PUBLICATIONS:
1- Influence of iridium (Ir) doping on the structural, electrical, and dielectric properties of LuFeO3 perovskite compound, O Polat, M Coskun, P Roupcova, D Sobola, Z Durmus, M Caglar, T Sikola, A. TURUT, Journal of Alloys and Compounds 877 (2021) 160282. https://doi.org/10.1016/j.jallcom.2021.160282
Abstract
Rare-earth ferrites have been intensively investigated owing to their magnetic, electrical, and optical features in the literature. The present quest goals to examine the electrical properties of LuFeO3 (LFO) and LuFe1−xIrxO3 (LFIO) ceramics with different mol%, x = 0.05 and 0.10. X-ray diffractometer (XRD) method was utilized to identify the crystal nature of the obtained powders. The scanning electron microscope (SEM) was exploited to examine the surface topography of the fabricated pellets. X-ray photoelectron spectroscopy (XPS) was employed to find out the valence states of lutetium (Lu) (data is not presented here), iron (Fe), and iridium (Ir). Electrical modulus, dielectric constant, and conductivity of LFO and LFIO ceramics were detailed by dielectric/impedance spectroscopy measurements, which were performed at between − 100 °C (173 K) up to 100 °C (373 K) with 20 °C temperature step. It was exhibited that the undoped LFO has a higher dielectric constant and conductivity than the Ir doped samples. Such a decrement in both dielectric constants and conductivity was related to i) reduction in the ratio of Fe2+ ions and ii) defects and/or distortion in the LFO structure due to Ir substitution.
2- Effects of measurement temperature and metal thickness on Schottky diode characteristics, AF Özdemir, T Göksu, N Yıldırım, A Turut, Physica B: Condensed Matter 616 (2021) 413125. https://doi.org/10.1016/j.physb.2021.413125
Abstract
Ti Schottky contact (SC) metal with 50 nm and 100 nm thickness on n-GaAs substrate was sputtered by DC magnetron into vacuum unite. It was checked whether the diode parameters changed with SC metal thickness and measurement temperature. As a result of measurements, the potential barrier values decreased while ideality factors remained unchanged with the increasing metal thickness. The results showed that the Ti film thickness has a considerable effect on the barrier potential value. The potential barrier value of the device with thickness of 50 nm was found to be 0.92 and 0.63 eV, and that of 100 nm thickness to be 0.80 and 0.56 eV at 300 and 60 K, respectively. That is, a different of 0.12 eV for the barrier potential was obtained depending on metal thickness at 300 K.
3- Role of Reduced Graphene Oxide-Gold Nanoparticle Composites on Au/Au-RGO/p-Si/Al Structure Depending on Sample Temperature, M Sağlam, B Güzeldir, A. TURUT, D Ekinci, Journal of Electronic Materials (2021) 1-10. https://doi.org/10.1007/s11664-021-09017-0
Abstract
In order to understand the current conduction mechanism in metal-semiconductor rectifer junctions, it is important to take electrical measurements depending on the sample temperature. Therefore, the current-voltage (I-V) measurements of the Au/Au-RGO/p-Si/Al structure were taken in the temperature range of 80–300 K by steps of 20 K. In the fabrication of the Au/Au-RGO/p-Si/Al structure, p-type Si was used as a base material. First, an ohmic contact was made by evaporating Al metal on the polished surface of the chemically cleaned p-Si and annealing in a nitrogen atmosphere at 580°C. Afterwards, mercaptoundecanoic acid-capped Au nanoparticles assembled on reduced graphene oxide (RGO), namely Au-RGO nanocomposite, was grown as an interfacial layer on the p-Si semiconductor substrate by the spin coating technique. The morphological and optical properties of the Au-RGO nanocomposite thin film were examined by atomic force microscopy (AFM) and Raman spectroscopy measurements. The I-V measurements of the Au/Au-RGO/p-Si/Al structure were taken depending on sample temperature and the basic electrical parameters such as ideality factor (n), barrier height (Φb) and dynamic resistance were calculated by means of thermionic emission method. It was observed that the ideality factor decreased and the barrier height increased with increasing sample temperature. The results were interpreted with the barrier inhomogeneity model and using Richardson plots.
