Structural, morphological and photoluminescent properties of annealed ZnO thin layers obtained by the rapid sol-gel spin-coating method

ZnO thin layers were deposited on p-type silicon substrates by the sol-gel spin-coating method and, then, annealed at various temperatures in the range of 573-873 K. Photoluminescence was carried out in the temperature range of 20-300 K. All samples showed two dominant peaks that have UV emissions from 300 nm to 400 nm and visible emissions from 400 nm to 800 nm. Influence of temperature on morphology and chemical composition of fabricated thin layers was examined by XRD, SEM, FTIR, and Raman spectroscopy. These measurements indicate that ZnO structure is obtained for samples annealed at temperatures above 573 K. It means that below this temperature, the obtained thin films are not pure zinc oxide. Thus, annealing temperature significantly affected crystallinity of the thin films

Evaluation of elastic properties of Cd(x)Zn(1-x)Te crystals by picosecond laser ultrasonic techniques

International audienceCd(x)Zn(1-x)Te is a popular material for the production of radiation detectors and solar cells. Therefore, the investigation of its homogeneity and elastic parameters by various techniques is very important. Non-destructive contactless picosecond laser ultrasonics [1] provides very promising opportunities for the evaluation of the elastic properties of the materials absorbing light. We apply this technique to the study of Cd(x)Zn(1-x)Te crystals in the form of 8 mm-diameter discs of 1 mm thickness using classical pump-probe experimental set-up based on Tsunami femtosecond laser and delay line with moving retro-reflector. Typical signal of this set-up, in the case of normal incidence of probe beam, includes so-called Brillouin oscillations with a frequency <i>f</i><sub>B</sub>=2<i>nv</i>/λ, determined by the index of refraction <i>n</i>(λ) of media under study, the sound velocity <i>v</i> in it and the wavelength of probe light λ. To evaluate the elastic properties of Cd(x)Zn(1-x)Te crystals from <i>f</i><sub>B</sub>, we used the data on the index of refraction from [2]. Our studies have been performed for the parameter 1-x of Zn composition , ranging from 0 to 1. The value of the longitudinal sound velocity in the direction perpendicular to the surface of sample was obtained as a function of 1-x. We have realized a preliminary comparison of obtained sound velocities with their available theoretical evaluation [3], which should be improved after the determination of crystalline orientations of our Cd(x)Zn(1-x)Te samples. This work has been supported by the project of the international exchanges PHC Polonium 44991PL. [1] H. Grahn, H. Maris, J. Tauc, IEEE J. Quantum Electron. 25, 2562 (1989). [2] A.E. Merad, H. Aourag, B. Khelifa, C. Mathieu, G. Merad, Superlatt. Microstruct. 29, 241 (2001). [3] N. Korozlu, K. Colakoglu, E. Deligoz, J. Phys.: Condens. Matter 21, 175406 (2009)

Evaluation of elastic properties of Cd(x)Zn(1-x)Te crystals by picosecond laser ultrasonic techniques

International audienceCd(x)Zn(1-x)Te is a popular material for the production of radiation detectors and solar cells. Therefore, the investigation of its homogeneity and elastic parameters by various techniques is very important. Non-destructive contactless picosecond laser ultrasonics [1] provides very promising opportunities for the evaluation of the elastic properties of the materials absorbing light. We apply this technique to the study of Cd(x)Zn(1-x)Te crystals in the form of 8 mm-diameter discs of 1 mm thickness using classical pump-probe experimental set-up based on Tsunami femtosecond laser and delay line with moving retro-reflector. Typical signal of this set-up, in the case of normal incidence of probe beam, includes so-called Brillouin oscillations with a frequency <i>f</i><sub>B</sub>=2<i>nv</i>/λ, determined by the index of refraction <i>n</i>(λ) of media under study, the sound velocity <i>v</i> in it and the wavelength of probe light λ. To evaluate the elastic properties of Cd(x)Zn(1-x)Te crystals from <i>f</i><sub>B</sub>, we used the data on the index of refraction from [2]. Our studies have been performed for the parameter 1-x of Zn composition , ranging from 0 to 1. The value of the longitudinal sound velocity in the direction perpendicular to the surface of sample was obtained as a function of 1-x. We have realized a preliminary comparison of obtained sound velocities with their available theoretical evaluation [3], which should be improved after the determination of crystalline orientations of our Cd(x)Zn(1-x)Te samples. This work has been supported by the project of the international exchanges PHC Polonium 44991PL. [1] H. Grahn, H. Maris, J. Tauc, IEEE J. Quantum Electron. 25, 2562 (1989). [2] A.E. Merad, H. Aourag, B. Khelifa, C. Mathieu, G. Merad, Superlatt. Microstruct. 29, 241 (2001). [3] N. Korozlu, K. Colakoglu, E. Deligoz, J. Phys.: Condens. Matter 21, 175406 (2009)