Using Nanoelectrical Solutions to expand the capability of AFM Dr. Peter De Wolf

Transcription

1 Using Nanoelectrical Solutions to expand the capability of AFM Dr. Peter De Wolf

2 2 Atomic Force Microscopy (AFM) Microscopy technique based on raster-scanning and small tipsample force interactions Resolution <1-5nm Sample topography Property measurements: Mechanical Electrical Thermal, Ambient & fluid conditions

3 3 Electrical Property Measurements with AFM Surface Potential / Workfunction: KPFM Conductivity & Resistivity: C-AFM, TUNA, SSRM Carrier density: SCM, SSRM, smim Electric Fields, Charge: EFM, KPFM Piezoelectric properties: PFM Impedance: smim Other: Scanning Gate, Pyro-Electric AFM, Photoconductive AFM,

4 Electrical Property Measurements with AFM Height Height Height TUNA Current TUNA Current Carbon NTs (4x2 µm) KPFM Potential InP nanowire (2x1 µm) SECM Current Pt nanoparticles in solution Height SCM dc/dv Si DMOSFET (1x0.7 µm) Height smim Capacitance Capacitor references (60x40 µm) 3/29/2018 Bruker Webinar 4

5 5 Imaging & Spectroscopy Tunneling AFM (TUNA) on a carpet of standing carbon nanotubes (1x1 µm scan) Height (nm) Current (pa) I-V Spectra

6 6 Expand the Capability on 3 levels: Capture electrical spectra in every pixel Correlate electrical & mechanical properties Eliminate contact mode limitations, and expand to soft & fragile samples

7 7 Expand the Capability on 3 levels: Capture electrical spectra in every pixel Correlate electrical & mechanical properties Eliminate contact mode limitations, and expand to soft & fragile samples PeakForce Tapping PeakForce TUNA on P3HT:CNT blends (700x700 nm scan) Height Adhesion Current Collaboration with Ph. Leclere, Uni Mons, Belgium See also: Nanoscale 4, no. 8 (2012), 2705.

8 8 DataCubes

9 9 DataCubes Electrical Characterization Principle Fast Force Volume imaging: a force-distance spectrum in every pixel Z Force Insert a hold segment (= dwell time ) and perform an electrical measurement during the hold segment: electrical spectrum in every pixel DC Sample Voltage Electrical Channel

10 10 DCUBE-TUNA (Tunneling AFM) on Maghemite (γ-fe 2 O 3 ) Force-distance & I-V spectrum in every pixel (110 ms/pixel) TUNA current slices shown as movie (movie)

11 11 DCUBE-TUNA (Tunneling AFM) on Maghemite (γ-fe 2 O 3 ) The datacube can be analyzed as current slice data The datacube can be analyzed as I-V spectra

12 12 DataCubes Electrical Characterization Principle Ramp Parameter Output Channel MECHANICAL Force Volume DCUBE-TUNA DCUBE-SSRM DCUBE-SCM DCUBE-sMIM DCUBE-PFM Distance V DC V DC Force Stiffness Adhesion Modulus Current log(resistance) ELECTRICAL V DC V AC f AC Phase dc/dv Amplitude dc/dv Phase V DC V AC f AC Phase dc/dv Amplitude dc/dv Phase smim-c smim-r V DC V AC f AC Phase PFM Amplitude PFM Phase Example Spectra

13 13 Capture electrical spectra in every pixel More information than other electrical AFM modes Access previously inaccessible material properties and device data

14 DCUBE-TUNA (Tunneling AFM) on Maghemite (γ-fe 2 O 3 ) Using Matlab export/import functions, one can perform custom analysis: Here we fit all I-V spectra to extract potential barriers: y = ae bx + ce dx Data processing by N. Chevalier & D. Mariolle at Uni. Grenoble Alpes, CEA, LETI No Conduction (movie) V b+ = ln (a) > 0 b 3/29/2018 Bruker Webinar 14 Ohmic

15 15 DCUBE-SCM (Scanning Capacitance Microscopy) on SRAM Transistors Sample voltage ramp from -2V to 2V 128x128 pixels, 2x2 µm scan 100 ms/pixel (27 min/cube) Data courtesy: N. Chevalier & D. Mariolle at Uni. Grenoble Alpes, CEA, LETI, France dc/dv Amplitude -1.6V -1.2V -0.8V -0.4V p n p p n p (movie)

