Metallic transition metal dichalcogenides (MTMDCs) have manifested a wealth of intriguing properties in their bulk states, such as magnetism, charge density waves, and superconductivity. Very recently, nano-thick MTMDCs have been reported to be essential building blocks for constructing next-generation electronic and energy-storage applications, as well as for exploring unique physical issues associated with the dimensionality effect. However, batch production of such envisioned few-layer MTMDCs remains challenging. Our group reported the direct synthesis of high-quality semiconducting and metallic TMDCs materials of MoS2, WS2, VS2, and TaS2, etc., on both on conducting Au foil substrates and insulating substrates, towards in-depth understanding of their atomic-scale structures and electronic properties at the as-grown states, as well as their different applications. Particularly, we achieved thickness-tunable 2H-TaS2 flakes and centimeter-size ultrathin films on an electrode material of Au foil via a facile CVD route. We also detected the transition from nearly commensurate to commensurate CDW phases on ultrathin 2H-TaS2 flakes. Remarkably, we obtained extra high hydrogen evolution reaction (HER) efficiency on as-grown 2H-TaS2 flakes, and clarified the internal mechanism with DFT calculations. [5] Morevoer, we also realized the first synthesis of wafer-scale uniform monolayer 2H-TaSe2 film and thickness-tunable flakes on Au foils. Dramatically enhanced CDW transition temperature from ~90 (bulk value) to ~125 K is observed for monolayer 2H-TaSe2, which is well explained by the enhanced electron–phonon coupling mechanism. All these work provides brand new insights into direct synthesis and novel property investigations of nano-thick metallic 2D TMDCs. 

报告人简介：张艳锋，研究员，杰青，2005年7月于中科院物理所凝聚态物理专业获博士学位。2006-2009在日本东北大学做博士后，获得日本学术振兴会(JSPS）的资助。2010年4月受聘北京大学优秀青年人才计划（“百人计划”），加入工学院材料科学与工程系。目前致力于二维新材料及其异质结构的可控制备、精密表征以及新奇特性研究。主要研究成果包括： 1）开拓了石墨烯生长的新体系，获得了石墨烯玻璃、三维仿生石墨烯等新材料；2）实现了截至目前最大的均匀单层MoS2(6英寸)，以及相关叠层结构(MX2/Gr, MX2/MX2)的可控制备，建立了材料微观形貌、电子态、光/电催化析氢特性的构效关系；3) 在国际上率先开展了二维金属性硫属化合物(TaS2，VS2等) 的可控制备研究，发现了其超高的电催化析氢特性。研究成果受到国际同行高度评价，被发表在Nature, Science, Chem. Soc. Rev.等刊物文章多次引用。已在Science, Nat. Commun., Adv. Mater.等杂志发表论文160余篇。在国内外学术会议上做邀请报告20余次。曾获得2012年国家优秀青年科学基金资助，2015年入选教育部长江学者奖励计划“青年项目”，2019年获国家杰出青年科学基金资助。