The effect of annealing conditions on the crystallization of Er-Si-O formed by solid phase reaction

Er-Si-O crystal is one of the promising materials for Si-based opto-electronic devices. Crystallization of Er-Si-O is obtained by solid phase reaction of an amorphous preform which contains Er-O and Si-O bonds. However detailed crystallization mechanism is not clear. This study reports that the control of oxygen content of the sample in the annealing process for crystallization affects the fine arrangements of Er-Si-O crystals, resulting in three different types of XRD patterns and correspondingly different PL spectrum fine structures. The sol-gel method was used to prepare the amorphous preform. The samples were then annealed at 1250 degrees C in Ar for the solid phase growth of Er-Si-O crystals. The obtained Er-Si-O crystals showed, however, some different types of XRD patterns and the PL spectra. It was speculated that a slight amount of residual oxygen in the annealing furnace affected the Er-Si-O crystal structure. To study the effect of oxygen, during solid phase growth three processes were applied; putting a Si cap on the sample to reduce the influence of the atmosphere, additionally putting a carbon sheet as oxygen getter on the sample covered with a Si cap and no Si capping. Three kinds of XRD patterns, PL spectrum fine structures, PLE spectra and PL time decays were observed, depending on the three processes. These results indicate that the fine arrangements of Er-Si-O crystals are affected by oxygen content in the crystal which is very sensitive to oxygen in the annealing Ar atmosphere during the solid phase growth and their properties are come from their particular crystalline structures. (c) 2005 Elsevier B.V. All rights reserved.