Infrared absorption peak due to Ta=O bonds in Ta2O5 thin films

Ta2O5 films deposited on Si substrates were investigated using transmission Fourier-transform infrared spectroscopy. We found a new absorption peak at 2340 cm(-1) that can be characterized as a stretching vibration mode due to Ta=O bonds in the films. This peak appeared following annealing in O-2 ambient, but not in N-2 ambient. It was located at 2335 cm(-1) in amorphous Ta2O5 films and shifted to 2340 cm(-1) after crystallization by annealing at over 700 degrees C. The bonds associated with the peak were homogeneously distributed in the film. We demonstrated that Ta2O5 films can include strong double bonds between Ta and O (Ta=O) in the structure, independent of whether they are crystalline or amorphous. (C) 2000 American Institute of Physics. [S0003-6951(00)00636-7].