CAREER: Understanding Photo-thermoelectric Phenomena in Bulk and Nanomaterials for Better Optical Sensing

非技术红外探测器在工业、农业、医疗保健和国家安全方面有着重要的用途。大多数探测器都是基于半导体对红外光的吸收，从而产生电流。然而，随着波长的增加，它们的灵敏度降低，噪声增加。另一种涉及光和热的不同现象显示了在宽波长范围内具有高灵敏度的红外探测器的前景。这种现象被称为光热电效应，是材料暴露于光和温度梯度时的电子响应。该职业奖将促进对光热电效应的基本理解，包括材料特性的潜在原因和影响。PI的团队将合成单晶薄膜和纳米材料，并通过一系列先进的表征技术对它们进行研究。该项目的目的是开发材料，使红外探测器具有前所未有的光敏性能和光谱响应。该项目有多管齐下的教育努力，以满足国家半导体劳动力的需求。PI将开发培训模块和快速证书课程，并探索以解决问题为重点的课程改革。本科生将参与研究，PI将参与到以半导体技术为主题的K-12学生的推广活动中。技术：光热电现象是由多种机制引起的。虽然有些可以用经典框架来描述，但其他的则远离平衡状态，并且不能很好地理解。为了解决这一知识差距，PI将制定战略和技术，以区分来自不同机制的贡献，允许对每种机制进行量化和解释。将使用改进的扫描光电流显微镜检查光子产生的载流子的漂移。热载流子的贡献将通过瞬态光热电电压测量来区分。材料性质的影响将以硫化铅为原型进行研究，比较单晶薄膜和纳米粒子组件对由声子瓶颈引起的慢热载流子冷却感兴趣。缺陷的性质及其影响将使用改进的热电光谱技术进行研究。这些研究工作将由泵浦探测光谱、同步加速器衍射和吸收来补充。本研究将使基于不同因素共同作用的光热电效应的红外传感器件的合理设计成为可能。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NontechnicalInfrared detectors have important uses in industry, agriculture, healthcare, and national security. Most detectors are based on absorption of infrared light by a semiconductor that in turn generates an electrical current. However, their sensitivity decreases, and the noise increases, as the wavelength increases. A different phenomenon involving both light and heat shows promise for infrared detectors with high sensitivity across a wide range of wavelengths. This phenomenon, called the photo-thermoelectric effect, is the electronic response of a material when exposed to both light and a temperature gradient. This CAREER award will advance the fundamental understanding of the photo-thermoelectric effect, including underlying causes and impact of materials properties. The PI’s team will synthesize single crystal films and nanomaterials and study them by a suite of advanced characterization techniques. The aim of this project is to develop materials that would enable infrared of detectors with unprecedented light-sensing performance and spectral response. The project has a multi-pronged educational effort to address the nation’s semiconductor workforce needs. The PI will develop training modules and rapid certificate programs and explore curriculum reform focused on problem-solving. Undergraduate students will participate in research and the PI will engage in outreach to K-12 students themed in semiconductor technology.TechnicalPhoto-thermoelectric phenomena arise from varied mechanisms. While some can be described with classic frameworks, others occur far from equilibrium and are not well understood. In order to address this knowledge gap, the PI will develop strategies and techniques to separate contributions from different mechanisms, allowing for the quantification and interpretation of each. The drift of photon-generated carriers will be examined using modified scanning photocurrent microscopy. Contributions from hot carriers will be distinguished using transient photo-thermoelectric voltage measurements. The influence of materials properties will be studied using lead sulfide as an archetype, comparing single crystalline thin films with nanoparticles assemblies of interest for slow hot carrier cooling caused by phonon bottlenecks. The nature of defects and their influence will be studied using a modified thermoelectric spectroscopy technique. These research efforts will be complemented by pump-probe spectroscopy, and synchrotron diffraction and absorption. This research will enable rational design of infrared sensing devices based on photo-thermoelectric effects where different factors constructively contribute.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.