The spectrally resolved photoluminescence decay in YAG:Er, ZnO and SiO₂ crystals

Abstract

We present an optical setup for measuring spectrally resolved photoluminescence (PL) mean decay time using conventional UV LED with sinusoidal excitation and a phase shift method. The phase sensitive detection was applied on the Er-doped yttrium aluminium garnet single crystal (YAG:Er, grown by the micro-pulling-down method) and hydrothermally grown zinc oxide micro-crystallites (ZnO). Commercial ZnO and silicon oxide (SiO2) microcrystalline powders were measured for comparison. SiO2 powder was annealed in O2 plasma at 500 °C for cleaning. While YAG:Er shows well resolved greenish PL peaks with mean decay time about 15 μs related to the Stark splitting of Er3+ (4f11) states and ZnO micro-powder broad reddish PL with similar PL decay time, the plasma treated SiO2 powder shows weak bluish defect-related PL with significantly faster mean decay times below 100 ns.

Enhanced Photoluminescence of Plasma-Treated Recycled Glass Particles

“…The steady-state PL was excited at room temperature using UV band pass filter #FBH360-10 transparent in 350-370 nm spectra range (Thorlabs, Newton, NJ, USA) and 1 mW UV LED #XSL-360-5E (Roither Lasertechnik, GmbH, Vienna, Austria) directly powered by a #3390 waveform generator (Keithley Instruments, subsidiary of Tektronix, Solon, Ohio, USA) [19]. Our setup measures the PL emission in the 375-750 nm spectral range using the #34-302 long-pass optical filter fully absorbing below 370 nm and fully transparent above 375 nm (Edmund Optics, Barrington, NJ, USA), a 300-800 nm monochromator H20VIS (Horiba, Kyoto, Japan), a red-sensitive photomultiplier (PMT) #XP2203B (Photonis, Orsay, France), a low-noise current preamplifier #5182 with 10 5 V/A transimpedance (AMETEK, Berwyn, PA, USA), and a 100 kHz #SR830 lock-in amplifier (Stanford Research Systems, Sunnyvale, CA, USA) TTL referenced to the LED frequency.…”

“…The setup is also suitable for time-resolved PL measurements, with the time resolution in the order of 10 ns using the method based on the phase shift between the sinusoidal excitation and emission. Prior to the phase shift measurements, the lock-in amplifier was set to zero phase at the UV LED wavelength [19]. The setup was spectrally calibrated with an #63358 halogen lamp (Oriel Instruments, subsidiary of Newport Corporation, Stratford, CT, USA)).…”

“…Therefore, the plasma treatment of glass powder has generated considerable interest in both basic and applied research. Recently, we modified the microcrystalline sand powder using a low-temperature, low-pressure plasma treatment and high-temperature annealing in different atmospheres [18,19] and observed that the low-temperature plasma treatment in hydrogen or oxygen atmospheres resulted in weak changes in the PL emission spectra. Significant changes in the PL emission spectra of SiO2 microparticles, attributed to changes in the defects in the glass particles, were observed only for annealing in hydrogen atmosphere at a temperature of 800 °C and above.…”