ZnGeP2晶体轴向成分均匀性的XPS分析

通过改进ZnGeP2晶体的合成和生长工艺,获得了尺寸为φ24 mm×60 mm的ZnGeP2单晶体.采用X射线光电子能谱(XPS)对生长出的晶体轴向成分进行了分析.结果表明,晶体在籽晶、放肩和主体部分成分一致,在尾部存在X射线衍射(XRD)未能检测出的极少量的P和Ge的氧化物,说明生长出的ZnGeP2单晶体的轴向成分比较均匀.红外透过率测试显示,晶体的轴向各部分在3 ～8 μm波长范围内透过率均在56;以上,而尾部在近红外波段(1.3～2.6 μm)的吸收明显要高于其他各部分.     

磷锗锌晶体的热处理研究

采用改进垂直布里奇曼法生长出的磷锗锌(ZnGeP2,ZGP)晶体中存在各种缺陷,导致其红外透过率较低,刚生长的晶体不能直接用于制备红外非线性光学器件.分别采用真空、同成分粉末包裹和真空-同成分粉末包裹的复合退火工艺对生长的ZGP晶体进行了退火热处理研究.应用傅立叶红外光谱仪(FTIR)、高阻仪(HRM)、X射线能谱仪(EDS)等对退火前后的晶体性能和成分进行了测试分析.结果表明,三种方法退火后晶体的红外透过率和电阻率都得到改善,其中复合退火工艺的改善效果最为显著,晶体红外透过率由41;提高到60;,电阻率由2.5×108 Ω·cm提高到7.2 ×108 Ω·cm,晶体成分接近ZGP理想化学配比,退火后晶体的光学和电学性能得到显著改善,可用于ZGP-OPO器件制作.     

红外非线性晶体ZnGeP2的生长及品质研究

采用高温元素反应法直接合成ZnGeP2多晶料,用竖式Bridgman法生长出ZnGeP2单晶,晶体棒毛坯尺寸达φ15×70mm3.对多晶料和单晶体进行了X射线粉末衍射(XRD)、低倍率红外显微镜、红外分光光度计检测;对晶体切片进行退火处理,使得在2μm吸收系数降到α＝0.10cm-1;加工出一块5×6×6.5mm3的晶体倍频元件,在一台射频激励CO2激光器上实现了从9.24μm到4.26μm的倍频.     

ZnGeP2单晶生长温场研究

根据ZnGeP2(ZGP)晶体的生长特性,自行设计组装了三段式独立控温生长炉,优化了温场分布.采用改进的垂直布里奇曼法成功生长出外观完整、无裂纹的ZGP单晶体,尺寸达15 mm×35 mm.对晶体进行解理实验和X射线衍射分析,发现ZGP晶体易沿(101)面解理,其回摆峰尖锐无劈裂.对未经退火处理的晶片进行红外透过率测试,在2～12 μm波段内红外透过率达45;以上.研究结果表明所设计的温场适合于ZGP单晶生长,生长出的ZGP晶体完整性好、质量较高.     

黄铜矿结构中红外高功率非线性光学晶体及其器件研究

本文论述了黄铜矿结构中红外高功率非线性光学晶体ZnGeP2、CdGeAs2和CdSiP2的研究进展。以高纯(6N)Ge、Si、Zn、Cd、P和As单质为原料,按化学计量比并富P 0.1～0.5%和适当富Cd和As配料,采用气相输运和熔体机械相结合的新方法,有效地克服了合成容器爆炸等问题,成功地合成出高纯单相的ZnGeP2和CdSiP2多晶材料;采用高温机械和温度振荡、以及快速降温法,有效地避免了杂相形成,合成出高纯单相的CdGeAs2多晶材料。采用改进的Bridgman法,生长出较大尺寸的ZnGeP2、CdGeAs2和CdSiP2单晶体,并制备出ZnGeP2光参量振荡器(ZGP-OPO)和CdGeAs2(CGA)倍频器件,采用2.1μm泵浦的ZGP-OPO获得3.5～5μm中红外激光调谐输出。结果表明:ZnGeP2、CdGeAs2和CdSiP2晶体,是中红外高功率激光频率转换最有前途的先进新材料。     

