Sürdürülebilir Kalkınma Amaçları

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• MakaleYalnız künye2026Scopus SJRQ1/r/munzur/4915
  Influence on the thermoelectric characteristics of the growth parameters of BiSeTe thin films

  Yüzüak, G. Durak; Yüzüak, E.

  This study systematically investigates the influence of magnetron sputtering parameters on the structural, electronic, and thermoelectric properties of 100 nm thick Bi2SexTe3-x thin films deposited on Si(100). The initial parameters for applied film deposition are used to set the x value. The films are fabricated with sputtering powers ranging from 30 to 100 W and pressures from 3 to 15 mTorr, with films grown under optimal conditions selected for post-deposition annealing at 523 K. A comprehensive characterization suite, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and Kelvin probe force microscopy (KPFM), is used to establish direct correlations between processing, structure, and performance. XRD analysis reveals that increasing the sputtering pressure from 3 to 15 mTorr was critical for enhancing film crystallinity and promoting a strong (015) preferred orientation, while AFM showed a corresponding increase in average grain size from similar to 46 to similar to 60 nm via heat treatment (HT). EDS shows that films grown at 10 mTorr were almost certainly stoichiometric, but increasing the power to 15 mTorr caused tellurium deficiency. The films exhibited a power factor ranging from 2.5 to 2.8 mW m(- 1) K- 2 at 40 degrees C. HT improved the Seebeck coefficient from -115 mu V K- 1 to -140 mu V K- 1 and decreased the electrical resistivity by over 25 % through defect reduction and enhanced crystalline order. KPFM supported these findings, directly linking the crystallographic texture to the surface electronic structure and enhanced Seebeck effect.

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  AtıfWoS2·OpenAlex2

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• MakaleYalnız künye2026Scopus SJRQ1/r/munzur/1523
  Compositionally segmented thermoelectric BiSbTe thin films on Cr/Si(100)

  Yüzüak, G. Durak; Yüzüak, E.

  Compositionally segmented thermoelectric (CS-TE) structures improve thermal energy conversion efficiency across large thermal gradients. However, their increased design complexity complicates performance modeling and optimization. In this study, we fabricate CS-TE BiSbTe thin films on Cr-buffered Si(100) substrates. By adopting a multidisciplinary approach, we aim to broaden the technological applicability and strategic relevance of advanced TE systems. We systematically analyze the influence of deposition pressures (5, 7, and 10 mTorr) on TE performance. Variations in working pressure alter the Bi/Sb atomic ratio in the films, while the Te content remains stable. This enables the controlled formation of CS structures. At 323 K, the power factor (PF) of TE thin films reaches 0.7, 2.4, and 7.3 mW/mK2 under 5, 7, and 10 mTorr deposition conditions, respectively. The Cr-buffered layer significantly improves the electrical conductivity of CS-TE BiSbTe films. We further engineer a p-type single-leg device integrating nanostructured Bi0.35Sb1.65Te3, Bi0.37Sb1.63Te3, and Bi0.4Sb1.60Te3 layers. These materials are optimized to achieve peak TE PF values across a wide temperature range (320 to 500 K) while ensuring robust interfacial adhesion. The CS-TE device generates 3 mW/cm2, showing a 15% improvement over single-composition samples at a 100 K temperature difference.

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  AtıfScopus3·WoS3·OpenAlex2

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• MakaleYalnız künye2026Scopus SJRQ1/r/munzur/1062
  Engineering high-performance BiSeTe ultra-thin film on flexible FEP

  Yüzüak, G. Durak; Yüzüak, E.

