Effects of Mechanical Bending on the Photoconducting and Luminescent Properties of Epitaxial ZnO Films

A study of the influence of mechanical bending on the electrical resistance, photoconductivity (PC), and photoluminescence (PL) of epitaxial ZnO films is presented. We have found a systematic decrease in the electrical resistance and of the energy gap extracted from the photoconductivity and photoluminescence spectra as the bending of the film is increased. From the photoconductivity spectra, it is also possible to extract the electric field present on the film, obtaining a systematic increase of this field as the bending of the film is increased in accordance with an increment of the induced polarization due to this applied flexion. This result suggests that the observed reduction in the effective energy gap can be due to the Franz–Keldysh effect.