Metal oxide interfaces are key elements of future energy conversion devices to maximize electrical voltage, which strongly depend on surface charges due to adsorbed oxygen or positively charged oxygen vacancies. We can effectively change these charges by annealing in oxygen or nitrogen. ZnO nanostructures are prepared by hydrothermal growth from aqueous solutions of zinc nitrate hexahydrate and examethylenetetramine. Similarly, we also prepare MoO3 nanocolumns from molybdenum trioxide dihydrate in aqueous solution. Thin layers, which also serve as substrates for hydrothermal growth, are prepared in cooperation with the Faculty of Electrical Engineering of the Czech Technical University in Prague by magnetron sputtering or pulsed laser deposition.