ELECTRON-STIMULATED AND THERMAL-DESORPTION STUDY OF TRIMETHYLSILANE FROM SI(100)

The adsorption and decomposition of trimethylsilane, HSi(CH3)3, on Si( 100) has been studied at T approximately 120 K for a variety of trimet hylsilane exposures. The trimethylsilane molecule is not observed by q uadrupole mass spectrometry during temperature programmed desorption f rom the Si(100) sample, but various fragments of trimethylsilane can b e seen. The primary species seen desorbing during electron bombardment of the Si(100) surface were the H+, H-, and CH3+ ions. Both H+ and H- KEDs exhibit bimodal kinetic energy peaks, most likely due to hydroge n bound in multiple states. The bimodal H+ and H- kinetic-energy distr ibutions (KEDs) exhibit an interesting reversal of intensities that su ggests that the state giving rise to the low-energy peak in one KED gi ves rise to the high-energy peak in the other KED, and vice versa. Kin etic energy distributions for the CH3+ ions consisted of only one peak , indicating a high probability that the CH3+ originates from only one surface state. Our results indicate that electron-simulated desorptio n can be used as an adsorption state sensitive probe of chemical speci es on semiconductor surfaces.