Pulsed laser deposition of single phase n- and p-type Cu2O thin films with low resistivity

Syed Farid Uddin Farhad*, David Cherns, James Smith, Neil Fox, David Fermin

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

Low resistivity (ρ~3-24 mΩ.cm) with tunable n- and p-type single phase Cu2O thin films have been grown by pulsed laser deposition at 25-200 0C by varying the background oxygen partial pressure (O2pp). Capacitance data obtained by electrochemical impedance spectroscopy was used to determine the conductivity (n- or p-type), carrier density, and flat band potentials for samples grown on indium tin oxide (ITO) at 25 0C. The Hall mobility (µH) of the n- and p-type Cu2O was estimated to be ~ 0.85 cm 2.V-1-1 and ~ 4.78 cm 2.V-1s-1 respectively for samples grown on quartz substrate at 25 0C. An elevated substrate temperature ~ 200 0C with O2pp = 2 - 3 mTorr yielded p-type Cu2O films with six orders of magnitude higher resistivities in the range, ρ ~ 9 - 49 kΩ.cm and mobilities in the range, µH ~13.5 - 22.2 cm 2.V-1s-1. UV-Vis-NIR diffuse reflectance spectroscopy showed optical bandgaps of Cu2O films in the range of 1.76 to 2.15 eV depending on O2pp. Thin films grown at oxygen rich conditions O2pp ≥ 7 mTorr yielded mixed phase copper oxide irrespective of the substrate temperatures and upon air annealing at 550 0C for 1 hour completely converted to CuO phase with n-type semiconducting properties (ρ~12 Ω.cm, µH ~1.50 cm2V-1s-1). The as-grown p- and n-type Cu2O showed rectification and a photovoltaic response in solid junctions with n-ZnO and p-Si electrodes respectively. Our findings may create new opportunities for devising Cu2O based junctions requiring low process temperatures.
Original languageEnglish
Article number108848
Number of pages9
JournalMaterials and Design
Volume193
Early online date5 Jun 2020
DOIs
Publication statusPublished - 1 Aug 2020

Keywords

  • pulsed laser deposition
  • cuprous oxide (Cu2O) thin film
  • p- and n-type conductivity
  • Hall coefficient measurement
  • Fermi level
  • Mott-Schottky analyses

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