Q.Y Zhang

Influence of annealing atmosphere and temperature on photoluminescence of Tb3+ or Eu3+-activated zinc silicate thin film phosphors via sol–gel method

Abstract Thin films of Zn 2 SiO 4 :Tb 3+ or Eu 3+ were deposited on silicon wafers by a sol–gel method. The films exhibited prominent green or red photoluminescence, due to the sharp and strong intra-4f n -shell electronic transitions. The thermogravimetric analysis curve shows a remarkable weight loss in the temperature range 50–400 ° C , and a slow loss at higher temperature. The increases in fluorescence intensity and decay lifetimes of rare-earth ions sensitive to microstructure and chemical components are attributed to OH removal, nano-crystallite formation and the increased surface roughness by treatment of temperature. Strongly enhanced photoluminescence was observed in samples annealed at 950 °C in a nitrogen atmosphere.

Luminescent properties of rare-earth ion doped yttrium silicate thin film phosphors for a full-colour display

In this paper, we report our results on the sol–gel preparation and spectral properties of (RExY1−x)2SiO5 (RE3+ = Eu3+, Tb3+, Ce3+, x = 0.005, 0.01, 0.02, 0.03 and 0.05) thin films. Effects of annealing temperatures on the thin films structure and optical properties, including luminescence, decay kinetics and CIE colour coordinates have been investigated. Upon exposure to the UV source, films containing Eu3+ and Tb3+ have exhibited bright red- and green-phosphorescent colours, due to the prominent transitions of 5D0→7F2 at 613 nm of Eu3+ and 5D4→7F5 at 543 nm of Tb3+ arising because of the intra-4f n electronic transitions, respectively. The photoluminescence spectrum of (CexY1−x)2SiO5 film mainly shows a broader emission band at 488 nm, which originates from the 5d→4f electron transitions of Ce3+. Luminescence mechanisms of these phosphor thin films have been discussed in detail.

Effects of composition and structure on spectral properties of Eu3+-doped yttrium silicate transparent nanocrystalline films by metallorganic decomposition method

Abstract Transparent thin films of (Eu x Y 1− x ) 2 SiO 5 and (Eu x Y 1− x ) 2 Si 2 O 7 ( x =0.005∼0.05) have been prepared using a metallorganic decomposition sol–gel process. A strong room temperature red emission with predominant wavelength at 614 nm, corresponding to the 5 D 0 → 7 F 2 intra-4f n electric transition of Eu 3+ , has been observed as a function of the annealing temperature. Correlations were observed between optical properties and film structures. As a consequence, a great change in luminescence and CIE coordinates of Eu 3+ -doped Y 2 SiO 5 at high temperature around 1050 °C was attributed to phase transformation of nanocrystalline films. Upon exposure to the UV source, these thin films have shown bright red-phosphorescent color with excellent color saturation.

Low optical loss germanosilicate planar waveguides by low-pressure inductively coupled plasma-enhanced chemical vapor deposition

This Letter reports on the preparation and properties of germanium-doped silica thin films by a new technique namely inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD). 13.56 MHz ICP was generated inside the chamber upon the supplying of 1 KW r.f. power at 2.5 Pa. The Films have been deposited on Si-wafers from the tetraethoxysilane, tetramethoxygermane and oxygen system at 400 °C. The behaviors of ∼200 and ∼240 nm UV absorptions under different treatment conditions comprising annealing temperatures and excimer laser exposure have been systematically investigated. A low propagation loss of ∼0.1 dB/cm at 1550 nm has been achieved.

Temperature-insensitive Ge–B–SiO2 planar lightwave circuits by inductively coupled plasma-enhanced chemical vapor deposition

Low-propagation-loss Ge–B–SiO2 planar waveguides have been achieved by inductively coupled plasma-enhanced chemical vapor deposition. The significant effects due to annealing temperature, hydrogen loading, and KrF excimer ultraviolet laser irradiation on the optical properties of Ge–B–SiO2 films have been investigated. A temperature-insensitive Mach–Zehnder interferometer-like optical filter has been demonstrated by means of a double-core fabrication method using 10GeO2–90SiO2 (10G90S) and 8GeO2–5B2O3–87SiO2 (8G5B87S) as two different waveguide cores. We have achieved less than 0.5 pm/°C temperature dependence of the central wavelength of the filter at 1550 nm while varying the temperature from −20 to 80 °C.

Luminescence properties of sol-gel-derived organic-inorganic composite films dispersed with erbium and neodymium oxalate nanoparticles

Erbium oxalate and neodymium oxalate nanoparticles/titania/organically modified silane composite sol-gel thin films for photonic applications have been prepared by combining an inverse microemulsion technique and the sol-gel technique at low temperature. Transmission electron microscopy observation shows that the size of these oxalate nanoparticles is in the range from 10 to 40 nm. Up- conversion emission properties of these composite thin films on silicon substrates have been studied. A relatively strong room-temperature green up-conversion emission at 544 nm has been measured for the composite films dispersed with erbium oxalate nanoparticles upon excitation at 993 nm. An up- conversion emission in violet color from neodymium oxalate nanoparticles upon excitation with a yellow light emission, two UV emissions at 341 nm and 376 nm and a weak blue emission at 467 nm have been obtained. The mechanism of the up-conversion emission has been explained by means of an energy level diagram. The lifetimes of the violet emissions have been measured.

Fabrication and optical properties of sol-gel derived interference coating for high power laser applications

A single layer sol-gel derived TiO2 thin films and 6 periods SiO2/TiO2 multilayer coating were designed and prepared on GaAs substrates as anti-reflection coating or near-IR-reflective coating for high power semiconductor laser applications. Crack free TiO2 thin films having thickness of 80-150 nm, and refractive indices of 1.8-2.1 have been obtained by simply sol-gel method upon heating at different temperatures. The obtained TiO2 thin films on GaAs substrates have shown reflectance of <EQ 1 percent in the wavelength of about 808 nm. Thin films of TiO2 and SiO2 were also used to fabricate near IR reflector ion GaAs substrates. The reflector consisted of 6 SiO2/TiO2 bi-layers, designed with a high-reflective band in the wavelength of 1064 nm. A minimum transmittance of <EQ 2 percent in the wavelength range between 950 and 1100 nm has been obtained in the present multilayer SiO2/TiO2 coating.