Wiwat, Wongkokua

Suranaree University of Technology Intellectual Repository

1 Graduate Student, School of Physics, Institute of Science, Suranaree University of Technology, NakhonRatchasima, 300002 Ph.D., Lecturer, School of Physics, Institute of Science, Suranaree University of Technology, NakhonRatchasima, 300003 National Synchrotron Research Center, Nakhon Ratchasima, 30000* Corresponding authorSuranaree J. Sci. Technol. 12(1):47-53INVESTIGATION OF GAS SPECIES GENERATED IN THEPHOTOEMISSION SPECTROSCOPY SYSTEM AT THE SIAMPHOTON LABORATORYWiwat Wongkokua1 and Prayoon Songsiriritthigul2,3*Received: Jan 21, 2004; Revised: Oct 27, 2004; Accepted: Nov 2, 2004AbstractThis report describes the design of the vacuum system of the photoemission spectroscopy system installedat the first beamline of the Siam Photon Laboratory, and shows the results from the investigation of gasspecies generated in the system. The base vacuum pressure of the system after the well bake-out processesis approximately 2 × 10-10 mbar. The vacuum pressure increases more than one order of magnitude whenthere is a linear movement of the sample manipulator or when the UV lamp, the electron gun or theX-ray source is operated. The gas species generated in the system were analyzed by the quadrupole massspectrometer. Adsorption of the gas molecules on a clean well-defined Ni(111) surface has been observedby low-energy electron diffraction and Auger electron spectroscopy measurements.IntroductionIn the investigation of the electronic structuresof surfaces of solids, good vacuum conditionshave to be maintained to prevent contaminationson the surfaces.  It is well-known that even atthe pressure of 1 × 10-6 mbar, residual gases cantheoretically form a monolayer of coverage ona clean surface within one second at roomtemperature assuming that the sticking coefficientequals 1.0 (Hoffman et al., 1998). At lowerpressures, the time for forming a monolayer ofcoverage becomes longer. To obtain invaluableinformation of surfaces, the time required forgases to form a monolayer of coverage must bemuch longer than the time required for themeasurement. Thus the vacuum pressure requiredfor research on the electronic structures ofsurfaces of solids must be in the range of 10-10mbar or lower. With the current vacuumtechnology, a base vacuum pressure of 10-10 mbarcan be produced without great difficulties byreducing the out gassing rate of the chambersand vacuum components (Readhead, 1996;Readhead, 2002). However, it is difficult tomaintain the vacuum in any measurement systemat this pressure when an excitation source suchas an X-ray source, an electron gun or a UV

Investigation of gas species generated in the photoemission spectroscopy system at the Siam photon laboratoy

http://sutir.sut.ac.th:8080/sutir/bitstream/123456789/1858/1/BIB1117_A.pdf

Investigation of gas species generated in the photoemission spectroscopy system at the Siam photon laboratoy

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