Ion Beam-Based Characterization of Multicomponent Oxide Thin Films and Thin Film Layered Structures

Abstract

The fabrication of thin film layered structures of multi-component materials such as high temperature superconductors, ferro-electric and electro-optic materials, and alloy semiconductors, and the development of hybrid technologies incorporating some or all of these materials into a single device requires a detailed understanding of film growth and interface properties. Some of the relevant interfaces are within a few Å of the surface, while others may be at a depth of several μm. Interfaces may be either atomically abrupt or be spread over a significant depth, with no clearly identifiable transition.

For materials such as the High Temperature Superconductors (HTSC's), the superconducting coherence length is extremely short (5 15 Å), and the fabrication of reliable devices utilizing these materials will require control of film properties at extremely sharp interfaces; It will be necessary to verify the integrity of thin layers and layered structure devices over thicknesses comparable to the atomic layer spacing. Analytical techniques which probe the first 1–2 atomic layers are therefore necessary for in-situ characterization of relevant thin film growth grocesses. However, most surface-analytical techniques are sensitive to a region within 10–40 Å of the surface. Additionally, they are physically incompatible with existing thin film deposition technologies and are typically restricted to ultra high vacuum conditions, whereas the growth of multi-component oxide or nitride films is usually carried out in an ambient partial pressure of oxygen or nitrogen up to several hundred mtorr.

A review of ion beam-based analytical methods for the characterization of thin film and multi-layered thin film structures incorporating layers of multicomponent oxides is presented. Particular attention is paid to the use of time-of-flight techniques based on the utilization of 1–15 keV ion beams which show potential for use as non-destructive, real-time, in-situ surface diagnostics for characterization of the growth of multicomponent metal and metal oxide thin films.