| AVS 55th International Symposium & Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS2+NC-WeM |
| Session: | Functional Metal Oxides and Quantum Metal Structures |
| Presenter: | S.Y. Qin, University of Texas at Austin |
| Authors: | S.Y. Qin, University of Texas at Austin J.D. Kim, University of Texas at Austin A.A. Khajetoorians, University of Texas at Austin C.K. Shih, University of Texas at Austin |
| Correspondent: | Click to Email |
Ultra-thin Pb films on semiconductor substrates have exhibited many intriguing phenomena manifested by the quantum confinement of electronic states. Quantum stability has been a topic of interest for many years. Recently, it was shown that quantum confinements also play an interesting role on superconductivity. Oscillations of superconductivity gap and Tc as a function of film thickness have been observed in Pb/Si(111) and Pb/Ge(111) systems. Moreover, it is found that the superconductivity remains very robust even for films as thin as 5 ML. An interesting question arises as to what extent the robustness of superconductivity remains in even thinner regime. By using a different surface template, namely Pb/Si(111) root 3 surface, we have grown uniform Pb films down to 2 ML. The film shows preferred thicknesses of 2ML and 4ML, presumably a manifestation of the quantum stability. While superconducting gap remains robust down to 4ML and shows BCS-like temperature dependence, superconductivity of 2ML Pb film exhibit several interesting features. First of all, the superconducting transition temperature is significantly lower. Moreover, we find that even with nearly perfect 2ML films, the magnitude of superconducting gap is strongly suppressed by a minute concentration of hole defects. On the contrary, the gap is not affected by distribution of small excess nano-islands.