Atomic Layer Deposition of Photoconductive Cu2O Thin Films

Tomi Iivonen; Mikko J Heikkilä; Georgi Popov; Heta-Elisa Nieminen; Mikko Kaipio; Marianna Kemell; Miika Mattinen; Kristoffer Meinander; Kenichiro Mizohata; Jyrki Räisänen; Mikko Ritala; Markku Leskelä

doi:10.1021/acsomega.9b01351

Atomic Layer Deposition of Photoconductive Cu₂O Thin Films

ACS Omega. 2019 Jun 27;4(6):11205-11214. doi: 10.1021/acsomega.9b01351. eCollection 2019 Jun 30.

Affiliations

¹ Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland.
² Department of Physics, University of Helsinki, P.O. Box 43, FI-00014 Helsinki, Finland.

Abstract

Herein, we report an atomic layer deposition (ALD) process for Cu₂O thin films using copper(II) acetate [Cu(OAc)₂] and water vapor as precursors. This precursor combination enables the deposition of phase-pure, polycrystalline, and impurity-free Cu₂O thin films at temperatures of 180-220 °C. The deposition of Cu(I) oxide films from a Cu(II) precursor without the use of a reducing agent is explained by the thermally induced reduction of Cu(OAc)₂ to the volatile copper(I) acetate, CuOAc. In addition to the optimization of ALD process parameters and characterization of film properties, we studied the Cu₂O films in the fabrication of photoconductor devices. Our proof-of-concept devices show that approximately 20 nm thick Cu₂O films can be used for photodetection in the visible wavelength range and that the thin film photoconductors exhibit improved device characteristics in comparison to bulk Cu₂O crystals.