Sreedharan Remadevi Sreeja, Ganesan Vedachalaiyer, Sudarsanakumar Chellappan Pillai, Bhavsar Kaushalkumar, Prabhu Radhakrishna, Mahadevan Pillai Vellara Pappukutty Pillai
Department of Optoelectronics, University of Kerala, Thiruvananthapuram, India.
UGC-DAE Consortium for Scientific Research, Indore, India.
Nano Rev. 2015 Mar 11;6:26759. doi: 10.3402/nano.v6.26759. eCollection 2015.
Background : Zinc oxide (ZnO) is a wide, direct band gap II-VI oxide semiconductor. ZnO has large exciton binding energy at room temperature, and it is a good host material for obtaining visible and infrared emission of various rare-earth ions. Methods : Europium oxide (Eu2O3) doped ZnO films are prepared on quartz substrate using radio frequency (RF) magnetron sputtering with doping concentrations 0, 0.5, 1, 3 and 5 wt%. The films are annealed in air at a temperature of 773 K for 2 hours. The annealed films are characterized using X-ray diffraction (XRD), micro-Raman spectroscopy, atomic force microscopy, ultraviolet (UV)-visible spectroscopy and photoluminescence (PL) spectroscopy. Results : XRD patterns show that the films are highly c-axis oriented exhibiting hexagonalwurtzite structure of ZnO. Particle size calculations using Debye-Scherrer formula show that average crystalline size is in the range 15-22 nm showing the nanostructured nature of the films. The observation of low- and high-frequency E2 modes in the Raman spectra supports the hexagonal wurtzite structure of ZnO in the films. The surface morphology of the Eu2O3 doped films presents dense distribution of grains. The films show good transparency in the visible region. The band gaps of the films are evaluated using Tauc plot model. Optical constants such as refractive index, dielectric constant, loss factor, and so on are calculated using the transmittance data. The PL spectra show both UV and visible emissions. Conclusion : Highly textured, transparent, luminescent Eu2O3 doped ZnO films have been synthesized using RF magnetron sputtering. The good optical and structural properties and intense luminescence in the ultraviolet and visible regions from the films suggest their suitability for optoelectronic applications.
氧化锌（ZnO）是一种宽带隙的直接带隙II-VI族氧化物半导体。ZnO在室温下具有较大的激子结合能，是获得各种稀土离子可见光和红外发射的良好基质材料。方法：采用射频（RF）磁控溅射在石英衬底上制备了掺杂浓度为0、0.5、1、3和5 wt%的氧化铕（Eu2O3）掺杂ZnO薄膜。薄膜在空气中于773 K温度下退火2小时。使用X射线衍射（XRD）、显微拉曼光谱、原子力显微镜、紫外（UV）-可见光谱和光致发光（PL）光谱对退火后的薄膜进行表征。结果：XRD图谱表明薄膜具有高度的c轴取向，呈现出ZnO的六方纤锌矿结构。使用德拜-谢乐公式计算粒径表明平均晶体尺寸在15-22 nm范围内，显示出薄膜的纳米结构性质。拉曼光谱中低频和高频E2模式的观察支持了薄膜中ZnO的六方纤锌矿结构。Eu2O3掺杂薄膜的表面形貌呈现出密集的晶粒分布。薄膜在可见光区域表现出良好的透明度。使用Tauc图模型评估薄膜的带隙。利用透射率数据计算诸如折射率、介电常数、损耗因子等光学常数。PL光谱显示出紫外和可见光发射。结论：利用RF磁控溅射合成了高度织构化、透明、发光的Eu2O3掺杂ZnO薄膜。薄膜良好的光学和结构性质以及紫外和可见光区域的强发光表明它们适用于光电子应用。
