Structural and Photoelectrochemical Properties of GaP Nanowires Annealed in NH₃

Abstract

Nitrogen alloyed gallium phosphide (GaP1–x N x ) nanowires have been prepared by annealing gallium phosphide (GaP) nanowires in flowing NH3(g) at 750 °C. X-ray diffraction patterns and electron microscopy showed that changes in the annealing conditions afforded controlled alloying of N without effecting a complete conversion to gallium nitride (GaN). Raman measurements on nanowire films and individual nanowires highlighted intense new signatures, consistent with symmetry reduction from N incorporation in the zincblende lattice. The resultant optical properties and photoresponse of the GaP1–x N x nanowire films were investigated by wavelength-dependent diffuse reflectance and photoelectrochemical measurements, respectively. Diffuse reflectance measurements showed progressively lower reflectivity of visible light for nanowire films annealed in increasingly higher levels of NH3(g), indicating an increased light absorption. Corresponding photoelectrochemical measurements of the GaP1–x N x nanowires revealed an increased quantum efficiency, relative to GaP, for energy conversion of light with wavelengths longer than 545 nm. The presented data set thus identifies a methodology for improving the solar energy conversion properties of GaP nanowire film photoelectrodes for visible light.

Wet Chemical Functionalization of GaP(111)B through a Williamson Ether-Type Reaction

“…Coomassie Blue is a particularly attractive dye since it absorbs strongly at λ > 545 nm and has a standard potential for oxidation that suggests it could sensitize GaP by injecting a hole. 10 To attach Coomassie Blue, a reaction between the surface hydroxyl groups on etched GaP(111)B and a sulfonyl chloride group on the dye was envisioned. A clear F 1s signal in the high-resolution XP spectra after reaction of GaP(111)B with o-CF 3 C 6 H 4 CH 2 SO 2 Cl indicated that this strategy was viable ( Table 2).…”

“…1−7 Employing high aspect ratio photoelectrode form factors has proven effective in overcoming the intrinsically poor lightabsorbing properties of GaP, 8 as both macroporous 3 and nanowire 9, 10 GaP photoelectrodes have been demonstrated. However, such architectures do not address the two issues with the native surface chemistry of GaP, i.e., poor innate electrocatalytic activity for water splitting reactions and chemical instability.…”

Preparation of photoactive ZnGeP2 nanowire films

“…In contrast to other strategies for the preparation of ternaryphase semiconductor nanowires, 56,57 the single-step approach shown here for ZnGeP 2 nanowires is simple. The direct ternaryphase crystallization avoids compositional inhomogeneity as seen in many two-step binary-phase conversion strategies.…”

“…2). Without catalyst patterning, the thermal CVD growth system does not inherently favor highly aligned nanowires, 57 limiting further comment on the substrate orientation and growth direction based on electron microscopy observations. Related III-V and I-III-VI 2 semiconductor nanowires typically exhibit twinning defects perpendicular to their long axis.…”

Elongated nanostructures for radial junction solar cells

“…At present, the research on water splitting using III-V NWs is focused mainly on the materials GaAsP, InP and InGaN due to their suitable band structure [321,[323][324][325][326][327][328][329][330][331][332]. Basically, they can be divided into two categories, with and without a p-n junction.…”