New Developments in AFM Oscillatory Resonance Modes: Imaging & Modulation Sergei Magonov NT-MDT Development Inc., Tempe AZ USA
Outline. Classification of Oscillatory Resonant AFM modes 2. Practical Realization of Imaging and Modulation 3. Modulation Mode: Applications 4. Imaging Mode: Applications 5. Conclusions 2 of 20 2 of 23
3 of 20 Atomic Force Microscopy Oscillatory Modes Atomic Force Microscopy Contact Mode Lateral force imaging, force modulation, contact resonance, PFM Oscillatory Resonant Modes Amplitude modulation, frequency modulation, phase imaging, frequency imaging Oscillatory Non-Resonant Modes Jumping mode, HybriD mode, etc Oscillatory Resonance Mode: AFM Amplitude Operator Loading Modulation & of Operating a Sample Procedures Loading & Aligning a Probe Manual and automatic loading Single probe and multi-probe Engagement of a Probe cartridge; manual and automatic alignment Manual and automatic engagement; soft approach algorithm Oscillatory Non-Resonance Mode: Hybrid Mode Measurements Routines Studies at variable tip-forces; automated and non-attended multi-site and multi-probe experiments
4 of 20 Euler-Bernoulli Equation Classification of Oscillatory AFM Modes Dissipative Conservative G G F a, F r tip-sample forces on approach and retract 2 2 sin KBM asymptotic solution N cos N F F Z Acosy F F Z Acosy 2 A0 SL N ; G 2Q 4Q sin ydy a r c 0 0 cosydy G a r c 0 0 A A A A, Q, A 0, resonant frequency, quality factor, initial amplitude and phase of the probe Four variables : Topography (Zc); (G); Amplitude (A); Phase () But only two equations If topography (Zc) is the variable to be found then 3 modes can be realized: # 2 Fixed Variables Control Imaging/Measurement Name G(f)=0, A(f 0 )=const Generator with F res ; Z&/A& by LIA AM-PI Z-servo of A(f 0 ) 2 =90 o ; G(f)=const PLL for -servo; Z-servo for G(f) 3 =90 o ; A(f)=const PLL for -servo; Z-servo for A(f) Z&A/A&G(f) by PLL Z&G(f)/A&G(f) by PLL FM AM-FI Amplitude Modulation with Phase Imaging (AM-PI) Amplitude Modulation with Imaging (AM-FI) Modulation (FM) Fixed G, A Fixed, A Fixed, G
4 of 20 Phase Similarities Specifics cos AM N a 0 A G Fa Fr A N 2 Q A A0 G a r c k 0 Energy in Dissipation/Energy out FM, AM-FI, = 90 NT-MDT Convention Amplitude 0 F F Z Acos ysin ydy 0 Classification of the Oscillatory AM Modes F F Z Acos y r Z Acos y c c f G 2Q f P tip cos ydy cos ydy Dissipation A T F a Fr Zc z A AM-PI, = FM, AM-FI, = 90 Bifurcation modelling with Lennard-Jones potential AM-PI, = dz 2 ka sp A 2 Q A 0 2 ka A0 2 Q A sp sin AM 2 2 A A G sp G 2 kasp 0 2 Q FM, AM-FI, = 90 sp Phase H. Holscher et al. (2009); A. Temiryazev et al (204) Amplitude Amplitude
6 of 20 Classification of Oscillatory AM Modes f f ka 0 F Z c Acos y cos ydy Tip Acos y Position of a tip apex during oscillation f f E * ka 0 4 3 F Tip-induced deformation * 4 * 3/ 2 h; E E Rh 3 Z Zc Acos y h max 0, Z R max 0, Z c Acos y 3/ 2 Hertz model cos ydy Z sample = 0 Tip Tip Z c h E * 4 f 0 R 3fkA max 0, Z c Acos y 3/ 2 cos ydy
7 of 20 Imaging and Modulation Imaging, AM-FI HDPE Gen Amplitude Shaker Gen PSPD PLL with Amplitude & Phase Calculation Phase Shift Sample Amplitude f Z Z servo 2 mm 2 mm Modulation, FM Gen Amplitude F4H20/mica Amplitude Shaker Gen PSPD PLL with Amplitude & Phase Calculation Phase Shift Sample Z Z servo f Amplitude
8 of 20 Modulation Mode: Applications Modulation Single crystal of C242H486 ultra-long alkane on HOPG C36H74 layer on HOPG 20 mm 40 nm Triblock copolymer SBS, Modulation -25 Hz +44 Hz -5 Hz 0.5 mm 0.5 mm 0.5 mm
Modulation Mode: Applications Modulation F4H20/mica d= -0 Hz 2 mm 0.5 mm 200 nm 9 of 20 200 nm 200 nm
Modulation Mode: Applications Amplitude Modulation C242H486 alkanes on HOPG 0.6 mm 0.6 mm Amplitude Modulation Modulation mm 0 of 20 mm mm
of 20 Modulation Mode: Applications Amplitude F4H20/mica AGC Signal Amplitude PS/PBD Blend PBD PS 3.5 mm 3.5 mm
2 of 20 Imaging: Applications C36H74 on HOPG Imaging, AM-FI 00 nm 00 nm 40 nm 40 nm
3 of 20 Imaging: Applications SBS (20-40-20) A sp /A 0 = 4nm/5.6nm Phase
Imaging: Applications AM-PI Phase Triblock copolymer SEBS 600 nm 600 nm AM-FI Hybrid Mode Elastic Modulus 4 of 20 600 nm 600 nm 500 nm
Imaging: Applications A sp /A 0 = nm/3nm AM-PI LLDPE, hot pressed AM-FI A sp /A 0 = 2nm/3nm Phase A sp /A 0 = 6nm/3nm AM-PI Phase AM-FI A sp /A 0 = nm/3nm 5 of 20
6 of 20 Imaging: Applications A sp /A 0 = 0nm/26nm AM-PI Phase LLDPE, hot pressed A sp /A 0 = 6nm/26nm AM-FI Hybrid Mode Deformation mm
Imaging: Applications LDPE, hot pressed A sp /A 0 = 8nm/0nm A sp /A 0 = 6.0/0nm Phase AM-PI mm A sp /A 0 = 9nm/0nm A sp /A 0 = 8nm/0nm AM-FI 7 of 20 mm
8 of 20 Imaging: Applications AM-PI mm 00 nm 00 nm C242H486 on HOPG AM-FI 00 nm 00 nm
Imaging: Applications Amplitude Modulation, Imaging C242H486 on HOPG 200 nm 200 nm 9 of 20 200 nm 200 nm
Conclusions A full set of the resonant oscillatory AFM modes (amplitude modulation modes with phase and frequency imaging and frequency modulation mode) became available for NT-MDT microscopes. Modulation Mode was used in a number of applications on smooth and corrugated surfaces. A possibility of imaging of weak-bonded surface structures was demonstrated. Measurements of local energy dissipation are helpful for compositional mapping of heterogeneous materials. imaging in Amplitude Modulation mode showed similar and different capabilities for compositional mapping of heterogeneous materials compared to the conventional phase imaging. In many cases the correlation between the frequency changes and elastic modulus of material looks quite rational. Further developments of the demonstrated modes will include tuning fork applications, operations at different Eigen modes and AFM-based electric measurements. Acknowledgment The everyday invaluable support of my colleagues: John Alexander, Sergey Belikov and Marko Surtchev, is highly appreciated. 20 of 20