Electrodeposition and Photocharacterization of In2Se3 Thin Films Using PP-ALD for Use As a Potential Photoanode

Abstract

Indium (III) selenide is an n-type semiconductor that displays 4 main crystal structures. While the more prevalent α and β structures have a direct bandgap of 1.62 eV, the γ structure has been found to have a bandgap of 1.9 eV.1,2 In current work, In2Se3 films were deposited using a pulse potential atomic layer deposition (PP-ALD) technique derived from E-ALD that relies upon the principles of ALD and underpotential deposition (UPD) to create ordered atomic layers. In PP-ALD both precursors, In and Se, are present in one solution that is pumped through the flow cell introducing the ions to the substrate. A cathodic pulse is then used to reductively deposit limited amounts of In and Se on the substrate surface, followed by an anodic pulse used to oxidatively strip any bulk In away from the surface leaving atomic layers of In2Se3. At pH=1, the deposition process creates bubbles in the flow cell that lead to regions of limited deposition. However, at pH=2, less bubbles are formed during the deposition process, leading to more uniform samples. Further investigations into the optimal cathodic and anodic deposition potentials for the PP-ALD program at pH=2 need to be done. These In2Se3 films have been demonstrated to have good photocurrent and have potential as an n-type photoanode in photoelectrochemical cell applications. Czerniawski, J.; Stickney, J.; Electrodeposition of In2Se3 Using Potential Pulse Atomic Layer Deposition. J. Phys. Chem. C 2016. 120, 16162-16167.Chang, K.; Lahn, S.; Chang, J. Growth of single-phase In2Se3 by using metal organic vapor deposition with dual-source precursors. Appl. Phys. Lett. 2006. 89, 182118.