Optical parameters induced by phase transformation in RF magnetron sputtered TiO2 nanostructured thin films
Optical parameters induced by phase transformation in RF magnetron sputtered TiO2 nanostructured thin films
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射频磁控溅射 TiO2 纳米结构薄膜中相变引起的光学参数
DOI：
10.1016/j.pnsc.2014.05.010
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
P. Thomas
中科院分区：
文献类型：
--
作者：
Prabitha B Nair;V. B. Justinvictor;G. P. Daniel;K. Joy;K. Raju;D. Kumar;P. Thomas
采用射频磁控溅射法，在573 K的高温下，用陶瓷靶材在石英衬底上制备了纯TiO 2薄膜，并对薄膜的结构、光学和光致发光特性进行了分析。使用X-射线衍射的结构研究表明，沉积膜是非晶的性质。在873 K空气中热退火2 h，形成了金红石相，在1073 K时观察到了向金红石相的转变。在退火时也观察到晶粒尺寸的增加和结晶度的改善。在1273 K退火的薄膜的SEM图像中观察到棒状金红石微晶.沉积态薄膜和退火温度为1073 K的薄膜在可见光区具有较高的透明性，透明度> 80%。薄膜的光学带隙随退火温度的升高而减小，这是由于薄膜的相结构由非晶态转变为金红石型。随着退火温度的升高，薄膜的折射率、光学电导率和光学介电常数等光学参数均增大。由于金红石是光学活性相，在1073 K退火的薄膜的上级折射率沿着其在可见光区的高透明度表明该薄膜在减反射膜中的应用。在873 K退火的薄膜中观察到最大强度的光致发光发射，其表现出α相。在该膜中观察到的强烈蓝光发射使其适合用于光电显示器件。
Pure TiO2thin films were deposited onto quartz substrates using a ceramic TiO2target at an elevated substrate temperature of 573 K by RF magnetron sputtering, and an analysis of structural, optical and photoluminescence characteristics of the films upon phase transformation is reported in this paper. Structural investigations using X-ray diffraction revealed that the as-deposited film was amorphous in nature. Thermal annealing for 2 h at 873 K in air resulted in the formation of anatase phase, and a phase transformation to rutile was observed at 1073 K. An increase in grain size and an improvement in crystallinity were also observed on annealing. Rod- like rutile crystallites were observed in the SEM images of the film annealed at 1273 K. As-deposited films and films annealed up to 1073 K were highly transparent in the visible region with a transparency >80%. Optical band gap of the films decreased upon thermal annealing which is attributed to phase transformation from amorphous to anatase and then to rutile. Optical parameters such as refractive index, optical conductivity and optical dielectric constant increased with increase in annealing temperature. Since rutile is the optically active phase, the superior refractive index of the film annealed at 1073 K along with its high transparency in visible region suggests the application of this film in antireflective coatings. Photoluminescence emission of maximum intensity was observed for the film annealed at 873 K, which exhibits anatase phase. Intense blue emission observed in this film makes it suitable for use in optoelectronic display devices.