ADSORPTION AND DECOMPOSITION OF TRIETHYLINDIUM ON SI(001) AND GAP(001) STUDIED BY HREELS AND TPD

Adsorption and decomposition of triethylindium (TEI) on Si(001) and Ga P(001) surfaces have been studied by using temperature-programmed deso rption (TPD) and high-resolution electron energy loss spectroscopy (HR EELS). For TPD spectra of TEI on the Si(001) surface, desorption peaks are found at about 373 and 583 K for ethylene and at about 400 (broad ), 773, and 923 K for hydrogen. HREELS spectra of the Si(001) surface adsorbed TEI indicate that TEI is adsorbed molecularly at 100 and 290 K and that the orientation of an In-C2H5 bond of TEI is near parallel to the surface above 290 K. Changes in the HREELS spectra at elevated temperatures suggest that the TPD peaks at about 373 and 583 K are due to ethylene produced by cracking TEI molecules in the mass spectromet er and by decomposition of TEI on the surface, respectively. Si-H spec ies are suggested to be formed by decomposition of the ethyl group of TEI through a beta-hydride elimination. Two peaks of hydrogen in the T PD spectra at about 773 and 923 K are discussed in terms of adsorption sites. For the GaP(001) surface, adsorbed states of TEI at 100 and 30 0 K are the same as for the Si(001) surface. Changes in the HREELS spe ctra at elevated temperatures are consistent with the previous TPD res ult that ethylene evolved at about 323-473 K and 523-623 K. In contras t to the result for the Si(001), the vibration mode of nu(Ga-H) is not found, which is discussed in terms of the decomposition mechanisms of TEI and Ga-H species. The ethyl group of TEI is suggested not to be s witched off to the Si(001) and GaP(001) surfaces. The difference in th e desorption behavior of TEI from the Si(001) and GaP(001) surfaces is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.