Studies of the interfacial structure of LaAlO3 thin films on silicon by x-ray reflectivity and angle-resolved x-ray photoelectron spectroscopy

Abstract

The microstructures of amorphous LaAlO3 thin films deposited on silicon substrates by the laser molecular-beam epitaxy were studied by the x-ray reflectivity and the angle-resolved x-ray photoelectron spectroscopy. It was shown that the film∕substrate interface contains a La-rich LaxAlyOzSi layer and a SiOx layer. It was shown that the electron density of the LaAlO3 layer and the LaxAlyOzSi layer is not homogeneous along the growth direction due to the diffusion of La, Al, and Si. The growth kinetics of the LaAlO3 film was described by three processes: (1) formation of the SiOx layer at the early stage whose thickness saturates rapidly at about 13Å; (2) formation of the LaxAlyOzSi layer by the out diffusion of Si and the inner diffusion of La, Al (mostly La). This stage continues as the film grows (3) In the deposition process of LaAlO3, the distributions of La and Al in the LaAlO3 layer change from inhomogeneous to homogeneous.

Influences of different structures on the characteristics of H 2 O-based and O 3 -based La x Al y O films deposited by atomic layer deposition

“…These phenomena are attributed to the formation of positive fixed charge because of the formation of oxygen vacancies in sample D. The increase of the positive oxide charge is due to the interdiffusion of Si, Al, La, and O atoms, and the growth of the silicate interfacial layer is attributed to the formation of LaSiO x , AlSiO x , and LaAlSiO x . [19] Compared to the La x Al y O films with H 2 O as the oxidant, the films with O 3 as the oxidant possess smaller V FB . This indicates that the La x Al y O films with O 3 as the oxidant have smaller EOT and better quality interfacial layers.…”

Thermal Annealing Effects on the Atomic Layer Deposited LaAlO[sub 3] Thin Films on Si Substrate

“…12 The Si 2s peak of the 2.7 nm thick film is located at 153.4 eV, which is still slightly deviated from the BE of Si atoms in SiO 2 films ͑154.1 eV͒. 1 This suggests that this thin layer is still a silicate, not SiO 2 . The chemical shift due to a change in composition is also shown in O 1s spectra.…”

“…In many cases, inevitable interface layer formation between the amorphous LaAlO 3 thin films and Si substrate during film deposition and postdeposition annealing ͑PDA͒ have been reported. 1,2,[5][6][7][8][9] Interface layer formation normally has an adverse effect on the device performance. In this study, the equivalent oxide thickness of a LaAlO 3 film increased from 2.23 to 2.46 nm after PDA at 800°C.…”