Study on the Epitaxial Growth of Oxide Films in Sputtering focusing on Negative Oxygen Ion Behavior

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In this project, we performed depositions of titanium dioxide films on single crystalline MgO substrates by using inductively coupled plasma (ICP)-assited sputtering. In addition, we fabricated a new sputtering device which can realize in-situ sequential depositions utilizing movable multi targets.Through depositions of titanium dioxide (TiO_2) films on MgO substrates, we showed oriented growth of rutile-type crystalline films having in-plane two orientations. It is interpreted that higher density plasma production and lowered target self bias voltage in ICP-assisted sputtering brig about epitaxial growth of high-temperature stable phase of rutile Ti0_2. Based on the Langmuir probe studies which were done by the cooperation with co-researcher, Professor Haruo Shindo, kinetic effects of negative oxygen ions are supposed to be very important issue due to their effects different from positive ions. This issue of the roles of negative oxygen ions and active oxygen atoms is to be continued … More in next study. In addition to the TiO_2 growth on MgO substrates, we performed deposition of Nb-doped TiO_2 films on SrTiO_3 single substrates. As the results, transparent TiO_2 films with lower resistivity on the order of 10^<-4> Ωcm were achieved.Further, we deposited vanadium dioxide (VO_2) films by using ICP-assisted sputtering technique. As a promising result, we obtained stoichiometric VO_2, films which show metal-insulator transition at relatively low temperature around 65℃. Such film with transition characteristic can be applied to newly concept switching and memory devices.Newly fabricated sputtering device with in-situ changeable two targets enabled sequential sputter deposition of different kinds of material. As a representative, we performed depositions of ferromagnetic Co film on pre-deposited Al film. As the result, crystalline hcp-Co film was deposited on Al under-layer without the magnetron effect, revealing the potential ability to realize superior multi-layered film growth by the introduction of in-situ sequential deposition. Less