ZnGeP2单晶生长与安瓿设计研究

根据晶体自发成核几何淘汰规律,结合ZnGeP2晶体的结晶习性,研究设计出生长完整ZnGeP2单晶体的双层镀碳石英安瓿,其关键技术参数为:安瓿长径比6～7,籽晶袋长度≥25 mm,安瓿主体与籽晶袋之间的放肩角在25°左右.在上述生长安瓿中,采用改进的垂直布里奇曼法,分段控制下降速率,成功生长出尺寸为22 mm×40 mm的ZnGeP2单晶.对晶体进行X射线分析,获得(204)面单晶衍射谱和回摆谱,衍射峰峰形尖锐无劈裂,回摆谱对称性好,半峰宽为0.063 °;晶片在2～12 μm波段范围内的红外透过率达50;以上.实验结果表明,研究设计的生长安瓿适合于磷锗锌单晶生长,能够获得较高质量的单晶体.     

ZnGeP2晶体点缺陷影响光学性能的研究进展

ZnGeP2晶体具有非线性系数大和透光波段宽的特点,是目前重要的中红外频率转换介质材料。然而,点缺陷的存在却引起了ZnGeP2晶体的额外光学吸收,影响了其应用发展。本文对ZnGeP2晶体点缺陷影响光学性能的研究进展情况做了详细的综述。利用电子顺磁共振技术研究了ZnGeP2晶体中存在的点缺陷类型;结合光学吸收和电子顺磁共振方法分析了ZnGeP2晶体点缺陷影响光学性能的机理;介绍了降低ZnGeP2晶体额外光学吸收的方法;最后,展望了围绕ZnGeP2晶体点缺陷及光学性能将开展的研究方向。     

高能电子辐照和退火对磷锗锌晶体红外光学性质的影响

对采用改进的垂直布里奇曼法生长出的磷锗锌(ZnGeP2)单晶体样品,在300 K,10 MeV高能电子束下进行辐照实验,测试辐照前后其红外透过率.同时,对样品进行同成分粉末包裹退火处理,对比两种工艺对磷锗锌晶体红外透过率的影响.实验结果表明,退火和高能电子辐照都能对磷锗锌晶体的红外光学性质产生影响,提高其红外透过率.在本文的实验条件下,退火工艺对磷锗锌晶体红外透过率的提高更为明显.     

磷锗锌晶体器件定向加工研究

研究报道了坩埚下降法自发成核生长的ZnGeP2(ZGP)晶体光学器件定向加工新方法.即首先结合晶体的易解理面((112)面、(101)面)和标准极图以及X射线衍射仪,快速寻找c轴方向,确定晶体的(001)面;再由相位匹配角、方位角以及(101)和(102)晶面确定ZGP晶体的通光面,定向切割加工得到ZGP光参量振荡(OPO)器件初坯,经X射线衍射仪修正角度和后续抛光镀膜处理,制备出11 mm×11 mm×22 mm的ZGP-OPO器件.采用2.1μm、7 kHz激光泵浦ZGP-OPO,实现了3～5 μm中红外调谐激光输出,功率达0.48 W.此方法不仅适用于ZGP晶体的定向加工,也适用于具有类似结构的其他晶体器件定向加工.     

两温区气相输运和机械振荡合成ZnGeP2多晶材料

ZnGeP2多晶的合成是其单晶生长的前提和基础,多晶材料的质量是生长高质量单晶的关键.因此,要获得高质量的ZnGeP2单晶体,必须提供高质量的ZnGeP2多晶材料.对两温区气相输运机械振荡法合成ZnGeP2多晶材料的工艺进行了研究,利用高纯(6N)P、Ge、Zn单质为原料,采用两温区气相输运和机械振荡合成出了ZnGeP2多晶材料.合成出的多晶材料经比重测试和X射线粉末衍射测试证明与标准值一致.采用改进的布里奇曼法生长出外观完整、无裂纹的φ15 mm × 25 mm单晶体,在2.5～10 μm范围内红外透过率达50;以上.     

