Fabrication of a resistive switching gallium oxide thin film with a tailored gallium valence state and oxygen deficiency by rf cosputtering process

Abstract

Resistive switching gallium oxide base thin films with tailored oxygen deficiency were fabricated by rf cosputtering of Ga₂O₃ and Cr. XPS and STEM-EDX analyses were used to determine that the resultant film was made of a homogeneous oxide glass layer with mixed valance states of Ga(III)–Ga(I). The amount of Ga(I) and the corresponding oxygen deficiency was precisely controlled because the following redox reaction subsequently progresses within the deposited films: 3Ga(III) + 2Cr(0) → 3Ga(I) + 2Cr(III). The on/off resistance ratio was largely varied by changing the Ga(I) fraction in relation to the oxide ion conductivity, and Ga_0.82Cr_0.18O_1.2 thin film was found to exhibit an optimal switching performance. The film resistance state was tunable by 100's of μs pulse biasing and was incrementally changed by increasing the applied pulse numbers. The strongly time-dependent switching events and area dependent current level of Cr-GaO_x films were distinct from the abrupt switching behavior of the filamentary mechanism TiO_x thin film devices. It was demonstrated that rf cosputtering of the metal oxides and the corresponding oxygen scavenging metals was a powerful technique to design the bulk state resistive switching devices based on nonstoichiometric metal oxide thin films.