Effects of N-implantation on the composition depth profile, the chemical bonds and the optical transmittance of AlNx films have been investigated by means of Auger Electron Spectroscopy (AES), Fourier Transform Infrared (FT-IR) spectroscopy and visible transmission spectroscopy. AINx films were deposited on silicon (111) and commercial glass by an Activated Reactive Eyaporation (ARE) technique near room temperature. The 40 and 80 keV N+ -implantations were carried out at room temperature with doses ranging from 5×1016 to 5×1017 ions/cm2. The result of AES measurements revealed that the as-deposited AlNx film on Si consists of the AIN layer near the topsurface and the Al-rich layer near the interface. The concentration of nitrogen in the films increases as the N-dose increases up to 1×1017 ions/cm2. The N-implantation at a dose of 5×1017 ion/cm2 causes the interface between the film and the Si substrate to mix rather than increase the nitrogen concentration in the film. This higher dose implantation makes the FT-IR absorption peak corresponding to Al-N bonding become clear, and it makes the optical transmittance at a wavelength of 4400 Å go from 7% for as-deposited AINx film up to 70–90%. It is concluded that N-implantation into AlNx films causes the formation of AIN with a stoichiometric ratio to improve optical properties of the film.