二维过渡金属硫族化合物材料的制备及光电器件研究

Research on preparation and photoelectoelectric device of two-dimensional transition metal dichalcogenide material

黄锐

11749037

硕士

物理学

张立源

2019-05-14

2018-07-11

哈尔滨工业大学

深圳

自2004 年发现石墨烯以来，研究者陆续发展了许多新的二维材料成员，譬如二维过渡金属硫族化合物（TMDCs）。TMDCs 具有独特的物理、光电性能且种类丰富，使它们非常适合用于光电子器件的研究。而且，不同种类的TMDCs 可以通过范德华（vdW）力逐层堆叠以形成二维异质结。这样不仅绕过了传统半导体异质结外延时的晶格匹配困难，而且还提供了设计可以超越其传统半导体带隙限制的新型光电子器件的方案。尽管如此，在多种类、高质量、大面积的二维TMDCs薄膜的可控合成方面，还存在严峻挑战。此外，单一的二维材料光电探测器存在或探测波段窄、或响应时间较长、或探测率低等缺点。而大多数报道的vdW p−n结器件主要在可见光谱中工作，且光响应度比较小。因此，通过设计具有超出可见光谱的光活性2D 层的vdW p−n 结并在宽光谱范围内实现优越的综合性能光探测越来越受到研究者们的关注。为克服这些挑战，本课题首先探索化学气相沉积（CVD）法制备几种常见的二元TMDCs 和三元TMDCs 薄膜材料，然后尝试制备出一种综合性能优异的二维TMDCs 垂直异质结构光电探测器。在本课题中，我们首先对比了氯化钠助融剂的添加与否对二维TMDCs 材料生长的影响，验证了氯化钠在整个生长过程中的作用。我们对实验参数进行一系列探究，例如，在控制其他条件不变的情况下，分别探究氩气通量及不同温度对MoSe2和MoS2 生长的影响。在实现单一TMDCs 材料生长的基础上，我们进一步成功实现了三元合金MoSxSe(2-x)和MoSexS(2-x)薄膜的原位制备。此外，为了解决大面积生长TMDCs 薄膜的难题，我们提出了一种新型的二维TMDCs 材料二步法生长方法，即采用原子层沉积（ALD）先制备薄层过渡金属氧化物，然后通过CVD 硫族元素还原的生长大面积的TMDCs 薄膜。基于该二步法，我们成功制备了大面积的薄层WSe2。该方法具有一定的普适性，可用于大面积生长其它种类的TMDCs 薄膜。我们将部分样品制作成场效应晶体管器件，对其电学输运性能和光电探测特性进行表征，证实了我们CVD 合成的二维TMDCs 薄膜具有较高的晶体质量。最后，我们设计构建了MoTe2/MoS2 异质结结构的光电探测器件，并系统研究其光电探测性能。相比于单一的TMDCs 材料（MoTe2 和MoS2），该器件的光探测性能（光响应度和比探测率等性能）都有了数量级的提升。本课题的研究结果对于推进二维材料工业化制备以及在光电子器件中的应用，尤其是在宽光谱光电探测器件方面以及未来的柔性光电子与智能传感器件方面的实际应用具有重要的参考意义。

The discovery of graphene had stimulated the development of many new groups of two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDCs). TMDCs have unusal physical, optoelectronic properties, and a wide variety, making them the ideal platform for optoelectronic devices. Moreover, different kinds of TMDCs can be stacked layer-by-layer by van der Waals (vdW) force to form two-dimensionalheterojunctions. This not only bypasses the lattice-matching difficulties of conventional semiconductor heterojunction epitaxy ， but also provides an alternative solution for designing new optoelectronic devices that can overcome the limitations of the single band in the traditional semiconductor. However, there are still extremely challenges in the controllable growth and large scale of high quality 2D TMDCs films. Usually, the single 2D material photodetector has a following shortage, such as narrow detection bands, long response times, or low detection rates. Most of the reported vdW p–n junction devices are operating primarily in the visible band with a reasonably low photo-responsivity. It is therefore essential benefits to combine both high detectivity by increasing the photoresponsivity, and broadband beyond the visible spectrum by thedesign of vdW p–n junctions with photoactive 2D layers. To overcome these challenges in growth, we firstly try the new method for the synthesis of several binary TMDCs and ternary TMDCs thin film materials by chemical vapor deposition. In order to obtain and check better comprehensive performance in the device, and we explored to improve the a 2D TMDCs vertical heterostructure photodetector.In this thesis, we first check the effect of the addition of sodium chloride flux on the growth of two-dimensional TMDCs, then compared the results between the samples with or without sodium chloride flux, and verified the enhanced role of sodium chloride in the whole growth process. During this process, we explored a series of experimental parameters, for example, the effects of argon flux and different tube temperature were investigated on the growth of MoSe2 and MoS2, respectively, while fixing other conditions. Furthermore, based on the growth of single TMDCs, we successfully realized the in-situ CVD synthesis of ternary alloys MoSxSe(2-x) and MoSexS(2-x) films. In addition, in order to address the challenge of growing single-crystalline TMDCs films with large area, we proposed a novel two-step process to grow large-area 2D TMDCs, namely, thin-layer transition metal oxides are prepared using atomic layer deposition (ALD), followed by reducing them using chalcogenide by CVD. With this two-step method, we successfully prepared a large-area WSe2 film. Obviously, this method has more generality and can be used for the growth of other kinds of TMDCs films with a large area. We fabricated some field-effect transistors (FET) devices with these samples, and studied their electrical transport properties and photo-detecting characteristics, which confirmed that our CVD-synthesized 2D TMDCs films have fairly high crystal quality. Finally, we designed and constructed the photodetectors of the MoTe2/MoS2 in heterojunction structure, and systematically investigated their photo-detecting performance. The device's performance (photo-responsibility and specific detectivity) has orders of magnitude improvement than that of the single TMDCs materials (MoTe2 and MoS2). The results of this thesis have a good reference for promoting the industrial preparation of 2D materials and their application in optoelectronic devices, especially in future practical applications of broadband photodetectors, flexible optoelectronics and smart sensor devices.

二维材料 过渡金属硫族化合物 化学气相沉积 生长 光电特性

two-dimensional material transition metal dichalcogenide chemical vapordeposition growth photoelectric property

中文

联合培养

南方科技大学

黄锐. 二维过渡金属硫族化合物材料的制备及光电器件研究[D]. 深圳. 哈尔滨工业大学,2019.