Development of a microlateral force sensor and its evaluation using lateral force microscopy

Abstract

A microlateral force sensor (MLFS) was developed and evaluated using atomic force microscopy (AFM). The sensor was attached to a sensing table supported by a suspension system. The lateral motion of the sensing table was activated by a comb actuator. The driving voltage to the comb actuator was controlled to maintain a constant position of the sensing table by detecting the tunneling current at a detector, which consisted of two electrodes where the bias voltage was applied. An AFM was used to apply a lateral force to the sensing table of the sensor. When the probe of a cantilever was pressed against the sensing table and a raster scanning was conducted, the driving voltage of the comb actuator changed to compensate the friction force between the probe and sensing table. AFM measurements of an asperity array on the sensing table were conducted, and a lateral force microscopy image (LFM) was obtained from the change in driving voltage. The image by MLFS was very similar to the LFM image that was conventionally obtained from torsion of the cantilever. The LFM image strongly correlated with the gradient image calculated from the AFM topographic image. The force sensitivity of the MLFS was determined by comparing the LFM image obtained by using the MLFS with the tangential force derived from the gradient of the AFM image.

Detailed Study on the Failure of the Wedge Calibration Method at Nanonewton Setpoints for Friction Force Microscopy

“…9 The first class, known as indirect or multistep techniques, requires an initial step that relates the applied lateral forces to the torsion of the cantilever, followed by a second procedure that correlates the torsion to the laser read out at the PSD. 9 These multistep techniques include the method based on the direct force application on the cantilever by another AFM or optical tweezers, 10 the static loading technique, 11 the approach using lateral deflection of a reference beam, 12 direct read out of a lateral force on a sensor plate, 13 or a thermographic noise method of the torsional resonance frequency 14 combined with the torsional Sader method. 15 Geometrical cantilever analysis techniques, 16,17 where the torsion spring constant is directly estimated from a high-resolution scanning electron microscopy (SEM) image of a cantilever and the properties of the material, are the other indirect techniques often used to calibrate the cantilever lateral deflection.…”

Force calibration in lateral force microscopy: a review of the experimental methods

“…Considering the way a torsional CL deformation is induced, five major groups of calibration methods can be identified. Essentially, it can be induced by direct application of a force acting at a position off the long axis of the CL [17,29,[33][34][35][36][37][38], by loading the tipsubstrate contact in a lateral direction [28,[39][40][41], by loading a compliant structure of known stiffness [42][43][44], by scanning across a surface and utilizing the frictional forces [20,[45][46][47][48][49][50] or by exciting the torsional CL resonance [51,52].…”

Traceable Lateral Force Calibration (TLFC) for Atomic Force Microscopy

“…1. Like other spring-based AFM lateral force calibration methods [3,13,16,17], TFLC uses a reference lever (spring), a method to quantify the reference lever spring constant (Step 1), and the calibrated reference lever to quantify AFM lateral forces and force calibration constants (Step 2).…”

“…However, the method is susceptible to significant and unknowable calibration error, particularly at high loads [14,15], based on the following facts: (1) its spring constant is determined without load; (2) the diamagnetic spring constant (normal and lateral) changes with applied load; (3) loading of the diamagnetic spring during AFM calibration changes the spring constant, which affects the calibration constant. While there are a number of distinct spring-based lateral force calibration methods [3,16,17], DLFC is considered the gold standard among them.…”