Aspnes D E, Studna A A
Bell Laboratories, Murray Hill, NJ 07974, USA.
Rev Sci Instrum. 1978 Mar;49(3):291. doi: 10.1063/1.1135394.
We describe simple modifications to photometric polarimeter and ellipsometer systems that greatly reduce nonlinearity, component drift, and digital noise effects. A photomultiplier feedback circuit is described and analyzed that varies the effective system linearity by means of a single control. Linearity to 5 x 10(-4) over more than three orders of magnitude of incident light intensity is obtained. Effective double-beam stability to 5 x 10(-5) is achieved by blocking the source intensity over part of an extended measurement cycle. These refinements permit photometric instruments to approach accuracy capabilities compatible with their precision capabilities, and also allow measurements to be made in the presence of ambient scattered light, at high sample temperatures, or using solid-state detectors for which the zero reference is not well defined. As an example, we give the dielectric function of Ge measured from 1.5 to 5.8 eV at a sample temperature of 800 degrees C.
我们描述了对光度计偏振计和椭偏仪系统的简单改进，这些改进极大地降低了非线性、组件漂移和数字噪声效应。描述并分析了一种光电倍增管反馈电路，该电路通过单一控制来改变有效系统线性度。在超过三个数量级的入射光强度范围内实现了高达5×10⁻⁴ 的线性度。通过在延长的测量周期的部分时间内阻挡光源强度，实现了高达5×10⁻⁵ 的有效双光束稳定性。这些改进使光度计能够达到与其精度能力相匹配的准确度，并且还允许在存在环境散射光、高样品温度或使用零参考定义不明确的固态探测器的情况下进行测量。例如，我们给出了在800摄氏度的样品温度下从1.5到5.8电子伏特测量的锗的介电函数。
