The design and building of an alternating current scanning tunneling microscope for nanometer scale imaging of insulating surfaces

An alternating current scanning tunneling microscope (ACSTM) has been designed and built for the study of insulating surfaces on the nanometer scale. The instrument consists of an STM built within a microwave resonant cavity. This design allows for simultaneous operation for both DC and ACSTM. The instrument is housed in a nitrogen atmosphere glovebox for the observation and handling of air-sensitive samples. In order to achieve the detailed resolution of STM on insulating surfaces the ACSTM uses the application of a high frequency alternating current bias voltage across a tip-sample junction, the resulting alternating current can be measured. Specifically, the non-linearilty of the STM junction allows the third harmonic (TH) of the driving frequency to be used as the measured quantity for imaging and control. By using the third harmonic of the fundamental driving voltage as the measured quantity to control the tip-sample distance, STM quality images have been produced without the reliance on a conductive surface.; The atomic scale resolution of a silicon dioxide surface and the growth of such layers appeared to provide an ideal system for imaging with the ACSTM. Through the use of DC STM we have shown how the H-Si(111) surface morphology is effected by the length of etch time and the kinetic effect of stirring the etchant solution.; Several experimental results make use of the ACSTM employing the TH signal for measurement under both DC feedback control and under AC feedback control. We will address the experimental procedure, signal generation and sample dependence upon ACSTM image resolution. By comparing three sulfides (CuS, MoS2. and PbS) and H-Si(111), the TH signal generation and ultimate ACSTM resolution is explored.; A more in depth analysis covers the application of the ACSTM to investigate the probe induced surface oxidation of natural PbS. With the ACSTM, the complete transformation from a semiconductive to an insulating surface is imaged in real-time for the first time.