PVT法同质外延制备大尺寸Al极性氮化铝晶体生长工艺及其表征分析研究

本文基于自主设计的氮化铝生长炉,开展了四组不同工艺条件下Al极性面氮化铝籽晶同质外延生长氮化铝单晶的生长特征及其结晶质量表征研究。研究发现:不同工艺条件下生长的晶体的拉曼图谱E₂(high)特征峰峰位表明,晶体内部均存在较小的拉应力;在坩埚顶部在相对较高温度2 210 ℃、坩埚底部与顶部温差42 ℃的低过饱和度生长条件下,晶体表面光滑,呈现阶梯流生长形貌,并具有典型的氮化铝单晶生长习性面,晶体初始扩张角大于40°,高分辨率X射线衍射(HRXRD)测得0002、1012反射摇摆曲线及拉曼光谱检测结果表明,该条件下生长的氮化铝晶体结晶质量优异,并可实现快速扩径。基于该生长条件,通过外延生长后成功获得尺寸ϕ45~47 mm的氮化铝单晶锭,相关表征结果表明生长的氮化铝晶体具有优越的结晶性能。     

Estimation of growth rate in unidirectionally solidified multicrystalline silicon by the growth-induced striation method

Multicrystalline silicon was grown by unidirectional solidification method using the accelerated crucible rotation technique. The application of the accelerated crucible rotation technique in unidirectional solidification method induced growth striations across the axial direction of the grown crystal. This striation pattern was observed from carbon concentration distribution, obtained by using Fourier transform infrared spectroscopy. The generated striation pattern was found to be weak and discontinuous. Some striations were absent, probably due to back melting, caused during each crucible rotation. From the growth striations and applied time period in crucible rotation, the growth rate was estimated by using Fourier transformation analysis.     

无约束二次物理气相法CdSe单晶体的生长研究

在物理气相法的基础上,通过无约束二次气相输运法生长出具有自然显露面的尺寸约为6mm×7mm×2mmCdSe晶体.对生长晶体的结构、成分和形貌进行表征,测试发现:XRD粉末衍射图谱强度高无杂峰,CdSe晶体的3个自然显露面分别是(100)、(002)和(110)面,回摆曲线半峰宽度较小;ICP-MS结果显示样品中杂质含量有效降低;红外透过率测试结果显示无约束二次气相法生长的CdSe晶体红外透过率高;SEM观测发现其解理面呈阶梯状且台阶方向一致.结果表明,采用无约束二次气相法生长的CdSe晶体结晶质量较好,纯度高,红外透过率高,并根据BFDH模型分析CdSe晶体自然显露面出现的原因.     

Growth of dl-malic acid-doped ammonium dihydrogen phosphate crystal and its characterization

Single crystals of dl-malic acid-doped ammonium dihydrogen phosphate have been grown using slow evaporation method and also by Sankaranarayanan–Ramasamy (SR) method with the vision to improve the properties of the ADP crystals. The characterization of grown crystals was made by single-crystal X-ray diffraction, powder X-ray diffraction, UV–vis. spectroscopy, Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), Vicker's microhardness, dielectric measurements, high-resolution X-ray diffraction (HRXRD) and second-harmonic studies. Structural difference between pure and doped crystal has been studied by XRD analysis. Functional groups were identified by FTIR spectroscopy. The grown crystals were found to be transparent in the entire visible region. Decomposition temperatures of the grown crystals were measured by DTA. Vicker's hardness study carried out on (0 0 1) face at room temperature shows increased hardness of the doped crystals and SR-method-grown crystals. Dielectric measurements reveal that SR-method-grown DLM-doped ADP crystals have low dielectric loss. Crystalline perfection of the grown crystals is analyzed using HRXRD. Preliminary measurements indicate that the second harmonic generation efficiency of the doped crystals at a fundamental wavelength of 1064 nm is roughly 1.5 times greater than that of pure ADP.     

