title: Negative ion clusters in self-condensation of GeH4.
abstract: Formation of negative ion clusters from GeH4 has been studied as a function of germane pressure, in the 25-450 mTorr range, by chemical ionisation mass spectrometry. At the lowest pressures, only the GeHn- (n = 0-3) ion family is formed, whilst at increasing pressures GemHn- (m = 1-9) ion clusters of increasing size are observed in the mass spectra. A variable contribution of the ions with different hydrogen content is observed as a function of the pressure of germane in all the GemHn- (m = 1-9) clusters. Increasing pressures induce a general increase of ion species with a low content of hydrogen atoms. In fact, at 450 mTorr, 38% of the ion current is due to the bare Gem- (m = 2-5) clusters and 83% to the sum of abundances of the GemHn- ions without hydrogen (n = 0) and with a number of hydrogen atoms not higher than the number of germanium atoms (n = 0-m). This trend suggests that a contribution of negative clusters to the deposition of the amorphous solid a-Ge:H from gaseous systems containing GeH4, activated by radiolytic methods, can enhance the formation of solids with a low hydrogen content, which show better photoelectrical properties.
authors.affiliation: Dipartimento di Chimica Generale e Organica Applicata, Università degli Studi di Torino, Corso Massimo d'Azeglio 48, 10125 Torino, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Antoniotti
authors.forename: Lorenza
authors.initials: L
authors.lastname: Operti
authors.forename: Roberto
authors.initials: R
authors.lastname: Rabezzana
authors.forename: Gian Angelo
authors.initials: GA
authors.lastname: Vaglio
authors.forename: Alessandro
authors.initials: A
authors.lastname: Guarini