D. R. Kammler

Point defects and electrical properties of Sn-doped In-based transparent conducting oxides

Abstract In-based transparent conducting oxides (TCOs) share the prevailing defect structure of indium–tin oxide (ITO), i.e. electrons, isolated Sn In ⋅ donors, and neutral associates, believed to be (2Sn In ⋅ O i ″) x . The present work reviews the state of the literature, presents calculated Brouwer diagrams vs. oxygen partial pressure and vs. dopant concentration, and reports intermediate temperature electrical property data (thermopower, conductivity) vs. p O 2 and Sn concentration for three systems — polycrystalline bulk ITO, nanocrystalline ITO, and the recently reported ternary cation TCO, Ga 3− x In 5+ x Sn 2 O 16 . The influence of non-reduceable tin–oxygen complexes at high doping levels is identified for ITO. Ramifications for In-based TCO properties are discussed.

Comparison of thin film and bulk forms of the transparent conducting oxide solution Cd1+xIn2−2xSnxO4

Physical and structural properties of thin films prepared via rf magnetron sputtering of the transparent conducting oxide spinel Cd1+xIn2−2xSnxO4 are compared to those reported for bulk specimens (prepared via high-temperature solid state reaction at 1175 °C). Optical band gaps measured on thin films of Cd1+xIn2−2xSnxO4 were 3.5, 3.70, and 3.65 eV for x=0.15, 0.45, and 0.70, which where 0.57, 0.94, and 0.95 eV higher than their bulk counterparts. Thin film Seebeck coefficients were −18.0, −15.5, and −15.5 μV/K for x=0.15, 0.45, and 0.70, respectively, which were 27, 24, and 19 μV/K smaller in magnitude than their bulk counterparts. Sn-Mossbauer spectroscopy revealed isomer shifts that averaged 0.2 mm/s for both bulk and thin films specimens. The presence of quadrupole splitting, which averaged near 0.48 mm/s for film specimens and 0.39 mm/s for bulk specimens, suggests that Sn+4 in all specimens is in octahedral coordination. The difference in quadrupole splitting suggests that thin films have a different...

Thin films of the spinel Cd1+xIn2−2xSnxO4 transparent conducting oxide solution

Thin films of a transparent conducting oxide solid solution Cd1+xIn2−2xSnxO4 (x=0.15, 0.45, and 0.70) were deposited via rf magnetron sputtering. X-ray diffraction indicated the films consisted of a polycrystalline spinel phase. Atomic force microscopy measurements revealed a surface root mean square roughness between 1.3 and 6.0 nm. Optical absorption was 10% or less in the visible for x=0.15, 0.45, and 0.70. Optical gaps averaged near 3.5, 3.70, and 3.65 eV for films annealed in Ar/CdS of compositions corresponding to x=0.15, 0.45, and 0.70. Conductivity exceeded 2000 S/cm for x=0.15 and 4000 S/cm for x=0.45 and 0.70. Mobilities of 43, 50, and 56 cm2/V s were measured for films annealed in Ar/CdS of compositions corresponding to x=0.15, 0.45, and 0.70, respectively. Composition data obtained via electron probe microanalysis indicate the films are becoming Cd deficient during the annealing process. This suggests an excess of In+3 and/or Sn+4 on Cd+2 sites may play a role in carrier production in these fi...