Photoluminescence of Si/SiO 2 , RE 2 O 3 /Si/SiO 2 and RE 2 O 3 /Si/Al 2 O 3 (RE = Er, Nd, Tm) Sputtered Thin Films
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PHOTOLUMINESCENCE OF Si/SiO2, RE2O3/Si/SiO2 AND RE2O3/Si/Al2O3 (RE = Er, Nd, Tm) SPUTTERED THIN FILMS C. ROZO, L. F. FONSECA, O. RESTO, S. Z. WEISZ Physics Department, University of Puerto Rico at Rio Piedras, San Juan, PR, USA ABSTRACT Si/SiO2, RE2O3/Si/SiO2 and RE2O3/Si/Al2O3 films were sputtered. Si/SiO2 films were annealed to 1100ºC for 30 min in Ar. RE2O3/Si/SiO2 films were annealed to 700ºC, 1000ºC, or 1100ºC for 30 min in Ar. RE2O3/Si/Al2O3 films were annealed to 700ºC for 30 min in Ar. Raman spectra and photoluminescence (PL) obtained for the Si/SiO2 films show relation between Si nanocrystal (nc) presence, Si nanoparticle (np) PL and Si target area. Nd2O3 co-sputtered films presented PL for the (4F5/2, 2H9/2) → 4I9/2, 4F3/2 → 4I9/2, 4F3/2 → 4I11/2, and 4F3/2 → 4I13/2 transitions. Er2O3 co-sputtered films presented PL for the 4I11/2 → 4I15/2, and 4I13/2 → 4I15/2 transitions. Tm2O3 co-sputtered films presented PL for the 3H4 → 3H6 transition. Different spectral shapes were observed for the infrared (IR) PL of the Er3+ ions and of the Nd3+ ions for the RE2O3/Si/Al2O3 films with respect to the RE2O3/Si/SiO2 films. INTRODUCTION The wavelength range of emission of Si np has proved appropriate for the use of Si nc as sensitizers for certain rare earth (RE) ions [1,2]. Research concerning Si nc PL has concentrated on Si/SiO2 films, although there is indication of research on Si np embedded in other oxide matrices [3,4]. Preparation of films of Si np embedded in different oxide matrices leads to research on the effect of different oxide matrix environments on the PL of Si np sensitized RE ions. This is important considering the research done on a wide variety of RE doped oxide glasses for development of lasers, waveguides, and optical amplifiers [5,6]. Silicate glasses with varying concentrations of Al,Ca,Na, as well as heavy metal oxide glasses are among the many types of glasses studied [7,8]. Oxide matrices are appropriate considering the fact that Si np can be passivated by the O present in the oxide matrix. Here, we present results from spectroscopic study of Si/SiO2 films and RE2O3/Si/SiO2 films, and compare them to the results from the study of RE2O3/Si/Al2O3 films and an additional film of Er2O3/Si/Al/SiO2. EXPERIMENTAL All films were prepared by rf-sputtering. Unless otherwise stated the deposition time for the films was 6 hr. After film deposition their thickness was measured. The films were annealed. PL measurements were made for the films as-deposited and after annealing as well. Raman measurements were made for some samples after annealing. Details of the sputtering equipment, film thickness measurement, annealing, and PL equipment are given in [9]. Raman spectra were obtained using the same spectrometer described for PL. The deposited films are 12.7 cm in length and subdivided in 50 sections, each section corresponding to a “position” (P). The Si target is placed near one end of the substrate close to P50 leaving the other end richer in oxide.
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Details of the films prepared and their a
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