.htm" \l "Peak" }, cmbining the benefits f bth mdes. { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM%20HV%20Imaging.htm" } cmbines Bruker's prprietary { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\operatingprin ciples.htm" \l "Peak" } with an AC technique that enables measurement f surface ptentials up t apprximately ±200 V. Electrical Sample Preparatin The sample shuld be electrically cnnected directly t the chuck, s that it can be held at grund ptential (nrmal peratin) r biased thrugh the chuck. The sample can either be munted directly n the chuck r nt a standard sample puck using cnductive epxy r silver paint as shwn belw: Figure 1: Schematic diagram shwing hw t electrically cnnect a sample nt a sample puck. HINT: If the surface f yur sample is cnductive and the base f the sample is insulative, yu will need t ensure that the cnductive epxy r paint cntacts ne edge f the sample surface and ne edge f the cnductive munt (either sample puck r the chuck itself). Ensure that the large "glb" f glue/paint required is NOT lcated directly underneath the cantilever substrate, as the substrate may cme in cntact with the glue/paint, cmpleting the circuit and preventing the tip frm cntacting the sample: Surface Ptential Detectin Figure 2: Schematic diagram shwing hw NOT t electrically cnnect a sample nt a sample puck. Bruker prvides several methds fr surface ptential imaging:

8 { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\liftmde%20surfa ceptentialdetectinprinciples.htm" \ "Link t Surface Ptential Detectin" } (aka AM-KPFM) measures the effective surface vltage f the sample by adjusting the vltage n the tip s that it feels a minimum electric frce frm the sample. (In this state, the vltage n the tip and sample is the same.) Samples fr surface ptential measurements shuld have an equivalent surface vltage f less than ±10 V, and peratin is easiest fr vltage ranges f ±5 V. The nise level f this technique is typically 10 mv. Samples may cnsist f cnducting and nncnducting regins, but the cnducting regins shuld nt be passivated. Samples with regins f different materials will als shw cntrast due t cntact ptential differences. Quantitative vltage measurements can be made f the relative vltages within a single image. { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" } cmbines the { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptent ial%20detectin.htm" } mde with Bruker's prprietary { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\operatingprin ciples.htm" \l "Peak" }. { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" } uses a frequency mdulatin technique t measure surface ptential. FM-KPFM is generally mre accurate and has higher spatial reslutin than AM-KPFM. { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- FM- KPFM.htm" } cmbines { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" } with Bruker's prprietary { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\operatingprin ciples.htm" \l "Peak" }, cmbining the benefits f bth mdes. { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM%20HV%20Imaging.htm" } cmbines Bruker's prprietary { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\operatingprin ciples.htm" \l "Peak" } with an AC technique that enables measurement f surface ptentials up t apprximately ±200 V. Lift Mde Surface Ptential Imaging (AM-KPFM) Lift Mde surface ptential imaging, als referred t as Amplitude Mdulated KPFM (AM-KPFM), is a tw-pass prcedure where the surface tpgraphy is btained by standard { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\tappingmde%20afm\\tapping Mde%20AFM.htm" \ "Link t TappingMde AFM" } in the first pass and the surface ptential is measured n the secnd pass. The tw measurements are interleaved: that is, they are each measured ne line at a time with bth images displayed n the screen simultaneusly. A blck diagram f the this Surface Ptential measurement system is shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\liftmde %20SurfacePtentialDetectinPrinciples.htm" \l "SPMBlckDiagram" }.

9 Figure 1: Blck diagram f signals fr Lift Mde Surface Ptential Detectin On the first pass, in TappingMde, the cantilever is mechanically vibrated near its resnant frequency by a small piezelectric element. On the secnd pass, the tapping drive piez is turned ff and an scillating vltage V AC sin(ωt) is applied directly t the prbe tip. If there is a DC vltage difference between the tip and sample, then there will be an scillating electric frce n the cantilever at the frequency ω. This causes the cantilever t vibrate, and an amplitude can be detected. 1. Cantilever measures surface tpgraphy n first (main) scan (trace and retrace). 2. Cantilever ascends t lift scan height. 3. Cantilever fllws stred surface tpgraphy at the lift height abve the sample while respnding t electric influences n secnd (interleave) scan (trace and retrace). If the tip and sample are at the same DC vltage, there is n frce n the cantilever at frequency ω and the cantilever amplitude will g t zer. Lcal surface ptential is determined by adjusting the DC vltage n the tip, V tip, until the scillatin amplitude becmes zer and the tip vltage is the same as the surface ptential. The vltage applied t the prbe tip is recrded by the NanScpe Cntrller t cnstruct a vltage map f the surface. Surface Ptential Detectin Thery { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptential% 20Detectin.htm" \ "Link t Surface Ptential Detectin" } micrscpy can be mdeled as a parallel plate

