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Correlations between optical properties, microstructure, and processing
conditions of Aluminum nitride thin films fabricated by pulsed
laser deposition
Jonghoon Baek a,⁎, James Ma b, Michael F. Becker a, John W. Keto c, Desiderio Kovar d
a Department of Electrical and Computer Engineering, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA
b Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA
c Department of Physics, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA
d Department of Mechanical Engineering, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA
Received 3 May 2006; received in revised form 28 December 2006; accepted 3 March 2007
Available online 12 March 2007
Abstract
Aluminum nitride (AlN) films were deposited using pulsed laser deposition (PLD) onto sapphire (0001) substrates with varying processing conditions (temperature, pressure, and laser fluence). We have studied the dependence of optical properties, structural properties and their correlations for these AlN films. The optical transmission spectra of the produced films were measured, and a numerical procedure was applied to accurately determine the optical constants for films of non-uniform thickness. The microstructure and texture of the films were studied using various X-ray diffraction techniques. The real part of the refractive index was found to not vary significantly with processing parameters, but absorption was found to be strongly dependent on the deposition temperature and the nitrogen pressure in the deposition chamber. We report that low optical absorption, textured polycrystalline AlN films can be produced by PLD on sapphire substrates at both low and high laser fluence using a background nitrogen pressure of 6.0 × 10− 2 Pa (4.5 × 10− 4 Torr) of 99.9% purity.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Aluminum nitride; Optical properties; Structural properties; Pulsed laser deposition