Simultaneous detection of vertical and lateral forces by bimodal AFM utilizing a quartz tuning fork sensor with a long tip

Abstract

Simultaneous detection of vertical and lateral forces at nanoscale by atomic force microscopy (AFM) provides important knowledge in nanotribology. Although silicon (Si) cantilevers are capable of detecting both the forces, it has not been achieved by quartz tuning fork (QTF) sensors including qPlus sensors. In this study, we found that the tip apex of the qPlus sensor with a long tip oscillates vertically at the lowest resonance frequency (ƒ1) and laterally at the second lowest resonance frequency (ƒ2) by the finite element method (FEM) simulation. The lateral oscillation was experimentally confirmed by atomic resolution imaging, where the imaged atoms were apparently connected as increasing the oscillating amplitude at ƒ2. We also demonstrated the nanometer-scale friction force measurement by using the developed bimodal AFM. The obtained result was in good agreement with the contact-mode lateral force microscopy utilizing a Si cantilever.

Biaxial atomically resolved force microscopy based on a qPlus sensor operated simultaneously in the first flexural and length extensional modes

“…One approach to combine vertical and lateral movement of the tip was shown by Yamada et al 19 using the second flexural mode of a qPlus sensor with a long tip. Increasing the tip length and the moment of inertia results in a shift of the node of the second flexural mode along the beam direction (x-direction).…”

Chemical bond imaging using torsional and flexural higher eigenmodes of qPlus sensors

“…48,50,53 It has also been reported that higher eigenmodes can lead to lateral movements of the tip that could be useful for dynamic lateral force microscopy (LFM). 53 Recently, we demonstrated that higher eigenmodes of qPlus sensors allow bond imaging of individual organic compounds. 51…”

“…[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] The suitability of qPlus sensors for the application of such modern multifrequency operation modes has, however, only been scarcely studied until now. [48][49][50][51][52][53][54] For example, it has been observed that flat crystalline NaCl and KBr surfaces can be imaged with atomic resolution using a higher eigenmode or bimodal AFM in UHV and ambient conditions. 48,50,53 It has also been reported that higher eigenmodes can lead to lateral movements of the tip that could be useful for dynamic lateral force microscopy (LFM).…”

“…[48][49][50][51][52][53][54] For example, it has been observed that flat crystalline NaCl and KBr surfaces can be imaged with atomic resolution using a higher eigenmode or bimodal AFM in UHV and ambient conditions. 48,50,53 It has also been reported that higher eigenmodes can lead to lateral movements of the tip that could be useful for dynamic lateral force microscopy (LFM). 53 Recently, we demonstrated that higher eigenmodes of qPlus sensors allow bond imaging of individual organic compounds.…”

Determining amplitude and tilt of a lateral force microscopy sensor

“…More recently, we used LFM with a CO-terminated tip to investigate the internal structure of a molecular adsorbate [ 11 – 12 ]. Moreover, other methods, including the use of a long tip on a qPlus sensor that oscillates laterally at a higher flexural mode are also possible [ 13 ].…”