Crystalline silicon growth in the aluminium-induced glass texturing process

Aluminium-induced texturing (AIT) is a method to texture glass surfaces by utilising the reaction between aluminium (Al) and glass at high temperature (above 500 degrees C) and a subsequent wet-chemical treatment that removes the reaction products. In this work, we studied the solid state reaction between a sputtered Al layer and a borosilicate glass sheet during AIT annealing. Raman spectroscopy showed that crystalline silicon (c-Si) is formed during the AIT process. An optical microscope was used to visualise the evolution of the c-Si growth. Plan-view scanning electron microscopy (SEM) investigations performed on samples after completed AIT reaction showed that separate c-Si clusters formed at the glass surface. Atomic force microscopy revealed that the c-Si clusters grew upwards and were on top of the glass surface. Cross-sectional SEM examination showed that the c-Si layer is not uniform and that crater-shaped nodules are embedded into the glass. The widths and depths of the nodules are in the micrometre range. Energy-dispersive X-ray spectroscopy showed that the nodules consist mainly of aluminium oxide (Al2O3). X-ray diffraction analysis showed that the c-Si grains are preferentially (111) oriented. The activation energy of the reaction between Al and borosilicate glass is 3.0 +/- 0.2 eV based on in-situ XRD analysis of the c-Si growth. Finally, a phenomenological model of the AIT process is proposed and we suggest that the topology of the glass texture strongly depends on the size, depth and lateral separation of the Al2O3 nodules embedded in the glass. (C) 2012 Elsevier B.V. All rights reserved.