Large-scale synthesis of high-quality two dimensional(2D)semiconductors,such as molybdenum disulfide(MoS_(2)),is a prerequisite for their lab-to-fab transition.It is crucial to systematically explore and understand the influence of key synthetic conditions on the nucleation,uniformity,and quality of MoS_(2) wafers.Here,we report the epitaxial growth of high-quality and uniform monolayer MoS_(2) films on 2-in c-plane sapphire by chemical vapor deposition(CVD)method under optimized growth conditions(0–1 mg NaCl,adequate S/Mo ratio,and the addition of 0–1 sccm O2).We systematically explore the influence of critical synthetic conditions on the nucleation,and stitching of MoS_(2) domains over the wafer scale,including the dosage of the alkali metal salt NaCl additive,the evaporation temperature of MoO_(3),the distance between MoO_(3) and the substrate,and the flow rate of O_(2).Among them,the dosage of NaCl and the S/Mo ratio have important influences on the quality and film coverage of MoS_(2),while the flow rate of O_(2) plays a key role in controlling the nucleation density and domain size.We further discovered that a-plane sapphire could easily guide the unidirectional growth of MoS_(2) without the need for other specific synthetic conditions compared with c-plane and m-plane sapphire.The field-effect transistors(FETs)fabricated from the full-coverage films show an average and the highest mobilities of 28.5 and around 45 cm^(2)·V−1·s^(-1),respectively.
宝石包裹体的研究一直是珠宝领域的热点之一,但对于五大名贵宝石之一的蓝宝石包裹体的对比研究还不多。前人运用常规宝石学测试、谱学测试如拉曼光谱等现代测试手段,对选自澳大利亚、阿扎德克什米尔、中国山东、非洲几内亚等产地的蓝宝石样品的宝石学特征进行测试分析。本文在前人的相关研究成果的基础上,对蓝宝石矿床特征以及澳大利亚、阿扎德克什米尔、中国山东、非洲几内亚等产地的蓝宝石的宝石学特征进行了归纳与总结。通过初步探讨不同产地的蓝宝石包裹体特征的独特表现,以及它们在包裹体特征方面的差异性,不仅为蓝宝石的产地溯源提供了重要依据,而且为珠宝市场也提供了更可靠的鉴定依据。The study of gemstone inclusions has long been a hot topic in the jewelry field. However, comparative research on inclusions in sapphires, one of the five precious gemstones, is still limited. Previous researchers have used conventional gemological tests and modern spectroscopic techniques, such as Raman spectroscopy to analyze the gemological characteristics of sapphire samples from Australia, Azad Kashmir, Shandong, China, and Guinea in Africa. Based on the previous research results, this paper summarizes the characteristics of sapphire deposits and the gemological features of sapphires from Australia, Azad Kashmir, Shandong, China, and Guinea in Africa. By initially exploring the unique manifestations of inclusions in sapphires from different origins and their differences in inclusion characteristics, this study not only provides important evidence for the origin traceability of sapphires but also offers more reliable identification criteria for the jewelry market.
在蓝宝石衬底上生长一层AlN缓冲层是LED芯片提升器件质量的常用手段,其薄膜质量与器件整体性能息息相关。为了进一步提高AlN薄膜的结晶质量,本文首先使用PVD、HTA以及MOCVD方法对蓝宝石衬底上的AlN薄膜进行制备,制备出了高结晶质量的AlN薄膜。随后引入不同的c/m衬底斜切角去探索斜切角度对薄膜结晶质量的影响。最终成功在c面蓝宝石衬底上制备出1 μm的摇摆曲线半高宽51 arcsec,表面粗糙度为0.987 nm的高质量c轴取向的AlN薄膜。并通过对比不同衬底斜切角的形貌特征变化,认为造成结晶质量提升的原因是一种由衬底斜切角诱导的台阶终止位错的机制。在此基础上,对不同衬底斜切角的AlN薄膜进行了UV光学性能的表征,通过紫外透过率实验证实了0.2˚的c/m衬底斜切角确实给薄膜的性能带来了提升,其紫外透过率和光学禁带宽度都有了一定程度的提升,最终达到了80%透过率,6.09 eV光学带隙的优异性能。A layer of AlN buffer on a sapphire substrate is a common method for improving the device quality of LED chips, and the quality of the film is closely related to the overall performance of the device. In order to further enhance the crystallinity of AlN films, this study first employs PVD, HTA, and MOCVD methods to fabricate AlN films on sapphire substrates, achieving AlN films with high crystallinity. Subsequently, different offcut angles of the c/m substrates are introduced to explore the impact of the offcut angle on the crystallinity of the films. As a result, high-quality c-axis oriented AlN films with a rocking curve full width at half maximum (FWHM) of 51 arcseconds and a surface roughness of 0.987 nm were successfully prepared on c-plane sapphire substrates. By comparing the morphological changes of films with different substrate offcut angles, it is proposed that the improvement in crystallinity is due to a mechanism where the substrate offcut angle induces the termination of st
