Luminescence of Rare Earth Doped Si/ZrO 2 Co-Sputtered Films
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LUMINESCENCE OF RARE EARTH DOPED Si/ZrO2 CO-SPUTTERED 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 Er3+, Nd3+ and Tm3+ doped Si/ZrO2 thin films have been prepared by rf co-sputtering. The films are 5 inches long and divided into 50 sections or positions, labeled from P1 to P50. The target configuration is such that the main target is ZrO2 (181.46 cm2), the rare earth (RE) oxide pellet (1.43 cm2) is placed on the main target below the middle of section of the film and the Si chip (6.67 cm2 or 6.00 cm2) is placed on the main target below one end of the film (P40 to P50). The films were annealed to 700ºC. The Er3+ 4 I13 2 → 4 I15 2 emission was detected but no I11 2 → 4 I15 2 emission was detected. The 4 I13 2 → 4 I15 2 emission shows a narrow peak at 1527 nm (FWHM = 6.5 nm for P20) with two weaker side bands from 1430 nm to 1500 nm and from 1550 nm to 1600 nm. The Nd3+ 4 F3 2 → 4 I 9 2 , 4 F3 2 → 4 I11 2 , and 4 F3 2 → 4 I13 2 emissions were 4
detected being the 4 F3 2 → 4 I11 2 peaked at 1065 nm (FWHM = 39.5 nm for P30) the strongest. The
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F3 2 → 4 I 9 2 emission is relatively weak, less than one-fourth the peak intensity of the
F3 2 → 4 I11 2 emission but is broad (FWHM = 92 nm for P30). No Er3+ 4 I13 2 → 4 I15 2 emission or Nd3+ 4F3/2 emissions were detected for the Si rich ends of the respective films, being the emission stronger from the Si poor end of the film towards the middle of the film. The maximum Er3+ 4 I13 2 → 4 I15 2 emission is for P20 and the maximum peak intensity for the Nd3+ 4
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F3 2 → 4 I11 2 emission is for P30. The excitation wavelength dependence behavior for the Nd3+
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F3 2 → 4 I11 2 emission is that typical of energy transfer from the Si nanoparticles to the emitting
Nd3+ ions. The excitation wavelength behavior for the Er3+ 4 I13 2 → 4 I15 2 emission reflects a mix of energy transfer from the Si nanoparticles and strong absorption for excitation wavelengths of 488.0 nm and 514.5 nm. The Tm3+ doped Si/ZrO2 thin film does not exhibit infrared (IR) PL from the 3 H 4 → 3 F4 emission or the 3 F4 → 3 H 6 emission. The intense band from 500 nm to 800 nm observed for all of the RE doped Si/ZrO2 films, due to defects in ZrO2, barely permits the detection of the Tm3+ 3 H 4 → 3 H 6 emission which is best observed for P35. INTRODUCTION Zirconium oxide has been proposed as an excellent material for optical applications due to its hardness, optical transparency, and high refractive index [1]. With a wide optical band gap of 5.22 eV – 5.8 eV [2], that reduces the probability of non-radiative decay, and with a low phonon energy (470 cm-1), lower than that of SiO2 (1100 cm-1) and of Al2O3 (870 cm-1) [3], that reduces the probability of phonon-assisted non-radiative relaxation, the number and probability of radiative transitions in rare earth doped ZrO2 increases, which has made such rare earth doped oxides interesting for photonic applications. Luminescence in Pr3+-, Tb3+-, Eu3+-, Sm3+,
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