Scanning Tunneling Microscope with a Field Ion Microscope
- PDF / 1,577,850 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 107 Downloads / 297 Views
SCANNING TUNNELING MICROSCO)PE WITH A FIELD ION MICROSCOPE H. W. PICKERING** & T. HASHIZUME, I. KAMIYA, Y. HASEGAWA, T. IDE*, T. SAKURAI The Institute for Solid State Physics, The University of Tokyo, Minato-ku, Tokyo, Japan *NEC Fundamental Research Laboratory, Miyamae-ku, Kawasaki, Japan **Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 USA ABSTRACT A ccmbined field ion (FIM) and scanning tunneling microscope (STM), which we call "FI-STM," was designed and constructed with multiple surface analytical functions. The system is equipped with a LEED/AES system and a sputtering gun and/or heating devices for preparing and characterizing specimen surfaces. The field ion microscope (FIM) is operated at room temperature to observe the geometry of the STM scanning tip in-situ in the course of STM investigations. The instrument has been operated successfully by observing the structures of the graphite (0001), the Si (111) 7x7 and the Si (100) 2xi surfaces. INTRODUJCTION The scanning tunneling microscope (SThM)/I/ has found great use in the study of the geometrical topography and electronic structure of surfaces since its invention in 1983. Great power of the STM is evident in the recent reports on reconstructed structures of the Si(111) 7x7,/I/ Ge(111) 2x8/2/ and many other surfaces./3/ It is generally believed that the resolution of the STM depends critically on the geametry of the cap of the STM tip and that the atomic resolution is realized only when a single atom emission site is established on the STM tip surface. Nevertheless, little progress has been made in the past in an attempt for the characterization of the exact role of a STM tip on an atomic scale. Realizing the importance of evaluating the tip geometry, we have constructed a new type of the STM equipped with a field ion microscope (FIM),/4/ which we call a "FI-STM (field ion-scanning tunneling microscope)."/5/ With this instrument, the atomic geonetry of a STM tip can be monitored in-situ of the STM using the FIM before and after the STM scanning of a specimen surface. A LEED/AES system also incorporated in the system is used to prepare and characterize a specimen surface. A special vacuum port is also designed in the STM section, for a RHEED system to be included to monitor the specimen surface. INSTRUMETATION The design of the FI-STM is schematically shown in Fig. 1. The STM is located in the left side of the UHV system and the entire STM device is mounted on a horizontal 8" O.D. UHV flange. A FIM is also located at the left side with a 10" O.D. vertical flange. A LEED/AES system equipped with evaporators of several metal elements and a heating device is located on the right side of the instrument using a 10" O.D. vertical flange. A small sample exchange device is mounted on the 8" O.D. lower horizontal flange on the right side with a vacuum interlock. A flat specimen with a dimension of 4x1 8 mm2 and thickness of less than 1 mm can be introduced in the UHV system through the sample exchange dev
Data Loading...
