CRITICAL SHEET RESISTANCE OBSERVED IN HIGH-TC OXIDE-SUPERCONDUCTOR ND2-XCEXCUO4 THIN-FILMS

High-T(c) oxide-superconductor Nd(2-x)Ce(x)CuO4 single-crystal thin films were used to observe the critical sheet resistance at the insulator-superconductor transition. The films were epitaxially grown on SrTiO3(100) by the method of molecular-beam epitaxy. The electron transport properties of these films are drastically influenced by oxygen-impurity concentration and show clearly the evidence of Anderson localization attributed to two dimensionality. It is found that the critical sheet resistance R-open square box at the onset of superconductivity takes a value within a range from 6 to 8 k-OMEGA, which is close to the value h/4e2 = 6.45 k-OMEGA. Our results provide clear evidence that Anderson localization induces the universal behavior observed at the superconductor-insulator transition.