Preparation and Electrochemical Characterization of WSe2 Electrodes Having a Wide Range of Doping Densities.

Abstract The preparation and electrochemical characterization of n-type and p-type tungsten diselenide (WSe 2 ) crystal electrodes with doping densities ranging from 5×10 15 to 3×10 19 cm −3 is reported. The growth of these layered crystals was accomplished using chemical vapor transport. The doping of the crystals is described; it was found that using Cl 2 as the transport agent and rhenium as dopant produced n-type crystals, while the p-type were obtained using I 2 as transporting agent and niobium as dopant. The exceptional stability and the layered lattice structure of these crystals are desirable features not found in most small bandgap semiconductors. These features permit accurate electrochemical (Mott-Schottky) determinations of the interfacial energetics. Electrodes prepared from these crystals were characterized electrochemically, which indicated ideal behavior of the space charge region (SCR) over wide range of potential and frequency, and photoelectrochemically, which revealed fill factors from 0.37 to 0.65. Doping densities, within a given batch of crystals, were found to be relatively uniform. Band edge potentials did not shift due to doping, frequency or the presence of metallocene redox couples. The utility of this series of semiconductor electrodes for fundamental studied is discussed.