Browsing by Author "Pat, Suat"

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Detailed transmittance analysis of high-performance SnO₂-doped WO₃thin films in UV-Vis region for electrochromic devices
(Springer, 2020-09-18) Olkun, Ali; Pat, Suat; Akkurt, Nihan; Mohammadigharehbagh, Reza; Demirkol, Uğur; Özgür, Mustafa; Korkmaz, Şadan; Olkun, Ali; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0003-0061-0573; KVY-3644-2024
WO(3)is a popular electrochromic device and therefore it has extensively used for the electrochromic (EC) devices such as display and smart window applications. In this study, SnO2-doped WO(3)thin films have been deposited to obtain high-performance EC device and detailed transmittance analysis was determined. At the end of this study, general coloring-bleaching mechanism for SnO2-doped WO(3)active layer is presented. Li ion intercalation/de-intercalation is seen in Nyquist graph for the SnO2-doped WO(3)thin film deposited onto ITO coated glass substrate. All tests were done in 80 s in coloring and bleaching of the SnO2-doped WO(3)layer. Reversibility values of the EC devices mounted in this study were calculated to be 79 and 90% for the device with ITO or FTO conductive layers, respectively. According to the morphological analysis, grain distribution on the surfaces defined as to be perfect. Thanks to Raman analyses, the SnO2-WO(3)phases are seen. Finally, the EC devices have been working in the UV-Vis region. As a result, to obtain the high-performance EC device, SnO2-doped WO(3)active layer is a good choice. TVA method is also proper technology to device manufacturing.
Electrochromic properties of graphene doped Nb2O5 thin film
(Electrochemical Society, 2020-12-01) Akkurt, Nihan; Pat, Suat; Korkmaz, Şadan; Olkun, Ali; Mohammadigharehbagh, Reza; Bursa Uludağ Üniversitesi.; 0000-0003-0061-0573; 0000-0002-0333-487X; DJH-5166-2022; X-5375-2018; 57216253716; 57189905524
Electrochromic device plays a key role in energy efficiency management and modern display technology. As a cathodic coloration material, Nb2O5 is one of the important material used in the electrochromic device. The capacity of a layer is related with the intercalation and deintercalation behavior. Graphene Doping is a promising process for the high-capacity ion storage application. Graphene is a two-dimensional material and it possesses excellent mechanical and electrical properties. In this paper, graphene doped Nb2O5 thin films have been deposited onto ITO coated glass substrate by a thermionic vacuum arc (TVA) technique. The coloring efficiency has been calculated as 91 and 56 cm(2) C-1 at 414 and 550 nm, respectively. The transmittance variation of graphene doped Nb2O5 layer have determined as 42%. According to the Raman spectroscopy, the peaks for orthorhombic phase of Nb2O5 and graphene bands have been observed. According to obtained results, graphene is a promising dopant material for the high performance electrochromic device with Nb2O5 active layer.
Investigation of substrate effect on Co-doped ZnO thin films prepared by thermionic vacuum arc technique
(Elsevier, 2022-10-17) Özkan, Mehmet; Erdem, Sercan Sadık; Mohammadigharehbagh, Reza; Kurtaran, Sema; Pat, Suat; Mohammadigharehbagh, Reza; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; X-5375-2018
In this paper, the substrate effect on cobalt-doped ZnO thin films and crystal defects on optical properties of the sample have been investigated. The structural, elemental, surface and optical properties of the films were characterized using X-ray diffraction (XRD), atomic force microscopy, field emission scanning electron micro-scopy and UV-vis spectrophotometry. The XRD results confirm the polycrystalline nature and formation of ZnO (10 0) plane for both substrates was detected. Metal oxide and bimetal oxide structures were determined using by XRD analyses. Average crystallite size of the films has been computed as 20 and 25 nm on the glass and Si substrates, respectively. The thicknesses of the films were recorded as 85 and 90 nm on the glass and Si sub-strates, respectively. The mean transmittance value was measured as 71 %. The band gap value of Co-doped ZnO thin film was calculated as 3.22 eV. The Urbach energy was achieved as 227 meV depending on the lattice distortions and structural defects. According to obtain results, TVA is a promising method for Co doped ZnO thin film production.
