Characteristics and UV detectors applications of Co-doped ZnO nanostructures grown by PLD

• Main Authors: Tzu-Ching Hsu, 徐子清
• Other Authors: Ray-Hua Horng
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/23296172776232719537

碩士 === 國立中興大學 === 精密工程學系所 === 103 === In this research, the Co-doped ZnO (CZO) nanorod structures with the thickness around 1.5 m were grown on Si substrates by pulsed laser deposition (PLD) equipped with a KrF excimer laser. The target composition for the preparation of CZO nanorods was selected to Co0.05Zn0.95O. Moreover, the CZO nanorod structures were used for the photodetector applications. During the growth of CZO nanorod structures, the GaN and CZO thin films were employed as the seed layers, respectively. Additionally, the conditions consisting of substrate temperature, gas atmosphere, laser repetition rate, laser pulse and annealing treatment were modified to prepare various seed layers. There are ten seed layers deposited in this study. After growing the CZO nanorod structures on the seed layers, the structural, morphological, and magnetic characteristics of these CZO samples were investigated. Then, the CZO nanorod structures were used to fabricate the metal-semiconductor-metal (MSM) ultraviolet photodetectors, and the device performances were also analyzed. Based on the observations by transmission electron microscopy and the measurements by x-ray diffraction, it can be found that the crystal structure of CZO nanorods are belonged to polycrystalline and wurtzite structure. The wurtzite structure of CZO nanorod is the same with that of the conventional ZnO materials. This confirms that the crystal structure of CZO nanorod can''t be transformed by doping the Co element.The results of Raman measurements indicate that the Co elements are indeed doped into these nanorods. In addition, according to the results of magnetization versus magnetic field strength, it reveals that the saturation magnetization value of CZO nanorod structure is increased with increasing the substrate temperature. The maximum saturation magnetization value of CZO nanorod structure can reach to 2.5 × 10-5 emu. Furthermore, when the GaN seed layer was grown at the substrate temperature of 950 C without introducing any gas, the ultraviolet photodetector fabricated with the CZO nanorod structure possesses the optimum device performances. At a bias voltage of 5 V, the signal-to-noise ratio between the dark current and photocurrent of this photodetector is 1.44 × 103, while its responsivity is measured to be 1.18 × 104 A/W (at a wavelength of 380 nm).