RUI: Time-Resolved Point Kelvin Probe Force Microscopy for Non-Traditional Semiconductors

非技术性描述：聚合物和量子点等非传统半导体为灵活、廉价的电子产品和新型设备提供了巨大的希望。 然而，由于它们的无序性质或对环境的敏感性，电荷在这些材料中移动的方式可能很复杂。 人们对这些材料及其界面上的电荷运动了解得越好，就越能为太阳能电池、高效照明和电子设备等应用设计出更好的材料。 鉴于其无序的性质，这些材料的完整表征必须以纳米级分辨率进行。 此外，有可能使用原子力显微镜--一种能够在纳米尺度上对材料进行成像的工具--来真实的实时地可视化通过这些材料的电荷运动。该项目利用原子力显微镜开发一种技术，用于精确探测各种非传统半导体中的电荷运动。 这种技术可以通过跟踪不同点处的实时电荷运动来响应变化的条件，从而深入了解材料行为。来自蒙特霍利奥克学院的女大学生参与了研究的各个部分。 女性在物理学和工程学领域的代表性严重不足，只有不到25%的学士学位授予了物理学领域的女性，而早期参与研究会鼓励女性坚持这一专业。 为了促进公众对科学的参与，PI组织并主持了每月一次的SciTech Café，向公众开放，参与者在非正式的环境中与研究人员讨论科学话题。 技术说明：该提案开发了一种扫描探针技术，该技术记录薄膜中的实时电荷运动以响应电场的变化，并将该技术应用于非传统半导体。 这些材料表现出复杂的传输行为，通常是由于它们对环境的无序或敏感性。 许多这些材料中的形态不均匀性和界面的重要性需要提供空间分辨率的表征工具，而对长时间尺度和短时间尺度的时间依赖性需要时间分辨率。 时间分辨点开尔文探针力显微镜记录的电位的薄膜在一个点，因为它演变的时间后，施加栅极电压，电荷被注入或提取的膜屏蔽栅极电位。 这种实时屏蔽行为允许表征载流子陷阱，这对于理解器件中的滞后以及预测和理解太阳能电池中的开路电压至关重要。 空间分辨率使得能够区分对所观察到的输运行为的贡献。 在研究胶体量子点薄膜和二硫化钼单层之前，研究表征良好的有机半导体用于验证该技术。 该项目在霍利奥克山学院进行，女本科生团体参与了研究的各个方面。 该项目还支持SciTech Café，该咖啡馆将科学家带入一个非正式的环境，与公众分享他们对工作的兴奋。 PI于2012年成立了SciTech Café，并继续组织和举办活动，每月吸引60 - 100人参加。

Nontechnical description: Non-traditional semiconductors such as polymers and quantum dots offer great promise for flexible and cheap electronics and novel devices. However, the way charges move through these materials can be complex due to their disordered nature or sensitivity to their environment. The better one understands charge motion in these materials and at their interfaces, the better one can devise materials for applications such as solar cells, efficient lighting and electronic devices. Given their disordered nature, full characterization of these materials must be done with nanoscale resolution. Furthermore, it is possible to use an atomic force microscope - a tool that enables imaging of materials on the nanoscale - to visualize charge motion through these materials in real time. This project harnesses an atomic force microscope to develop a technique for accurate probing of charge motion through a variety of non-traditional semiconductors. This technique can provide insights into material behavior by following real-time charge motion at different points in response to changing conditions. The female undergraduate students from Mount Holyoke College are involved in every part of the research. Women are severely underrepresented in physics and engineering - fewer than 25% of the bachelor's degrees are granted to women in physics - and early involvement in research encourages persistence in the major. To promote public engagement with science, the PI organizes and hosts a monthly SciTech Café open to the public, where participants discuss scientific topics with researchers in an informal setting. Technical description: This proposal develops a scanning probe technique that records real-time charge motion in thin films in response to a changing electric field, applying the technique to non-traditional semiconductors. These materials show complex transport behavior, often due to their disorder or sensitivity to the environment. The morphological non-uniformity within many of these materials and the importance of interfaces necessitates characterization tools that provide spatial resolution, while the time dependence on long and short timescales requires time resolution. Time-resolved point Kelvin probe force microscopy records the potential of the thin film at a point as it evolves in time after the application of a gate voltage, as charges are injected or extracted from the film to screen the gate potential. This real-time screening behavior permits characterization of the carrier traps, critical for understanding hysteresis in devices and in predicting and understanding open circuit voltage in solar cells. The spatial resolution enables discrimination among contributions to the observed transport behavior. Studying well characterized organic semiconductors is used to validate the technique before investigating colloidal quantum dot thin films and monolayers of molybdenum disulfide. The project is conducted at Mount Holyoke College, with the female undergraduate student body participating in all aspects of the research. The project also supports SciTech Café, which brings scientists into an informal setting to share their excitement about their work with the general public. The PI founded SciTech Café in 2012 and continues to organize and host the events, which draw 60 - 100 people each month.