Study on the Space Charge Distribution by Using a Pulsed Laser

Research Project

Project/Area Number	61550018
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	Applied materials
Research Institution	College of Engineering, University of Osaka Prefecture
Principal Investigator	AITA Osamu (1987) College of Engineering, University of Osaka Prefecture, 工学部, 助教授 (30006457) 鎌田雅夫 (1986) 阪府大, 工学部, 助手 (60112538)
Co-Investigator(Kenkyū-buntansha)	OKUSAWA Makoto College of Engineering, University of Osaka Prefecture, 工学部, 助手 (50112537) 会田修大阪府立大学, 工学部, 助教授 (30006457)
Project Period (FY)	1986 – 1987
Project Status	Completed (Fiscal Year 1987)
Budget Amount *help	¥2,100,000 (Direct Cost: ¥2,100,000) Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000) Fiscal Year 1986: ¥1,600,000 (Direct Cost: ¥1,600,000)
Keywords	Pulsed Laser / Space Charge / Exoelectron / KCl:Tl / Surface Potential / TSEE / OSEE / KCl:Tl
Research Abstract	1. The main object of this project is to study the mechanism of the exoelectron emission and the relation between this mechanism and the space charge caused under the irradiation of a pulsed laser. 2. The pulsed laser system was constructed and connected to the high-vacuum apparatus for the present purpose. 3. The energy spectra of optically stimulated exoelectrons were studied together with the surface potential in a KCl:Tl crystal, which recently attracts much interests in the application of this material to the solid state laser. It was found that the exoelectrons are accelerated by the internal electric field due to the space charge in their transport process to the surface and also they are affected by the non-uniform spread fo the surface potential at their escape stage. Moreover, it was found that a direct photoionization from F centers dominates the mechanism of the optically stimulated exoelectron emission and also the two-step model involving the photo-ionization and thermal-ionization from F centers should be modified to interpret the present experimental results. 4. The Monte Carlo calculation of the energy spectra of thermally stimulated exoelectrons indicates that the space charge distributes within several hundreds of angstrom from the surface in an X-irradiated KCl:Tl crystal, and thus, its range is less than the limitation of the present experimental apparatus. Further improvements are desired in order to see the relation between the space charge distribution and the exoelectron emission by using the pulsed laser.