Transparent, conducting, amorphous oxides: Effect of chemical composition on electrical and optical properties of cadmium germanates
- Tokyo Inst. of Tech., Yokohama (Japan). Materials and Structures Lab.
- National Inst. for Research in Inorganic Materials, Tsukuba (Japan)
Amorphous cadmium germanate thin films with the chemical composition xCdO{center_dot}(100 {minus} x)GeO{sub 2} ({approximately}20 < x < {approximately}80 mol%) were prepared by a radio-frequency sputtering method in an Ar-O{sub 2} atmosphere. The electrical and optical properties of the as-sputtered films and films after proton (H{sup +}) implantation were measured in the temperature range 300-6 K. The optical band gaps of the as-sputtered films were >3.1 eV for all specimens; therefore, they were transparent to visible radiation. Direct-current conductivities of all the films prepared were <10{sup {minus}9} S{center_dot}cm{sup {minus}1} at room temperature. Upon proton implantation to a fluence of 2 {times} 10{sup 16} cm{sup {minus}2}, the conductivity of the film with x {approx} 78 at room temperature was enhanced to 210 S{center_dot}cm{sup {minus}1}, 11 orders of magnitude greater than the conductivity of the as-sputtered film, and the conductivities remained almost constant to {approximately}6 K, whereas those of films with x < {approximately}55 remained at {approximately}10{sup {minus}9} S{center_dot}cm{sup {minus}1}. The carrier electron density and the mobility of carriers in the former films, both of which were evaluated from the Hall measurements, were {approximately}1 {times} 10{sup 20} cm{sup {minus}3} and 12 cm{sup 2}{center_dot}V{sup {minus}1}{center_dot}s{sup {minus}1}, respectively. Effects of the chemical composition on persistent photocurrents also were examined. Significant photocurrents were observed in the films with x > {approximately}50, and they were greatly enhanced in the films with x > {approximately}75. This result indicated that the bottom part of the conduction band, which was composed mainly of 5s orbitals of cadmium cations, was extended for the films with x > {approximately}75.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 455155
- Journal Information:
- Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 1 Vol. 80; ISSN 0002-7820; ISSN JACTAW
- Country of Publication:
- United States
- Language:
- English
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