Chen Baojun

XPS Analysis and Determination of Surface Damage Layer of CdGeAs2 Single Crystal

Abstract An integral CdGeAs 2 (CGA) single crystal with the size of Φ15 mm×45 mm was obtained by the modified Bridgman method. For the reasonable application of the CGA crystal, different polishing techniques have been employed in this work. The as-grown ingot was cut and wafers with (101) plane were mechanically polished by means of metallographic abrasive papers. Then the surface element composition and valences of (101) plane on the CGA crystal were analyzed by the X-ray photoelectron spectroscopy (XPS). Finally, the wafers were chemically polished by a bromine-methanol corrosive solution. The samples chemically polished for different time were studied by X-ray diffraction (XRD) and optical microscopy. It is found that after etching by bromine-methanol solution for 50 s at room temperature, the CdGeAs 2 wafer has no scratch marks, and possesses a narrow full width at half maximum (FWHM). Meanwhile, the thickness of the surface damage layer of CdGeAs 2 wafer was also calculated.

Differential Thermal Analysis and Crystal Growth of CdSiP2

Thermal properties of CdSiP2 polycrystalline were studied by differential thermal analysis (DTA) technique with a quartz capillary column. It is found that the melting point and crystallization temperature of CdSiP2 are 1139 and 1126 °C, respectively, and the supercooling degree of CdSiP2 melt is evaluated to be 13 °C. According to the results of DTA, the structure of a furnace and the temperature profile of the crystal growth for CdSiP2 were optimized. A crack-free CdSiP2 crystal with 15 mm in diameter and 40 mm in length was grown by the modified vertical Bridgman (VB) method. The X-ray diffractionmeter (XRD), X-ray energy dispersive microanalysis (EDX) and infrared spectrophotometer (IR) were employed to characterize the properties of as-grown crystal. A new cleavage face of (112) was identified in XRD spectrum. The results of EDX indicate that the crystal is of good stoichiometry. The infrared transmission is up to 55% in the infrared region from 7000 to 1500 cm−1. All the characterization results show that the obtained crystal is integrated in structure and good in optical quality which can be used in devices fabrication.

Growth and Characterizations of ZnGeP2 Crystal by a Vertical Bridgman Method

Abstract ZnGeP 2 (ZGP) single crystal with size of 24 mm in diameter and 70 mm in length was grown by a modified vertical Bridgman (VB) method in a three-zone furnace. The crystal was annealed in ZnGeP 2 powder at 600 °C for 500 h. X-ray diffraction (XRD), X-ray fluorescence (XRF) and Fourier transform infrared spectrophotometry (FTIR) were employed to characterize its properties. A ZGP optical parametric oscillator (ZGP-OPO) device was fabricated from the annealed sample. Laser experiment was carried out on the device. Tunable mid-infrared laser in the range of 3∼5 μm was realized on the ZGP-OPO pumped by 2.1 μm, 7 kHz laser. All the results indicate that our grown crystal is in good quality and can be used for nonlinear optical applications.