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首页> 外文期刊>Journal of physical chemistry letters >Mapping Carrier Dynamics on Material Surfaces in Space and Time using Scanning Ultrafast Electron Microscopy
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Mapping Carrier Dynamics on Material Surfaces in Space and Time using Scanning Ultrafast Electron Microscopy

机译：使用扫描超快电子显微镜在时空上映射材料表面上的载流子动力学

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Selectively capturing the ultrafast dynamics of charge carriers on materials surfaces and at interfaces is crucial to the design of solar cells and optoelectronic devices. Despite extensive research efforts over the past few decades, information and understanding about surface-dynamical processes, including carrier trapping and recombination remains extremely limited. A key challenge is to selectively map such dynamic processes, a capability that is hitherto impractical by time-resolved laser techniques, which are limited by the laser's relatively large penetration depth and consequently these techniques record mainly bulk information. Such surface dynamics can only be mapped in real space and time by applying four-dimensional (4D) scanning ultrafast electron microscopy (S-UEM), which records snapshots of materials surfaces with nanometer spatial and subpicosecond temporal resolutions. In this method, the secondary electron (SE) signal emitted from the sample's surface is extremely sensitive to the surface dynamics and is detected in real time. In several unique applications, we spatially and temporally visualize the SE energy gain and loss, the charge carrier dynamics on the surface of InGaN nanowires and CdSe single crystal and its powder film. We also discuss the mechanisms for the observed dynamics, which will be the foundation for future potential applications of S-UEM to a wide range of studies on material surfaces and device interfaces.
机译：选择性地捕捉材料表面和界面上的电荷载流子的超快动力学对太阳能电池和光电器件的设计至关重要。尽管在过去的几十年中进行了广泛的研究，但是关于表面动力学过程的信息和理解仍然非常有限，包括载流子的俘获和复合。一个关键的挑战是有选择地映射这样的动态过程，这是时间分辨激光技术迄今无法实现的功能，而时间分辨激光技术受到激光相对较大的穿透深度的限制，因此这些技术主要记录大量信息。这种表面动力学只能通过应用四维（4D）扫描超快电子显微镜（S-UEM）才能在真实的空间和时间中进行映射，该技术可记录具有纳米空间和亚皮秒时间分辨率的材料表面的快照。在这种方法中，从样品表面发出的二次电子（SE）信号对表面动力学极为敏感，并且可以实时检测到。在几个独特的应用中，我们在空间和时间上可视化SE能量的得失，损耗，InGaN纳米线和CdSe单晶及其粉末薄膜表面的电荷载流子动力学。我们还讨论了观察到的动力学的机制，这将成为S-UEM未来潜在应用到材料表面和设备界面的广泛研究的基础。

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