Quantifying bonding strength of CuO nanotubes with substrate using the nano-scratch technique.

CuO is a narrow bandgap semiconductor demonstrating applications in/as catalysts, gas sensors, adsorbents, and superconductors, and as electrodes of photocells, super-capacitors, and lithium-ion batteries. One-dimensional (1D) CuO nanostructures are of particular interest in most of these device applications, owing to their huge surface area. Strong bonding between nanomaterials and substrate is essential for extended device life. Hence, knowledge about the strength of the nanomaterial-substrate bond is highly desired. In this research work, CuO nanotubes were synthesized directly on a Cu substrate, and its adhesion strength was quantified using the nano-scratch-based technique. The adhesion energy of CuO nanotubes (for 7 h of reaction period) on the Cu substrate was measured to be 82 Jm(-2). The bonding strength can be correlated with the structure of the material. Results of this research will be valuable in analyzing and improving the lifetime of CuO nanotube-based devices, and the technique could be further extended to other 1D transition metal oxide nanostructures.