Optical and Structural Changes of Fe Implanted Sapphire
- PDF / 929,717 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 89 Downloads / 191 Views
OPTICAL AND STRUCTURAL CHANGES OF FE IMPLANTED SAPPHIRE Carlos P. Marques 1,2, Eduardo J. Alves 1,2, Carl J. McHargue3, Maria F. da Silva Soares 1,2, Rosário Correia 4, Manuel J. Soares4 and Teresa Monteiro 4 1 ITN, Estrada Nacional 10, 2686-953 Sacavém, Portugal. 2 CFNUL, Av. Prof. Gama Pinto nº 2, 1649-003 Lisboa, Portugal. 3 Center for Mat. Processing, Univ. of Tennessee, Knoxville, TN 37996-2350, USA. 4 Universidade da Aveiro, Dept. Física, 3810-193 Aveiro, Portugal.
1,2
, José C.
ABSTRACT Single crystalline colorless α-Al2O3 samples were implanted with several fluences of Fe+ ions in the range of 1×1016 to 5×1017 Fe+ cm-2 at room temperature. Optical absorption and luminescence measurements were carried out before and after annealing in reducing and oxidizing atmospheres. The structural changes were studied with RBS/channeling and x-ray diffraction. After implantation, the damage induces a brownish coloration in the samples for fluences below 2×1017 Fe+ cm-2. The optical spectra are characterized by an absorption band centered at 200 nm. This band is strongly reduced after annealing at 1100 oC in reducing atmosphere and a new well-defined band develops around 350 nm. This new band shifts to lower values with the implanted fluence, which is an indication of its correlation with the dimensions of the iron precipitates formed in the implanted region. The existence of these precipitates was confirmed by x-ray diffraction and TEM. The samples implanted with fluences above 1×1016 Fe+ cm-2 annealed in oxidizing atmosphere display different optical absorption spectra, with respect to those annealed in reducing atmosphere, characterized by an increase in the intensity of the peak at 200 nm. Luminescence measurements show the presence of F and F+ centers in the samples. The existence of these defects can be explained by the need of charge compensation and strain release due to the formation of mixed iron oxide or metallic precipitates. INTRODUCTION Ion irradiation effects in sapphire have been widely investigated for several implanted species, with the aim of improving their mechanical properties [1]. The outcome of these studies was a global understanding of the ion induced damage and defect recovery [2-4]. Recently a potential application of sapphire in the optoelectronic field was noticed by some authors by doping with optically active ions using ion implantation [5]. Furthermore the doping of sapphire with other metallic ions to high concentrations can also lead to the formation of nanoprecipitates that could provide us with a large variety of new optical properties. Particularly the non-linear optical effects introduced by metallic precipitates into optical materials have significant interest for applications. However, while the optical properties of isolated atoms are relatively well established for some transition metal ions in sapphire [6-8] the properties of isolated Fe and metallic clusters are still under investigation. In this work we study the behavior of the optical spectra of α-Al2O3 when implanted at r
Data Loading...
