Polycrystalline, tetragonal (P42/nmc) zinc phosphide (Zn3P2) thin films were deposited on borosilicate glass substrates by reactive radio frequency (r.f.) sputtering of zinc (Zn) in the presence of phosphine gas (PH3). Various sputtering parameters, including substrate temperature (T-sub), gun power, gas flow rates of PH3 and argon (Ar), and total sputtering pressure (P-Tot) were varied to optimize crystalline growth. Under optimal growth conditions [T-sub similar to 200-230 degrees C, PH3:(PH3 + Ar) < 0.1, and P-Tot: 1.30-2 Pa], films were polycrystalline in nature, with crystallite sizes up to 100-150 nm and orientation along the (004) direction. Lowering the T-sub or increasing the PH3 content resulted in amorphous growth. The stoichiometry of the films was measured by top-down energy dispersive Xray spectroscopy (EDS), and cross-sectional EDS mapping indicated compositional homogeneity throughout the film depth. The average surface roughness under optimal growth conditions was less than 10 nm. As-grown films were p-type, with high carrier concentrations (similar to 10(16) cm(-3)) but low mobilities (<1 cm(2)/V.s). Ex situ annealing of films in nitrogen or argon/hydrogen (Ar/H-2) led to an order of magnitude decrease in the film's resistivity. Films exhibited a direct and an indirect optical bandgap of 1.58 and 1.44 eV, respectively, as measured by ellipsometry. Equipment limitations defined the reactive sputtering conditions explored here, but the data suggest that film properties may be further improved with deposition at higher substrate temperatures (>250 degrees C) and higher sputtering pressures (>2 Pa). (C) 2015 Elsevier B.V. All rights reserved.