10 capacitr. When tw materials with different wrk functins are brught tgether, electrns in the material with the lwer wrk functin flw t the material with the higher wrk functin (see { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptential% 20Detectin%20Thery.htm" \l "UnequalEnergies" }). If these materials are charged, the system can be thught f as a parallel plate capacitr with equal and ppsite surface charges n each side. The vltage develped ver this capacitr is called the cntact ptential. Measuring the cntact ptential is dne by applying an external backing ptential t the capacitr until the surface charges disappear. At that pint the backing ptential will equal the cntact ptential. In surface ptential micrscpy (scanning Kelvin prbe frce micrscpy), this zer-charge pint is determined by adjusting the tip vltage s the electrical frce felt by the AFM cantilever is 0. Figure 1: The electric energy level diagram fr 2 cnducting specimens, where Φ 1 and Φ 2 are the respective wrk functins. E f1 and E f2 are the respective Fermi energies. If an external electrical cntact is made between the tw electrdes, their Fermi levels equalize and the resulting flw f charge (in the directin indicated in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptential% 20Detectin%20Thery.htm" \l "EqualPtentials" }) prduces a ptential gradient, termed the cntact ptential V c, between the plates. The tw surfaces becme equally and ppsitely charged. Figure 2: Electrical cntact between 2 specimens Inclusin f a variable backing ptential, V b, in the external circuit permits biasing f ne electrde with respect t the ther. When V b = Vc = (Φ 1 Φ 2 )/e, the electric field between the plates vanishes (see { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptential% 20Detectin%20Thery.htm" \l "VariablePtential" }).

11 Figure 3: Variable backing ptential, V b, added A gd way t understand the respnse f the cantilever during Surface Ptential peratin is t start with the energy in a parallel plate capacitr: Equatin 4: where C is the lcal capacitance between the AFM tip and the sample and ΔV is the vltage difference between the tw. The frce n the tip and sample is the rate f change f the energy with separatin distance: Equatin 5: The vltage difference, ΔV, in Surface Ptential peratin cnsists f bth a DC and an AC cmpnent. The AC cmpnent is applied frm the scillatr, V AC sinωt, where ω is the resnant frequency f the cantilever: Equatin 6: ΔV DC includes applied DC vltages (frm the feedback lp), wrk functin differences, surface charge effects, etc. Squaring ΔV and using the relatin 2sin 2 x = 1 cs(2x) prduces: Equatin 7: The scillating electric frce at ω acts as a sinusidal driving frce that can excite mtin in the cantilever. The cantilever respnds nly t frces at r very near its resnance, s the DC and 2ω terms d nt cause any significant scillatin f the cantilever. In regular TappingMde, the cantilever respnse (RMS amplitude) is

12 directly prprtinal t the drive amplitude f the tapping piez. Here the respnse is directly prprtinal t the amplitude f the F ω drive term: Equatin 8: The gal f the Surface Ptential feedback lp is t adjust the vltage n the tip until it equals the vltage f the sample (ΔV DC =0), at which pint the cantilever amplitude shuld be zer (F ω = 0). The larger the DC vltage difference between the tip and sample, the larger the driving frce and resulting amplitude will be. But the F ω amplitude alne des nt prvide sufficient infrmatin t adjust the vltage n the tip. The driving frce generated frm a 2 V difference between the tip and sample is the same as frm a 2 V difference (see { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptential% 20Detectin%20Thery.htm" \l "FrceVsVltage" }). Figure 9: Frce as a functin f vltage What differentiates these states is the phase. The phase relatinship between the AC vltage and the frce it generates is different fr psitive and negative DC vltages (see { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptential% 20Detectin%20Thery.htm" \l "VatW" } thrugh { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptential% 20Detectin%20Thery.htm" \l "OutOfPhase" }). Figure 10: V AC at ω, ΔV DC= 2 V

