Ellipsometry Of Transparent Optoelectronic Materials

Spectroscopic Ellipsometry (SE) is an optical technique used for analysis andmetrology. It is based on the measurement of the variation of the polarization state ofthe light atfer reflection on a plane surface. Because of the Characteirstics of thenon-disturbance，non-destructive and high accuracy and sensitivity, ellipsometrytechniques have been widely used in the measurement of the physical properties ofmateirals，including thickness, refractive index n, extinction coeiffcient k，etc.This thesis gives a systematic review of the developments of SpectroscopicEllipsometry at home and abroad and also introduces the common types of ellipsometer.Moreover, the theory of Spectroscopic Ellipsometry on the isotropic interface andanisotropic interface is introduced. Then, we prepared neodymium-doped lithium borateglass and the Sr3NbGa3Si2〇i4(SNGS) crystal and studied their optical properties.Neodymium-doped lithium borate glass is a new kind of laser glass. The borateglasses have low threshold value, small thermal-expansion coefifcient and can besimply made into bulks with big size and good optical properties. First of all, weprepared neodymium-doped lithium borate glass; Second, the transmission spectrumand reflection spectrum of the lithium borate glass doped with Nd3+were measured as afunction of the wavelength at room temperature in the range190-850nm, usingTXJ-1901double beam UV-Vis spectrophotometer. The absorption spectrum of the glasswas calculated from the transmission spectrum and reflection spectrum. Finally, wemeasured the sample with the GES-5ellipsometer. The refractive indices n andextinction coeiffcient k were obtained by using the sotfware of GES-5ellipsometer. Bycomparing the absorption spectrum and n/k-curve? we can see that the peaks ofn/k-curve are the characteirstic absorption peaks of neodymium ion. Therefore, it willprovide us a new method to study the spectral properties of laser materials doped withrare earth ions.Sr3NbGa3Si20i4(SNGS) crystal are new piezoelectric crystals with orderedlangasite-structure in recent years. The SNGS crystal belongs to trigonal system and isisostructural compound of LGS(La3Ga5SiOu) crystal. The SNGS crystal with orderedlangasite structure was grown in the State Key Laboratory of Crystal Materials of Shandong University，using the Czochralski(CZ) method. The transmission spectraalong z-axis (optical axis) and x-axis of SNGS crystal were measured as at roomtemperature in the range190?3000nm，using Hitachi UV-VIS-NIR U-4100spectrophotometer. According to interfeirng theory of parallel polairzed light, thebirefringence of SNGS crystal was calculated through recording the interferencespectrum, using the measuring device of specific rotation which has applied for patentprotection. By analyzing the interference spectrum in the range680-780nm, thebirefringence of SNGS crystal is between0.089and0.096. In the SE measurement ofSNGS crystal, the optical axis lies perpendicular to the sample surface (and thereforeparallel to the plane of incidence). The angles of incidence we chose were70°and75°.The ellipsometric dates were measured as a function of the wavelength at roomtemperature in the range300-800nm, using a SOPRA GES-5SE instrument. In theprocess of date analysis, we focused on the influence of tiny extinction coeiffcients tothe refractive indices in the process of numerical inversion and drawn the conclusionthat the extinction coeiffcient could not be replaced by zero in the analysis oftransparent material. Further, we propose a relatively simple method to estimate theextinction coeiffcient. On that basis, we calculated the refractive index of SNGS crystaland analyzed the dates with Cauchy dispersion model, using MATLAB programming.