Han Sang Sub, Kim Jong Hun, Noh Chanwoo, Kim Jung Han, Ji Eunji, Kwon Junyoung, Yu Seung Min, Ko Tae-Jun, Okogbue Emmanuel, Oh Kyu Hwan, Chung Hee-Suk, Jung YounJoon, Lee Gwan-Hyoung, Jung Yeonwoong
Department of Materials Science and Engineering , Yonsei University , Seoul 03722 , South Korea.
Analytical Research Division , Korea Basic Science Institute , Jeonju 54907 , South Korea.
ACS Appl Mater Interfaces. 2019 Apr 10;11(14):13598-13607. doi: 10.1021/acsami.9b01078. Epub 2019 Mar 20.
Two-dimensional (2D) transition-metal dichalcogenides (2D TMDs) in the form of MX (M: transition metal, X: chalcogen) exhibit intrinsically anisotropic layered crystallinity wherein their material properties are determined by constituting M and X elements. 2D platinum diselenide (2D PtSe) is a relatively unexplored class of 2D TMDs with noble-metal Pt as M, offering distinct advantages over conventional 2D TMDs such as higher carrier mobility and lower growth temperatures. Despite the projected promise, much of its fundamental structural and electrical properties and their interrelation have not been clarified, and so its full technological potential remains mostly unexplored. In this work, we investigate the structural evolution of large-area chemical vapor deposition (CVD)-grown 2D PtSe layers of tailored morphology and clarify its influence on resulting electrical properties. Specifically, we unveil the coupled transition of structural-electrical properties in 2D PtSe layers grown at a low temperature (i.e., 400 °C). The layer orientation of 2D PtSe grown by the CVD selenization of seed Pt films exhibits horizontal-to-vertical transition with increasing Pt thickness. While vertically aligned 2D PtSe layers present metallic transports, field-effect-transistor gate responses were observed with thin horizontally aligned 2D PtSe layers prepared with Pt of small thickness. Density functional theory calculation identifies the electronic structures of 2D PtSe layers undergoing the transition of horizontal-to-vertical layer orientation, further confirming the presence of this uniquely coupled structural-electrical transition. The advantage of low-temperature growth was further demonstrated by directly growing 2D PtSe layers of controlled orientation on polyimide polymeric substrates and fabricating their Kirigami structures, further strengthening the application potential of this material. Discussions on the growth mechanism behind the horizontal-to-vertical 2D layer transition are also presented.
以MX（M：过渡金属，X：硫族元素）形式存在的二维（2D）过渡金属二硫属化物（2D TMDs）具有固有的各向异性层状结晶性，其材料特性由构成的M和X元素决定。二维二硒化铂（2D PtSe）是一类相对未被充分研究的2D TMDs，其中贵金属Pt作为M，与传统的2D TMDs相比具有明显优势，如更高的载流子迁移率和更低的生长温度。尽管有预期的前景，但其许多基本结构和电学性质及其相互关系尚未阐明，因此其全部技术潜力大多仍未被探索。在这项工作中，我们研究了大面积化学气相沉积（CVD）生长的具有定制形态的2D PtSe层的结构演变，并阐明其对所得电学性质的影响。具体而言，我们揭示了在低温（即400°C）下生长的2D PtSe层中结构 - 电学性质的耦合转变。通过籽晶Pt薄膜的CVD硒化生长的2D PtSe的层取向随着Pt厚度的增加呈现从水平到垂直的转变。虽然垂直排列的2D PtSe层呈现金属传输，但对于用小厚度的Pt制备的薄水平排列的2D PtSe层观察到了场效应晶体管栅极响应。密度泛函理论计算确定了经历水平到垂直层取向转变的2D PtSe层的电子结构，进一步证实了这种独特的结构 - 电学耦合转变的存在。通过在聚酰亚胺聚合物衬底上直接生长具有可控取向的2D PtSe层并制造其折纸结构，进一步证明了低温生长的优势，进一步增强了这种材料的应用潜力。还讨论了水平到垂直二维层转变背后的生长机制。
