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Phosphorus zinc germanium infrared crystal growth and properties of

Author: LinYanZuo
Tutor: LiuHong；GuQingTian
School: Shandong University
Course: Materials Science
Keywords: Phosphorus zinc germanium crystals Polycrystalline material synthesis Crystal growth Defect characterization Crystal orientation Thermal properties Optical Properties
CLC: O782
Type: Master's thesis
Year: 2006
Downloads: 79
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Abstract


Continuously adjustable mid-infrared laser light source in the military field, such as: infrared-guided laser directed infrared jamming, laser communications, infrared remote sensing, infrared camera, infrared range, laser targeting, as well as in civilian areas, such as: environmental protection, biology, medicine, and other aspects have a wide range of applications. At present, the use of infrared crystal mixer such as of ZnGeP 2 , CdSe, AgGaS 2 , AgGaSe 2 , CdGeAs 2 and frequency difference frequency, optical parametric oscillation, optical parametric resonance nonlinear optical effects on the existing wavelength laser frequency conversion is an important means of mid-infrared laser output. The nonlinear optical crystal growth and mid-infrared laser output key. Zinc Germanium Phosphide (ZnGeP 2 ) crystal is considered to be the best infrared nonlinear optical crystal one. Zinc Germanium Phosphide (ZnGeP 2 ) crystal has a large nonlinear optical coefficient; has good permeability and wide through the band in the infrared region; suitable birefringent phase matching, easy to implement ; thermal conductivity, thermal lens effect; stable physical and chemical properties, not easy to deliquescence, excellent mechanical properties, easy processing characteristics. In the country in a foreign country, through decades of research, design and control of the growth process, and annealed using the Bridgman method can get good quality, big size zinc germanium phosphide single crystal; phosphorus zinc germanium crystal growth and the nature of the research is still at a preliminary stage. Due to the special military use of phosphorus zinc germanium crystal, foreign phosphorus zinc germanium crystal growth process has been shrouded in secrecy. Currently, only Russia, the United States can provide a small amount of zinc germanium phosphide single crystal, and the price is very expensive. Therefore, this thesis ZnGeP 2 polycrystalline material synthesis, crystal growth, structure, defects and their basic properties, including the following aspects of work: First, the synthesis of polycrystalline material due to more volatile phosphorus and zinc, phosphorus in the synthesis process can produce a large vapor pressure, we weighed in accordance with the stoichiometric ratio of the reaction raw material case, the purity of 5N as red phosphorus, germanium and zinc simple substance through direct combination reaction successfully synthesized ZnGeP 2 polycrystalline material. We analyzed the chemical composition of the synthetic product; synthetic ZnGeP 2 in the process of polycrystalline material need to pay attention to several issues, including the design of a suitable the synthesis furnace temperature field; safe reaction raw material ratio; appropriate starting materials the reaction time and temperature control; maximize the degree of vacuum inside the quartz tube; use of good quality, suitable for the thickness of the quartz tube. Second, crystal growth using the Bridgman method, successfully grown under conditions of spontaneous nucleation ZnGeP 2 single crystal. Because the crystal growth is a complex physical - chemical processes, we combine the thermodynamics and kinetics of crystal growth system to discuss the main factors to affect the crystal growth and crystal quality. Including the establishment of appropriate control of the growth process parameters with the design reasonable growth temperature field;: using appropriately shaped quartz crucible, control crystal nucleation and the geometry of the seed eliminated. The causes and impact characteristics of the different factors at the same time, the corresponding solutions. Third, crystal composition, structure and defects using X-ray fluorescence analysis and electron spectroscopy analysis were used to measure the concentration of ZnGeP 2 crystal component elements. The measurement results show that the analysis results obtained by the different analytical methods vary, which is mainly caused different characteristics of the sample preparation and analytical methods. The measurement results show that the growth of ZnGeP deviated from the stoichiometric ratio ZnGeP 2 2 single crystal to a certain extent. Growth ZnGeP 2 crystal structure using X-ray powder diffraction (XRD) and four-circle diffractometer. According to the X-ray powder diffraction to determine the growth of ZnGeP 2 crystals belong to the tetragonal space group I42d, cell parameters alpha = beta = gamma = 90 °, a = b = 5.4661 A, c = 10.7031 A; according to the results of the four-circle diffractometer, also determine the growth ZnGeP 2 crystals belong to the tetragonal space group I42d, cell parameters alpha = beta = gamma = 90 °, a = b = 5.4624A, c = 10.7030A. Both the analysis result is almost the same. Chemical etching and high-resolution X-ray diffraction ZnGeP 2 crystal defects were observed, combined with the crystal growth of defect formation mechanism, which provides a basis for the growth of high-quality crystal. A major drawback in the ZnGeP 2 crystal dislocations and grain boundaries. The presence of these defects affect the integrity of the crystal lattice. Exist in ZnGeP 2 crystal defects inclusions bubbles. Fourth, the crystal orientation with the processing and utilization of the X-ray direction finder as well as high resolution X-ray diffractometer to determine the direction of the crystal, the use of the number of times of the crystal obtained in the orientation process, we conclude that spontaneous nucleation and growth of the resulting ZnGeP 2 crystal growth direction substantially along the c-axis growth of the crystal easy cross-sectional view along the growth direction of the fracture, the fracture surface (116) angled. We have successfully determined the crystal a, b, c three crystal axes directions. , The basic nature of the crystal was measured ZnGeP 2 crystal density, hardness and thermal properties, and discusses the of these basic nature of the crystal growth and application. Buoyancy method measured ZnGeP 2 crystal density 4.169g · cm -3 . ZnGeP 2 crystal Mohs hardness of about 6.5. DTA and TG curves of the ZnGeP 2 crystal. More important peak in the DTA curve analysis, TG curve to explain the reasons for weight gain phenomenon. 2 crystal ZnGeP specific heat in the temperature range of 329K.15 ~ 866.15K as 0.54 J · g -1 K -1 ~~ 0.71 J · g -1 · K -1 . Dilatometer measurement in 98.15K ~ 764.15K temperature range within ZnGeP 2 crystal thermal expansion coefficient of the master values ??respectively to alpha a = 2.4138 × 10 -6 / K, α c = 4.1706 × 10 -6 / K. Discussed the impact of the thermal properties of the ZnGeP 2 crystal growth and application. UV - visible spectrophotometer and Fourier transform infrared spectrophotometer measured ZnGeP 2 crystal at room temperature transmission spectrum. The experimental results show that the transmittance of the ZnGeP 2 crystal band 1800nm ??~ 11947nm, covering the near-infrared and mid-infrared, it can be implemented in a wide range of wavelengths continuously tunable mid-infrared laser output. The lower the transmittance of the crystal, the absorption coefficient is larger, therefore need to further improve the crystal quality to improve the processing of the crystals.

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