Washington, D.C. : United States. Dept. of Energy. Office of Basic Energy Sciences ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2016
Book — 1 online resource (Article No. 1500396) : digital, PDF file.
All transparent conducting materials (TCMs) of technological practicality are n-type; the inferior conductivity of p-type TCMs has limited their adoption. Additionally, many relatively high-performing p-type TCMs require synthesis temperatures > 400 °C. Here, room-temperature pulsed laser deposition of copper-alloyed zinc sulfide (Cu <sub>x</sub> Zn <sub>1- x</sub> S) thin films (0 ≤ x ≤ 0.75) is reported. For 0.09 ≤ x ≤ 0.35, Cu <sub>x</sub> Zn <sub>1- x</sub> S has high p-type conductivity, up to 42 S cm <sup>-1</sup> at x = 0.30, with an optical band gap tunable from ≈3.0–3.3 eV and transparency, averaged over the visible, of 50%–71% for 200–250 nm thick films. In this range, synchrotron X-ray and electron diffraction reveal a nanocrystalline ZnS structure. Secondary crystalline Cu<sub> y</sub> S phases are not observed, and at higher Cu concentrations, x > 0.45, films are amorphous and poorly conducting. Furthermore, within the TCM regime, the conductivity is temperature independent, indicating degenerate hole conduction. A decrease in lattice parameter with Cu content suggests that the hole conduction is due to substitutional incorporation of Cu onto Zn sites. This hole-conducting phase is embedded in a less conducting amorphous Cu <sub>y </sub>S, which dominates at higher Cu concentrations. Finally, the combination of high hole conductivity and optical transparency for the peak conductivity Cu <sub>x</sub> Zn <sub>1- x</sub> S films is among the best reported to date for a room temperature deposited p-type TCM.