摘要：The electrical phase transition in van der Waals (vdW) layered materials such as transition-metal dichalcogenides and Bi
2Sr
2CaCu
2O
8+
x
(Bi-2212) high-temperature superconductor has been explored using various techniques, including scanning tunneling and photoemission spectroscopies, and measurements of electrical resistance as a function of temperature. In this study, we develop one useful method to elucidate the electrical phases in vdW layered materials: indium (In)-contacted vdW tunneling spectroscopy for 1
T-TaS
2, Bi-2212 and 2
H-MoS
2. We utilized the vdW gap formed at an In/vdW material interface as a tunnel barrier for tunneling spectroscopy. For strongly correlated electron systems such as 1
T-TaS
2 and Bi-2212, pronounced gap features corresponding to the Mott and superconducting gaps were respectively observed at
T = 4 K. We observed a gate dependence of the amplitude of the superconducting gap, which has potential applications in a gate-tunable superconducting device with a SiO
2/Si substrate. For In/10 nm-thick 2
H-MoS
2 devices, differential conductance shoulders at bias voltages of approximately ± 0.45 V were observed, which were attributed to the semiconducting gap. These results show that In-contacted vdW gap tunneling spectroscopy in a fashion of field-effect transistor provides feasible and reliable ways to investigate electronic structures of vdW materials.
