Electronic and vibrational electron energy loss studies of the formation of SiO 2 and carbonaceous layers on Si(111)7×7 by thermal and ion-assisted deposition techniques

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Electronic and vibrational electron energy loss spectroscopy (EELS) and Auger electron spectroscopy (AES) were used to characterize the formation of SiO 2 and SiC on Si(111)7×7. The differences between thermal deposition and ion-assisted deposition of these films were investigated. Thermally formed SiO 2 layers obtained by annealing the silicon sample in O 2 at 700 K can be characterized by the electronic transitions near 5 and 7 eV and by the blue shifts in its vibrational features from that of atomic oxygen adsorption. The formation of SiO 2 could also be achieved by ion irradiation at room temperature (RT). Carbonaceous layers formed at different ethylene dosages and sample temperatures were characterized by EELS and AES. Like the oxide formation, a higher efficiency in producing the carbonaceous layer was obtained by using ion-assisted deposition than thermal deposition. In particular, a SiC layer could be obtained by cycles of ethylene ion irradiation at RT and annealing to 800 K, whereas a very large dosage of ethylene ions at RT was found to produce a graphite layer.