  Flexible thermoelectric (TE) devices hold great promise for powering wearable electronics by harvesting the temperature difference between human skin and the environment. Conventional Bi2Te3, although efficient, suffers from rigidity and limited suitability for flexible applications, while organic alternatives typically lack sufficient TE performance. Here, we demonstrate an n-type BiSeTe thin film deposited on a flexible fluorinated ethylene propylene (FEP) substrate, incorporating a Cr buffer layer, achieving a room-temperature power factor of ∼3.9 μW.cm−1.K−2, which is within the range reported for flexible thin-film TE devices on polymer substrates. The film exhibits excellent mechanical resilience, retaining 90 % of its initial conductivity after 5000 bending cycles, and shows high thermal stability over 50 heating–cooling cycles with deviations below 1.5 %. A four-leg n-type prototype generates 10 mV and 70 nW at ΔT = 40 K, demonstrating its potential for powering low-energy wearable sensors. This work presents a scalable inorganic thin-film TE platform that effectively balances mechanical flexibility, device stability, and practical energy conversion performance for wearable and localized power generation applications.

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  AtıfScopus2·WoS2·OpenAlex2

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• MakaleYalnız künye2026Scopus SJRQ2/r/munzur/800
  Oxide Dispersion, Microstructure, and Functional Evolution in La2O3 Modified Cu-Al-Mn-Fe Shape Memory Alloys

  Karaduman, Oktay; Doğan, Fatih; Dehghanpour, Heydar; Yüzüak, Gizem Durak; Yüzüak, Ercüment; Canbay, Canan Aksu

  Cu-Al-Mn-Fe high-temperature shape memory alloys containing 0-1.0 wt.% La2O3 were fabricated by vacuum arc remelting to investigate oxide-dispersion effects on microstructure, martensitic transformation, wear, and corrosion behavior. XRD and SEM analyses revealed that low La2O3 additions (0.2-0.4 wt.%) promoted β1′ martensite refinement and enhanced crystallinity, while higher contents induced structural heterogeneity. The alloy with 0.4 wt.% La2O3 exhibited the highest transformation enthalpy (7.49 J g−1), reduced friction coefficient (~0.55), and the narrowest wear scar (~501 µm). Electrochemical tests in 3.5 wt.% NaCl showed a fivefold decrease in corrosion current density and increased charge-transfer resistance (2512 Ω cm2) for the same composition. Excessive La2O3 led to performance degradation due to particle agglomeration and interfacial defects. The results demonstrated that controlled La2O3 addition enabled microstructural refinement and multifunctional performance enhancement in Cu-based shape memory alloys.

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• MakaleAçık Erişim2026Scopus SJRQ2/r/munzur/751
  Engineering Superior Soft Magnetic Properties Through FeCo/Cr and FeCo/Fe Nanocrystalline Architectures

  Yüzüak, Gizem Durak

  Soft magnetic materials are integral to various technologies, including high-frequency transformers, spintronic devices, and magnetic sensors, because of their low coercivity (HC) and high magnetization. This study investigates nanocrystalline Fe70Co30(100 nm)/Cr(2-10 nm) and Fe70Co30(100 nm)/Fe(2-10 nm) thin films, deposited via magnetron sputtering. X-ray diffraction analysis reveals that Fe70Co30 films without buffer layers crystallize in a body-centered cubic phase. The Cr and Fe buffer layers enhance it by minimizing lattice mismatch and promoting a uniform crystalline growth of the Fe70Co30 layer. The most significant particle size variations observed were approximately 24% for the Cr buffer and 31% for the Fe buffer. Microstructural characterization using atomic force microscopy and scanning electron microscopy identified nanograins with an average size of 30–80 nm. Magnetic characterization with a vibrating sample magnetometer showed a marked reduction in HC. Additionally, the remanence-to-saturation magnetization ratio remains nearly constant at 0.95 across all Fe-buffered films, whereas it increases from 0.80 to 0.92 in Cr-buffered films as the Cr thickness increases. The results highlight the importance of buffer layer engineering in enhancing the microstructural and magnetic properties of FeCo thin films, thereby increasing their suitability for advanced magnetic technologies.

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• MakaleYalnız künye2025Scopus SJRQ1/r/munzur/2197
  Mechanisms of hardness enhancement in CrB2 thin films with varying VB2 concentrations

  Yüzüak, G.D.; Tomakin, M.

