title: A chemically driven insulator-metal transition in non-stoichiometric and amorphous gallium oxide.
abstract: Insulator-metal transitions are well known in transition-metal oxides, but inducing an insulator-metal transition in the oxide of a main group element is a major challenge. Here, we report the observation of an insulator-metal transition, with a conductivity jump of seven orders of magnitude, in highly non-stoichiometric, amorphous gallium oxide of approximate composition GaO(1.2) at a temperature around 670 K. We demonstrate through experimental studies and density-functional-theory calculations that the conductivity jump takes place at a critical gallium concentration and is induced by crystallization of stoichiometric Ga(2)O(3) within the metastable oxide matrix-in chemical terms by a disproportionation. This novel mechanism--an insulator-metal transition driven by a heterogeneous solid-state reaction--opens up a new route to achieve metallic behaviour in oxides that are expected to exist only as classic insulators.
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany.
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Nagarajan
authors.forename: Roger A
authors.initials: RA
authors.lastname: De Souza
authors.forename: Dominik
authors.initials: D
authors.lastname: Samuelis
authors.forename: Ilia
authors.initials: I
authors.lastname: Valov
authors.forename: Alexander
authors.initials: A
authors.lastname: Börger
authors.forename: Jürgen
authors.initials: J
authors.lastname: Janek
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Becker
authors.forename: Peter C
authors.initials: PC
authors.lastname: Schmidt
authors.forename: Manfred
authors.initials: M
authors.lastname: Martin