Comprehensive investigation of Er2O3 thin films grown with different ALD approaches

Abstract

The effect of Er precursor nature (Er(CpMe)3 or Er(tmhd)3) and annealing treatment at 500–1100 °C on the structural and optical properties of Er2O3 films grown on Si substrates by thermal or O2-plasma-assisted atomic layer deposition was studied by means of spectroscopic ellipsometry, Fourier-transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy coupled with energy dispersive X-ray spectroscopy as well as photoluminescence method. An annealing at 500–800 °C resulted in the film crystallization mainly. Thermal treatment at high temperatures caused the formation of Er silicate phase due to the diffusion of Si atoms from the substrate in the films depth. This phase was found to be Er2SiO5 being crystallized at 1100 °C. Light emitting properties of the films are determined by Er2O3 native defects (like oxygen vacancies) and intra-4f shell transition in Er3+ ions. The latter dominated in the films annealed at 1000–1100 °C. The most intense Er3+ emission, observed in the films grown with O2-plasma-assisted approach, was explained by a lower contribution of oxygen vacancies as well as by pronounced crystallization of Er silicate phase. In this latter, the effect of concentration quenching of Er3+ luminescence was lower due to a larger distance between Er3+ neighbor ions.