Recent Developments of Ultrafast Electron Beam Treatment of Transparent Conductive Films
Transparent conducting oxides (TCO) materials have gained increasing importance for mobile optoelectronic devices. These applications require transparent electrodes on lightweight flexible and thin substrates. Transparent conducting oxides, mainly indium tin oxide are the most popular materials for this purpose. The deposition of high quality layers is closely linked to an elevated substrate temperature during the coating process, normally in the range between 200ºC and300ºC. Most flexible materials have restrictions with respect to that. Various types of rapid annealing processes have been developed to overcome this technological obstacle. This contribution presents the results of a fast annealing process using the electron beam technology. The interaction of 10keV electrons with the coated substrate was simulated by the specially adapted code eBeam MultiPhysicsFoam based on the framework OpenFOAM 2.1. The code allows both temporal and spatial temperature field calculations in dependence of the deflection pattern of the electron beam. The simulation provided temperature peaks of up to 800ºC in the ITO layer on glass over several milliseconds. The effect of this short time annealing was verified experimentally with ITO samples on float glass. The specific resistance could be reduced from630 mOcm (as deposited at room temperature) to 300 mOcm.