Investigation of the structural, magnetic, and cooling performance of AlFe thin film and AlFeGd nanometric giant magnetocaloric thin films
(Springer, 2021-02-02) Pat, Suat; Bayer, Özgür; Akay, Sertan Kemal; Mohammadigharehbagh, Reza; Kaya, Metin; AKAY, SERTAN KEMAL; Mohammadigharehbagh, Reza; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; 0000-0002-0333-487X; R-7260-2016; X-5375-2018
Giant magnetocaloric thin films are promising materials for new generation energy-efficient cooling systems. To investigate the cooling performance of AlFe and AlFeGd alloys, thin films have been deposited onto a glass substrate by thermionic vacuum arc (TVA) deposition system. TVA is a physical vapor deposition technology; it works in high vacuum and low-temperature conditions. AlFe and AlFeGd thin films are of significant importance for giant magnetocaloric materials. The surface and magnetic properties of a magnetic material are strongly dependent on the deposition process. In this paper, the structural, magnetic, and cooling performances of AlFe alloys with and without the Gd element have been investigated. When the Gd elements are added to AlFe alloys, the size of crystallite and the surface morphology of the giant nanometric magnetocaloric thin films are altered. The size of crystallite decreases to a lower value due to the Gd element added. According to the results of the elemental analysis, the elemental ratios of the AlFe and AlFeGd thin films were measured as (87:13) and (84:4:12), respectively, which are different from the ones reported previously. Magnetic cooling performance and magnetization strongly depend on these ratios. The mean values of crystallite size for the AlFe thin film and AlFeGd nanometric giant magnetocaloric thin film were measured as 50 nm and 12 nm, respectively. Following the Curie temperature of AlFeGd thin film, and the temperature difference it produces in the studied magnetic fields, 60 successive units of this material are assumed to form a magnetic refrigeration cycle. The coefficient of performance of this cycle is calculated to be 2.084-nearly two times better than the suggested cascade vapor-compression cycles in the same temperature range. This fact alongside the solid-state and environmentally friendly attributes of magnetic refrigeration cycles makes the AlFeGd thin films a strong candidate for accomplishing an efficient refrigeration system.
Investigation of TiO2 thin films as a cathodic material for electrochromic display devices
(Springer, 2020-04-26) Akkurt, Nihan; Pat, Suat; Mohammadigharehbagh, Reza; Özgür, Mustafa; Demirkol, Uğur; Korkmaz, Sadan; Olkun, Ali; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; DJH-5166-2022; 57216253716
Titanium dioxide is a preferred material in many fields of applications and is also used as one of best electrochromic display (ECD) candidates due to its chemical stability. Electrochromic devices are innovative, low-cost and low energy consumption for using as displays. In this work, electrochromic, morphological, structural, and some optical properties of tandem structures were comprehensively investigated. The mean thicknesses of the samples were measured as 86 and 120 nm on ITO- and FTO-coated glass substrates, respectively. The chronoamperometry test was performed to determine some electrochromic properties of the ECD. It was observed that the amounts of ions intercalated/de-intercalated from the coated TiO2 layer were almost equal to each other. According to the chronocoulometric analysis, the superior reversibility and coloration efficiency of the assembled ECD were found to be 83% and 26 cm(2)/C, respectively, onto ITO substrates. Higher reversibility is revealed in thinner films, which is consistent with the obtained thickness results. In a similar manner, highest coloration efficiency obtained for our ECD has demonstrated good contact between the TiO2-deposited layer and the ITO-coated glass substrate. Also, the highest porosity was reached by taking the highest coloration efficiency value into account. Moreover, coloration efficiencies and Delta T ratios are changed due to the interlayer transparent conductive oxide layers. Raman spectroscopy measurement reveals the anatase phase of TiO2 films on both substrates. Another important finding is related to the defect structures of the TiO2 phase. TiO2, TiO3 and TiO4 mixed phases show the lower coloration efficiency according to the TiO2 phase, for the first time. TiO3 and TiO4 phases were grown by using the FTO-coated glass substrate. Comparing results with reports has shown that our investigated design and technology for ECD applications are good candidates for such applications.
P-type transparent Cu2S thin film grown by thermionic vacuum arc for optoelectronic applications
(Elsevier, 2021-01-01) Kaplan, Hüseyin Kaan; Akay, Sertan Kemal; Pat, Suat; Henini, Mohamed; KAPLAN, HÜSEYİN KAAN; AKAY, SERTAN KEMAL; 0000-0001-9414-8492; R-7260-2016; GWV-7916-2022
In this study, we have used a new single-step method for producing Cu2S thin films, which have good transparency in the visible range and high hole conductivity properties suitable for a wide range of optoelectronic device applications. Cu2S thin films are deposited by the Thermionic Vacuum Arc method, which is capable of very high deposition rates with high uniformity. The structural properties were determined by XRD analysis, and the morphological features were examined by AFM and SEM techniques. From XRD studies, the thin films were found to have a nano-crystalline form. The morphology images showed that the thin films have very low surface roughness. The bandgap of the film was calculated. The electrical properties of the films such as resistivity, majority carrier, and concentration were determined by Hall Effect measurements. In addition, the figure of merit value was calculated for p-type Cu2S transparent conducting thin films using the Haacke's formula.
