Quantitative Local Conductivity Imaging of Semiconductors Using Near-Field Optical Microscopy
Quantitative Local Conductivity Imaging of Semiconductors Using Near-Field Optical Microscopy
复制标题
DOI：
10.1021/acs.jpcc.1c10498
复制
发表时间：
2022-02
期刊：
影响因子：
--
通讯作者：
E. Ritchie;C. Casper;Taehyun A. Lee;J. Atkin
中科院分区：
文献类型：
--
作者：
E. Ritchie;C. Casper;Taehyun A. Lee;J. Atkin
我们展示了使用相位分辨红外 (IR) 散射型近场光学显微镜 (s-SNOM) 对局部电导率、自由载流子密度和迁移率进行非接触式纳米级测量。我们的方法通过结合分析和有限元方法来提取定量电导率信息，以预测特定样品几何形状的散射近场振幅和相位，而不依赖于体积迁移率假设或经验拟合参数。我们发现有限偶极子模型 (FDM) 高估了非平面或纳米结构材料中的预期近场振幅和相位，因此我们采用有限元建模来选择对 FDM 的适当修正并考虑样本几何形状。该模型使用硅校准样本进行验证，我们的结果返回基于编码的掺杂剂分布的预期自由载流子浓度。还发现迁移率和电导率与已建立的块体硅模型非常一致。这项工作展示了 IR s-SNOM 进行定量局部电导率测量的潜力，包括自由载流子密度和电子迁移率的分离，并且代表了朝着使用 s-SNOM 定量载流子分析和迁移率映射的目标迈出了一步。
We demonstrate contactless, nanoscale measurements of local conductivity, free carrier density, and mobility using phase-resolved infrared (IR) scattering-type near-field optical microscopy (s-SNOM). Our approach extracts quantitative conductivity information by combining analytical and finite-element methods to predict the scattered near-field amplitude and phase for specific sample geometries, without relying on bulk mobility assumptions or empirical fitting parameters. We find that the finite-dipole model (FDM) overestimates the expected near-field amplitude and phase in nonplanar or nanostructured materials, so we employ finite-element modeling to choose appropriate corrections to the FDM and account for sample geometry. The model is validated using a silicon calibration sample, and our results return the free carrier concentration expected based on the encoded dopant profile. Mobility and conductivity are also found to be in good agreement with established models for bulk silicon. This work demonstrates the potential of IR s-SNOM to perform quantitative local conductivity measurements, including the separation of free carrier density and electronic mobility, and represents a step toward the goal of quantitative carrier profiling and mobility mapping using s-SNOM.