13 Figure 11: Majr frce cmpnent in phase with V AC at Frequency ω, ΔV DC= 2 V Figure 12: ΔV ACat ω, ΔV DC= 2 V Figure 13: Majr frce cmpnent 180 ut f phase with V AC at Frequency ω, ΔV DC= 2 V In the case where ΔV DC = 2 V, the frce is in phase with V AC. When ΔV DC = 2 V, the frce is ut f phase with V AC. Thus, the cantilever scillatin will have a different phase, relative t the reference signal V AC, depending n whether the tip vltage is larger r smaller than the sample vltage. Bth the cantilever amplitude and phase are needed fr the feedback lp t crrectly adjust the tip vltage. The input signal t the Surface Ptential feedback lp is the cantilever amplitude multiplied by the sign f its phase (i.e., psitive value vltage fr phase 0 degrees, negative value vltage fr phase < 0 degrees). This signal can be accessed in the sftware by selecting Ptential Input (interleave scan line) in ne f the channel panels. If ΔV DC = 0, the electric drive frce is at the frequency 2ω. The cmpnent f the frce at ω is zer s the cantilever des nt scillate (see { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptential% 20Detectin%20Thery.htm" \l "DVis0" } and { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\surface%20ptential% 20Detectin%20Thery.htm" \l "2W" }). The Surface Ptential feedback lp adjusts the applied DC ptential n

14 the tip, V tip, until the cantilever s respnse is zer. V tip is the Ptential data that is used t generate a vltage map f the surface. Figure 14: V AC at ω, ΔV DC= 0 V Figure 15: Frce at Frequency f 2ω, ΔV DC= 0 V LiftMde Surface Ptential Detectin (AM-KPFM) Prcedure Sample Preparatin Prepare the sample as described in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\electric %20Techniques.htm" \l "Sample_Preparatin" }. Prbe Selectin { HYPERLINK " mesp.aspx" \t "_blank" \ "Link t MESP prbe infrmatin n brukerafmprbes.cm" } (cst-effective electrically cnductive prbes cated with cbalt/chrmium) Custm-cated { HYPERLINK " fesp.aspx" \t "_blank" \ "Link t FESP prbe infrmatin n brukerafmprbes.cm" } silicn TappingMde cantilevers (ensure that any depsited metal yu use adheres strngly t the silicn cantilever) { HYPERLINK " scm- pit.aspx" \t "_blank" \ "Link t SCM- PIT infrmatin n brukerafmprbes.cm" } (platinum/iridium cated prbes) { HYPERLINK " scm- pt.aspx" \t "_blank" \ "Link t infrmatin abut OSCM- PT tips at brukerafmprbes.cm" } (platinum cated prbes)

15 FESP r { HYPERLINK " ltesp.aspx" \t "_blank" \ "Link t infrmatin abut LTESP tips at brukerafmprbes.cm" } (uncated, highly-dped Si) Prcedure 1. Munt a sample nt the sample hlder. 2. Munt a metal-cated cantilever int the standard prbe hlder (see { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\basic%20afm%20operatin\\pr epare%20and%20lad%20the%20cantilever%20hlder.htm" \ "Link t Prepare and Lad the Cantilever Hlder" } fr details). 3. Click the Select Experiment icn. 4. Select the fllwing: Experiment Categry: Electrical & Magnetic Experiment Grup: Electrical & Magnetic Lift Mdes Select Experiment: Surface Ptential (AM-KPFM) 5. Click Lad Experiment. 6. Set up the AFM fr { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\tappingmde%20afm\\basic% 20TappingMde%20Operatin.htm" \ "Link t basic TappingMde AFM prcedure" }. 7. Use the AutTune buttn in the Tune Cantilever panel f the Setup view t lcate the cantilever s resnant peak. If yu were t click the Manual Tune buttn, the Cantilever Tune windw wuld appear displaying 2 peaks the amplitude curve and the phase curve. In the event yu find mre than ne resnance, use Manual Tune and select a resnance that is sharp and clearly defined, but nt necessarily the largest. It is als helpful t select a resnant peak where the lck-in phase als changes very sharply acrss the peak. Multiple peaks can ften be eliminated by making sure the cantilever hlder is clean and the cantilever is tightly secured. See { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\tappingmde%20af M\\Manual%20Cantilever%20Tuning.htm" \ "Link t Manual Cantilever Tuning" } fr mre infrmatin. 8. Engage the AFM and make the necessary adjustments fr a gd TappingMde image while displaying height data. 9. Activate the Expanded Mde t see all the Interleave parameters available (in the Check Parameters r Scan view frm the wrkflw tlbar).

16 10. In the Interleave panel, set the fllwing: Integral Igain: 0.5 Prprtinal Gain: 5 Interleave Mde: Lift Lift Scan Height: 100 nm (can be ptimized later) 11. In the Ptential (Interleave) panel, set the fllwing: Ptential Feedback: On Leave the Drive2 Frequency at the main Feedback value (gray) 11. Enter a Drive2 Amplitude. This is the AC vltage that is applied t the AFM tip. Higher Drive Amplitude prduces a larger electrstatic frce n the cantilever and this makes fr mre sensitive ptential measurements. Cnversely, the maximum ttal vltage (AC + DC) that may be applied t the tip is ±10 V, s a large Drive Amplitude reduces the range f the DC vltage that can be applied t the cantilever. If the sample surface ptentials t be measured are very large, it is necessary t chse a small Drive Amplitude, while small surface ptentials can be imaged mre successfully with large Drive Amplitudes. A suggested starting Drive Amplitude is 500 mv.

