This paper reviews the use of optical sum frequency generation (SFG) and second harmonic generation (SHG) microscopy under\r\nultra-high vacuum (UHV) conditions to observe the dynamics of a hydrogen terminated Si(111)1 Ã?â?? 1 surface. First, we took SFG\r\nand SHG microscopic images of the surface after IR light pulse irradiation and found that the SHG and nonresonant SFG signals\r\nwere enhanced, probably due to the formation of dangling bonds after hydrogen desorption. Second, we observed time-resolved\r\nSFG intensity images of a Hââ?¬â??Si(111)1 Ã?â?? 1 surface. After visible pump light irradiation, the nonresonant SFG signal increased at\r\nprobe delay time 0 ps and then decreased over a life time of 565 ps. The resonant SFG signal reduced dramatically at 0 ps and then\r\nrecovered with an anisotropic line shape over a life time of 305 ps. The areas of modulated SFG signals at delay time 277 ps were\r\nexpanded with an anisotropic aspect. Finally, we observed SFG intensity images of hydrogen deficiency on a Si(111)1 Ã?â?? 1 surface as\r\na function of temperature. These images of the Hââ?¬â??Si(111) surface, taken with a spatial resolution of 5 Ã?µm at several temperatures\r\nfrom 572 to 744 K, showed that the hydrogen desorbs homogeneously.
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