Functional Materials for Energy

Pulsed Laser Deposition of Photoresponsive Two-Dimensional GaSe Nanosheet Networks

Pulsed laser deposition (left) from a crystalline GaSe target was adjusted to directly grow networks of interconnected triangular GaSe crystalline nanosheets ~200 nm across (inset shows atomic-resolution transmission electron microscopy and nanodiffraction). The plot shows the measured external quantum efficiency of the networks, which exhibit high photoresponsivity across a broad spectral range.

Researchers demonstrated a pulsed laser deposition (PLD) approach to synthesize networks of interconnected metal chalcogenide (GaSe) nanosheets that exhibit high photoresponsivity. Demonstrating PLD as a method to rapidly explore the synthesis of new families of two-dimensional layered materials is of significant interest for emerging optoelectronic applications of materials, where the properties depend upon the layer number and crystallite size.

Researchers used PLD to overcome difficulties in the control of stoichiometry, layer number, growth location, and density in the growth of metal chalcogenide single-crystalline domains. Using in situ imaging and plasma diagnostics, they adjusted the spatial confinement of the plume of laser-ablated precursor materials to preserve the stoichiometric transfer of material from a GaSe target to a substrate through the formation of clusters, while providing sufficient kinetic energy for their surface diffusion. The digital delivery of the precursor flux was shown to control the thickness of the nanosheets with both in-plane and out-of-plane orientations. The networks, composed of interconnected triangular crystals of few-layer GaSe nanosheets, ~200 nm across, exhibited high spectral responsivity and external quantum efficiencies, from the near-IR to the ultraviolet (see Figure).  

M. Mahjouri-Samani, R. Gresback, M. Tian, K. Wang, A. A. Puretzky, C. M. Rouleau, G. Eres, I. N. Ivanov, K. Xiao, M. A. McGuire, G. Duscher, and D. B. Geohegan “Pulsed Laser Deposition of Photoresponsive Two-Dimensional GaSe Nanosheet Networks,” Advanced Functional Materials (in press).   DOI: 10.1002/adfm.201401440

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