Inhomogeneity of composition in near‐stoichiometric LiNbO3 single crystal grown from Li rich melt

A near‐stoichiometric LiNbO₃ single crystal has been grown by the Czochralski technique from a melt of 58.5 mol% Li₂O. Its composition homogeneity was assessed by measuring the UV absorption edge. It was found that the maximum composition difference is about 0.03 mol% in the radial direction and 0.05 mol% in the axial direction. Differential scanning calorimetry (DSC) analysis was performed on the powder from the synthesized raw material and the frozen melt after crystal growth. The analytical results indicate that, during crystal growth, the magnitude of lithium volatilization from the melt surface is more than the degree of segregation from the crystal. The volatilized lithium diffuses into the crystal to compensate for the lithium segregation in the LiNbO₃ crystal. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nucleation, growth and characterization of L-tartaric acid—nicotinamide NLO crystals

The solubility, metastable zone width and nucleation parameters of organic nonlinear optical material L-tartaric acid–nicotinamide (LTN) have been determined. The crystals of LTN are grown by the slow cooling method. The grown crystals are morphologically interpreted. The crystalline powder of the grown crystals has been examined by X-ray diffraction and thermogravimetric analysis. The different modes of vibrations present in the crystal are identified by the Fourier infrared spectroscopy analysis. The powder SHG efficiency of LTN is comparable with that of KDP.     

Influence of growth conditions on microstructure and properties of GaSe crystals

GaSe crystals have been grown from melt. There are several reasons why it is difficult to meet ideal demands for nonlinear optic material, GaSe single crystal. First, these crystals have a tendency towards lamination because of great difference in a and c crystal lattice parameters and very weak Vander der Waals forces in c direction. Next, there is a great difference in saturation vapor pressure of the components, which can cause nonstoichiometry of a melt-grown crystal composition. Another obstacle in the growth of perfect GaSe crystals is dendrite formation caused by instability of the growth front. To overcome this obstacle we used Bridgman technique and have found the temperature and pressure conditions, and growth velocity which provide growth of perfect bulk single crystals of about 100 mm in length and 20 mm in diameter. Sharp Laue patterns and a rocking curve confirm perfect structure of the grown crystals. Electron-probe X-ray microanalysis shows stoichiometric composition of GaSe crystals and X-ray phase analysis reveals presence of single-phased hexagonal structure.     

提拉法生长镓酸锂晶体及缺陷研究

研究了提拉法生长的镓酸锂单晶的生长习性和结晶质量.晶体表面呈乳白色且表面粗糙.通过光学显微镜、四晶X射线衍射、透射光谱和电感耦合等离子体发射光谱对样品进行了表征,结果表明,在(001)面的抛光样品上存在三种缺陷: [110]和[-110]方向的十字线、[010]方向排列的气泡包裹物以及平行于(010)面的界面,界面的产生起因于(010)晶面的滑移;晶体的结晶质量从顶部到底部逐渐下降,这是由于在生长过程中氧化锂的挥发导致熔体成分偏离化学计量比造成的.     

Characterization of a newly synthesized organic nonlinear optical crystal: Urea ninhydrin monohydrate

Urea ninhydrin monohydrate (UNM) was synthesized and grown for the first time from aqueous solution employing the slow evaporation method. Single crystal structure was determined by X-ray diffraction data and it reveals that the crystal belongs to centrosymmetric with space group of P2₁/c. The grown crystals were characterized by thermogravimetric analysis (TGA), differential thermal analysis (DTA) and UV–vis–NIR spectroscopy. Preliminary Z-scan measurement indicates that nonlinear refractive index of this crystal is −4.1×10⁻⁸ cm²/W. The etching study was performed to assess the growth pattern of the crystal. Dielectric response of the crystal was analyzed for different frequencies and temperatures.     

熔盐法和水热法KTP晶体的晶胞参数及拉曼光谱特征

利用X射线衍射和显微激光拉曼光谱研究熔盐法自发结晶的KTP晶体、顶部籽晶熔盐法KTP晶体和水热法KTP晶体的晶胞参数和拉曼光谱特征,分析和比较不同方法生长的KTP晶体的晶体结构与化学键特征峰.研究表明:KTP晶体的晶胞参数与晶体生长方法有关,熔盐法自发结晶的KTP晶体生长过程中降温速率较快,晶胞体积相对较小;熔盐法和水热法KTP晶体中部分拉曼特征峰的位置因生长方法不同呈现一定的差异,水热法KTP晶体在782 cm-1、744 cm-1和515 cm-1处出现的特征峰可视为水热法KTP晶体的标志峰,借此可将其与熔盐法晶体相区分.