Abstract
Photovoltaic effects of Ag/MgB2 system induced by continuous wave purple-laser irradiation have been systemically investigated between 10 K and 250 K. The results show that the photo-induced voltage has a photovoltaic nature arising from a built-in electrical field in the interface between silver and MgB2, which provides the separation force for the photo-induced electron-hole pairs. No contributions from laser heating have been observed. The direction of the built-in electric field points from superconductor MgB2 to metal silver electrode below the superconducting transition temperature Tc, consisting with that found in SmO0.7F0.3FeAs, YBCO, Bi-2223 and Bi-2212 based systems. The built-in electric field of Ag/MgB2 system above Tc directs from Ag to MgB2, as a result of charge carrier diffusion at the interface. The temperature and laser intensity dependence of Voc data can be satisfactorily fitted to an empirical formula above the superconducting transition, indicating that the intrinsic and/or impurity based thermal excitation of charge carriers plays an important role in the photovoltaic behavior of MgB2. The Voc peak near 30 K can be ascribed to the competition between the contributions from the built-in electric field and the thermally excited electron-hole pairs. The polarity reversal and nonlinear behavior of Voc in the vicinity of Tc are direct consequences of superconducting transition. Our data provide a new dimension of information for depicting a more comprehensive picture of metal/superconductor system and may lead to new applications in the field of photo-electron sensing devices.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
