| Ever since the first demonstration of Binnig and Rohrer (1, 2) in early 1980's, Scanning Tunneling Microscopy (STM) has been shown to be unique among surface analysis techniques in that it allows measurements of geometric and electronic structure with extremely high vertical and lateral resolution. However, the contrast in the STM image includes the geometric and electronic structures of both the sample and the tip. Thus the geometric and electronic structure of the tip become extremely important in interpretation of the STM images, as well as the achievement of image resolution. The main goals of my research have been the fabrication of reproducible polycrystalline tungsten tips, the study of the tip geometry effects on the STM images, and tip electronic influences on image resolution.; Reproducible STM tips, prepared from polycrystalline W wire, were also used for the topographic study of the Au/InP system after annealing. Tips were prepared by electrochemical polishing or a combination of electrochemical polishing and ion milling.; An important new technique that has emerged from the STM for the study of the subsurface interface electronic structure is Ballistic Electron Emission Microscopy (BEEM). It utilizes STM in a three-electrode configuration, allows characterization of interface properties and measurement of Schottky barriers with nanometer spatial resolution.; Modification of an existing STM to BEEM is carried out, including the design of electronic circuitry and programming. The performance of electronic circuits and the quality of the interfaces will have dominant effects on BEEM. BEEM studies on the Au/Si (100) system show that the modification is successful. Initial experiments of BEEM on metal/InP systems have been carried out. Although these trials have failed, further directions of BEEM measurements on these systems are proposed. |
