Gas-Phase Ion Chemistry of GeH4/B2H6 Mixtures

Abstract

The gas phase ion-molecule reactions in positively and negatively ionized germane/diborane mixtures have been studied by ion trap mass spectrometry. Reaction sequences and rate constants for the most interesting processes have been determined. In positive ionization, formation of Ge-B bonds exclusively occurs through condensation reactions of B nH m+ ions with germane, followed by H2 or BH3 loss. No reactions of ions from germane with B2H6 were observed under the experimental conditions used here. In negative ionization, the Ge nH m ( n = 1, 2) ion families react with diborane to yield the Ge nB pH q -( p = 1, 2) ions, again via dehydrogenation and BH3 loss, while diborane anions proved to be unreactive. In both positive and negative ionization, Ge-B ions reach appreciable abundances. The present results afford fundamental information about the intrinsic reactivity of gas-phase ions and provide valuable indications about the first nucleation steps ultimately leading to amorphous Ge and B-doped semiconductor materials by chemical vapor deposition methods.