化学气相沉积法制备六方氮化硼单晶及薄膜的研究

STUDY ON SINGLE GRYSTAL AND FILMGROWTH OF HEXIGONAL BORON NITRIDEWITH LOW-PRESSURE CHEMICAL VAPORDEPOSITION

王伟军

14649105

硕士

材料学

程春

2018-06-04

2018-06-19

哈尔滨工业大学

深圳

六方氮化硼（h-BN）是一种具有与石墨相似结构的层状材料，也是一种具有广泛应用前景的绝缘材料，其带隙为 5.2-5.97 eV。h-BN 中电荷杂质的数量少，且具有原子级的表面平整度，与常用的二氧化硅基底相比，可将负载石墨烯的载流子迁移率可提高一个数量级，所以在电子器件领域具有众多的潜在应用，因此单层或少层 h-BN 作为石墨烯和其他二维材料的基底受到了广泛关注。不过，如何制备大面积、高质量的 h-BN，仍然是面临的首要问题。基于此，我们在原有化学气相沉积法（CVD）的基础上，通过引入分子流生长模型，并在此基础上，制备得到了高质量的 h-BN。 在 h-BN 单晶及薄膜的制备过程中，我们首先从流体力学角度出发，通过将Cu 片简单地放置于石英片表面，构筑了基于分子流原料供给的生长模型，并在此基础上对 h-BN 制备的各种因素，如 Cu 片表面粗糙度、Cu 片退火温度和退火压力和氧气等因素，进行了实验分析，并最终制备得到了横向尺寸可达 70um 的 h-BN 单晶。我们发现在分子流生长系统中，可通过对退火压力的控制，改变物料在衬底表面的传输，从而实现 h-BN 单片边缘形貌由外凸型到内凹型的转变；如果将 Cu 片放置于氧释放的基底（如新的石英片和氧化铝等）上，在能够大大降低成核密度的基础上，还能够实现将 h-BN 形貌，由三角形转变为菱形或不对称金刚石结构；通过对复杂形貌 h-BN 片形貌演变中间态的研究，我们发现 h_x005f_x005f_x005f BN 单片之间融合，符合点对边的融合方式，并能够最终能够形成规则的互补结构。若此时同时存在刻蚀，则这些规则的互补结构，将演化为多种形态的，更为复杂的形貌。此外，我们还对 h-BN 在氢气中的刻蚀行为进行了研究，发现 h-BN 单晶与薄膜具有相似的刻蚀行为，两者的刻蚀均是从边缘开始的，在刻蚀的初期，均表现为各向异性刻蚀，但随着刻蚀的进行，刻蚀速率的不断加速，刻蚀行为的无序性增加，并表现为各向异性的无序化状态。

Hexagonal boron nitride (h-BN), an insulator with a bandgap of 5.2-5.97eV, is a layered material with the similar structure to graphite,which has a wide range of potential applications in microelectronics. Compared with the traditional SiO2/Si substrate, the amount of charge impurities in h-BN is lower and the surface flatnessof h-BN film is closer to atomic level. As reported, the carrier mobility of graphene can be increased by at least one order of magnitude, when the h-BN films is as the supporting layer of graphene. In recent years, owning to numerous potential applications in the field of electronic devices, the single or few layers h-BN films have attracted increasing attentions as a substrate of graphene and othere 2D materials. However, how to prepare large-area, high-quality h-BN is still a big challenge. In the light of the challenges faced to h-BN fabrication, the molecular flow growth modelbased on LPCVD is introduced to prepare large-area, high-quality h-BN.In the process of preparing h-BN single crystals and thin films, a molecular-flowgrowth model, based on the precursor supply, was constructed by simply placing Cu foils on the top of quartz substrates. Based on this molecular-flow model between Cu foil and quartz substrates, various factors of h-BN preparation, such as the surface roughness, annealing temperature, annealing pressure and oxygen, were analyzed systematically. Finally, h-BN single crystals with a large lateral size of about 70um were obtained under the extrem low nucleation sites of h-BN on Cu foils. We found that in the molecular-flow growth system the precursor transport on growth substratecould be changed by controling annealing pressure, which could change edge profilefrom positive curve to negative curve. If the Cu foils are placed on oxygen-releasingsubstrates, such as fresh quartz plates, aluminas, etc., the morphologies of h-BN single crystal could be transformed from triangle shapes to rhombus or asymmetric diamond structures. Through the study of the intermediate state of the morphologies evolution of h-BN, we discovered that the morphologies evolution of h-BN was conformed to point-to-edge processes, which eventually formed a regular complementary structure. If there were etching processes at the same time, these complementary structures would form into more various and complex shapes.In addition, we also studied the etching behavior of h-BN in hydrogen, and found that h-BN single crystals and the thin films shared with similar etching behaviors. Namely, in the initial stage both of these etch processes were started from the edges, which showed an anisotropic etching behavior. However, with the etching of h-BN the etching rate is continuously accelerated, and finally the disorder etching process occurs.

六方氮化硼（h-BN 化学气相沉积法（CVD） 分子流生长模型 形貌演变 刻蚀

Hexagonal boron nitride (h-BN) Chemical Vapor Deposition (CVD) Molecular Flow Growth Model Morphology Evolution Etching

中文

联合培养

南方科技大学

王伟军. 化学气相沉积法制备六方氮化硼单晶及薄膜的研究[D]. 深圳. 哈尔滨工业大学,2018.