A new approach mechanism for scanning probe microscope

More than 20 years since the invention of scanning tunneling microscope (STM), many scanning probe techniques have been developed and established. Different sensing methods, like atomic force and near field light wave, are used in these scanning probe microscopes (SPM). Many of these SPMs require an approach mechanism to place the sensor close to the sample surface. The approach mechanism will directly affect the performance of an SMP. A bulky approach mechanism may reduce the rigidity of the SPM and lower the resonance frequency of the SPM [1]. A poorly designed approach mechanism may not provide the needed resolution and lead to frequent clashing between sensor and sample. In this paper I will discuss a compact design we use in our low temperature STM. The design is based on a piezoelectric tube moving inside a triangular prism shaped cavity. The approach mechanism works in any orientation from horizontal to vertical and its motion is found to be linear with the applied voltage above a threshold voltage. The STM size is reduced considerably by mounting the scanner tube inside of the approach mechanism tube.