Effects of Outer Shell Layer on the Electronic Transport Behaviors of Sn@SnO_x Nanoparticles

Abstract

Tin oxide-encapsulated tin nanoparticles (Sn@SnO x NCs) are in situ prepared by a modified DC arc-discharge plasma process. The as-prepared Sn@SnO x NCs are typically 50-70 nm in diameter with 6 nm of the SnO x shell. The diameter of Sn@SnO x NCs is 50-80 nm and the thickness of the SnO x shell increases to %25 nm after heat treatment in a vacuum tube furnace. The effect of SnO x shell thickness on the electrical properties of Sn@SnO x NCs is measured by the four-probe technique. The results show that the resistivity is described using Bloch-Grüneisen's equation with SnO x shell thickness-dependent resistivity and SnO x shell thickness-dependent Debye temperature above the superconducting transition temperature T c. Superconductivity occurs in both Sn@SnO x NCs with different shell thicknesses when the temperature is lower than T c. The T c of the two NCs (3.98 K, 4.15 K) is slightly higher than that of the metal block (3.73 K) due to the electron-scattering effect of the particles' surface shell. The resistances of the two samples below T c show an exponential decay mode, which is the result of the thermally activated phase slip (TAPS) and quantum phase slip (QPS).