Vanadium disulfide (VS₂) attracts elevated interests for its charge-density wave (CDW) phase transition, ferromagnetism, and catalytic reactivity, but the electronic structure of monolayer has not been well understood yet. Here we report synthesis of epitaxial 1T VS₂ monolayer on bilayer graphene grown by molecular-beam epitaxy (MBE). Angle-resolved photoemission spectroscopy (ARPES) measurements reveal that Fermi surface with six elliptical pockets centered at the M points shows gap opening at low temperature. Temperature-dependence of the gap size suggests existence of CDW phase transition above room temperature. Our observations provide important evidence to understand the strongly correlated electron physics and the related surface catalytic properties in two-dimensional transition-metal dichalcogenides (TMDCs).

二硫化钒（VS ₂）的电荷密度波（CDW）相变，铁磁性和催化反应性引起了人们的广泛兴趣，但单层电子结构尚未得到很好的理解。在这里我们报告外延1T VS _2的合成通过分子束外延（MBE）生长的双层石墨烯上的单层。角度分辨光发射光谱（ARPES）测量表明，费米表面上有六个以M点为中心的椭圆形凹坑，在低温下显示出缝隙开口。间隙尺寸的温度依赖性表明在室温以上存在CDW相变。我们的观察结果提供了重要的证据，以了解二维过渡金属二卤化金属（TMDCs）中强相关的电子物理学和相关的表面催化性能。