NANOMETER-SCALE INSTABILITY AT SLIDING INTERFACES - TRIBOLOGICAL CONSIDERATIONS IN SCANNING TUNNELING MICROSCOPY

We have developed a scanning tunneling microscope based upon an Inchworm(R) motor for coarse approach control. Our aim was to fabricate an instrument from materials with matched thermal expansion coefficients to minimize thermal drift. The inchworm pushes a ceramic sled which carries the tunneling unit towards the sample until it is in range of the tube piezoscanner. When its motion is reversed (to disengage from the sled) interfacial forces at the sliding interface move the sled backwards (over distances between 100 nm and 20-mu-m) rather than allowing it to remain stationary. These forces vary depending upon the materials employed and we offer some recommendations regarding the choice of materials and the sled design.