Ultrasonic Microspectroscopy of LiTaO_3 Single Crystals for Optoelectronic Devices

超声微光谱技术，特别是利用线聚焦光束（LFB）声学显微镜系统，通过V (z)曲线分析来测量受水试样上激发的泄漏表面声波（LSAWs）的速度，是非常有用和独特的定量材料表征技术。该系统已应用于LiTaO_3晶体的科学和工业领域的材料问题，用于建立晶体生长条件和评价光子交换层和畴反转层等光电器件的制造工艺。建立了可靠的LFB系统，测量LSAW速度精度高，绝对精度在（]SY.+- .[）0.01%以内，相对精度在（]SY.+- .[）0.001%以内。用不同的li_2o_mol % （48,48.5, 49_mol %）组成生长的3个直径为3英寸的LiTaO_3晶体进行了速度测量。结果表明，随着Li_2O浓度的增加，X、Y、z切割面三个基本晶面上的速度和传播方向均单调增加，而相应的密度单调降低。将测量到的LSAW速度与测量到的居里温度、化学成分和密度进行了比较。结果表明，LFB系统在化学成分测定方面具有比差热分析（DTA）、x射线荧光分析（XRF）和电感耦合等离子体原子发射光谱法（ICP-AES）等传统方法更高的灵敏度和分辨率。利用LSAW速度分布评价了直径为4英寸的光学级同相LiTaO_3单晶的声均匀性。当晶体长度为60mm时，速度增加了0.45 m/s，对应的化学成分变化为+0.015 li22o -mol%。该系统已用于表征Z-cut LiTaO_3衬底上的质子交换层和畴反转层。结果表明，该系统能够分辨质子交换层1 nm的扩散深度变化和1 nm的畴反转层厚度变化。本文编制了上述层状结构中LSAW传播特性数值计算的计算机程序。少

Ultrasonic microspectroscopy technology, especially using the line-focus-beam (LFB) acoustic microscopy system, is very useful and unique for quantitative material characterization by measuring the velocity of leaky surface acoustic waves (LSAWs) , excited on the water-loaded specimen, through V (z) curve analysis. This system has been applied to material problems in the scientific and industrial fields of LiTaO_3 crystals for establishment of the crystal growth conditions and for evaluation of the optoelectronic device fabrication processes such as proton-exchanged and domain-inversion layrs.1.The reliable LFB system with high measurement accuracy in LSAW velocity has been established, resulting in the absolute accuracy within(]SY.+-。[)0.01% and the relative accuracy within(]SY.+-。[)0.001%.2.Three LiTaO_3 crystals of 3-inch-diameter, grown with the different compositions of the starting materials of 48,48.5,49 Li_2O-mol%, have been employed for velocity measurements. It has been shown … More that the velocities on the three basic crystal surfaces of X-, Y-, and Z-cut planes increase for all the surfaces and all the propagation directions monotonically as the Li_2O concentration increases, and the corresponding density decrease monotonically.3.The measured LSAW velocities have been compared with the measured, Curie temperatures, chemical composition, and densities. It has been shown that the LFB system has a much greater sensitivity and resolution in the determination of chemical composition than any other conventional methods such as differential thermal analysis (DTA) , X-ray fluorescence anlysis (XRF) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) .4.Acoustic homogeneity of an optical-grade congruent LiTaO_3 single crystal with 4-inch diameter has been evaluated by LSAW velocity distributions. The velocities have increased by 0.45 m/s, corresponding to the chemical composition change of +0.015 Li_2O-mol%, along the crystal length of 60mm.5.The system has been applied to characterization of proton-exchanged and domain-inverted layrs fabricated on Z-cut LiTaO_3 substrates. It has been demonstrated that the system has the capability to resolve the change of diffusion depth of 1 nm for the proton-exchanged layr and the change of the domain-inverted layr thickness of 1 nm.6.The computer program of numerical calculations of the LSAW propagation characteristics for the layred structures described above has been developed. Less