Thermally induced evolution of optical and structural properties of Er2O3 films grown on Si substrates by thermal atomic layer deposition

Abstract

Thermally induced evolution of structural and optical properties of Er 2 O 3 films prepared by atomic layer deposition was investigated. The films were grown on Si substrates by water-assisted approach from (tris (methylcyclopentadienyl)erbium(III). As-deposited films showed cubic Er 2 O 3 phase, and compressive stress. Isochronal (30 min) heating at 600-1100°C in nitrogen flow caused strain relaxation, decrease of the lattice parameters and the increase of coherent domain size. Besides, in the films annealed at 1000-1100°C, the formation of Er silicate phase was observed. This phase formed due to Si diffusion from substrate in film volume, and the presence of Si was found not only at the film/substrate interface, but also on the top surface of the film. This fact was explained by spinodal decomposition of Er silicate with the formation of Er 2 SiO 5 phase on top surface. It was shown that both oxygen vacancies and Er 3+ ions contribute to light emission, however, no energy transfer from vacancies to Er 3+ ions was detected.

Optical and structural investigations of annealing impact on phase separation of Erbium-doped Al2O3 layers

“…These latter can be explained by the formation of a SiO 𝑥 interfacial layer as well as by the diffusion of Er towards film/substrate interface and/or Si diffusion into film volume towards its surface. Similar behavior was reported by us earlier for the Er 2 O 3 films grown on Si substrates with the same ALD approach [20]. These findings are in agreement with the ellipsometry data.…”

“…Since no additional peaks appear in the FTIR spectra of the samples annealed at 1100 • C, one can assume the main contribution in these spectra is given by the 𝛾−Al 2 O 3 phase. This assumption is supported by the observation of the effect of SiO 2 addition into Al 2 O 3 materials demonstrating the retarding of the formation of 𝛼−Al 2 O 3 phase [22] that usually appears at 𝑇 𝐴 ≥1100 • C [20]. However, FTIR spectra of such samples demonstrate additional vibration bands with the maxima near 1256, 1090, and 820 cm −1 (at 𝑇 𝐴 = 1000-1100 • C) that are the features of Si-O vibrations [20].…”

“…While the reduction of the refractive index observed at the maximum annealing temperature can be attributed to the formation of specific phases with low n within the films, such a transformation of the film characteristics allows for the expectation of crystallization of the films for 𝑇 𝐴 = 850-1100 • C. The latter can consist of voids or cavities as well as silicon-rich phases due to the diffusion of Si into the film volume from the substrate. We previously reported a comparable outcome for Er 2 O 3 films produced using the same ALD strategy [20]. It was demonstrated that Si diffusion toward the film surface was controlled by the mismatch between the lattice parameter of the film and substrate.…”

Staggered band alignment of n-Er2O3/p-Si heterostructure for the fabrication of a high-performance broadband photodetector

“…Panigrahi and Dhar investigated post-annealing effects on photodetection properties [22]. Khomenova reported on high-temperature annealing effects [23], while Kahraman highlighted the need for alternative methods to reduce interfacial trap states [18]. While Er 2 O 3 films continue to be studied for various applications [3], to the best of the authors' knowledge, no study exists on simple n-Er 2 O 3 /p-Si heterostructures fabricated through RF magnetron sputtering for BBPD applications.…”