Photon emission in CuInSe2 thin films observed by scanning tunneling microscopy -: art. no. 143115

We report on the observation of photon emission from CuInSe2 (CIS) thin films by scanning tunneling microscopy (STM), which results from the radiative recombination induced by tunneling electrons. Scanning tunneling luminescence (STL) spectroscopy suggests that photons are emitted near the surface of CIS. STL is excited by recombination of tunneling electrons with available holes in CIS or electron-hole recombination by impact ionization-unipolar and bipolar excitation, respectively. Which process becomes predominant depends on the voltage applied to the STM tip. Under unipolar excitation, the photon intensity decreases on grain boundaries when compared to grain interiors. Under bipolar excitation, on the other hand, no differences are observed in photon intensity. A reduction of the density of holes in grain boundaries, relative to grain interiors, can explain the observed behavior. (C) 2005 American Institute of Physics.