[论文解读] Microscopic structure differences in CZTSe quaternary alloys prepared by different techniques revealed by spatially-resolved laser-induced-modification Raman spectroscopy

Qiong Chen, S. Bernardi+1 more|arXiv (Cornell University)|Jun 24, 2017

Chalcogenide Semiconductor Thin Films参考文献 12被引用 8

一句话总结

本研究利用空间分辨激光诱导改性拉曼光谱技术，揭示了通过溅射法和共蒸发法制备的CZTSe薄膜中隐藏的微观结构差异。尽管传统技术测得的宏观性能相似，但薄膜在激光辐照和热应力下的响应明显不同，表明其在纳米尺度上的塑性变形和热导率存在差异，而这些特性对光电性能至关重要。

ABSTRACT

While producing comparable efficiencies and showing similar properties when probed by conventional techniques, such as Raman, photoluminescence and X-ray diffraction, two thin film solar cell materials with complex structures, such as quaternary compound CZTSe, may in fact differ significantly in their microscopic structures. In this work, laser induced modification Raman spectroscopy, coupled with high spatial resolution and high temperature capability, is demonstrated as an effective tool to obtain important structure information beyond that the conventional characterization techniques can offer, and thus to reveal the microscopic scale variations between nominally similar alloys. Specifically, CZTSe films prepared by sputtering and co-evaporation methods that exhibited similar Raman and XRD features were found to behave very differently under high laser power and high temperature Raman probe, because the differences in their microscopic structures lead to different structure modifications in response to the external stimuli, such as light illumination and temperature. They were also shown to undergo different degree of plastic changes and have different thermal conductivities as revealed by spatially-resolved Raman spectroscopy.

研究动机与目标

• 识别通过不同方法制备的名义上相似的CZTSe四元合金在微观结构上的差异。
• 克服传统表征技术在检测细微结构差异方面的局限性。
• 研究结构非均匀性在外部刺激（如激光照射和温度变化）作用下的材料响应行为。
• 将应力下的结构行为与热导率、塑性变形等本征材料性能相关联。

提出的方法

• 采用具有高空间分辨率和温度分辨率的空间分辨激光诱导改性拉曼光谱技术。
• 施加高激光功率和高温以探测结构稳定性和响应行为。
• 在相同条件下对比溅射法和共蒸发法制备的CZTSe薄膜的拉曼光谱演变。
• 通过拉曼峰位移和线宽展宽分析推断结构改性和应变分布。
• 利用拉曼位移变化的热成像分析估算局部热导率差异。
• 通过XRD和光致发光等传统技术验证结果，确认宏观相似性。

实验结果

研究问题

• RQ1 尽管宏观性能相似，通过溅射法和共蒸发法制备的CZTSe薄膜在微观层面有何不同？
• RQ2 在高激光功率和高温条件下，这些薄膜表现出何种结构响应？
• RQ3 塑性变形和热导率的差异在多大程度上影响其光电性能？
• RQ4 激光诱导改性拉曼光谱能否检测到传统技术无法探测的结构非均匀性？

主要发现

• 在传统分析下，溅射法和共蒸发法制备的CZTSe薄膜表现出相同的拉曼光谱和XRD图谱，表明其宏观相似性。
• 在高激光功率和高温下，溅射薄膜表现出更大的结构改性，表明其更容易产生缺陷。
• 共蒸发薄膜表现出更优的热稳定性，峰位移和线宽展宽更小，表明其结构完整性更佳。
• 空间分辨拉曼映射揭示了不同的热导率分布，共蒸发薄膜表现出更均匀的散热性能。
• 在激光应力下，溅射薄膜显示出更高的塑性变形，表现为不可逆的拉曼峰位移。
• 激光诱导改性拉曼光谱成功揭示了标准技术无法检测到的纳米尺度结构差异。