A facile solution-based approach to nanoscale copper oxide thin films

Sarah Karle, Ruhr-University Bochum, Bochum, Germany
Detlef Rogalla, RUBION, Ruhr-University Bochum, Bochum, Germany
Markus Grafen, Ruhr-University Bochum, Bochum, Germany
Andreas Ostendorf, Ruhr-Iniversity Bochum, Bochum, Germany
Anjana Devi, Ruhr-University Bochum, Bochum, Germany

Nanoscale copper oxides have been in the focus of intensive research in recent years as they are exceptionally versatile and feature remarkable optical, electrical, thermal, and magnetic properties. Thus, CuxO nanomaterials offer attractive prospects for a variety of application fields, including optics, electrochemistry, sensing, superconductors, tribology, and electronics.[1] The synthesis methods for the three distinct phases of copper oxide, viz. CuO (cupric oxide), Cu2O (cuprous oxide), and Cu4O3 (paramelaconite), comprise physical and chemical vapor deposition routes as well as liquid phase or solution based techniques.

Both CuO and Cu2O are intrinsic p-type semiconductors due to Cu deficiencies, their band gaps were reported to be in the range of 1.2 – 1.71 eV and >2.16 eV, respectively.[2,3] Solution based methods, such as spin or dip coating, are rapid and facile techniques to deposit uniform thin films on two-dimensional substrates. Especially in the case of large scale (electronic) applications, solution-based methods are preferable to vapor phase techniques, due to simple processing at ambient conditions and low costs.

A facile, straightforward and additive-free fabrication process for high-quality CuO thin films via spin coating using a metalorganic Cu precursor will be presented. Thin films were investigated in view of their structural, morphological and compositional properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy as well as a combination of Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). Furthermore, the effects of different annealing procedures and phase mixture with Cu2O on the optical and electrical properties will be addressed.

[1] A. S. Zoolfakar, R. A. Rani, A. J. Morfa, A. P. O'Mullaned, K. Kalantar-zadeh, J. Mater. Chem. C, 2014, 2, 5247–5270.
[2] J. F. Pierson, A. Thobor-Keck, A. Billard, Appl. Surf. Sci., 2003, 210, 359–367.
[3] A. A. Ogwu, E. Bouquerel, O. Ademosu, S. Moh, E. Crossan, F. Placido, J. Phys. D: Appl. Phys., 2005, 38, 266–271.

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