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Communication Dans Un Congrès Année : 2023

Strontium Vanadate Deposited by ALD: Toward a New Synthesis Approach

Résumé

Transparent conductive oxides (TCOs) have a wide range of potential applications in fields such as photovoltaics, touch screens, and smart windows. The challenging task when developing conventional TCOs like tin-doped indium oxide (ITO) by the traditional method is to make them more conducting by increasing the concentration of charge carriers without compromising the optical transparency [1]. Another novel approach involves increasing the plasma energy to widen the transparency window by increasing the charge carriers' effective mass. This approach has led to growing interest in perovskite transition metal oxides such as CaVO3 and SrVO3 due to their strong electronic correlation, which results in plasma energy shifting to higher energies than classical TCOs [2,3]. However, obtaining a crystallized film in the perovskite SrVO3 phase for optimal electrical conduction and optical transparency is challenging, particularly at low growth temperatures and when deposited on amorphous substrates like glasses [2, 4]. As a result, atomic layer deposition (ALD) has emerged as a promising technique for depositing conformal layers on large surfaces with high aspect ratios and low thermal budgets. In this study, we investigated the deposition of strontium vanadium oxide films by ALD using vanadium tri-isopropoxide (VTIP) as the vanadium precursor, strontium bis(isopropylcyclopentadienyl) (Sr(iPr3Cp)2) from Air Liquide company as the strontium precursor, and water as a reagent, respectively. We deposited SrVO3 films on (100) Silicon and glass substrates at 240°C and annealed them under forming gas (95% Ar, 5% H2) at 500°C for one hour. We paid particular attention to the deposition of an anatase TiO2 buffer layer to promote the crystallization of SVO. The unannealed films were found to be completely amorphous whatever the substrate, and regardless of the presence or not of the TiO2 crystallized buffer. The EDX, STEM-HAADF and SIMS analyses revealed that the buffer is a key element to avoid the Si diffusion in SVO layer, before, and even more upon annealing. The annealed samples with a buffer layer deposited on both substrates were crystallized into various SrxVyOz phases according to the Sr amount, controlled by the Sr cycles ratio (RSR) (figure). The XRD data allowed the identification of the Sr3VO8 and Sr2VO4 phases, where the last one favors the higher Sr amount. The influence of the substrate is significant and discussed. Furthermore, we characterized the films' optical properties using spectroscopic ellipsometry in the UV-visible range. We analyzed the refractive index and extinction coefficient behavior according to the Sr amount and evaluated the effect of annealing. We estimated the band gap energy using Tauc-Lorentz and Tauc plot models and discussed it in relation to the Sr amount and the obtained phases. Our study provides not only valuable insights into the deposition and characterization of SrVO3 thin films for potential TCO applications, but also on Sr3VO8 and Sr2VO4 phases, which may be of interest for their transparent oxide optical properties. New ALD growth strategies to improve the SrVO3 phases will be presented as a perspective of this study and as an example of using different V precursor or reactive atmospheres during ALD process.
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Dates et versions

hal-04384320 , version 1 (10-01-2024)

Identifiants

Citer

Aline Jolivet, Julien Cardin, Aimane Cheikh, Cédric Frilay, F. Gourbilleau, et al.. Strontium Vanadate Deposited by ALD: Toward a New Synthesis Approach. 244th ECS Meeting, ECS, Oct 2023, Göteborg, Sweden. ⟨10.1149/MA2023-02291489mtgabs⟩. ⟨hal-04384320⟩
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