An ultrahigh vacuum scanning tunneling microscope for the investigation of clean surfaces

Abstract

An ultrahigh vacuum (UHV) scanning tunneling microscope (STM) has been built into a VG surface analysis system consisting of a VG Escalab and three additional UHV chambers. Samples and tips can be prepared in UHV. Surface analysis can be performed by low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), UV-photoelectron spectroscopy (UPS), and scanning electron/Auger microscopy (SEM/SAM). The STM design is based on an electromagnetically driven approach system. Easy exchange of samples is possible since the scanner is incorporated in a scan head which can be flipped backwards. The performance of the STM was tested by resolving the surface structure of graphite and Si(111)7×7. However, the main application will be the investigation of well characterized metal surfaces. We have studied the Au(111) surface where series of monoatomic steps could be imaged. In addition, we resolved the atomic surface structure. The conditions for atomic resolution imaging on close-packed metal surfaces are discussed. For comparison, we have also studied polycrystalline Au films vacuum deposited onto various substrates. For the first time, atomic resolution could also be obtained on these polycrystalline films. Finally, we present preliminary results of STM studies on a gallium single crystal.