Raman spectra of carbon nanowalls (CNWs) grown using dc plasma-enhanced chemical vapor deposition were analyzed. The Raman spectra of CNWs exhibited G and D bands at ∼1580 and ∼1350cm−1, respectively. It is found that the bandwidth of the G band is relatively narrow, even when the peak intensity ratio of D band to G band is significantly high. This spectral feature of CNWs is distinguished from those of typical graphitelike carbons reported so far. From the comparison of these spectral features, it is shown that CNWs are composed of small crystallites with a high degree of graphitization.

Thin films of zinc, phosphorus, and zinc phosphide (Zn3P2) have been deposited by photodissociation of dimethylzinc (DMZ) and phosphine (PH3) on various substrates using a low-pressure mercury lamp as a light source. The substrate temperature was varied between room temperature and 250 °C. The deposition rates of the films were significantly affected by the UV light intensity, the density of gases, the PH3/DMZ molar ratio, and the substrate temperature. Zn3P2 microcrystallites were grown on Si(111) substrates at a temperature of 250 °C. Those crystallites were studied by using a scanning electron microscope and reflection high-energy electron diffraction. A very weak photoluminescence spectrum at 808 nm (1.53 eV) was observed at room temperature.

Heterojunction solar cells of Zn3P2/ITO have been fabricated by rf sputter depositing ITO films onto Zn3P2 multiple crystal, and their electrical and photovoltaic properties are studied. Multiple crystal boules of Zn3P2, 12–16 mm in diameter and 3 cm long with grain size of 1–5 mm in diameter, and resistivity ρ of 40–105 Ω-cm have been formed by vapor phase transport. The ρ of as-grown Zn3P2 has been reduced significantly by Ag doping above 400°C. A V oc of 0.24–0.32 V and a J sc of 13–26 mA/cm2 are measured and the power conversion efficiency of 1.1% is obtained without AR coating at simulated AM 1. The J-V characteristics suggest tunneling as the dominant conduction mechanism. A spectral response of J sc shows a good band-pass behavior between 360 nm and 830 nm.

Zinc phosphide (Zn3P2)/indium-tin oxide (ITO) heterojunction solar cells are fabricated by rf sputter depositing ITO on large grain polycrystalline Zn3P2 wafers. An AES analysis indicates that sputter etching of the Zn3P2 wafer surface before depositing ITO is of great importance in achieving a better performance as a solar cell. The passivation of Zn3P2 by reaction with atomic hydrogen is found to improve the cell performance significantly. Consequently, a power conversion efficiency of 2.1% (6 mm2 in active area) has been obtained without antireflection coating.

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