Ion-beam texturing at nucleation [electronic resource] : investigation of the fundamental mechanism of biaxial texture development in ion beam assisted deposition and applications
- James Randal Groves.
- 2010, c2011.
- Physical description
- 1 online resource.
- Groves, James Randal.
- Clemens, B. M. (Bruce M.), primary advisor.
- Nix, William D., advisor.
- Salleo, Alberto, advisor.
- Stanford University. Department of Materials Science and Engineering
- Low-energy ion-beam irradiation (< 1 keV) during the concurrent deposition of cubic oxide materials results in the growth of crystallographically textured thin films. A model system, magnesium oxide (MgO), has been successfully used as a biaxially textured template fillm for the heteroepitaxial deposition of many materials with texture dependent properties like high temperature superconductors, tunable microwave materials, and ferroelectrics. The ion beam assisted deposition of MgO is unique in that it requires only a few nanometers (< 10nm) at room temperature to develop texture very near that of a single crystal substrate and is substrate independent (glass, metal, etc.). Here, I present data on the nucleation of biaxial crystallographic texture in this model system using a novel in situ quartz crystal microbalance (QCM) substrate combined with in situ reflected high-energy electron diffraction (RHEED). Correlation of mass uptake with the RHEED images of the growing surface shows that the development of crystallographic biaxial texture in this material system occurs suddenly as the initially polycrystalline MgO films reaches a critical film thickness of 2 nm. This texture continues to improve during subsequent growth. I use a combination of in-situ RHEED and ex situ transmission electron microscopy to elucidate the mechanism of this sudden texture formation. I have also investigated these ultra-thin films using synchrotron radiation and report some of the most complete analysis of their in-plane orientation. I present a model to describe this behavior and further explain the role of ion-to-molecule arrival ratio and underlying nucleation surface on texture development. In addition, I will present some empirical rules for selecting new materials for IBAD processing. I will discuss the use of IBAD materials as template layers for several applications. Among these, I have recently developed a new template layer, CaF2, for use in photovoltaic applications. I present my recent effort to develop this system for the deposition of biaxially textured polycrystalline Si and Ge thin films.
- Publication date
- Copyright date
- Submitted to the Department of Materials Science and Engineering.
- Thesis (Ph.D.)--Stanford University, 2011.