Excimer laser processing of indium-tin-oxide films: An optical investigation

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Abstract
Dc sputtered indium‐tin‐oxide films have been excimer laser irradiated at subablation threshold fluences (2). Optical characterization of irradiated products has been performed aiming at resolving the finer structure appearing in the IR–visible absorption spectra, as a function of laser fluence, and assigning such features to specific electronic defects which are produced upon irradiation. Four individual Gaussian‐like contributions to absorption spectra are identified at 0.7, 1.0, 1.6, and 2.6 eV, the intensity of which is observed to vary with fluence. Being absent in the original films and emerging in optical spectra at fluences exceeding 300 mJ/cm2, the 2.6 eV contribution is most characteristic to excimer laser processing and is responsible for the darkening of the film. Thermal model calculations reveal that such defects are produced only upon melting and fast resolidification of the film. The evolution of the chemistry actually taking place in the film upon irradiation is followed by x‐ray photoelectron spectroscopic analysis. A chemical approach to the production of such defects is proposed in which oxygen displacement in the atomic matrix leads to the formation of neutral ternary complexes of the type SnIn2O4.