Crystallized Cu₂O films fabricated at low substrate temperature of 50–90 °C by spin-spray method

Abstract

Crystalline Cu₂O films were fabricated via the spin-spray method at substrate temperature (T_s) below 90 °C, without the post heat treatment. Grain size, crystal orientation and optical band gap controls of Cu₂O films were achieved by changing T_s. The film orientation was delicately tuned in sequence from {111} to {200} with T_s increasing from 50 to 90 °C. The Cu₂O film fabricated at T_s of 70 °C had a film thickness of 1.19 µm and consisted of a columnar structure with an average diameter size of 0.8 µm. In contrast, the films fabricated at T_s of 90 °C were composed of nanoparticles with diameters less than 0.1 µm. It was observed that a smaller grain size on the film surface corresponded to a wider optical band gap. Notably, the film fabricated at T_s of 50 °C exhibited a relatively wide band gap of 2.97 eV due to the quantum size effect.