主讲人简介:蔡勖升博士，现职台湾中央研究院应用科学研究中心博士后研究员，博士毕业于台湾清华大学材料科学工程学系，先后于台湾清华大学核子工程与科学研究所担任博士后研究员，捷克科学院核物理研究所担任访问学者，德国亥姆霍兹研究中心离子束物理与材料研究所担任客座研究员，并于近期荣获德国洪堡学者奖项（Humboldt Research Fellowship）。蔡博士长期致力于等离子体以与离子束合成制备各种二维材料及其潜质应用，时常担任知名SCI期刊审稿人，目前共发表了23篇SCI期刊论文并获准1项美国专利。
讲座主题一【2019年3月4日周一 9:00 明德楼E604会议室】:
Facile Synthesis and Transistor Fabrication of Multilayer Graphene via Plasma Implantation-Assisted Process
Graphene, a two-dimensional material with honeycomb arrays of carbon atoms, has shown outstanding physical properties that make it a promising candidate material for a variety of electronic applications. To date, several issues related to the material synthesis and device fabrication need to be overcome. Despite the fact that large-area graphene films synthesized by chemical vapor deposition (CVD) can be grown with relatively few defects, the required transfer process creates wrinkles and polymer residues that greatly reduce its performance in device applications. Graphene synthesized on silicon carbide (SiC) has shown outstanding mobility and has been successfully used to develop ultra-high frequency transistors; however, this fabrication method is limited due to the use of costly ultra-high vacuum (UHV) equipment that can reach temperatures over 1500 °C. Here, we show a simple and novel approach to synthesize graphene on SiC substrates that greatly reduces the temperature and vacuum requirements and allows the use of equipment commonly used in the semiconductor processing industry. In this work, we used plasma treatment followed by annealing in order to obtain large-scale graphene films from bulk SiC. After exposure to N2 plasma, the annealing process promotes the reaction of nitrogen ions with Si and the simultaneous condensation of C on the surface of SiC. Eventually, a uniform, large-scale, n-type graphene film with remarkable transport behavior on the SiC wafer is achieved. Furthermore, graphene field effect transistors (FETs) with high carrier mobilities on SiC were also demonstrated in this study.
讲座主题二【2019年3月6日周三 9:00 明德楼E604会议室】:
Synthesis of Multilayer Transition Metal Dichalcogenides (TMDs) by using Ion Beam
All of the analytical results verify that the lower part of Mo film is selenized and the O atoms of sapphire near the surface are substituted by the Se ions introduced by the implanter during the thermal treatment to form the vertical Al2Se3/MoSe2 heterojunction on a sapphire substrate. This is the first work utilizing ion implantation technique to directly synthesize the vertical heterojunction of TMD/III-VI semiconductor on sapphire substrate. This simple ion beam-assisted process possesses much potential to be expanded for fabricating other kinds of heterogeneous junctions.
The multilayer HfSe2 on sapphire was first fabricated by the ion beam-assisted process combining ion implantation with the post annealing. The A1g mode of HfSe2 is shown in the Raman spectrum, the XPS results indicate the existence of Hf-Se bonding, and the TEM analysis exactly identifies the crystal structure of HfSe2. The 6L 1T-HfSe2, whose band structure is well realized by utilizing photoluminescence spectroscopy compared with the results of the density functional theory calculation, is formed via the Hf selenization during annealing.