Applied Surface Science, Vol.374, 143-150, 2016
Multi-stage pulsed laser deposition of aluminum nitride at different temperatures
We report on multi-stage pulsed laser deposition of aluminum nitride (AlN) on Si (100) wafers, at different temperatures. The first stage of deposition was carried out at 800 degrees C, the optimum temperature for AlN crystallization. In the second stage, the deposition was conducted at lower temperatures (room temperature, 350 degrees C or 450 degrees C), in ambient Nitrogen, at 0.1 Pa. The synthesized structures were analyzed by grazing incidence X-ray diffraction (GIXRD), transmission electron microscopy (TEM), atomic force microscopy and spectroscopic ellipsometry (SE). GIXRD measurements indicated that the two-stage deposited AlN samples exhibited a randomly oriented wurtzite structure with nanosized crystallites. The peaks were shifted to larger angles, indicative for smaller inter-planar distances. Remarkably, TEM images demonstrated that the high-temperature AlN "seed" layers (800 degrees C) promoted the growth of poly-crystalline AlN structures at lower deposition temperatures. When increasing the deposition temperature, the surface roughness of the samples exhibited values in the range of 0.4-2.3 nm. SE analyses showed structures which yield band gap values within the range of 4.0-5.7 eV. A correlation between the results of single and multi-stage AlN depositions was observed. (C) 2015 Elsevier B.V. All rights reserved.