硅酸盐学报

石英玻璃作为光电子领域的关键基础材料，其微观结构状态及分布对使用性能至关重要。通过对石英玻璃样品高温均化处理，利用拉曼光谱表征均化前后的结构变化，并借助主成分分析(PCA)进行数据分析。结果表明，均化前样品峰中心离散，表面结构不均一；均化后数据点分布集中，结构均一性增强，拉曼位移数据离散程度显著降低，各峰指标标准差减小，其中对D2峰相关指标影响最大。同时利用PCA算法进行数据降维可视化，对于峰中心及半峰宽的变化分析结果，在整个均化过程中，D2峰的变化是引导整个数据发生变化的主要因素。本工作揭示了均化工艺对材料热应力分布与微观结构的空间异质性调控机制，为获取准确物质结构和成分信息、优化材料性能提供了依据。

Introduction Quartz glass is a type of inorganic amorphous material prepared by ultra-clean high-temperature melting process with high-purity natural quartz or synthetic silicon compounds as raw materials,having an outstanding physical and chemical property.This material possesses superior optical performance,extreme thermal stability,ultra-low thermal conductivity,and superior dielectric properties.In the development of optoelectronic technology industry in China,quartz glass with its unique synergy of physical and chemical parameters becomes a strategic basic material in the field of optoelectronic devices.The feature size of devices is in a hundred-micron scale based on the iterative evolution of microelectromechanical systems and wafer-level packaging technologies,further demanding a deeper analysis of the surface structure of quartz glass.Methods The glass was firstly prepared in a deposition furnace,and then heated in a high-temperature homogenization furnace at 1800 ℃ for 2 h.Afterwards,the glass was cooled to room temperature and discharged.The glass before and after homogenization was cut and polished to obtain glass samples with the sizes of 200 mm×200 mm×5 mm.Starting from the first point position in the upper left corner,some points were taken at intervals of 20 mm in all the directions(i.e.,up,down,left,and right) for the analysis of Raman spectroscopy.In addition,the PCA algorithm was utilized for data dimensionality reduction and visualization,and the results of the changes in peak center and half-peak width were also analyzed.Results and discussion Before homogenization,the standard deviations of LO FWHM and D2 FWHM are 15.43 cm^-1 and 11.73cm^-1 respectively,which are relatively larger than those of other indicators.The fluctuation range of the two sets of data is also larger,with the mean values of 114.13 cm^-1 and 47.30 cm^-1,respectively.The standard deviation of D1 center is only 0.18 cm^-1,indicating that the data for this indicator are concentrated,with small differences between each data point.The difference between the maximum and minimum values is also similar.For instance,the maximum value of LO FWHM is 178.79 cm^-1 and the minimum value is100.28 cm^-1;the maximum value of D2 FWHM is 115.58 cm^-1 and the minimum value is 42.77 cm^-1.This further indicates that the dispersion before homogenization of the two sets of data is large.After homogenization,the standard deviation of D2 center is 0.39 cm^-1,which is decreased by 79%,compared to that before homogenization.The standard deviation of D2 FWHM is 0.82 cm^-1,which is decreased by 93%,compared to that before homogenization.The standard deviation of LO FWHM is 8.03 cm^-1,which is decreased by 48%,compared to that before homogenization.The data fluctuations between different positions significantly reduce,and the standard deviation statistics for each indicator also show a certain degree of reduction.Among them,the influence of D2 peak is dominant,and the influence of D1 peak is subordinate.The D1 peak and D2 peak are respectively related to the tetra-siloxane ring and tri-siloxane ring in the structure.This indicates that on the same sample surface,the homogenization process has a dominant impact on the tri-siloxane ring in the silicon-oxygen structure.The tri-siloxane ring is expected in quartz glass because their Si—O—Si angle is less than the lowest energy(most likely) angle in the glass.The estimation of the energy required to generate such rings is more likely to reach the distribution of the D2 tri-siloxane ring.Also,the silicon—oxygen bond angles of all rings tend to be averaged,and the overall is more normalized.Conclusions The Raman spectroscopy could precisely characterize the microscopic structural differences of quartz glass before and after homogenization via detecting the vibration modes of atoms in the silicon-oxygen network(i.e.,Si—O—Si bond angles and ring structure defects).For the analysis of structural uniformity,some parameters such as peak center dispersion and half-width were used to quantify the structural uniformity of the glass surface and bulk phase,and to identify high-strain areas(i.e.,the regions with concentrated trimer ring defects).In the study of defect mechanisms,the D1 peak(tetramer ring) and D2 peak(trimer ring) defect characteristic peaks were utilized to reveal the migration and recombination laws of defects during homogenization,and to clarify the influence of thermal stress release on structural relaxation.Finally,combined with the data mining technology of the PCA algorithm,a correlation between the Raman parameters and homogenization processes was established,thus providing a theoretical support for precisely regulating the microscopic structure of quartz glass.