Condensed-Matter Physics & Materials Science Seminar
"Surface Evolution and Interface Stability of Patterned Single Crystal and the Fabrication and Characterization of Biaxially Textured Thin Film by Molecular Beam Epitaxy and Oblique Angle Deposition"
Presented by Chuan-Fu Lin, Rensselaer Polytechnic Institute
Friday, July 12, 2013, 10:30 am
Bldg. 480 conf. room
Hosted by: Ivan Bozovic
In the first part of this talk, I describe an approach toward investigating the question of surface evolution and interface stability on semiconductor GaAs(001), using lithographic patterning to perturb a flat crystalline surface over a range of spatial frequencies, followed by epitaxial growth. I will show via both kinetic Monte Carlo (kMC) simulations and molecular beam epitaxial (MBE) growth experiments that patterning in the presence of a kinetic (Ehrlich-Schwoebel) barrier can be used to direct the self assembly of nanostructures-islands. Atomic Force Microscopy (AFM) and in-situ reflective high energy electron diffraction (RHEED) were used to characterize the surface morphologies and to monitor the deoxidization process and the surface reconstructions associated with epitaxial growth. In the second part of the talk, I will mainly focus on the fabrication and characterization of biaxially textured thin films through oblique angle deposition (OAD). The use of biaxially textured semiconductor film has drawn considerable attention because it approximates the properties of single crystal film while providing a downstream cost benefit, especially on large area electronics applications such as displays and photovoltaic devices. (Interestingly, biaxial buffer layers have also been used to grow small angle grain boundary high Tc superconductor films that can achieve a high critical current and lowering the cost). In this part of the talk, I will demonstrate heteroepitaxial growths of biaxially textured Ge, CdTe (potentially photovoltaic devices) and GaN (optoelectronic devices) films on amorphous substrate (glass or oxide) with biaxially textured buffer layers. Real-space imaging, XRD pole figures and RHEED surface pole figures were involved to characterize the texture and its evolution of films during growth.