ION-BEAM DEPOSITION AND SURFACE CHARACTERIZATION OF THIN MULTICOMPONENT OXIDE-FILMS DURING GROWTH

Ion beam deposition of either elemental targets in a chemically active gas such as oxygen or nitrogen, or of the appropriate oxide or nitrid e target, usually with an additional amount of ambient oxygen or nitro gen present, is an effective means of depositing high quality oxide an d nitride films. However, there are a number of phenomena that can occ ur, especially during the production of multicomponent films such as t he ferroelectric perovskites or high temperature superconducting oxide s, which make it desirable to monitor the composition and structure of the growing film in situ. These phenomena include thermodynamic (Gibb sian), and oxidation or nitridation-driven segregation, enhanced oxida tion or nitridation through production of a highly reactive gas phase species such as atomic oxygen or ozone via interaction of the ion beam with the target, and changes in the film composition due to preferent ial sputtering of the substrate via primary ion backscattering and sec ondary sputtering of the film. Ion beam deposition provides a relative ly low background pressure of the sputtering gas, but the ambient oxyg en or nitrogen required to produce the desired phase, along with the g as burden produced by the ion source, result in a background pressure which is too high by several orders of magnitude to perform in situ su rface analysis by conventional means. Similarly, diamond is normally g rown in the presence of a hydrogen atmosphere to inhibit the formation of the graphitic phase. A surface analysis system incorporating pulse d beam ion scattering spectroscopy, direct recoil spectroscopy, and ma ss spectroscopy of recoiled ions (MSRI) with differentially pumped ion beam and detector lines has been integrated with a multi-target ion b eam deposition system, permitting the characterization of the surface composition and structure of a thin film surface during growth at ambi ent pressures in the range of 10(-8) bar. A number of phenomena are ob served which are not amenable to study in systems which require cessat ion of film deposition in order to study surface properties. In additi on, it has been found that the positive-to-negative ion ratio of the M SRI signal provides a unique 'phase fingerprint' which in a number of cases permits ready identification of the chemical phase of the growin g film. Data will be presented showing representative applications in the area or multicomponent oxide film growth for which the in situ ion beam characterization methods described here provide a unique means f or understanding thin film growth phenomena. (C) 1998 Elsevier Science S.A. All rights reserved.