Effect of crystal defects on the electrical properties in epitaxial tin dioxide thin films

Abstract

Epitaxial (101) tin dioxide thin films with thickness ranging from 6 and 100 nm were deposited on the (102) α-Al2O3(101̄2)α-Al2O3 substrate by femtosecond pulsed laser ablation. Due to the lattice and thermal expansion mismatch with the substrate, the SnO2SnO2 film shows interfacial misfit dislocations, antiphase boundaries (APBs), and partial dislocations. The APBs lie along the (01)(1̄01) planes with a displacement of 1/2[101]. The densities of APBs and partial dislocations vary with film thickness, whereas the average spacing of misfit dislocations remains constant. Hall effect measurements showed that both electron concentration and mobility decrease with a reduction in the film thickness, which is ascribed to the scattering of electrons by crystal defects and interfaces and the effect of a native space charge region at the near-surface region of the films. The response of the films to reducing gases was found to depend on the electron concentration of the film and the relative fraction, with respect to film thickness, of material that is depleted of electrons. © 2002 American Institute of Physics.