石墨烯/h-BN/石墨烯三明治结构日盲紫外探测器研究

As one of two-dimensional (2D) atomic crystals, hexagonal boron nitride (h-BN) is considered to be a promising material for fabricating ultraviolet (UV) detectors because of its wide direct band gap, high optical absorption, high dielectric strength, and good thermal stability. The following two issues have to be addressed for fabricating the ultraviolet detector based on 2D h-BN atomic crystals: the weak optical absorption owing to its few-atomic layer thickness and the poor conductivity due to its wide band gap. In the present project, we propose to enhance the light absorption of h-BN, and thus the photoresponsivity of the device, by the use of the field enhancement resulting from the excitation of surface plasmons of metal nanoparticles. On the other hand, to overcome the low conductivity of h-BN, a graphene/h-BN/graphene sandwich structure will be used to fabricate the UV detectors, in which the electron-hole pairs are produced in the h-BN layer after light absorption and subsequently are respectively injected into the top and bottom graphene layers due to the presence of a perpendicular electric field created by the applied gate or bias voltage. Furthermore, the carrier recombination in the devices will be avoided due to the electron-hole separation, which is also favorable for improving device performance. The goal of the present project is revealing the effects of local surface plasmons on the light absorption of h-BN, and elucidating the transport and recombination mechanism of photo-generated carriers, and eventually fabricating the solar-blind UV detectors with the high photoresponsivity. The findings of this project will offer a promising approach toward the fabrication of the solar-blind UV detectors for practical applications.

直接宽带隙六方氮化硼（h-BN）二维原子晶体具有高的光吸收系数、高的介电强度以及良好稳定性等优势，是制作紫外探测器的最佳候选材料。但二维原子晶体厚度有限导致光吸收较弱，同时其电输运性能较差，成为发展h-BN紫外探测器的两个瓶颈因素。本项目中，我们拟采用金属纳米颗粒表面等离激元的近场增强效应提高h-BN二维原子晶体光吸收，从而提高器件的光响应度。另一方面，利用石墨烯/h-BN/石墨烯三明治结构，通过外加栅压或偏压调控石墨烯费米能级，使电子和空穴分别注入到上下两层石墨烯中输运，实现光吸收与载流子输运的空间分离。该思路不仅可克服h-BN导电性不足的问题，还可以避免载流子复合，从而提高器件性能。通过该项目的实施，我们期望探明金属表面等离激元对h-BN光吸收的影响，揭示新型器件中载流子的输运与复合机制，最终实现h-BN紫外探测器的高效光电转化，为发展基于h-BN二维原子晶体的日盲紫外探测器奠定基础。

直接宽带隙六方氮化硼（h-BN）二维原子晶体具有高的光吸收系数、高的介电强度以及良好稳定性等优势，是制作紫外探测器的最佳候选材料。但二维原子晶体厚度有限导致光吸收较弱，且其电输运性能较差，是制约h-BN紫外探测器发展的两个瓶颈因素。本项目中，我们围绕h-BN二维原子晶体的可控制备及其深紫外探测器应用开展研究。我们制备出单晶畴尺寸达0.6毫米的h-BN二维晶体以及单一取向的h-BN单晶畴，为进一步通过晶畴融合实现晶圆级h-BN单晶薄膜生长奠定了基础。针对h-BN在缺乏催化活性的介质衬底上直接成核困难的问题，利用荷能氮离子氮化蓝宝石衬底表面，促进h-BN在蓝宝石衬底上直接成核，在蓝宝石衬底上实现了高质量h-BN二维原子晶体的直接生长。实现了组分全范围可调的碳掺杂h-BN薄膜的制备，发现碳掺杂浓度较低时，h-BN相可保持稳定，相应其电学性质从绝缘态可以连续变化到半导体。基于介质衬底上直接生长h-BN和碳掺杂显著提高了h-BN深紫外光电探测器的性能，器件不仅具有较高的光响应度和归一化探测率，同时具有良好的开关稳定性和较快的响应速度。本项目的成果不仅为制备高质量h-BN二维原子晶体提供了指导，也为h-BN深紫外光电探测器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Small, ACS Appl. Mater. Interfaces, Chem. Mater., Nanoscale,等学术期刊发表标注基金资助的学术论文11 篇，其中SCI论文10篇；申请5项国家发明专利，其中2项发明专利获得授权，培养博士研究生4人，硕士研究生1人（其中1人获中科院优秀博士论文，3人获中科院院长优秀奖、北京市优秀毕业生）。