17 12. Ensure the the Channel 4 image Data Type is set t Ptential. 13. Set the scan Line Directin fr the main and interleave scans t Retrace. Remember t chse the Retrace directin because the lift step ccurs n the trace scan and can cause artifacts in the data. 14. Set the Channel 4 Scan Line t Interleave. 15. Adjust the Input gains. As with the tpgraphy gains, the scan can be ptimized by increasing the gains t maximize feedback respnse, but nt s high that scillatin sets in. See { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanni ng\\trubleshting%20the%20surface%20ptential%20feedback%20lp.htm" \ "Link t Trubleshting the Surface Ptential Feedback Lp" } fr mre infrmatin. 16. Optimize the lift heights. Set the Lift Scan Height at the smallest value pssible that des nt make the Ptential feedback lp unstable r cause the tip t crash int the sample surface. When the tip crashes int the surface during the Ptential measurement, dark r light streaks appear in the Ptential image. In this case, increase the Lift Scan Height until these streaks are minimized. 17. Optimize the drive phase by clicking the Set Phase icn in the NanScpe tlbar. As discussed in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanni ng\\surface%20ptential%20detectin%20thery.htm" \ "Link t Surface Ptential Detectin Thery" }, the crrect phase relatinship must exist between the reference and the input signals t the lck-in fr the ptential feedback lp t perfrm crrectly. Lck-In Phase adjusts the phase f the reference signal t the lck-in amplifier and depends n the mechanical prperties f the cantilever. 18. Fr large sample vltages r qualitative wrk, set a Data Type t Phase (in additin t Channel 4 Data Type set t Ptential). When the cntrller has been cnfigured fr surface ptential measurements, the phase signal is actually the cantilever amplitude signal, as measured by a lck-in amplifier. If the feedback lp is nt enabled by selecting the Data Type = Ptential, the lck-in cantilever amplitude depends n the vltage difference between the tip and sample in a rughly linear fashin. (The lck-in amplifier prduces a vltage that is prprtinal t the cantilever amplitude.) Qualitative surface ptential images can be cllected using this lck-in signal. Als, if the sample has a surface ptential that exceeds ±10 V (greater than the range f the Ptential signal), it is pssible t use

18 the lck-in signal t prvide qualitative images that reflect the sample surface ptential. T view the lck-in signal with the recnfigured cntrller, select the Data type = Phase. Determinatin f Lck-in Phase Fr surface ptential micrscpy (als called scanning Kelvin prbe frce micrscpy, SKPFM) measurements, the feedback adjusts the DC vltage applied between the tip and sample t cmpensate their intrinsic ptential difference. The DC vltage map acrss the surface thus reflects surface ptential variatins f the sample surface. When the difference is perfectly cmpensated, the tapping scillatin amplitude f the metal cated AFM cantilever (excited by an AC bias field) appraches 0 the very reasn this technique is called a nulling technique. In ding s, the feedback uses the tapping amplitude and phase t determine whether t increase r decrease the DC vltage. T facilitate setting the Phase parameter, NanScpe Versin 8.15 sftware nw features a Set Phase tl, which enables the user t determine the lck-in phase with a single click. The fllwing describes the NanScpe prcedures initiated by the Set Phase tl: NOTE: Knwledge f the inner wrkings f Set Phase is generally nt necessary. Generic Sweeps are taken n Interleave. In sme cases, it is helpful t switch back and frth between Main and Interleave fr the sweep parameters t take effect. Sme incnsistency may ccur fr instance, ptential feedback may nt actually be n when Input Igain and Input Pgain are nn-zer. { HYPERLINK "javascript:vid(0);" } A phase difference ( 90 in the lwer graph in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\determi natin%20f%20lck-in%20phase.htm" \l "InterleaveTuneCurve" }) is usually seen between tip scillatin signal and the AC bias driving signal. This phase lag varies frm tip t tip, with perating frequency, and the ptential difference between the tip and the spt n the sample.

19 Figure 1: Interleave Tuning Curve - Phase Lag { HYPERLINK "javascript:vid(0);" } { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\determi natin%20f%20lck-in%20phase.htm" \l "AmplitudeAndPhaseVsBias" } shws a Generic Sweep f Sample Bias while the ptential feedback is turned ff. Nte that Input Igain and Input Pgain are 0.

