Novel 2D silicon with flat surface - Dr. Duckyoung Kim

FEBURAR 28, 2018

New work from a team of scientists including Dr. Duckyoung Kim from HPSTAR have predicted a serials of novel layered silicon crystals with stable flat surface structure and versatile electronic structures. They proposed that their study will help the development of silicon-based two dimensional electronic technology. The study is published in recent 2D Materials. 

Silicon, is one of the most common elements on Earth. Bulk silicon is extremely stable and has been used in integrated circuits and transistors that run most of our computers.

Silicene, is a two-dimensional form of silicon, an analog to graphene, which has been predicted to have promising properties and potential applications. While contrary to graphene, silicene cannot form a stable layered structure by itself since surface of the silicene is chemically reactive. Thus great challenges remained to fabricated silicene.

Instead of silicene, the team of scientists turned attention to a new direction— to find a novel two dimensional silicon structures. 

By using a newly developed ab initio computational method, the team of scientists including Drs. Kisung Chae of Korea Institute for Advanced Study, Duckyoung Kim of HPSTAR and Dr. Youn-Woo Son of Korea Institute for Advanced Study, have predicted a series of novel two dimensional silicon structures with versatile electronic properties. The predicted crystal is composed of two parts: the atomically flat surface layers and the inner layer connecting them through sp3-like covalent bonds. The surface layer features perfectly planar stable hexagonal framework unlike other 2D Si crystals with buckled surfaces. They classified the two dimensional Si structures into three groups and each of the groups possesses distinct electronic properties originated from structural variations such as semiconductor as well as semimetals.

“As we intentionally put together two symmetrically distinct parts (surface and inner layers) so that unsaturated bonds on both layers are fully compensated by each other, all the silicon atoms in the crystal have saturated bonds without any dangling bonds”, explained in the paper.

They believe that the new 2D Si crystals satisfy highly desirable characteristics of next generation electronic technology platforms only with a single atomic element and their oxides, very similar with the current 3D Si electronic devices.

“The method is especially suited for predicting 2D phases of covalent materials by designing the 2D crystals free of CN defects. This can be achieved by building surface and inner parts with different symmetries from each other, and by joining the two parts in such a way that under-coordinated atoms at the interface are compensated by one another. By doing so, the crystal becomes stabilized by eliminating dangling bonds”, stated in the paper.

相对石墨烯，硅的层状结构叫做硅烯。硅烯具有类似石墨烯的六角蜂窝结构，也被预言具有很好的应用前景。然而不像石墨，单层硅由于表明活性很难形成稳定的层状结构。因此硅烯在生成技术上存在很大的挑战。北京高压科学研究中心的Duckyoung Kim研究员参与的研究小组使用理论预言的方法提出了一种新的获得层状硅的方法。他们使用理论计算提出了一种复合结构的方法。这种结构由两部分组成—表面是完美平整的层状，内部是三维的sp³共价结构。他们预言的二维硅具有理想的表明平整度，不像其他二维硅材料的表面呈现褶皱的情况，并且这种复合的二维硅材料表现出丰富的电学性质。该研究为生成硅烯提出了一种新的指导，并为层状硅的应用指出了新的思路。