PYROLYSIS OF TETRAETHOXYSILANE ON MO(100) AT LOW-TEMPERATURES

Deposition of ultrathin silicon dioxide films on Mo(100) substrates by pyrolysis of tetraethoxysilane (TEOS) vapor has been investigated at temperatures between 300 and 860 K with X-ray photoelectron spectrosco py (XPS), temperature-programmed desorption (TPD), low-energy electron diffraction (LEED), and infrared reflection-absorption spectroscopy ( IRRAS). Up to temperatures of similar to 600 K, TEOS adsorbs on the Mo surface forming an ethoxysilyl intermediate, whereas at higher temper atures SiO2 is formed during the initial exposure, as evidenced by bot h XPS and IRRAS data. Deposition of silicon dioxide is reaction-limite d in the temperature range studied with roughly a monolayer forming on the surface at 860 K. Heating the TEOS-exposed Mo(100) surfaces to si milar to 1000 K yields ethylene as the predominant gas-phase decomposi tion product and improves both the stoichiometry and order of the film s as indicated by an increase in the stretching frequency of the Si-O IRRAS peaks. A decrease in the amount of desorbed ethylene is observed as the deposition temperature increases from 300 to similar to 600 K, and no significant desorption of any other decomposition products was detected at higher deposition temperatures. Carbon contamination is m inimal in these SiO2 films.