DYNAMIC OBLIQUE ANGLE DEPOSITION OF NANOSTRUCTURES FOR ENERGY APPLICATIONS

摘要

The century old oblique angle deposition (OAD) of porous films has received renewed attention recently. The technique can tailor not only the morphology, but also the texture of nanostructures. Nanostructures with a variety of morphologies and textures can be achieved by engineering the incident flux angle, substrate rotation speed, and rotation axis. These different deposition configurations can change the shadowing effect and the texture selection rale dynamically during the nanostructure self-assembly process. These artificially fabricated nanostructures have been used as sensors in many applications. Among the textured films, a particular class of biaxial films such as MgO has been used as a buffer layer to grow, for examples, high temperature superconductors and ferroelectrics. More recently, it has been shown that biaxial CaF2 nanorods can be coated on amorphous substrates at room temperature using OAD. We demonstrated that single crystal-like CdTe can be grown by metal organic chemical vapor deposition (MOCVD) directly on CaF2 on glass substrate despite a large lattice mismatch between CdTe and CaF2. We also showed that single crystal-like Ge can be epitaxially grown on biaxial CaF2 buffer on glass. These films have potential applications as low cost photovoltaic devices. We will also introduce a new oblique angle flipping rotation mode to grow biaxial metallic nanorods such as W and Mo. These films may also find applications as buffers to grow functional materials for energy applications.