4- Determining the potential barrier presented by the interfacial layer from the temperature induced IV characteristics in Al/p-Si Structure with native oxide layer, MC Ozdemir, O Sevgili, I Orak, A. TURUT, Materials Science in Semiconductor Processing, 125, (2021) 105629. https://doi.org/10.1016/j.mssp.2020.105629
Abstract
The temperature induced current-voltage (I–V-T) characteristics of the Al/SiO2/p-Si diodes with the interfacial native oxide layer were experimentally investigated in present our study. The values of 24.35 and 1.02 eV for the tunneling factor and the potential barrier presented by the interfacial layer (χ) were determined for the Al/SiO2/p-Si metal-insulator-semiconductor (MIS) diode. The χ value obtained from the forward bias I–V-T characteristics of the SiO2/p-Si diode is a crucial result according to those from only room temperature I–V curves in literature studies. Furthermore, the temperature dependence of the apparent barrier heights of the forward bias I–V-T characteristics displayed a Gaussian distribution (GD) of inhomogeneous barrier heights (BHs). Thus, the standard deviation values of σ1s0 = 147.65 mV for high temperature range and σ2s0 = 83.66 mV for low temperature range were obtained from the GD plot of the BHs (the apparent BH versus (2kT)-1 plot). Again, for the mean barrier height from the GD plot of the BHs, the values of 1.16 eV and 0.70 eV were obtained from the high temperature region and low temperature region, respectively. Furthermore, the Richardson constant values of 54.66 and 58.42 A/K2cm2 from these temperature regions are approximately 1.70 times higher than the theoretical value of 32 A/K2cm2 of the p-type Si semiconductor.
5- Effect of atomic-layer-deposited HfO 2 thin-film interfacial layer on the electrical properties of Au/Ti/n-GaAs Schottky diode, DE Yıldız, A Karabulut, I Orak, A. TURUT, Journal of Materials Science: Materials in Electronics, 32 (8), (2021) 10209-10223. https://doi.org/10.1007/s10854-021-05676-1
6- Electrical and optical characterization of Os-substituted rare-earth orthoferrite YbFeO 3-γ powders,O Polat, M Coskun, D Sobola, BZ Kurt, M Caglar, A. TURUT, Applied Physics A 127 (1 (2021) 1-11. https://doi.org/10.1007/s00339-020-04182-1
Abstract
The electrical properties of Os-doped YbFeO3 (YbFO) powders prepared by solid-state reaction have been studied by Impedance Spectrometer/Impedance Spectrometer. SEM, XPS and Raman spectroscopy were utilized for understanding chemical and structured analysis of the synthesized compounds. SEM images have revealed the void nature of the pellets. Furthermore, XPS studies have exhibited that Yb has 3+valance state. It is also revealed that the oxygen vacancies concentration drops as the Os doping level raises by XPS analysis. The frequency dependency of loss-tan(δ) examination has demonstrated that the
5 mol% Os-substituted sample has the lowest loss-tan(δ) values at high frequency regions at 100 °C. It has been also realized that the 5 mol% Os-doped compound exhibits the highest resistivity among the samples. Raman spectroscopy examination has unveiled that the samples have similar space group. In addition, the optical band gap of the synthesized powders was also extracted via utilizing the Kubelka–Munk technique. It was realized that the band gap of YbFO slightly increases as the Os dopant ratio advances.
