Development of Brillouin scattering technique to characterize minute spatial distribution of elastic properties of thin films.

为了实现无损非接触布里渊散射测量技术表征薄膜弹性特性分布，在该程序的支持下进行了以下研究。将拉曼散射显微系统应用于该光学系统，实现了空间分辨率为10微米的测量。引入反射诱导θ A （RIGA）散射也使得同时测量高超声速纵向声子和剪切声子的光散射成为可能。未观察到激光照射对样品表面的降解。除了提高光子计数部分的信噪比外，我们还尝试利用样品中的诱导高超声速波来放大散射光强。特别是对热剪切声子的微弱光散射进行了放大。为此，我们利用磁控溅射技术在样品上制备了单轴取向ZnO多晶薄膜。我们成功地制造出谐振频率在几百兆赫左右的薄膜。利用该薄膜的高共振模式，成功地向样品发射了GHz范围内的剪切波。这些相干高超声速波在测量数据中表现为非常强烈的布里渊散射峰，显示出不对称光谱。密集峰缩短了观测样品散射所需的时间，提高了信噪比和测量精度。为了实现微观布里渊散射的自动测量，构建了样品架的自动位置控制系统。此外，显微系统中附带的CCD可以提供被测区域的光学显微图像信息。

In order to realize the non-destructive and non-contact Brillouin scattering measurement technique for the characterization of elastic property distribution in thin films, following studies were performed by the support of this program.The microscopic system for Raman scattering was applied to this optical system and realized the measurement with the spatial resolution of 10 micron meter. The introduction of Reflection Induced theta A (RIGA) scattering also enabled the simultaneous measurements of the light scatterings from hypersonic longitudinal and shear phonons. The degradation of sample surfaces by the laser irradiation was not observed.In addition to the improvement of signal to noise ratio at the photon counting part, we have tried to amplify the scattering light intensity making use of the induced hypersonic waves in the sample. Especially, we made effort to amplify the very weak light scattering from thermal shear phonons. For this purpose, we have fabricated the uniaxially oriented ZnO polycrystallites films on the sample by magnetron sputtering. We have then succeeded in fabricating the film whose resonant frequency is around several hundreds MHz. Making use of the higher resonance mode of this film, shear waves in the GHz range was successfully emitted to the samples. These coherent hypersonic waves were observed as a very intensive Brillouin scattering peak in the measured data, showing the asymmetric spectra. The intensive peak shortened the necessary time to observe the scattering in the sample and improved the signal to noise ratio and the measurement precision.For the automatic measurement of this microscopic Brilllouin scattering, the automatic position control system of the sample holder was constructed. In addition, the attached CCD in the microscopic system can give us the information of optical microscopic image of the measured area.