20 Figure 2: Amplitude and Phase vs. Sample Bias (Feedback Off) The amplitude, shwn in the upper plt, dips t 0 when the sample is biased t match the tip ptential; as the bias vltage mves away frm that pint, the amplitude increases. Ptential feedback seeks that zer pint. Because amplitude alne can nt determine whether ne is n the left side r right side f that zer amplitude pint, the feedback relies n the phase t determine which directin t mve the DC bias. The bttm graph in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\determi natin%20f%20lck-in%20phase.htm" \l "AmplitudeAndPhaseVsBias" } shws the phase changing by 180 acrss 0 amplitude. Chse a Lck-In Phase t ffset the scillatin phase s that the phase is negative when the tip vltage is psitive relative t the sample. As yu can see in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\determi natin%20f%20lck-in%20phase.htm" \l "AmplitudeAndPhaseVsBias" }, when the sample bias is 2 V (tip is psitive), the utput Lck-In Phase is 90. The Interleave Lck-In Phase then needs t be set t 180 t make it 90.

21 { HYPERLINK "javascript:vid(0);" } It is lgical t sweep the lck-in phase in a full circle t determine the phase range where feedback is wrking while the feedback is turned n (Input Igain and Input Pgain are nn-zer). Figure 3: Phase vs. Lck-in Phase (Feedback On) The tp plt in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\determi natin%20f%20lck-in%20phase.htm" \l "PhaseVsLckIn" } shws hw the amplitude changes while lck-in phase is swept. In the mid-range f the phase sweep (apprximately 100 t +100 ), the amplitude stays nn-zer, indicating that the phase is nt crrect fr the feedback t wrk prperly. On bth ends, the amplitude remains arund 0, implying that feedback is wrking prperly in nulling the amplitude. In principle, it is fine t chse any lck-in phase in these tw regins 100 ~ 180 and 180 ~ 90 (equivalent t 180 ~ 270 ); actually a cmbined regin f 100 ~ 270. It makes practical sense, hwever, t chse a value smewhere in the middle t have a gd margin, e.g. 170.

22 The lwer plt in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\determi natin%20f%20lck-in%20phase.htm" \l "PhaseVsLckIn" } shws phase changing linearly in the middle f the sweep range, while jumping arund when feedback is wrking n either end. This is explained abve under Amplitude and Phase vs. Sample Bias Feedback Off. { HYPERLINK "javascript:vid(0);" } { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\determi natin%20f%20lck-in%20phase.htm" \l "AlternativePhase" } depicts a Generic Sweep f Lck-in phase while ptential feedback is ff and Input Igain and Input Pgain are 0. Figure 4: Alternative Phase vs. Lck-in Phase (Feedback Off) The tp plt in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\determi natin%20f%20lck-in%20phase.htm" \l "AlternativePhase" } shws the amplitude remaining unchanged while the Lck-In Phase is swept.

23 The bttm plt shws the phase changing linearly as the lck-in phase is swept. There is ne exceptin where the phase jumps frm 180 t 180, s-called phase wrapping. In case the plts in the previus sectin were nt btained (due t sftware incnsistency), d the fllwing: Frm the left bttm plt, chse a lck-in phase where scillatin phase falls within 180 ~0 (r 0~180 ), e.g. 10 ( 170 ) If this des nt wrk, add/subtract 180, e.g. 170 (10 ) Of curse, yu can simply pick any lck-in phase, if it wrks, fine. Otherwise, change the phase by 180. The difference is that with the abve utlined apprach yu knw what kind f margin yu have. Recall: Lck-In Phase depends n the mechanical prperties f the cantilever. Fr cantilevers with resnant frequencies frm khz (such as MESP, SCM-PIT, and FESP), use an interleave Lck-In Phase f 170 degrees. Fr cantilevers with higher resnant frequencies, increased electrnics phase lag must be cmpensated. Fr cantilevers with resnant frequencies arund 300 khz (such as TESP, RTESP) an interleave Lck-In Phase near 130 degrees ften wrks well. FM-KPFM Imaging FM-KPFM (Frequency Mdulated-Kelvin Prbe Frce Micrscpy) applies an AC signal t the prbe at a lw frequency, f m, while mechanically driving the prbe at its resnant frequency, f 0, and uses the amplitude f the 1st sideband at f 0 + f m as the errr signal t drive a DC vltage that nulls that signal. FM-KPFM is a { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\tappingmde%20afm\\tapping Mde%20AFM.htm" } single-pass technique and, unlike ther electric mdes, des nt use { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\interleav e%20scanning.htm" \l "LiftMde" }. FM-KPFM has higher spatial reslutin than { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\liftmde %20SurfacePtentialDetectinPrinciples.htm" } but its signal-t-nise rati is frequently lwer. { HYPERLINK "javascript:vid(0);" } An AC vltage with amplitude V AC and frequency f m (angular frequency ω m ) superimpsed n a DC vltage, V DC, is applied between the prbe tip and the sample. The resulting electrstatic frce is given by Equatin 1: where

