Ž . Thin Solid Films 315 1998 263–265 Room temperature photoluminescence from erbium-doped silica thin films prepared by cosputtering Gang Gu a, ) , Youwei Du a , Tsing Yu b a National Laboratory of Solid State Microstructures and Department of Physics, Nanjing UniÕersity, Nanjing 210093, China b Department of Chemistry, Nanjing UniÕersity, Nanjing 210093, China Received 16 June 1997; accepted 16 September 1997 Abstract The Er 3q ions were dispersed in silica matrix by rf magnetron cosputtering of silica and erbium oxide. Photoluminescence of Er 3q centered at 1.534 mm has been detected at room temperature as excited by a Nd-YAG laser line at 1.064 mm. The photoluminescence intensity is proportional to the annealing temperature. We believe that it is due to more radiative centers reaching Er 3q upon annealing. Besides the main peak at 1.534 mm, an additional peak at 1.522 mm was observed, which is considered to result from the Raman response of surface hydrogen bonds. q 1998 Elsevier Science S.A. Keywords: Luminescence; Silicon oxide; Sputtering; Raman scattering 1. Introduction Recently, there has been considerable interest in the fabrication of rare-earth-doped thin films for optically active waveguides. Erbium-doped silicon and oxides are of special interest due to their characteristic emission at 1.54 m m, which corresponds to the minimum loss window in silica-based fibers. Rare earth trivalent ions in some solid compounds emit light at characteristic wavelengths due to intra-4 f or internal 4 f –5 d transitions. In the case of Er 3q , the emission at 1.54 m m corresponds to a dipole forbidden intra-4 f transition 4 I to 4 I . Only when the crystal 13r2 15r2 field of the host breaks inversion symmetry and mixes states of opposite parity is transition allowed. This allowed emission has been found quite independent on the host and the temperature, and was observed in many different mate- w x Ž . rials 1–6 . Er-related photoluminescence PL enhance- ment has been achieved by increasing the number of radiative Er centers by annealing and additional doping, on the other hand, band gap widening of the host materials also makes the PL enhancement possible. In fact, Er w x doping of porous Si 7,8 and hydrogenated amorphous Si w x 9,10 have been carried out due to their wider band gaps in comparison to that of a crystalline Si. ) Corresponding author. 2. Results and discussion In this paper, we report on Er doping in silica thin films prepared by cosputtering from a partially erbium oxide Ž . Er O covered silicon oxide target. Erbium oxide was 2 3 utilized due to its high stability. Silica has been selected as a matrix due to its wide gap and based on the fact that it is a useful material for optical waveguides. The sharp PL at 1.534 m m was observed at room temperature in unan- nealed samples. Upon in-situ annealing, an enhanced PL at 1.534 m m was observed. The sideband peak at 1.522 m m is observed in both annealed and unannealed samples, which was considered as a Raman line of hydrogen bonds. All samples were prepared by radio frequency sputter- ing from a 6.0-cm-diameter 99% SiO target partially 2 Ž 2 . covered by small 99.9% erbium oxide platelets ; 3 mm . We can adjust the Er concentration in silica by changing the surface coverage of Er O . The thin films were grown 2 3 Ž . on p-type Si 100 wafer substrates which were kept at room temperature during sputtering. For optical absorption measurements, polished silica was selected as substrate. The system was evacuated to a base pressure of 10 y7 Torr. The deposition was carried out with a sputter-down configuration in a 0.6 Pa argon atmosphere and a rf power of 100 W for 1 h. A resistive heater was used to anneal the samples in situ up to a maximum temperature of 8008C. The sputtering system was controlled by a personal com- 0040-6090r98r$19.00 q 1998 Elsevier Science S.A. All rights reserved.