Biaxially Textured Titanium Thin Films by Oblique Angle Deposition: Conditions and Growth Mechanisms

摘要

Growing highly crystalline nanowires over large substrate areas remains anambiguous task nowadays. Herein, a time-efficient and easy-to-handle bottomupapproach is demonstrated that enables the self-assembled growth of biaxiallytextured Ti thin films composed of single-crystalline nanowires in a singledepositionstep. Ti thin films are deposited under highly oblique incidenceangles by electron beam evaporation on amorphous substrates. Substratetemperature, angle of the incoming particle flux, and working pressure arevaried to optimize the crystallinity in those films. Height-resolved structureinformation of individual nanowires is provided by a transmission electronmicroscopy (TEM) nanobeam, high-resolution TEM, and electron diffraction.Ti nanowires are polycrystalline at 77 K, whereas for ≥300 K, single-crystallinenanowires are tendentially found. The Ti crystals grow along the thermodynamicallyfavored c-direction, but the nanowires’ tilt angle is determined byshadowing. Biaxially textured Ti thin films require a certain temperature rangecombined with highly oblique deposition angles, which is proved by X-rayin-plane pole figures. A general correlation between average activation energyfor surface self-diffusion and melting point of metals is given to estimate thesignificant influence of surface self-diffusion on the evolution of obliquelydeposited metal thin films.