Developemtn of Low temperture Surface Electron Mictoscpy and its Application to Gas Adsotption on Surfaces.

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Surface electron mictosopy has been developed for these several years as a method which shows surface structures and their dynamic processes with high spactial resolution. However, studies have been done on hot surfaces. On the other hand. low remperature surfaces are very inreresting problems and some interesting works have been done on alkali-metal atoms on Si surfaces. The purpose of the present project is to make a special specimen holder for the study of low temperture surfaces and to study adsorption fo gasses on surcaes.The most difficult problem in the present project is to make a specimen holder. with which specimens can cooled for the obvservation and can be heated for cleaning. So that the speicmen should be thermally isolated during heating and it should thermally well contacted with the cooling reservoir, We used the characteristics of saphire crystal which is a good insulator at high temperatures byt is a good thermal conductor around 50K. It is as good as copper. We adopted a design of REM (reflection electron mictoscpy) holder which was developed by us for the studies of surfaces. Flow type cooling method is used where staianless tube cools a saphire frame of the specime holder and the specime can be cooles through the frame and the merallic electrode. Thus the heat floe during heating is refuced.As a preliminary experiment, we studied chanages of surface structues and step configurations when the Si(001) and (111) surface are exposed to molecular exygen and atomec hydrogen. In the case of atomic hydrogen, so called delta 7x7 structure is formed bur step shapes do not change. They do not change when the hydrgen atoms atoms desorb from the surfaces. In the case of oxygen step shapes do not change but on hearing SiO or SiO2 is formed and step configuration chenges.The method will be applide to solis gas adsoption problems.