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等领域有着重要的用途。大多数探测器都是基于半导体对红外光的吸收，而半导体反过来又会产生电流。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表明，红外探测器有望在广泛的波长范围内实现高灵敏度。这种现象被称为光热电效应，是一种材料在光和温度梯度下的电子反应。这一职业奖将促进对光电热电效应的基本理解，包括材料性质的潜在原因和影响。PI的团队将合成单晶膜和纳米材料，并通过一套先进的表征技术对其进行研究。该项目的目的是开发能够使探测器具有前所未有的感光性能和光谱响应的红外探测器的材料。该项目采取了多管齐下的教育努力，以满足美国半导体劳动力的需求。PI将开发培训模块和快速证书方案，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将以半导体技术为主题向K-12学生进行推广。技术上的光电热电现象来自不同的机制。虽然有些可以用经典的框架来描述，但其他的发生在远离均衡的地方，并且没有得到很好的理解。为了解决这一知识鸿沟，私营部门将制定战略和技术，将不同机制的贡献分开，以便对每种机制进行量化和解释。光子产生的载流子的漂移将使用改进的扫描光电显微镜进行检查。热载流子的贡献将通过瞬时光电热电电压测量来区分。材料性能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声子瓶颈导致的缓慢热载流子冷却的影响。缺陷的性质及其影响将使用一种改进的热电光谱技术进行研究。这些研究工作将得到泵浦-探测光谱学和同步加速器衍射和吸收的补充。这项研究将使基于光热电效应的红外传感设备的合理设计成为可能，其中不同的因素起到了建设性的作用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.