24 Equatin 2: where Δφ is the cntact ptential difference between the prbe and sample. Equatin 1 may be separated int three terms: Equatin 3: The electric field gradient is given by: Equatin 4: The applied AC vltage mdulates the frce and frce gradient at frequencies ω m and 2ω m. Frequency Mdulatin Hke's law states: Equatin 5: Taking the derivative, Equatin 6: The frce gradient and spring cnstant are thus seen t be equivalent. The electrstatic frce shifts the resnant frequency f a cantilever with effective mass m* as fllws: Equatin 7:

25 Figure 8: Schematic f the frequency spectrum f the prbe tip scillatin Reslutin Figure 9: Charged sphere at separatin z abve an infinite plane The frce between a charged sphere at separatin z abve an infinite plane, shwn in { HYPERLINK The applied AC vltage mdulates F el and F el / z accrding t { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "Eqn4" }. { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "Eqn6" } then shws that the mechanical resnance f the cantilever is mdulated with frequencies f m and 2f m with sidebands, shwn schematically in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "Fig1" }, appearing at f 0 ±f m and f 0 ±2f m. "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "ChargedSphere" }, is: Equatin 10: and its derivative is:

26 Equatin 11: The electric frce gradient has a steeper dependence n Z than the electric frce. It als has a steeper dependence n X and Y. FM-KPFM Prbe Requirements Bruker recmmends { HYPERLINK " \t "_blank" } prbes fr FM-KPFM measurements. Sample Preparatin Prepare the sample as described in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\electric %20Techniques.htm" \l "Sample_Preparatin" }. FM-KPFM Prcedure 1. Munt a sample nt the sample hlder. 2. Munt an apprpriate prbe int the standard prbe hlder (see Prepare and Lad the Cantilever Hlder fr details). 3. Click the Select Experiment icn t pen the Select Experiment windw, shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "SelectExperimentWindw" }. 4. Select the fllwing: Experiment Categry: Electrical & Magnetic Experiment Grup: Electrical & Magnetic Lift Mdes Select Experiment: Surface Ptential (FM-KPFM) 5. Click Lad Experiment. 6. Click the Setup icn t pen the Setup windw. 7. Align the laser n the cantilever and place the crsshair there. See { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "AlignLaser" }. 8. Fast Thermal tuning, used t find the cantilever resnance, is perfrmed when yu exit the

27 Setup view. This is made visible by the HDSC windw, shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "HSDC" }. 7. Engage the prbe nt the sample 8. Scan the sample 9. Entering a value in the Ptential Offset field adds that value t the measured value in the Ptential channel. This can be particularly useful when measuring wrk functins as this functin measures the difference in ptential between the prbe and the sample - entering the value f the wrk functin f the prbe will then prvide a direct measurement f wrk functin f the sample. NOTE: The stred data is unaffected by the Ptential Offset. I.e. ffline measurements d nt see this input. Advanced FM-KPFM Imaging Figure 15: Ptential Offset in the FM-KPFM Ptential windw Autmatic frequency selectin is the default fr FM-KPFM imaging. Yu may wish, hwever, t manually select an perating frequency. T d this: 12. Enter the Expanded mde. 13. Set Freq. Cntrl in the Ptential (Interleave), shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "FreqCntrl" }, panel t User-defined.

28 Figure 16: Selecting User-defined Frequency Cntrl 14. Yu may then, if yu wish, Tune the cantilever. FM- KPFM Parameters Yu may wish t manually adjust the parameters shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "FMKPFMParms" }. Parameter Lck-In BW Descriptin Needs t be smaller than twice the Drive 3 Frequency which is f m in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "Fig1" }. This lets the Lck-In respnd t f 0 while filtering f 0 ± f m. If the Lck-In BW is t lw, the tracking ability will be reduced. Autmatic Freq. Cntrl is thus easier t use than Userdefined Freq. Cntrl. Lck-In2 BW Needs t be larger than fur times the Drive 3 Frequency which is f m in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" \l "Fig1" }. This is used t include the first and secnd harmnics, f 0 ± 2f m. Extra bandwidth f Lck-In2 des nt degrade image quality as Lck-In3 fllws. Lck-In3 BW Drive3 Lck-In3, cascaded with Lck-In2, is used fr the surface ptential feedback. Higher Drive3 Amplitudes will result in higher signal-t-nise ratis.

