Effects of the Substrate Temperature, Annealing Temperature, and Hydrogen Presence During Sputtering on the Luminescence
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EFFECTS OF THE SUBSTRATE TEMPERATURE, ANNEALING TEMPERATURE, AND HYDROGEN PRESENCE DURING SPUTTERING ON THE LUMINESCENCE OF Eu-DOPED NANOCRYSTALLINE Si/SiO2 G. A. NERY*, L. F. FONSECA, H. LIU**, O. RESTO, S. Z. WEISZ Physics Department, University of Puerto Rico, San Juan, PR, USA *Physics and Chemistry Department, University of Puerto Rico, Arecibo, PR, USA ** Physics Department, University of Puerto Rico, Mayaguez, PR, USA ABSTRACT We synthesized RF co-sputtered Eu2O3, Si and SiO2 on quartz substrates at different temperatures, and with and without the presence of H2 gas during sputtering. The photoluminescence of the samples was measured using both the 514.5nm green line and 457.9nm blue line of an Ar laser. The samples were then annealed, their luminescence remeasured, and the process repeated for a range of temperatures from 470ºC to 1084ºC. The effects of substrate temperature, presence or absence of H2, annealing, and the use of the green or blue line on the observed luminescence are presented. INTRODUCTION Europium ions Eu(II) and Eu(III) are used for a variety of purposes ranging from phosphors ( Eu(II) & Eu(III) ), to biological markers and structure probes ( Eu(III) ). The last is due to Eu(III)’s sharp environment-sensitive 5D0 → 7FJ transitions. Eu(III)’s large quadrupole splitting and spin relaxation times also make it attractive for high resolution laser spectroscopy, and it has been proposed for use in a frequency domain optical data memory. Co-sputtered Si/SiO2 contains nanocrystals of Si (nc-Si) embedded in a SiO2 matrix. The nc-Si particles have enlarged bandgaps and luminesce visibly due to quantum confinement effects. It has now been shown that this material used as host interacts strongly with Eu used as a dopant, resulting in both Eu(II) and Eu(III) luminescence [1]. Expanding on our previous luminescence work [2] in which we synthesized RF cosputtered Eu2O3/Si/SiO2 , we now sputter onto quartz substrates at different temperatures, try using H2 in the sputtering gas mixture, anneal each sample in a succession of temperatures from 470ºC to 1084ºC, use Ar instead of N2 to control oxidation in our oven, and use blue 457.9nm excitation in addition to the green 514.5nm Ar laser line. The results are presented here. EXPERIMENT We deposited a series of samples by RF co-sputtering Eu2O3, Si, and SiO2 onto quartz substrates. One sample had a 16.6% H2, 83.4% Ar sputtering mixture. We also produced a Sifree sample, and an Eu-free sample. For sputtering, the substrate was held between two aluminum plates. The upper Al plate held either a coiled tube for water-cooling or quartz lamps for heating. The lower Al plate and the substrate were also heated by the plasma. Temperatures were measured in the lower (sometimes also upper) plate using thermocouples. The Si-free and H2 sputtered samples were initially at room temperature and heated up to about 100ºC (lower plate) by the end of the process. The Eu-free sample was kept at about 150ºC (lower plate). The F14.27.1
Eu2O3/Si/SiO2 samples were prepared at thre
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