Elementary Processes of Surface Photodissociation by Time-Resolved Photoelectron Spectroscopic and Laser Spectroscopic Techniques

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We have studied pyrolytic and photolytic dissociation of halogen and organometallic compounds on insulators, metals, and semiconductors with laser techniques and photoelectron spectroscopic techniques.Laser irradiation at 193 or 351 nm of a multilayer of Cl_3 of CH_3Cl on an Si wafer at 100 K leads to both photodissociation of these molecules and formation of photoetchig products. The kinetic energy distributions of photofragments (Cl, CH_3) and etching products (SiCl, SiCl_2) were measured.Pyrolytic dissociation of trimethylgallium (TMGa) and trimethylindium (TMIn) on Si, Au, and Al substrates was studied at various temperatures from 80 to 670 K by x-ray photoelectron spectroscopy. The results indicate that TMGa and TMIn on Si (111) dissociates into Ga, In, and CH_3 on the substrateeven at 200 K and CH_3 surther dissociates into C, CH, and CH_2 at higher temperatures. Photodissociation of a monolayer of TMGa and TMIn on Si, GaAs, or Au is observed with an incident wavelength of 193 and 226 nm ; direct absorption by the absorbed molecules occurs at this wavelength. A 355 nm, photodissociation does not occur.The photodissociation dynamics of organometallic compounds (tetramethyltin, trimethylgallium, trimethylindium and dimethylzinc) absorbed on a quatrz substrate at 100 K have been studied by time-of-flight massspectrometry, detecting mainly CH_3 photofragments.