Glancing Angle Deposition and Growth Mechanism of Inclined AlN Nanostructures Using Reactive Magnetron Sputtering

Glancing angle deposition (GLAD) of AlN nanostructures was performed at room temperature by reactive magnetron sputtering in a mixed gas atmosphere of Ar and N-2. The growth behavior of nanostructures shows strong dependence on the total working pressure and angle of incoming flux. In GLAD configuration, the morphology changed from coalesced, vertical nanocolumns with faceted terminations to highly inclined, fan-like, layered nanostructures (up to 38 degrees); while column lengths decreased from around 1743 to 1068 nm with decreasing pressure from 10 to 1.5 mTorr, respectively. This indicates a change in the dominant growth mechanism from ambient flux dependent deposition to directional ballistic shadowing deposition with decreasing working pressures, which is associated with the change of energy and incident angle of incoming reactive species. These results were corroborated using simulation of metal transport (SiMTra) simulations performed at similar working pressures using Ar and N separately, which showed the average particle energy and average angle of incidence decreased while the total average scattering angle of the metal flux arriving at substrate increased with increasing working pressures. Observing the crystalline orientation of GLAD deposited wurtzite AlN nanocolumns using X-ray diffraction (XRD), pole-figure measurements revealedc-axis growth towards the direction of incoming flux and a transition from fiber-like to biaxial texture took place with increasing working pressures. Under normal deposition conditions, AlN layer morphology changed from {0001} to {10 (1) over bar1} with increasing working pressure because of kinetic energy-driven growth.