External fields can be used to regulate the morphological and chemical properties of electrochemically synthesized materials. Examples include emergent morphological patterns in electrodeposited thin films or plasmon-induced shape control in nanocrystals. These illustrate the principle of phototropism, where the coaction of light absorption and carrier generation can induce controllable variations in the material as it grows under illumination. Here we describe the photoelectrodeposition of photocathodic cuprous oxide (Cu2O). Illuminating the growing film with photon energies larger than the band gap of Cu2O results in nanoscale morphological changes in the structure of thin films and intrinsically dopes the material during growth. The result is a ‘black’ Cu2O film that is chemically distinct but crystallographically identical an ordinary film grown in the dark. The flat band potential of the film is controlled by the growth illumination intensity and the photodoping is reversible under thermal oxidation. We explore the nature of the intrinsic dopant as evidenced by the emergence of nanocrystalline Cu metal inclusions in the Cu2O matrix. Finally, we explore the potential of for this effect to be used in new semiconductor heterostructures prepared by light-directed fabrication.

Physical and chemical applications of photodoping in electrodeposited cuprous oxide thin films

255th National Meeting (2018)

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