The recent development of magnetron sputter epitaxy to the growth of high quality GaN films^[1] and the band gap variation due to the incorporation of high concentrations of transition metals to GaN^[2] and TiO₂^[3] films without segregation has brought bold interest to deposition routes using reactive magnetron sputtering. In special this investigation reports on the combined effects of substrate orientation and temperature, and energetic particle collisions on the structure of GaN and TiO₂ (predominantly anatase) films grown by reactive sputtering. The investigated films are deposited using radio frequency (RF) reactive sputtering of metallic Ga and Ti targets in plasma generated from a gas mixture of N₂ or O₂ and Ar.

In most thin film deposition processes the substrate thermal energy directly influences the atomic arrangement, chemical bonding, film structure and morphology. In the glow discharge sputtering depositions the primary energy source is the kinetic energy of the depositing species provided by the plasma. In the latter the mean energies of the precursors are in the 1-40 eV range, which are well above the average thermal energy. This enhancement of the precursors´ energy produces important differences in the structure and morphology of the deposited films. The consequences of the energy enhancement to the morphology, structure, and electronic properties of TiO₂ and GaN films are presented and discussed in association with the reactive sputtering deposition parameters. Electron and atomic force microscopies, X-ray diffraction, and Raman scattering results, show that both produced compound films present compact columnar morphology and orientation texture characteristic of the energetic depositions. In the case of GaN, the association of the energetic depositions with high substrate temperatures produced substrate dependent crystallite orientation and surface morphology. Concerning the TiO₂ films, a modulation of the O₂ flow during reactive sputtering produces an increase of the optical absorption, without significant changes in structure, composition and morphology. The increase in the optical absorption is potentially useful for the improvement of the photocatalytical activity of the material. 

[1] M. Junaid et al., Appl. Phys. Lett., v.98, 141915 (2011). 

[2] D.M.G. Leite et al., Jour. Cryst. Growth, v.327, 209 (2011). 

[3] A.L.J. Pereira, et al., Jour. Phys. Chem. C, v. 116, 8753 (2012). 

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/30205 must be provided.

1. Substrate orientation, temperature and energetic atomic collisions effects on the structure of GaN films grown by reactive sputtering