Browsing by Subject "Strontium titanate"

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Open Access
Electro-optical performances of nanostructured SrTiOx films: The effect of plasma power, Ar/O2 ratio and annealing
(Wiley-Blackwell Publishing, Inc., 2021-01-01) Goldenberg, Eda; Bayrak, Türkan; Mohammadmoradi, O.
The present work evaluates the effects of plasma power and oxygen mixing ratios (OMRs) on structural, morphological, optical, and electrical properties of strontium titanate SrTiOx (STO) thin films. STO thin films were grown by magnetron sputtering, and later thermal annealing at 700°C for 1 h was applied to improve film properties. X-ray diffraction analysis indicated that as-deposited films have amorphous microstructure independent of deposition conditions. The films deposited at higher OMR values and later annealed also showed amorphous structure while the films deposited at lower OMR value and annealed have nanocrystallinity. In addition, all as-deposited films were highly transparent (~80%–85%) in the visible spectrum and exhibited well-defined main absorption edge, while the annealing improved transparency (90%) within the same spectrum. The calculated direct and indirect optical band gaps for films were in the range of 3.60-4.30 eV as a function of deposition conditions. The refractive index of the films increased with OMRs and the postdeposition annealing. The frequency dependent capacitance measurements at 100 kHz were performed to obtain film dielectric constant values. High dielectric constant values reaching up to 100 were obtained. All STO samples exhibited more than 2.5 μC/cm2 charge storage capacity and low dielectric loss (less than 0.07 at 100 kHz). The leakage current density was relatively low (3 × 10−8Acm−2 at +0.8 V) indicating that STO films are promising for future dynamic random access memory applications.
Open Access
Growth and characterization of nanocrystalline SrTiOx films: room temperature deposition using RF sputtering system in a pure argon environment
(Institute of Physics Publishing, 2017-05) Bayrak, Türkan; Goldenberg, Eda
We report a comprehensive description of the structure, optical and electrical properties of asdeposited and annealed SrTiOx (STO) thin films. Nanocrystalline STO films were deposited on p-type Si (1 0 0) and UV-grade fused silica substrates by RF magnetron sputtering at room temperature in a pure argon environment. Well adhered and transparent films with very smooth surfaces were obtained. As-deposited films showed 70% transparency in the visible spectrum, transparency increased to 77% after annealing at 700 °C. The direct and indirect optical band gaps were found to be 2.88 eV and 2.44 eV, for as-deposited films. For annealed films, indirect band gap increased to 2.57 eV while the direct optical band gap value remained constant. Upon annealing, the refractive indices (n) of the films decreased from 2.36 to 2.32. Ag/STO/p-Si device structures were also fabricated and characterized by current-voltage, capacitance-voltage and dielectric measurements. The calculated values are compared with experimental data from the literature and discussed in terms of device performances. A butterfly loop-type hysteresis curve was observed for the voltage-dependent capacitance measurement in annealed thin film devices. Dielectric constants were calculated as 31.7 and 57.4 for as-deposited and annealed films at 100 kHz, respectively. Charge storage capacity was found to be >4.5 μC cm-2 for as-deposited and 3.5 μC cm-2 for annealed films.
Embargo
Tunable photocatalytic activity of CoFe Prussian blue analogue modified SrTiO3 core–shell structures for solar-driven water oxidation
(American Chemical Society, 2023-12-18) Peighambardoust, N. S.; Sadigh Akbari, Sina; Lomlu, Rana; Aydemir, U.; Karadaş, Ferdi
This study presents a pioneering semiconductor-catalyst core–shell architecture designed to enhance photocatalytic water oxidation activity significantly. This innovative assembly involves the in situ deposition of CoFe Prussian blue analogue (PBA) particles onto SrTiO3 (STO) and blue SrTiO3 (bSTO) nanocubes, effectively establishing a robust p–n junction, as demonstrated by Mott–Schottky analysis. Of notable significance, the STO/PB core–shell catalyst displayed remarkable photocatalytic performance, achieving an oxygen evolution rate of 129.6 μmol g–1 h–1, with stability over an extended 9-h in the presence of S2O82– as an electron scavenger. Thorough characterization unequivocally verified the precise alignment of the band energies within the STO/PB core–shell assembly. Our research underscores the critical role of tailored semiconductor-catalyst interfaces in advancing the realm of photocatalysis and its broader applications in renewable energy technologies.