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AKAY, SERTAN KEMAL

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AKAY

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SERTAN KEMAL

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    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; 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.
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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-7916-2022
    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.
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    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; 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.