text: Wide band gap semiconductors like tin oxide  generally possess a high chemical stability and mobility, are cheap to fabricate and have a suitable band alignment, making these semiconductors often used in various electronics as thin film transistors, anodes in lithium ion batteries and as electron transport layer in solar cells. The large band gap of  () and large binding energy () make it useful in ultraviolet based devices.
  But a fundamental problem arises with its dipole forbidden band structure in bulk form: the transition from the valence to the conduction band is dipole forbidden since both types of states exist with even parity with the effect that band edge emission of  is forbidden in nature. This can be offset by employing its reduced dimensional structure, partially destroying the crystal symmetry, turning the forbidden dipole transition into allowed ones. Observing optical transitions in  at room temperature, however, is challenging due to the light absorbing efficiency in the UV region of the reduced  structures being very weak and background scattering of electrons with lower energies. Using electroreflectance the optical transitions of thin films can be recovered: by placing a thin film in an electric field, the critical points of the optical transition will be enhanced while, due to a change in reflectivity, low energy background scattering is reduced.