Hydrogen complexes in epitaxial BaTiO3 thin films are investigated using Fourier transform infrared spectroscopy. Both undoped and Er-doped layers were grown using low-pressure metal–organic chemical vapor deposition. From the infrared spectra of the undoped and Er-doped films grown at 750–800 °C, infrared absorption was observed at 3486 cm-1. The absorption peak is attributed to a vibrational mode of O–H in BaTiO3. Moreover, the Er-doped layers showed additional absorption peaks at 2905 and 2964 cm-1. The peaks are ascribed to the vibrational modes of C–H complexes in the Er-doped layers. © 1997 American Institute of Physics.