Abstract
The enhanced superconductivity in few layer 2H-TaS2 and suppressed CDW transition of nanoribbon 1T-TaS2 have been investigated in this thesis. Transport properties of different thickness 2H-TaS2 reveal the suppression of CDW transition signature in 2D region. Further, the electron dominant carrier density in the order of 1022 𝐶∙𝑐𝑚−3 manifests its metallic behavior. Superconductivity in atomically thin 2H-TaS2 is strongly enhanced, the critical temperature of a trilayer sample can be up to 2.6 K compared with 0.8 K in bulk crystals. Four-probe differential resistance method measured superconducting gap fits well with BCS model. The enhanced superconductivity may be a consequence of suppression of CDW transition and the enhancement of DOS at Fermi level. Moreover, the transport characterization of bulk crystal 1T- TaS2 demonstrates its unique three CDW evolutions with temperature. After eliminating the disturbances from measurements, the RIE etched decreased width nanoribbon like channels behave similar to the decreased thickness samples, showing a suppressed CDW transition signature. And when the width of channel still goes down, the CDW transition order will be concealed. To explain this trend, we proposed a free energy theory indicating that the decreased width will introduce higher and more stable barrier between CDW transitions. Our results establish that the decreased x or y-axis of 1T- TaS2 will also strongly affect the CDW order.