7- Temperature dependence of electrical parameters of the Cu/n-Si metal semiconductor Schottky structures, ÖF Bakkaloğlu, K Ejderha, H Efeoğlu, Ş Karataş, A. TURUT, Journal of Molecular Structure 1224 (2021) 129057. https://doi.org/10.1016/j.molstruc.2020.129057
Abstract
The main electrical characteristics of Cu/n-Si metal-semiconductor structures have been investigated in the temperature range 50 K to 310 K using current–voltage (I–V) and capacitance–voltage (C–V) measurements. It has been showed that the values of ideality factor and barrier height increase with increase in temperature and are clarified by invoking three different set of Gaussian distributions (GD) of barrier height at 50–160 K, 160–220 K, and 220–310 K. The values of ideality factor and barrier height for the Cu/n-Si metal-semiconductor structures were obtained as 1.435 and 0.487 eV at 50 K, 1.399 and 0.704 at 120 K, 2.192 and 0.701 at 220 K, and 4.286 and 0.759 eV at 310 K, respectively. This results showed fairly that in presence of inhomogeneity at metal semiconductor (MS) interface. The double Gaussian distribution of the temperature dependent I–V characteristics of the Cu/n-Si metal-semiconductor structures barrier diode gave the mean barrier heights of 0.532, 0.638 and 0.816 eV and standard deviations (σo) of 3120 mV, 37 mV and 53 mV, respectively. Thus, the values of the mean barrier height have been verified with the modified ln(I0/T2)−q2σ2/2k2T2 versus (kT)−1 plot which belongs the three different temperature regions. Furthermore, it was showed that a noticeable increase of the saturation current from 1.978 × 10–46 to 3.973 × 10–8 A, (from 50 K to 310 K). The increase in saturation current after temperature was attributed to the presence of interface states created by temperature induced defects.
8- Analysis and Comparison of the Main Electrical Characteristics of Cu/n-type Si metal semiconductor structures at wide temperature Range, ÖF Bakkaloğlu, K Ejderha, H Efeoğlu, Ş Karataş, A. TURUT, Silicon (2021) 1-8. https://doi.org/10.1007/s12633-021-01132-1
Abstract
In this work, we investigated and compared the difference in temperature dependence of ideality values, barrier heights, and series resistances obtained using current-voltage (I-V) characteristics from various methods for Cu/n-type Si structures in the temperature range of 50 K–310 K by 20 K steps. From the I-V measurements using Cheung’s and Norde methods, the temperature-dependent changes of ideality factors (n), barrier heights (Φb), and sequence resistances (RS) were obtained. The experimental findings showed that all the values obtained from the Cu/n-type Si structure of the main parameters (n, Φb, and RS) decreased with increasing temperature, and that these values were also in strong agreement with each other. In addition, the interface states (NSS) were derived from the current-voltage characteristics as a function of temperature (K), and the experiment revealed that with increasing temperature, the interface states decreased. The interface states values for 50 K and 310 K of the Cu/m n-type Si structure changed to be 8.10 × 1011 eV−1 cm−2 and 2.72 × 1011 eV−1 cm−2, respectively.
9- The temperature induced current transport characteristics in the orthoferrite YbFeO3−δ thin film/p-type Si structure, O Polat, M Coskun, H Efeoglu, M Caglar, F M Coskun, Y Caglar and A Turut, J. Phys.: Condens. Matter 33 (2021) 035704. https://doi.org/10.1088/1361-648X/abba69
Abstract
The perovskite ytterbium ferrite is a new ferroelectric semiconductor material. We presented the temperature induced current–voltage (I–V) characteristics of the Al/YbFeO3−δ/p-Si/Al hetero-junction. The orthoferrite YbFeO3−δ thin films were deposited on a single crystal p-type Si substrate by a radio frequency magnetron sputtering system. The potential barrier height (BH) and ideality factor n of the heterojunction were obtained by thermionic emission current method based on the recommendations in the literature. The fact that the calculated slopes of I–V curves become temperature independent implying that the field emission current mechanism takes place across the device, which has been explained by the presence of the spatial inhomogeneity of BHs or potential fluctuations. Moreover, a tunneling transmission coefficient value of 26.67 was obtained for the ferroelectric YbFeO3−δ layer at the Al/p-Si interface.
10- M. Ensari Özay, P. Güzel, E. Can “Consequence Modelling and Analysis of Methane Explosions: A prelimi-nary Study on Biogas Stations”, Journal of Advanced Research in Natural and Applied Science, V.7, N.1, pp. 132-144, 2021. https://doi.org/10.28979/jarnas.890649
Abstract
Biomass is one of the most important sources of renewable energy. Biomass resources can be utilized by producing biogas in the biogas stations, which include process equipment operating in critical conditions. In this study, a consequence analysis of a methane gas explosion carried out to estimate the explosion and the toxic threat zones of a biogas station in Turkey. ALOHA and PHAST Software Tools are used to realize an explosion by modelling scenarios and thus to estimate the effects of an explosion just to get an insight on methane gas explosion. By using ALOHA software, two different scenarios as leakage from the biogas tank and flammable chemical escaping directly into the atmosphere are designed and calculated by the Gaussian model. In addition to that, two different explosion scenarios as a leakage scenario from the biogas storage tank and a catastrophic rupture scenario are computed by using the PHAST Software. According to the first scenario results from ALOHA, explosions can cause destruction of buildings, serious injuries and shattering of glasses in the threat zones about 200 m while in the second scenario only shattering of glasses can be seen in 22 m of threat zone. The results from the PHAST show that threat zones do not change significantly at different weather conditions. It is found that the catastrophic rupture has maximum hazard zone limits among all the scenarios. It has been concluded that using different model-based software can be useful to understand possible results of biogas plant explosions.