Si-based photodiode and material characterization of TiO2 thin film
(Springer, 2021-05-01) Kaplan, Hüeseyin Kaan; Olkun, Ali; Akay, Sertan Kemal; Pat, Suat; KAPLAN, HÜSEYİN KAAN; Olkun, Ali; AKAY, SERTAN KEMAL; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; 0000-0002-4144-5837; R-7260-2016; GWV-7916-2022; DJH-5166-2022
This study proposes a different technique known as the thermionic vacuum arc to produce a TiO2/Si heterojunction photodiode with better electrical properties than literature like the ideality factor indicating that the method is very suitable to form an outstanding quality heterojunction interface. The heterojunction is highly sensitive to different light intensities and has stable photocurrent characteristics as a photodiode. Structural and morphological properties of the produced TiO2/Si heterostructure surfaces were investigated via XRD and AFM, respectively. According to XRD analysis, it was observed that the TiO2 thin film was in a polycrystalline structure with the Anatase and Brookite phases. Also, the film surface is homogenous, and a low roughness value was measured as 3 nm. The thin film thickness and the bandgap values (E-g) were determined based on optical methods. The electrical parameters of TiO2 thin film, such as conductivity type, charge carrier density, and mobility, were also determined by Hall Effect Measurement. The Ag/TiO2/Si/Ag heterojunction device characteristics were determined by conducting the current-voltage (I-V) measurement. The ideality factor (n) and the barrier height (Phi (b)) values were determined as 1.7 and 0.65 eV, respectively. The photo-response performance was measured via transient photocurrent (I-T) measurements for different light intensities.
Studies on the morphological, structural, optical and electrical properties of Fe-doped Zno magnetic nano-crystal thin films
(Elsevier, 2021-02-27) Mohammadigharehbagh, Reza; Pat, Suat; Akkurt, Nihan; Korkmaz, Şadan; Mohammadigharehbagh, Reza; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; 0000-0002-0333-487X; X-5375-2018
In this work, the effect of substrate material on the morphological, structural, optical and electrical properties of Fe-doped ZnO magnetic nano-crystal thin films was investigated. Fe-doped ZnO is a magnetic material and shows ferromagnetism at room temperature. FeO phases were detected in x-ray diffraction patterns. The surfaces of the films are fully occupied-spherical-like nano crystalline. The Fe/Zn ratios were calculated 1.6 and 5.9%. The optical transmittance value of the film is approximately 40%. The band gap value was shifted toward to lower value and the value was found as 3.15 eV. The maximum magnetic moments were obtained at 4000 and 2500 Oe for the film deposited onto glass and Si substrates, respectively. The electrical properties were determined at the maximum magnetic moment situation for the nano crystallites. It was found that diluted Fe-doped ZnO magnetic semiconductors have giant magnetic moment and electrical conductivity.
Studies on the surface and optical properties of ta-doped zno thin films deposited by thermionic vacuum arc
(Springer, 2021-11-09) Pat, Suat; Mohammadigharehbagh, Reza; Akkurt, Nihan; Korkmaz, Şadan; Mohammadigharehbagh, Reza; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-0333-487X; X-5375-2018
In this research, Ta doped ZnO thin films have been deposited onto glass and Si substrates by Thermionic vacuum arc (TVA) thin film deposition system. TVA is an anodic plasma thin film deposition system and it is used to relatively high-quality thin films deposition. ZnO thin films have direct optical band gap of 3.37 eV. Tantalum is an efficient higher-valance element. Ta atom gives the more electrons compared to Zinc atom and their ionic radius are very close to each other, so substituted element does not bring into additional stress in crystal network. The deposited thin films were analyzed by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, UV-Vis spectrophotometry and interferometer. To change the band gap properties of the ZnO thin film, Ta doping was used and band gap of Ta doped ZnO thin film was obtained 3.1 eV by Tauc's method. The wt% ratios for Zn/Ta were calculated as 0.45 and 0.42 for the films deposited onto glass and Si substrates, respectively. Crystallite sizes of Ta doped ZnO thin film was decreased by changing substrate material. To the best of our knowledge, substituted Ta elements connected to the oxygen atom in crystal network and orthorhombic beta '-Ta₂O₅ were detected in the all films structure. Their band gaps of the beta '-Ta₂O₅ were measured as 2.70 eV and 2.60 eV for Ta-doped ZnO thin films deposited onto glass and Si substrates, respectively. Up to day, the band gap of the beta '-Ta₂O₅ was calculated by density function theory. According to results, beta '-Ta₂O₅ structure was found as embedded from in the ZnO crystal network.
