二维黑磷晶体的场效应和量子行为及其压力效应的研究

Graphene itself shows gapless dispersive so that a relatively large “off” current can be usually observed on the devices based on graphene, which prevents the practical applications of graphene on nanoelectronics, in spite of the extremely high carrier mobility. Recently, a new type of 2D graphene-like semiconductor, few-layer black phosphorus (FLBP), was fabricated to field-effect transistor (FET). FLBP has unique properties, such as air-stability, high mobility, tunable direct gap with thickness and good contact to electrodes, which bring the black phosphorus a new system of 2D semiconductor with promising potential for new applications in nanoelectronics and optoelectronics. After that, 2D electron gas was realized in the FLBP, and integral quantum Hall effect (QHE) was observed therein. As well, theoretical studies suggest the possibility of pressure-induced Dirac cone in black phosphorus (BP) crystal. These results indicate that BP has novel quantum effect just resembling to graphene and becomes a new physical area. In the present project, we plan to carry out intensive investigations on the quantum effect in FLBP-based FET and high-pressure-induced quantum transition in bulk black phosphorus crystal. And we will also probe possible quantum phenomena in FLBP as high pressure is applied, such as QHE and room-temperature QHE. We also intend to perform theoretical studies on the quantum behavior under high pressure and electrical field in black phosphorus with different thickness. We present this project aiming to reveal the evolution of the topological electronic band structure with external pressure, electrical field and thickness, and understand the novel quantum phenomena in the system.

石墨烯有非常高的载流子迁移率，但因为能带色散关系上没有能隙，导致了由其制备的纳米电子器件具有相对大的“关”电流，阻碍了其实用化。最近我们制备出一类新的、空气中稳定、高迁移率、具有随厚度可调的合适的直接能隙、良好电极接触的二维半导体类石墨烯材料-少层黑磷，证实其在纳米电子学和光电子学新应用方面有很高的潜力,并随后在少层薄膜中实现了二维电子气以及观察到整数量子霍尔效应。而进一步研究表明其中可能存在压力诱导的Dirac锥。这些结果表明黑磷有着与石墨烯一样新奇的量子效应，成为了一个新的研究领域。本项目拟对少层黑磷的场效应管的量子效应、高压诱导的黑磷块体单晶的量子转变进行深入研究，还将开展少层黑磷薄膜的高压下可能的量子现象探索，如量子Hall效应等，对不同厚度黑磷在高压和电场调控下量子行为的理论研究，最终揭示黑磷的电子能带拓扑结构随压力、电场和厚度的演变，理解其中新奇的量子现象。

依据项目计划书制订的研究计划，项目组开展了黑磷薄膜制备工艺探索、黑磷单晶和少层薄膜中新量子现象的探索和能隙大小的调控、压力下能带拓扑特性的调控以及原型器件设计等方面的研究，顺利完成了计划书的各项研究内容，在黑磷薄膜的制备、新量子现象的探索以及量子调控等方向取得了多项原创性的科研成果，具体进展包括如下：.1..黑磷薄膜制备工艺探索方面，利用脉冲激光沉积的方法实现了晶圆规模的超薄黑磷薄膜的生长，并制备了圆晶规模的基于黑磷的场效应管阵列；通过国际合作，利用有机分子电化学插层的方法将磷烯单层更有效的分离出来，并在基于此构造的场效应管中展示了超过107的开关比率。.2..黑磷材料中新的量子现象探索、调控与机理研究方面，在基于黑磷薄层场效应的二维电子气中观察到了整数量子霍尔效应；利用厚度和应力实现了对黑磷能隙大小的有效调控，实现了较宽频率的且在技术上很重要的能隙区间；利用可弯曲的衬底施加机械应力，进一步实现了黑磷能隙大小的连续调控；理论解释新型层状黑磷中压力驱动的Dirac半金属相，并进一步在实验上观察到了压力下狄拉克半金属态中磁场诱导的电子相变以及反常自旋涨落现象。.3..基于二维黑磷材料的新器件和新结构方面，在纳米尺度的InSe/黑磷异质结中观察到了弹道雪崩现象；发展了基于黑磷材料的二维铁电场效应晶体管；实现了从少层黑磷中衍生磷原子链。.4..在新型二维材料的探索及其量子行为研究方面，首次在二维本征磁性拓扑绝缘体中实现的量子反常霍尔效应，量子化的温度提高到6.5K；在二维磁性材料Cr2Ge2Te6中通过有机离子电化学插层实现对电子态和铁磁性的调控；在二维磁性材料Fe3GeTe2中通过栅电压调控实现室温铁磁性。.项目执行期间共发表SCI论文47篇，其中影响因子大于3的论文44篇，包括Science 1篇、Nature 2篇、 Nature子刊6篇（含接收1篇）、Physical Review Letters 1篇，被他引超过1500余次，相关研究成果获得了国内外同行的广泛认可。