Ultra-fast growth of copper oxide (II) thin films using hydrothermal method

Abstract In this paper we present the extremely fast growth of polycrystalline CuO thin films using a modified hydrothermal method. The process takes place in an open system, at a low temperature (below 100 °C) and in a very short time (in the range of 6 min–38 s). The growth technology does not require the use of toxic precursors or sophisticated equipment. The reaction solution used consists only of deionized water and copper (II) acetate. Sodium hydroxide is used as a pH regulator. The method developed makes it possible to control the thickness of the films over a wide range. The impact of individual parameters: pH, heating power, process duration and Cu(II) concentration, on layer thickness is discussed. The obtained films consist of monoclinic CuO, which was proved by XRD and is consistent with EDX measurements. The structure of the layers is polycrystalline with nanocrystallites of 7–12 nm in size, which was extracted from SEM images and XRD data. The optical energy band gap estimated from transmittance measurements is in the range of 1.82–1.87 eV. The innovative method described is very promising for many applications, especially photovoltaic ones. Its simplicity, low cost, and high efficiency make this approach very interesting and competitive to commonly used technologies.