毫米级六方氮化硼单晶畴的可控制备及其电学器件应用

Hexagonal boron nitride (h-BN) has recently attracted tremendous interests due to its atomically flat surface free of dangling bonds and trapped charges, which can serve as an ideal insulating substrate and gate dielectric for electronic devices based on two dimensional materials. Chemical vapor deposition is most widely used method to prepare large-area h-BN. However, high nucleation density seriously restricts the domain size of h-BN and the self-limiting growth hinders the control over the number of layers. Small domain size combined with uncontrolled layer number are the central bottleneck for the application of h-BN in electronic devices. To solve this issue, we propose to synthesize millimeter-sized h-BN single crystal domains by decreasing the density of nucleation using oxygen-assisted space-confined chemical vapor deposition. The precursor can be efficiently catalyzed to be decomposed by the copper vapor on the substrate surface, achieving the tuning of layer numbers. On this basis, the application of the h-BN in MoS2 transistors was also systematically studied. The goal of the present project is realizing the preparation of millimeter-sized single crystal h-BN domains with control of layer numbers, elucidating the mechanism of nucleation and growth and analyzing its application in transistors. This project is significant from the view of both large-scale growth of large-sized h-BN single crystal domains and its device applications.

层状结构的六方氮化硼具有原子级平整的表面、极少的悬挂键和电荷陷阱，是二维材料电子器件绝佳的绝缘衬底及栅介质，因此成为近年来的研究热点。化学气相沉积法是制备大面积六方氮化硼的主要途径，但过高的成核密度严重限制了单晶畴的尺寸，且生长过程的自限性致使其层数难以调控。较小的晶畴尺寸及不可控的层数是阻碍六方氮化硼应用于电子器件的主要瓶颈。为解决这一问题，本项目拟采用氧辅助的空间限域化学气相沉积法，显著降低六方氮化硼的成核密度，获得毫米级单晶畴；利用衬底表面的铜蒸气有效催化前驱体分解，克服自限性生长的局限，调控六方氮化硼单晶畴的层数；在此基础上，开展六方氮化硼单晶畴在二硫化钼场效应晶体管中的应用研究。通过本项目的实施，我们期望实现毫米级六方氮化硼单晶畴的层数可控制备，揭示其成核及生长机理，分析其在场效应晶体管中的应用特性，为大尺寸六方氮化硼单晶畴的规模化制备及器件应用奠定基础。

层状结构的六方氮化硼具有原子级平整的表面、极少的悬挂键和电荷陷阱，是二维材料电子器件最理想的绝缘衬底及栅介质材料之一，因此成为近年来的研究热点。化学气相沉积法是制备大面积六方氮化硼的主要途径，但过高的成核密度严重限制了单晶畴的尺寸，且生长过程的自限性致使其层数难以调控。在本项目中，我们采用基于空间限域的低压化学气相沉积法，制备了大尺寸六方氮化硼单晶畴；利用限域空间生长的特点克服了自限性生长的局限，获得大面积均匀的多层六方氮化硼薄膜；进一步以制备的多层六方氮化硼为衬底，采用碱金属卤化物辅助的常压化学气相沉积法在六方氮化硼表面制备了单层二硫化钨；系统研究了六方氮化硼对二硫化钨的光学特性及电学器件性能的影响，证实六方氮化硼可以作为二维半导体的优良衬底材料。此外，在项目实施过程中，我们还采用常压化学气相沉积法制备了二硫化钼及二硫化铼纳米结构，研究了其在电化学产氢领域的应用。该项目为高质量六方氮化硼薄膜的可控制备提供了一条崭新的途径，为实现六方氮化硼的潜在器件应用奠定了坚实基础，具有重要的科学意义与实用价值。