29 Parameter Descriptin Amplitude Table 1: Adjustable FM-KPFM parameters PeakFrce KPFM-AM Imaging PeakFrce-KPFM-AM is a is a tw-pass prcedure where the surface tpgraphy and nanmechanical prperties are btained using Bruker's prprietary { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\oper atingprinciples.htm" \l "Peak" } in the first pass and the surface ptential r wrk functin in the secnd pass using the { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\liftmde %20SurfacePtentialDetectinPrinciples.htm" } mde: 1. The cantilever measures surface tpgraphy and nanmechanical prperties n the first (main) scan (trace and retrace). 2. The cantilever ascends t the Lift Scan Height. 3. The cantilever then fllws the stred surface tpgraphy at the lift height abve the sample while an scillating vltage V AC sin(ωt) is applied directly t the prbe tip. If there is a DC vltage difference between the tip and sample, then there will be an scillating electric frce n the cantilever at the frequency ω. This causes the cantilever t vibrate, and an amplitude can be detected n the secnd (interleave) scan. PeakFrce KPFM-AM leverages the advantages f PeakFrce Tapping: Direct frce cntrl, eliminating artifacts that result frm tip and sample damage Self-ptimizatin using ScanAsyst Dramatically imprved ease f use thrugh the ScanAsyst imaging mde Spatially crrelated nanmechanical infrmatin with PeakFrce QNM PeakFrce KPFM-AM Prbe Requirements Bruker recmmends { HYPERLINK " \t "_blank" } prbes fr PeakFrce KPFM measurements. Sample Preparatin Prepare the sample as described in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\electric %20Techniques.htm" \l "Sample_Preparatin" }. PeakFrce KPFM-AM Prcedure

30 1. Munt a sample nt the sample hlder. 2. Munt an apprpriate prbe int the standard prbe hlder (see Prepare and Lad the Cantilever Hlder fr details). 3. Click the Select Experiment icn t pen the Select Experiment windw, shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" \l "SelectExperiment" }. 4. Select the fllwing: Experiment Categry: Electrical & Magnetic Experiment Grup: Electrical & Magnetic Lift Mdes Select Experiment: PeakFrce KPFM-AM 5. Click Lad Experiment. 4. Click the Setup icn t pen the Setup windw. 5. Align the laser n the cantilever and place the crsshair there. See { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" \l "AlignLaser" }. 6. Fast Thermal tuning, used t find the cantilever resnance, is perfrmed when yu exit the Setup view. This is made visible by the HSDC windw, shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" \l "HSDC" }. 7. Engage the prbe nt the sample 8. Scan the sample. 9. Set the Lift Scan Height as lw as pssible withut hitting the sample, typically nm. 10. Entering a value in the Ptential Offset field adds that value t the measured value in the Ptential channel. This can be particularly useful when measuring wrk functins as this functin measures the difference in ptential between the prbe and the sample - entering the value f the wrk functin f the prbe will then prvide a direct measurement f wrk functin f the sample. NOTE: The stred data is unaffected by the Ptential Offset. I.e. ffline measurements d nt see this input. 11. Refer t the { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\o

31 peratingprcedures.htm" } sectins fr details regarding PeakFrce mde imaging. Advanced PeakFrce KPFM-AM Operatin Autmatic frequency selectin is the default fr PeakFrce KPFM imaging. Yu may wish, hwever, t manually select an perating frequency. T d this: 12. Enter the Expanded mde. 13. Set Freq. Cntrl in the Ptential (Interleave), shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" \l "FreqCntrl" }, panel t User-defined. Figure 4: Selecting User-defined Frequency Cntrl 14. Yu will then need t manually tune the cantilever: 15. Select Micrscpe > Generic Lckin frm the NanScpe Menu Bar. This pens the Generic Lck- In windw, shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" \l "LckIn" }.

32 Figure 5: The PeakFrce KPFM Generic Lck-In windw 16. Select Tapping Piez in the Drive Ruting panel f Lck-In Click Sweep t pen the Generic Sweep windw, shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" \l "GenericSweep" }. Figure 6: The Generic Sweep windw (Hver ver the image t view larger) 18. Standard tune prcedures, with the exceptin f Aut Tune, apply. Yu may use the Offset cmmand t center the peak n the cursr...

