基于二维h-BN中间层的HfS2远程外延生长及器件应用研究

Transition metal dichalcogenides HfS2 has been attracting intensive attention as promising candidates in the low-power electronic and optoelectronic fields, due to its higher calculated room-temperature acoustic-photon-limited mobility and sheet current density than those of widely studied MoS2. However, the research in preparation method of two-dimensional (2D) HfS2 is still at the infancy stage, and the material quality is not suitable for electronic applications, furthermore, substrates and interface play critical roles in the properties of 2D HfS2. In the present project, we propose the remote epitaxial growth of HfS2 through 2D hexagonal boron nitride (h-BN) on c-Al2O3 substrates utilizing chemical vapour deposition technique, as well as the fabrication of photodetectors based on HfS2/h-BN heterojuctions to check the material quality. By using the remote epitaxy of HfS2 on h-BN/Al2O3, the large-area, high quality 2D HfS2 single-crystalline films can be prepared. Simultaneously, h-BN has little influence on the carrier transport of HfS2 because of its atomically flat and dangling-bond-free surface. Moreover, due to the weak van der Waals force between h-BN and Al2O3 substrates, the grown single-crystalline HfS2 films can be easily released from the h-BN-coated substrate and transferred to a substrate of interest for diversiform applications. The goal of the present project is revealing the mechanism of remote epitaxy of HfS2 on h-BN/Al2O3, and elucidating the effects of HfS2/h-BN interface on the properties of HfS2. The findings of this project will serve as the foundation for applications of large-area HfS2-based electronics.

过渡金属硫族化合物HfS2具有高的声子极限迁移率和饱和电流密度，在低功耗电子器件等领域应用前景广泛。然而HfS2的制备研究尚在起步阶段，材料质量普遍不高，同时衬底和界面对其性质影响显著。本项目中，我们拟采用化学气相沉积技术，在蓝宝石衬底表面引入超薄二维h-BN中间层，借助晶格匹配衬底的势场作用，实现HfS2二维单晶薄膜的远程外延生长，并制备基于HfS2/h-BN异质结的光电探测器。利用远程外延生长不仅可制备出大面积、高质量HfS2二维单晶薄膜，而且由于原子级平整的h-BN表面极少存在悬挂键和电荷陷阱，可避免衬底对HfS2中载流子输运的影响，最大程度上保持HfS2本征的优异物理性质。此外，基于h-BN与蓝宝石间弱的范德瓦尔斯力，可实现HfS2简便、高质量的转移以及多样化应用。通过该项目的实施，我们期望探明HfS2远程外延生长机制及异质结界面对HfS2物理性质的影响，为其电子学应用奠定基础。

以HfS2、ZrS2为代表的过渡金属硫族化合物TMDs具有高的声子极限迁移率和饱和电流密度，在低功耗电子器件等领域应用前景广泛。然而HfS2的制备研究尚在起步阶段，材料质量普遍不高，同时衬底和界面对其性质影响显著。本项目中，我们围绕基于二维h-BN中间层的HfS2等TMDs的远程外延生长及其器件应用开展研究。采用CVD技术在c-Al2O3衬底上实现了高质量HfS2、HfSe2和HfS2(1-x)Se2x三元合金的外延生长，通过Se含量可调控HfS2( 1-x)Se2x光电探测器光电流以及光响应谱范围。实现了基于h-BN中间层的大面积二维HfS2单晶的远程外延，探明了HfS2在h-BN/c-Al2O3上的CVD成核和远程外延机制；研制出基于远程外延的HfS2/h-BN异质结光电探测器，发现h-BN可最大程度上还原HfS2本征的优异物理特性，如：显著降低衬底表面声子、缺陷及电荷陷阱的载流子散射作用，从而提高器件性能。进一步拓展研究到其他TMDs体系，在c-Al2O3衬底上实现了高质量ZrS2、ZrSe2和ZrS2(1-x)Se2x三元合金的外延生长、器件制备及性能测试，基于ZrS2外延薄膜的光电探测器表现出优异的综合性能，是目前基于IVB族TMDs的光电探测器中的最高值。本项目的成果不仅为发展高质量外延层材料的制备方法提供了一种新的途径，也为TMDs/h-BN异质结器件的实际应用奠定了基础，具有重要的科学意义与应用价值。基于本项目的研究成果，项目负责人作为通讯作者在ACS Appl. Mater. Interfaces, Nano Res., Nanoscale, J. Mater. Chem. C等学术期刊发表标注基金资助的学术论文12篇，其中SCI论文12篇；申请6项国家发明专利，其中3项发明专利获得授权，培养博士研究生5人（已毕业3人，其中2人获中科院院长优秀奖、北京市优秀毕业生），硕士研究生1人。

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