11- H. Ölmez, İ. Ergun, M. Ensari, E. Can “Normalleşme Sürecinde Ofis Çalışmalarında Covid-19’u Önlemede Balık Kılçığı Yöntemi İle Sebep Sonuç Analizi”, International Journal of Advances in Engineering and Pure Sciences, V.33,N.1, pp. 106-115, 2021. https://doi.org/10.7240/jeps.749452
Abstract
At the beginning of the normalization process, where COVID-19 has lost the rate of infection, the World Health Organization and the International Labor Organization make a wide range of suggestions and calls about the needs to be done for workplaces. Nevertheless, the scientific studies specific to workplace risk assessment, that needs to be updated at the first step, are very limited. In this study, risk assessment and effect for office studies were examined as part of the normalization process to return to work during COVID-19 pandemic. Within the scope of the study, the possible causes of the risk of infection of the virus were determined using the fish bone diagram, also called cause-and-effect analysis, and in order not to suffer COVID-19 disease, it was emphasized what measures should be taken depending on the risks. As a result, it was examined that COVID19 was mostly caused by the risks of 6 basic process. The components of these fundamental processes are identified as transportation, entrance and exits, working environment, meetings and educations, common areas and employees’ individual behaviors. The three most important measures are investigated. The first one is the preparation of the epidemic action plan and keeping it up to date and supervised in terms of mission definitions and activities. The second one is being example of office administrators for employees in terms of complying with the measures taken. At last, the third one is questioning and following the symptoms for COVID-19 such as measuring fire at entrances and exits to the offices. In addition, the business continuity plan was prepared for a selected SME by taking into account the risk assessment results under the guidance of the "Six-Steps Covid-19 Business Continuity Plan" published by the International Labor Organization (ILO).
12- D.İçkecan, N. Türkan, H. Gulbicim, “Investigation Of Shielding Properties Of Impregnated Activated Carbon For Gamma-Rays”, App. Rad. Isot., Vol. 172 (2021) 109687
Abstract
Carbon related structures are extraordinarily attractive materials for researchers and especially for organic chemistry, besides being the most important basic materials of daily life. The richness of various optical and electronic behaviors has made them one of the rapidly rising materials on the horizon of material science and condensed matter physics. Having the sheets of atoms that are stacked in a disorganized manner makes activated carbon being different from other forms of carbon –graphite- structures. The researches about the shielding properties of activated carbon atoms for gamma-rays are very rare and required to be improved. Since the use of radioactive sources in different fields (nuclear industry, shielding material, radiation biophysics and space research application, etc.) has been increasing expeditiously, the photon interactions with matter has gained more importance in the world of material science technology. In this article, we review the basics of the impregnated activated carbons (AC1 and AC2), as well as the link between the structural behaviors and the gamma shielding properties in terms of both quality and efficiency. Both XCom software and EGSnrc simulation code were used to obtain the theoretical calculations that are significantly important to be able to understand the shielding properties of impregnated activated carbons (AC1 and AC2) for gamma-rays. At the end, the mass attenuation coefficients (μm), the total atomic and the electronic cross-sections (σt,a and σt,e), the effective atomic number and the effective electron density (Zeff and Neff), the half value layer (HVL), the tenth value layer (TVL), and the mean free path (MFP) values of such materials were calculated and then compared with those of some other known shielding materials like lead, borosilicate, concrete and vermiculite. The calculated data showed that impregnated activated carbons (AC1 and AC2) are very appropriate and consistent to be one of the candidates for shielding materials of gamma-rays.