Gas-phase ion chemistry of GeH4/B2H6 mixtures

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 BnHm+ ions with germane, followed by H-2 or BH3 loss. No reactions of ions from germane with B2H6 were observed under the experimental conditions used here. In negative ionization, the GenHm- (n = 1, 2) ion families react with diborane to yield the GenBpHq- (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.