Development of a High-Speed Low-Energy Electron Diffraction System

Research Project

Project/Area Number	63850004
Research Category	Grant-in-Aid for Developmental Scientific Research
Allocation Type	Single-year Grants
Research Field	Applied materials
Research Institution	The University of Tokyo
Principal Investigator	KAWAZU Akira The University of Tokyo, Department of Applied Physics, Associate Professor, 工学部, 助教授 (20010796)
Co-Investigator(Kenkyū-buntansha)	MIZUSHIMA Nobuhiko Hamamastu Photonics Corp., Research Division, Senior Scientist, 研究室長 OKANO Tatsuo The University of Tokyo, Institute of Industrial Science, Associate Professor, 生産技術研究所, 助教授 (60011219) MURATA Yoshitada The University of Tokyo, The Institute for Solid State Physics, Professor, 物性研究所, 教授 (10080467) SHIGEKAWA Hidemi Tsukuba University Institute of Materials Research, Lecturer, 物質工学系, 講師 (20134489) YOSHIMURA Masamichi The University of Tokyo, Dept. of Applied Physics, Research Associate, 工学部, 助手 (40220743)
Project Period (FY)	1988 – 1989
Project Status	Completed (Fiscal Year 1989)
Budget Amount *help	¥16,800,000 (Direct Cost: ¥16,800,000) Fiscal Year 1989: ¥8,200,000 (Direct Cost: ¥8,200,000) Fiscal Year 1988: ¥8,600,000 (Direct Cost: ¥8,600,000)
Keywords	Low-Energy Electron Diffraction / Surface Structure / Image Process / Kinetic Processes on Solid Surfaces / Thin Film Growth / 高感度カメラ / 電荷結合素子 / 回折強度
Research Abstract	To study molecular processes on solid surfaces, a high-speed low-energy electron diffraction (LEED) system has been developed. The system consists of LEED optics, an image intensifier, a CCD camera, a CCD controller and a microcomputer. The LEED optics is a conventional type with four grids. The image intensifier is used to amplify the intensity of the brightness of LEED spots on the fluorescent screen. The LEED pattern on the image intensifier is taken by the CCD camera. To achieve high-speed data acquisition, only about one-fourth of the CCD sensors are exposed to light, and only the data in shift registers of these CCDs are transferred to the AD converter. Depending on the required acquisition rate of the LEED pattern, data in several neighboring CCDs of each vertical array are added to the shift registers. The analogue signals from the CCD camera are digitized by the AD converter, and these data are transferred to the 8Mbyte frame memory. This system can also be operated in a convent … More ional TV mode, with which the observation of molecular processes for long duration is possible. In this mode, video signals from the CCD camera are recorded by a video tape recorder. To accomplish speedy data acquisition, signals from the AD converter are directly transferred to the frame memory without any data processing. Data processing, such as background correction within the electronic windows around the diffraction spots, or integration of spot intensity, is performed after the measurement of the surface processes. The maximum frame rate of this system is 620/s (at 128 X64pixels/frame) with a clock frequency of 4.77MHz. By using a higher clock frequency, 1000 LEED patterns per second is also possible. Software for controlling data acquisition and for data processing has also been developed for this system. The expectancies for the performance of this system has been verified by observing the high-speed phenomena. The formation processes of a ROO<3>XROO<3> structure on a Si(111) surface by the adsorption of In atoms were studied through the observation of the change in the spot intensity of LEED. These experiments revealed this system to be very powerful in the study of kinetic processes such as the adsorption of molecules or growth of thin films on solid surfaces. Less