The Effect of Infrared Light’s Power on the Infrared Spectra of Thin Films

摘要

There are numerous evidences that a relationship exists between the average power P of electromagnetic waves and the mechanical motion of the objects interacting with them. We investigate the effects of infrared (IR) light’s average power P on the transmission Fourier transform infrared (FTIR) spectra of thin cubic Yb2O3 and rhombohedral LaAlO3 films deposited on silicon via atomic layer deposition. We find that different values of P of the IR light displace the minima of the absorption bands. This effect is reproducible in different sets of experiments and in different spectrometers. To interpret the experimental findings, we use the law of conservation of energy. We find a correlation among the energy of the IR waves and the number, moment of inertia, and vibrational/rotational frequency of the bonds involved in the vibrational or rotational motion. The law of conservation of energy unveils that larger values of P of the IR light and lower wavenumbers of the resonances involve a larger number of crystal bonds. One practical application of our approach is that it suggests a way to improve the sensitivity of the FTIR spectra of thin crystalline films in the far IR region.