Person: AKAY, SERTAN KEMAL
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AKAY
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SERTAN KEMAL
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Publication 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-7916-2022In 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.Publication 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; Fen Edebiyat Fakültesi; Fizik Bölümü; 0000-0002-4144-5837; R-7260-2016; GWV-7916-2022; DJH-5166-2022This 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.Publication 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; Fen Edebiyat Fakültesi; Fizik Bölümü; 0000-0002-0333-487X; R-7260-2016; X-5375-2018Giant 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.Publication A novel self-powered filterless narrow-band near-infrared photodiode of Cu₂S/Si p+-p isotype heterojunction device with very low visible light noise(Elsevier, 2022-07-08) Kaplan, Hüseyin Kaan; Akay, Sertan Kemal; Ahmetoğlu, Muhitdin; AKAY, SERTAN KEMAL; AHMETOĞLU, MUHİTDİN; KAPLAN, HÜSEYİN KAAN; Fen Edebiyat Fakültesi; Fizik Bölümü; GWV-7916-2022; R-7260-2016; KDM-6805-2024This study aims to achieve a filterless, narrow-band, near-infrared photodiode based on a p(+)-Cu2S/p-Si isotype heterojunction device. The device is developed by depositing 60 nm thick Cu2S thin film on Si substrates from Copper Sulfide pieces via the Thermionic Vacuum Arc technique (TVA). The molecular structure of the thin film is analyzed by utilizing Raman and X-Ray photoelectron spectroscopy (XPS) and confirmed to be in the Cu2S phase. Moreover, the high hole concentration in Cu2S is correlated with XPS results. The photodiode exhibits a response climax centered at 1049 nm and a full-width at half-maximum (FWHM) value of 10(4 )nm. An outstanding responsivity value of 375 mA/W (at 0 V bias) is obtained at a peak wavelength of 1049 nm, which surpasses most filterless, narrow-band photodiodes. Furthermore, while operating at 0 V bias, the photodiode showed an excellent specific detectivity value of 4.17 x 10(11) Jones with a 1.7 x 10(3) on/off ratio (at 1049 nm, 11.47 mW/cm(2)), in addition to its high photocurrent stability and response speed (under 0.8 s). In light of these findings, this proof-of-concept device is a great candidate as a filterless, narrow-band, NIR self-powered photodiode.Publication Production of agcu: Nio/ni foam electrode with high charge accumulation and long cycling stability(Springer, 2022-08-18) Ertürk, Kadir; Peksöz, Ahmet; Mohammadigharehbagh, Reza; Akay, Sertan Kemal; AKAY, SERTAN KEMAL; Sarsıcı, Serhat; Fen Edebiyat Fakültesi; Fizik Ana Bilim Dalı; 0000-0002-0333-487X; R-7260-2016Nickel oxide is a promising material for electrochemical energy storage devices due to its high specific surface area, rapid redox reactions, and short diffusion path in the solid electrode. It has been known that the loading of metallic elements into the NiO matrix enhances these superior properties. NiO material is electrochemically deposited on Ni foam, and then, Ag and Cu thin layers are coated on NiO by thermal evaporation. The produced NiO/Ni foam and AgCu:NiO/Ni foam electrodes are annealed at 400 degrees C for 1 h. Those are utilized as anode for high-performance energy storage electrode in an alkaline solution. The former has an energy density of 56.9 Wh kg(-1) at 3155.5 W kg(-1), while the latter has a high energy density of 107.6 Wh kg(-1) at the corresponding power density of 2957.7 W kg(-1). Although specific capacitance of the former decreases to 46.2% of its original capacitance at 10 A g(-1) after 5000 cycles, the latter exhibits higher cycling stability with 71.0% retention after 5000 charge-discharge cycles owing to the loading of Ag and Cu into NiO matrix. Charge transfer resistance of NiO/Ni foam, which is inversely proportional to electroactive surface area, reduces from 19.4 to 0.28 omega after the incorporation of Ag and Cu. Compared to NiO/Ni foam, AgCu:NiO/Ni foam with a higher electroactive surface area is more appropriate for charge accumulation. As mention above, the features of AgCu:NiO/Ni foam indicate that it is a promising material as an effective start-of-art energy storage device.