33 19. Yu will als need t fllw the manual prcedures described in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\determinati n%20f%20lck- in%20phase.htm" }. 20. Reset the Drive Ruting t Internal befre clsing the PF KPFM Generic Lck-In windw. See { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" \l "Internal" }. Figure 7: Set the Drive Ruting t Internal 21. Enter yur chsen frequency and amplitude int the Drive2 Frequency and Amplitude windws, shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" \l "FreqCntrl" }.

34 PeakFrce KPFM Imaging PeakFrce KPFM (PeakFrce Frequency Mdulated-Kelvin Prbe Frce Micrscpy) is a cmbinatin f Peak Frce Tapping Mde and frequency mdulated KPFM (FM-KPFM) mde. PeakFrce KPFM measures surface ptential r wrk functin using a { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\liftmde %20SurfacePtentialDetectinPrinciples.htm" } variatin f the { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\fm- KPFM.htm" } mde while simultaneusly prviding crrelated nanmechanical prperty infrmatin using the Bruker's prprietary { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\oper atingprinciples.htm" \l "Peak" }. PeakFrce KPFM leverages the advantages f PeakFrce Tapping: Direct frce cntrl, eliminating artifacts that result frm tip and sample damage Self-ptimizatin using ScanAsyst Dramatically imprved ease f use thrugh the ScanAsyst imaging mde Spatially crrelated nanmechanical infrmatin with PeakFrce QNM Because f PeakFrce's direct frce cntrl, sfter prbes may be used in this mde, thereby increasing sensitivity. PeakFrce KPFM Prbe Requirements Bruker recmmends { HYPERLINK " \t "_blank" } prbes fr PF FM-KPFM measurements. Sample Preparatin Prepare the sample as described in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\electric %20Techniques.htm" \l "Sample_Preparatin" }. PeakFrce KPFM Prcedure 1. Munt a sample nt the sample hlder. 2. Munt an apprpriate prbe int the standard prbe hlder (see { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\basic%20afm%20operatin\\pr epare%20and%20lad%20the%20cantilever%20hlder.htm" \ "Link t Prepare and Lad the Cantilever Hlder" } fr details).

35 3. Click the Select Experiment icn t pen the Select Experiment windw. 4. Select the fllwing: Experiment Categry: Electrical & Magnetic Experiment Grup: Electrical & Magnetic Lift Mdes Select Experiment: PeakFrce KPFM 5. Click Lad Experiment. 6. Click the Setup icn t pen the Setup windw. 7. Align the laser n the cantilever and place the crsshair there. See { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- FM- KPFM.htm" \l "AlignLaser" }. 6. Fast Thermal tuning, used t find the cantilever resnance, is perfrmed when yu exit the Setup view. This is made visible by the HSDC windw, shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- FM- KPFM.htm" \l "HSDC" }. 7. Engage the prbe nt the sample 8. Scan the sample 9. Set the Lift Scan Height as lw as pssible withut hitting the sample, typically nm. 10. Entering a value in the Ptential Offset field adds that value t the measured value in the Ptential channel. This can be particularly useful when measuring wrk functins as this functin measures the difference in ptential between the prbe and the sample - entering the value f the wrk functin f the prbe will then prvide a direct measurement f wrk functin f the sample. NOTE: The stred data is unaffected by the Ptential Offset. I.e. ffline measurements d nt see this input. 11. Refer t the { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\peakfrceqnm\\operatin\\o peratingprcedures.htm" } sectins fr details regarding PeakFrce mde imaging. A sample result shwing the surface ptentials (wrk functins) f three different materials is shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf-fm- KPFM.htm" \l "Scan" }.

36 Figure 4: PeakFrce KPFM scan f a Au-Si-Al (left t right) sample. Advanced PeakFrce KPFM Imaging Autmatic frequency selectin is the default fr PeakFrce KPFM imaging. Yu may wish, hwever, t manually select an perating frequency. T d this: 12. Enter the Expanded mde. 13. Set Freq. Cntrl in the Ptential (Interleave), shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- FM- KPFM.htm" \l "FreqCntrl" }, panel t User-defined.

37 Figure 5: Selecting User-defined Frequency Cntrl PeakFrce KPFM Parameters Yu can manually select the perating frequency f the LiftMde. Fr details, refer t { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf- KPFM.htm" \l "Advanced" }. Yu may wish t manually adjust the parameters shwn in { HYPERLINK "file:///d:\\prgram%20files\\nanscpe\\8.15\\help\\icn\\cntent\\interleave%20scanning\\pf-fm- KPFM.htm" \l "FMKPFMParms" }.