H.H. Shen

High-quality II-VI films grown on amorphous substrates using tunable tetradymite templates

We demonstrate the growth of highly oriented CdSe and ZnTe films at ∼300 °C on amorphous substrates such as glass and flexible polyimide using ultrathin tetradymite buffer layers composed of SbxBi2-xTe3 alloys lattice-matched to the film overgrowth. This leads to significant improvement of the crystallinity, roughness, grain size, and pit density of the II-VI overlayer along with enhancement of the optoelectronic properties. For example, photoluminescence emission is observed at ∼1.74 eV for optimized CdSe films, the same as in a single crystal reference. An in-plane carrier diffusion length of ∼500 nm is inferred from transient optical data. The use of tetradymite buffer layers to control II-VI compound deposition on non-crystalline substrates is a promising route for large area optoelectronic applications such as photovoltaic, light-emission, or infrared detector devices.

TEM Study of Microstructure of Superhard c-BN/WC-Co Interface

Advanced focused ion beam (FIB) technique, which has been well described by Mayer et al. [1], has been employed to prepare thin foils for transmission electron microscopy (TEM) investigation. It is a powerful tool for TEM sample preparation on nearly all kinds of materials. Especially, it can be served as an irreplaceable approach to prepare TEM specimens from some superhard materials that are difficult to be cut using regular methods such as diamond thin films [2]. The in situ FIB lift-out method mainly consists of extracting and transferring a wedge-shaped lamella, which is coated with a platinum (Pt) thin layer to avoid Ga+ irradiation damage. The lamella is transferred via an internal nanomanipulator and adhered to a TEM half-grid by Pt deposition. Finally, the lamella would be FIB milling to electron transparent and has a thickness of around 100 nm.