Observation of Switchable Photoresponse of a Monolayer WSe2-MoS2 Lateral Heterostructure via Photocurrent Spectral Atomic Force Microscopic Imaging
Observation of Switchable Photoresponse of a Monolayer WSe2-MoS2 Lateral Heterostructure via Photocurrent Spectral Atomic Force Microscopic Imaging
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DOI：
10.1021/acs.nanolett.6b00699
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发表时间：
2016-06-01
期刊：
影响因子：
10.8
通讯作者：
Strano, Michael S.
中科院分区：
文献类型：
--
作者：
Son, Youngwoo;Li, Ming-Yang;Strano, Michael S.
在追求石墨烯之外的二维（2D）材料的过程中，在探索过渡金属二硫属化物（TMDC）的令人兴奋和有用的特性方面取得了巨大的进展，例如可见光范围内的永久带隙和由于2D量子限制而从间接带隙到直接带隙的转变，以及它们在广泛的器件应用中的潜力。特别地，最近在通过化学气相沉积方法合成不同TMDC的无缝单层横向异质结构方面的成功已经提供了产生面内pn结的有效解决方案，面内pn结是电子和光电器件应用中的关键部件。然而，在整个均匀的合成异质结晶体的电子和光电子性质的空间变化，以及横向结区域和电荷载流子传输行为在其纳米级结与金属仍然没有解决。在这项工作中，我们使用光电流光谱原子力显微镜图像之间产生的电流和光电流偏置PtIr尖端和单层WSe 2 MoS 2横向异质结构。在黑暗中，在正向和反向偏置的电流测量揭示了相反的特性二极管的行为WSe 2和MoS 2，由于形成的肖特基势垒的不同属性。值得注意的是，通过改变所施加的尖端电压的极性和幅度，观察到显示异质结构的光响应的像素被选择性地接通和关断，从而允许实现可切换光电二极管像素的超分辨率阵列。这种实验方法对发展新的光电技术，区域选择性的光电探测和成像在纳米级分辨率具有重要意义。物理高度和电流图像的比较2D傅立叶分析示出了基板/MoS 2（或WSe 2）接触中的高空间频率变化，其超过了由下面的基板施加的频率。这些结果应该提供重要的见解，在设计和理解的电子和光电器件的基础上量子限制原子薄的二维横向异质结构。
In the pursuit of two-dimensional (2D) materials beyond graphene, enormous advances have been made in exploring the exciting and useful properties of transition metal dichalcogenides (TMDCs), such as a permanent band gap in the visible range and the transition from indirect to direct band gap due to 2D quantum confinement, and their potential for a wide range of device applications. In particular, recent success in the synthesis of seamless monolayer lateral heterostructures of different TMDCs via chemical vapor deposition methods has provided an effective solution to producing an in-plane pn junction, which is a critical component in electronic and optoelectronic device applications. However, spatial variation of the electronic and optoelectonic properties of the synthesized heterojunction crystals throughout the homogeneous as well as the lateral junction region and the charge carrier transport behavior at their nanoscale junctions with metals remain unaddressed. In this work, we use photocurrent spectral atomic force microscopy to image the current and photocurrent generated between a biased PtIr tip and a monolayer WSe2MoS2 lateral heterostructure. Current measurements in the dark in both forward and reverse bias reveal an opposite characteristic diode behavior for WSe2 and MoS2, owing to the formation of a Schottky barrier of dissimilar properties. Notably, by changing the polarity and magnitude of the tip voltage applied, pixels that show the photoresponse of the heterostructure are observed to be selectively switched on and off, allowing for the realization of a hyper-resolution array of the switchable photodiode pixels. This experimental approach has significant implications toward the development of novel optoelectronic technologies for regioselective photodetection and imaging at nanoscale resolutions. Comparative 2D Fourier analysis of physical height and current images shows high spatial frequency variations in substrate/MoS2 (or WSe2) contact that exceed the frequencies imposed by the underlying substrates. These results should provide important insights in the design and understanding of electronic and optoelectronic devices based on quantum confined atomically thin 2D lateral heterostructures.