Analysis of scanning tunneling microscopy feedback system: Experimental determination of parameters

We describe the experimental work necessary on a scanning tunneling microscopy (STM) system to obtain some important feedback parameters-to have stability and good imaging conditions-such as the mechanical resonance frequency omega(0), the delay time tau, and the damping factor zeta. We study and analyze each one of the main components involved on the STM such as the feedback system, the piezoelectric elements, the rigidity of the mechanical structure (the mechanical resonance), and its relation with the scanning rate for imaging. We conclude that it is necessary to obtain these parameters with the STM in tunnel conditions, in order to consider the effects of the tip, surface contamination, and tip sample interaction. We also conclude that tripod based STM can be better than STM based on piezo tubes scanners. (C) 1996 American Institute of Physics.