Thickness dependence of the physical properties of atomic-layer deposited Al2O3

Abstract

Inspired by nature, we investigate the short-range order effect on the physical properties of amorphous materials. Amorphous Al2O3 thin films exhibit a higher proportion of their 4-coordinated Al sites close to the surface, causing variations in the average short-range order of the film. Below some thickness, the density of these films changes with size. In this work, we address the short-range order effect, through the thickness, on the electronic and optical properties of atomic layer deposited (ALD) Al2O3 thin films. Both the refractive index and the permittivity were found to vary with size. The refractive index increased with thickness, and for thick films (~50 nm) it was comparable to that of bulk amorphous Al2O3. The permittivity increased with thickness as well, but did not attain those of the bulk material. We discuss how these effects correlate with the density and short-range order. These results shed light on the size effects in thin amorphous oxides, and may guide the design of electronic and optical components and devices.

Integration of perovskite Pb[Zr0.35Ti0.65]O3/HfO2 ferroelectric-dielectric composite film on Si substrate

“…Refractive index of the sputtered PZT film decreases from 2.9 to 2 with the annealing temperature from 500 to 650 ° C. For the PEALD HfO 2 film, the refractive index first increases from 1.8 to 2.6 with the annealing temperature from 450 to 500 ° C, the refractive index further decreases with increase in the annealing temperature. The PZT and HfO 2 film shows maximum refractive index at the annealing temperature of 500 ° C. Higher refractive index indicates higher film density, which was due to the solid phase crystallization of deposited films (Shih and Dove, 1994; Ottermann and Bange, 1996; Es-Souni et al , 2001; Mohamed et al , 2004; Iakovlev et al , 2005; Tarre et al , 2008; Wang et al , 2017; Singh et al , 2018a, 2018b; Etinger-Geller et al , 2019; Hatayama et al , 2019). Reduction in the refractive index with further increase in the annealing temperature was due to the loss in the film crystallization, observed from the plot.…”

Modeling of Conduction Mechanisms in Ultrathin Films of Al2O3 Deposited by ALD

“…The equation for Schottky emission is determined by: 𝐽 = 𝐴 * 𝑇 • 𝑒𝑥𝑝 −𝑞 𝜙 − 𝑞𝐸/(4𝜋𝜀 𝜀 ) 𝑘 𝑇 The average extracted value for φ T is 1.52 eV, which is related to energy below the conduction band due to defects in the oxide, such as oxygen vacancies and dangling bonds. On the other hand, the average oxide relative permittivity (ε ox ) extracted from the same expression is 7.57, which is an admissible value for Al 2 O 3 in the amorphous phase [18,19]. For this conduction mechanism in its own materials, first, electrons are transferred from the conduction band of n type silicon to this trap energy level in the Al 2 O 3 band gap via a tunneling process.…”

Recombination in Passivating Contacts: Investigation Into the Impact of the Contact Work Function on the Obtained Passivation

“…[42] 2) In the ALD process, a silicon oxide (SiO x ) interlayer was inevitably formed between the Si wafer and the AlO x film. [43][44][45] As a result, a SiO x /Si interface was considered in the developed model. The defect distributions at this interface were chosen based on experimental values reported in Refs.…”