Thin Films of Cupric Oxide: Crystallite Size and Conduction Mechanism Analysis
Nanocrystalline lms of cupric oxide (CuO) produced by thermal oxidation havebeen characterised using x-ray analysis, SEM image analysis and temperature-dependent con-duction measurements.We describe in detail the x-ray di ractometer calibration, paying partic-ular attention to a function- tting procedure which enables accurate subtraction of instrumentalcontributions to the sample di ractograms. The Scherrer and Williamson-Hall models are usedto calculate crystallite size and sample strain and also give some indication of spatial inhomo-geneity. Image analysis techniques which can discern individual `grains' (the circular Houghtransform and the ImageJ particle analyser) were used to evaluate the grain size distributionfrom SEM images. An average crystallite diameter of 30 nm - determined by the ImageJ par-ticle analyser - closely agrees with the various XRD analysis approaches. Electronic conductionin our samples is found to proceed via thermally activated transport, which we attribute tothe presence of a well-de ned trap state that lies 0.2 eV from the valence band edge. Thevoltage-dependence of the activation energy additionally shows that the activation is a bulke ect and not due to Schottky barriers between the sample and the metal contact.
B. J. Ruck and T. Kemmitt
S. Ravi et al., "Thin Films of Cupric Oxide: Crystallite Size and Conduction Mechanism Analysis", Materials Science Forum, Vol. 700, pp. 71-79, 2012