Browsing by Author "Kaya, S, Ozturk, O, Arda, L"

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Correlation between crystal defects and room temperature ferromagnetism of hydrothermally grown Eu substituted ZnO nanorods
(2022-11-15) Kaya S., Ozturk O., Arda L.; Kaya, S, Ozturk, O, Arda, L
The hydrothermal method has been used to grow zinc oxide nanorods on a glass substrate with different Europium (Eu) concentrations. The Eu doping effect on the structural, optical, and magnetic properties of the samples was systematically investigated. The undoped sample exhibited diamagnetic behaviour, while soft room temperature ferromagnetism was observed in all the Eu substituted samples. With regard to the hysteresis loops, the highest coercivity, saturated magnetic moment, and retentive magnetic moment values were observed to be 41.64 Oe, 18.86 × 10−6 emu, and 2.17 × 10−6 emu, respectively, for ZnO:Eu 7%. According to the relationships between the magnetic properties, Eu doping levels, and defects concentrations, it can be concluded that the room temperature ferromagnetism observed in the samples is caused by crystal point defects including oxygen vacancies and zinc interstitials, rather than carrier-mediated exchange interactions, which is also consistent with the bound magnetic polarons theory.
Roughness and bearing analysis of ZnO nanorods
(2020-07-01) Kaya S., Ozturk O., Arda L.; Kaya, S, Ozturk, O, Arda, L
It is essential to analyze the surfaces of thin films precisely to control the production process and the performance of nano-scale devices. Conventional techniques give limited information about the nano-scale surface morphology. Instead, atomic force microscopy (AFM) provides more accurate results about the surface parameters of nanostructures. Hence, in the current study, two-dimensional (2D) and three-dimensional (3D) morphological properties of zinc oxide (ZnO) nanorods (NRs) were investigated using AFM. ZnO NRs were produced via a hydrothermal method at different growth times and temperatures. The surface texture was also examined by scanning electron microscopy (SEM). The results revealed that the morphological parameters such as diameter, length, and shape of the nanorods could be tuned by changing growth time and temperature. Moreover, we analyzed the most crucial roughness and bearing analysis parameters, which affect the functional properties of ZnO in the surface engineering applications. The average roughness increased from 5.86 nm to 17.30 nm as growth time increased from 2 h to 5 h. The average roughness was obtained as 10.92 nm for the temperature of 90 °C and it reached 41.13 nm for 150 °C. In addition, height distribution and bearing area curves associated with the real contact area were reported. 90% of the area was spread at a depth of 48 nm for the growth time of 2 h while this value was obtained 183 nm for 5 h Addition, 90% of the area was spread at a depth of 88 nm and 457 nm for the temperature of 90 °C and 150 °C, respectively. We believe that our study would be a pioneering perspective on bearing analysis of ZnO nanorods.
Vertically aligned Nd substituted ZnO nanorods: Morphology, optical characteristics and room temperature ferromagnetism
(2022-03-01) Kaya S., Ozturk O., Arda L.; Kaya, S, Ozturk, O, Arda, L
Zn1-xNdxO (x = 0.00, 0.01, 0.03, 0.05, 0.07) nanorods (NRs) are grown vertically, perpendicular to the glass substrate using a hydrothermal method. Nd3+ ions are successfully substituted into the crystal lattice of ZnO. The crystal structure, morphology, optical, and magnetic properties are comprehensively studied by various techniques. Significant changes are observed in the morphological and optical properties of the Nd substituted ZnO NRs. According to the magnetic measurements, the maximum Hc value is observed to be 39.04 Oe at a concentration of 3% Nd and the maximum Ms value is observed to be 20.52 x 10−6 emu at 7% Nd, whereas the maximum Mr value is measured as 1.86 x 10−6 emu at 5% Nd, confirming that the magnitude of magnetic parameters are independent of Nd concentration. An opposing correlation is found between the Hc value and the morphological properties (including crystallite size, average roughness, and aspect ratio) of Nd substituted ZnO NRs.