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Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 21: Heterostructures, Interfaces and Surfaces I

HL 21.8: Talk

Tuesday, March 19, 2024, 11:30–11:45, EW 561

Chemical and energetical structure at P-rich InP(100)/TiO2 heterointerface — •Agnieszka Paszuk1, Jennifer Velázquez Rojas2, Mohammad Amin Zare Pour1, David Ostheimer1, Christian Höhn2, Roel van de Krol2, and Thomas Hannappel11Fundamentals of Energy Materials, Technische Universität Ilmenau — 2Institute for Solar Fuels, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany

In the photoelectrochemical cells with the highest solar-to-hydrogen conversion efficiencies, III−V photoabsorbers are integrated with a metal oxide passivation layer and a catalyst. Such devices require preparation of ideal (buried)interfaces to minimize the losses of the photogenerated charge carriers. Here, we study atomic layer deposition (ALD) of TiO2 on phosphorus terminated (P-rich) InP(100) surfaces prepared in a metalorganic vapor phase epitaxy reactor. Samples were transferred in ultra-high vacuum to an ALD chamber. Titanium tetrachloride and water were used as the titanium and oxygen precursors, respectively. The preparation of P-rich InP(100) and the deposition of the TiO2 were monitored in situ by ellipsometry and optical spectroscopy, respectively. After selected precursor pulses, the surface chemical composition and the electronic structure were determined by photoemission spectroscopy. We observed a nucleation delay of TiO2 and during the first deposition cycles, a limited interaction of the water and the Ti precursor due to stable P-P bonds on the InP(100) surface. The TiO2 layers show +4 oxidation state and we find no evidence of the presence of Ti3+ state, which might act as trap centres.

Keywords: metal oxide passivation layer; titanium dioxide; III-V semiconductors; photoelectrochemistry; X-ray photoelectron spectroscopy

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