Substrate effect on electrochromic properties of Nb2O5:TiO2 nanocomposite thin films deposited by thermionic vacuum arc
(Pergamon-elsevier Science Ltd, 2022-05-21) Özgür, Nihan Akkurt; Pat, Suat; Korkmaz, Sadan; Mohammadigharehbagh, Reza; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Anabilim Dalı.; 0000-0002-0333-487X; 0000-0003-0116-3795
In this paper, substrate effect on electrochromic properties of Nb2O5:TiO2 nanocomposite thin films have been investigated. Thin films have been deposited by thermionic vacuum arc deposition technology. Nb2O5 and TiO2 are known to be electrochromic materials. Nb/Ti rate was obtained 1.4. Average thicknesses of the films were found as 113 nm and 111 nm and band gap values for bleached states were calculated as 3.96 eV and 3.85 eV for the films deposited onto ITO and FTO coated glass substrates, respectively. The coloration efficiency values were calculated as 17 cm2/C and 26 cm2/C for the film onto ITO layered glass substrate and 31 cm2/C, 23 cm2/C and 24 cm2/C for the film onto FTO layered glass substrate at a different wavelength values in the visible region. The obtained results shows that films for each transparent conductive oxide material is promising material to obtain the high performance TiO2 active layer.
Surface, optical and electrochemical performance of indium-doped ZnO/WO3 nano-composite thin films
(Springer, 2020-10-06) Mohammadigharehbagh, Reza; Pat, Suat; Akkurt, Nihan; Olkun, Ali; Özgür, Mustafa; Demirkol, Uğur; özen, Soner; Korkmaz, Şadan; Olkun, Ali; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; 0000-0003-0061-0573; KVY-3644-2024
Great demand on replacing emission and pollution-free materials for energy storage by traditional fossil fuels has led to investigating of high-performance electrochromic materials. Nano-composite for electrochromic device may be a good choice. In this paper, stack-structured indium-doped ZnO/WO3 nano-composite thin films were deposited on glass, indium-doped tin oxide (ITO) and fluorine-doped tin oxide (FTO)-coated glass substrates, respectively. Surface, optical and electrochromic (EC) performance of the prepared nano-composite films has been investigated. Electrochromic impedance spectroscopy (EIS), cyclic voltammetry, repeating chronoamperometry (CA) and chronocoulometry (CC) measurements were taken.The Raman spectroscopy measurement shows that high-intensity peaks are related to ZnO wurtzite structure for all substrates. In the CA measurement, the rate of Li+ transfer between surface and electrolyte was faster for films coated onto ITO substrate. In addition, the intercalation/deintercalation of Li+ was obviously found faster for films onto ITO substrate due to roughness, structure differences than the other sample. As an advantage of our nano-composite material, the absence of current decay in the both coloration and bleaching stages has proved superiority and stability of films as well as indium contribution. The reversibility of stack-structured InZnO/WO3 nano-composite films was computed as 30 and 50% for the film with ITO and FTO substrates. The highest coloration efficiency value has calculated as 80 and 69 cm(2)/C for nano-composite thin films deposited onto FTO substrate @ 632 and 550 nm, respectively. Warburg impedance element values were determined from the equivalent circuit model. Also, calculated charges were determined for bleaching or coloring process for all films.
The effect of Cu doping on optical and surface properties of ZnO thin films fabricated by thermionic vacuum arc (TVA) deposition
(Springer, 2022-01) Özkan, Mehmet; Erdem, Sercan Sadık; Mohammadigharehbagh, Reza; Pat, Suat; Mohammadigharehbagh, Reza; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; 0000-0002-0333-487X; X-5375-2018
In this work, copper as a dopant was utilized in the ZnO thin film, and furthermore the structural, optical, elemental, and topological properties of the films have been carried out upon glass and Si substrates. All coating processes were operated via plasma-based thermionic vacuum arc technology. The mean crystallite sizes of the films were calculated as 78 and 30 nm on glass and Si substrates, respectively. According to the topological results, the RMS value of the films coated onto Si substrate are higher than the film deposited onto glass substrates. The surface images show smooth, compact, and free-crack characteristics of the films. Both films onto the aforementioned substrates have agglomeration. In the optical measurements performed by UV-Vis spectrophotometry, interferometry, and photoluminescence (PL), the refractive indices of the films were 1.63 and 1.82 on glass and Si substrates, respectively. The thicknesses of the films were ascertained as 84 and 80 nm onto the glass and Si substrates. Also, the reflection values of Cu-doped ZnO films were obtained 0.076 and 0.058. These values have revealed the suitability of using the film in the antireflective application. The PL patterns show a defect in the ZnO lattice as well as the shift in the center of the peaks due to copper substitution. The band gap was assessed as 3.17 eV. This narrowing in the band gap value is a demonstration of dopant substitution.