Browsing by Author "Goldenberg, Eda"
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Item 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.Item 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, EdaWe 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.Item Open Access Hollow-cathode plasma-assisted atomic layer deposition: A novel route for low-temperature synthesis of crystalline III-nitride thin films and nanostructures(IEEE, 2015) Bıyıklı, Necmi; Ozgit-Akgun, Çağla; Goldenberg, Eda; Haider, Ali; Kızır, Seda; Uyar, Tamer; Bolat, Sami; Tekcan, Burak; Okyay, Ali KemalHollow cathode plasma-assisted atomic layer deposition is a promising technique for obtaining III-nitride thin films with low impurity concentrations at low temperatures. Here we report our efforts on the development of HCPA-ALD processes for III-nitrides together with the properties of resulting thin films and nanostructures. The content will further include nylon 6,6/GaN core/shell and BN/AlN bishell hollow nanofibers, proof-of-concept thin film transistors and UV photodetectors fabricated using HCPA-ALD-grown GaN layers, as well as early results for InN thin films deposited by HCPA-ALD technique. © 2015 IEEE.Item Open Access Zno nanostructures via hydrothermal synthesis on atomic layer deposited seed-layers(IEEE, 2015) Orlov, A.; Ulianova, V.; Bogdan, O.; Pashkevich, G.; Bıyıklı, Necmi; Goldenberg, Eda; Haider, AliThe original results of two different types of ZnO nanostructures grown via hydrothermal synthesis on ZnO seed-layers coated by atomic layer deposition process on Si substrates were presented. Scanning electron microscopy and X-ray diffractometry were used for the analysis of resulting nanostructured ZnO samples. The influence of annealing on crystal properties of the ZnO nanostructures was shown. It was ascertained that solution composition had a significant influence on the morphology of nanostructures and post-growth annealing modified the crystal properties of nanostructures. © 2015 IEEE.