16 DCUBE-SCM (Scanning Capacitance Microscopy) on SRAM Transistors Sample voltage (V DC ) ramp from -2V to 2V in every pixel Slices through the datacube show how the pnp junction profile changes with V DC Data courtesy: N. Chevalier & D. Mariolle at Uni. Grenoble Alpes, CEA, LETI, France slice at fixed V DC dc/dv Amplitude DataCube slice at fixed Y position p n p Y p n p V DC V DC Y X 3/29/2018 Bruker Webinar 16

17 17 DCUBE-sMIM (Microwave Impedance Microscopy) on Doped Si Device C-V and dc/dv-v spectra (-2V to +2V) in every pixel smim-c dc/dv Amplitude dc/dv Phase -2.0V -1.5V -1.0V -0.5V 0.0V 0.5V 1.0V 1.5V 2.0V

18 18 DCUBE-sMIM (Microwave Impedance Microscopy) on Si with staircase carrier profile Sample voltage ramp from -2V to 2V in every pixel results in C-V spectra Sample source: Infineon Munich, DOI: /j.microrel smim-r vs. time p-type n-type -1V V + + smim-c vs. time

19 19 Practical Aspect: Speed? Typ. time (ms) Force-Distance Spectrum Electrical spectrum Total Mode Bandwidth (khz) TUNA 15 smim 300 SCM 1-10 PFM 1-10 *fac and LIA BW dependent Time per Image (min) Time per pixel 20 ms 100 ms 200 ms 64x Pixels 128x x ms 50 ms 12 ms 100 ms 25 ms smim C-V spectra on Si sample, collected at different speeds

20 20 DCUBE-PFM (Piezoresponse Force Microscopy) on BFO PFM Amplitude and PFM Phase data slices Domains switch as voltage is increased. Different domains switch at different voltages -6V -5V -4V -3V -2V -1V 0V Amplitude Phase

21 DCUBE-PFM (Piezoresponse Force Microscopy) on BFO Amplitude spectra along one line are shown The images represent the PFM amplitude & phase vs. voltage along the line Sample Bias (V) X -6 X 3/29/2018 Bruker Webinar 21

22 22 Correlate electrical & mechanical properties

23 DCUBE-TUNA (Tunneling AFM) on Battery Cathode Modulus, Adhesion, Stiffness & conductivity from -4V to +4V The data allow one to identify all elements (Li metal oxide, binder & carbon nanoparticles) and study differences between different metal oxide grains -3.5V -2.5V -1.5V -0.5V +0.25V Li metaloxide +1V +1.75V +2.5V +3.25V +4V Polymer binder Carbon black 3/29/2018 Bruker Webinar 23

24 24 DCUBE-TUNA (Tunneling AFM) on Battery Cathode +3V -3V Modulus, Adhesion, Stiffness & conductivity from -4V to +4V All I-V spectra in selected area displayed

25 25 DCUBE-sMIM (Microwave Impedance Microscopy) on Maghemite (γ-fe 2 O 3 ) smim-c smim-r During a short hold segment, the DC bias was kept constant (no spectra) Mechanical properties (Adhesion shown) acquired simultaneously smim-c vs. time spectra shown for 5 positions

26 26 DCUBE-CR-PFM (Contact Resonance PFM) on LiTaO 3 (movie)

27 27 Eliminate contact mode limitations Longer tip lifetime Characterize soft & fragile samples Better spatial resolution

28 28 DCUBE-TUNA (Tunneling AFM) on Battery Cathode -4.0V -3.0V -1.0V +1V +2.0V +3.0V +4.0V

29 29 Peakforce-TUNA (Tunneling AFM) on P3HT Organic conductive nanowires Height (nm) Adhesion (nn) Current (pa) +3V sample voltage, 3x3 µm scan

30 30 Summary Combining Fast Force Volume imaging with Electrical modes generates Datacubes enhancing the capabilities of conventional electrical AFM modes: Capture electrical spectra in every pixel Correlate electrical & mechanical properties Eliminate contact mode limitations & expand to soft & fragile samples Height Modulus Current (movie)

31 Copyright Bruker Corporation. All rights reserved.