  Transition metal borides are well-known for their high hardness, excellent wear resistance, chemical inertness, and electrical conductivity, making them promising for a wide range of applications. Understanding the interconnections between material structure, composition, and mechanical properties is essential for designing and synthesizing effective coatings. This study systematically investigates the structural and mechanical properties of CrB₂ thin films with varying concentrations of VB₂ (0–10 wt%), focusing on structure, hardness, elastic behavior and deformation characteristics mechanisms through atomic force microscopy and nanoindentation measurements. The results show that increasing VB₂ content leads to the formation of island cluster structures, which significantly strengthens atomic bonds and, in turn, enhances the hardness of the thin films. As particle size decreases, the higher proportion of surface atoms and increased surface energy have a more pronounced effect on the mechanical properties. In particular, the addition of VB₂ up to 10 wt% in CrB₂ thin films results in a marked improvement in superhard properties. 26 % increase in hardness value is also influenced directly by the changes in Young's modulus and Poisson's ratio that depend on the VB₂ concentration.

  AtıfScopus5·WoS5·OpenAlex6

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• Kitap BölümüYalnız künye2025/r/munzur/1649
  Magnetic energy conversion

  Yüzüak, Ercüment; Yüzüak, Gizem Durak; Dinçer, İlker; Elerman, Yalcin

  This paper provides a comprehensive and comprehensible analysis of the conversion of magnetic energy in magnetocaloric materials, as well as the application of magnetic refrigeration that relies on the magnetocaloric effect. The magnetocaloric effect (MCE) refers to the phenomenon of cooling or heating that takes place in a magnetic material when an external magnetic field is introduced or removed under adiabatic conditions. This effect also occurs in reverse, when the application or removal of an external magnetic field induces cooling or warming in the material. For a considerable period, the phenomena referred to as “adiabatic demagnetization” has been recognized, wherein the practical use of the magnetocaloric effect (MCE) in magnetic materials is observed. Magnetic materials exhibit the phenomenon known as the magnetocaloric effect close to their critical temperature. The magnetocaloric system exhibits superior environmental friendliness and efficiency compared to conventional refrigeration cycle systems that rely on vapor compression. Magnetic refrigeration is a cooling system that operates by utilizing the magnetocaloric effect. This methodology can be employed to achieve reduced temperatures, including those within the typical operational range of conventional refrigeration systems. In the realm of magnetic and electromagnetic energy conversion, the system's coefficient of performance (COP) attains a theoretical efficiency of 30%–60% of the Carnot cycle. The exploration of magnetic refrigeration is now underway, with a focus on utilizing low magnetic fields in the vicinity of room temperature. The objective is to facilitate the development of commercial devices that employ permanent magnets as the primary source of magnetic field. The utilization of a magnetocaloric heat pump in a magnetic refrigerator is employed as a cooling mechanism, relying on magnetocaloric materials. These materials present a promising substitute for conventional refrigeration technology that relies on compressors. Theoretical investigations have indicated that refrigeration systems utilizing the magnetocaloric effect have the potential to achieve energy efficiency levels that are around 35% higher compared to vapor compression systems. In addition, it should be noted that cooling systems utilizing magnetocaloric materials exhibit reduced noise levels as a result of the lack of a compressor. This particular technological approach involves the utilization of coolants that are water-based, as opposed to the conventional use of gaseous refrigerants.

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• MakaleYalnız künye2025Scopus SJRQ1/r/munzur/1309
  Modifying the magnetic characteristics of ferrimagnetic TbFeCo by adjusting the thickness of the L11-ordered CoPt

  Yüzüak, Gizem Durak

  This study investigates structural and magnetic properties of 200 nm TbFeCo ferrimagnetic thin films. These films were formed by depositing L11-ordered CoPt buffer layers on Si(100) substrates, followed by (111)-textured Pt layers. The TbFeCo films were produced at room temperature by magnetron sputtering, and their characteristics were analyzed using X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), vibrating sample magnetometry (VSM), atomic force microscopy (AFM), and magnetic force microscopy (MFM). The above-mentioned techniques were used to figure out the films’ crystallographic structure, magnetic properties, and the surface characteristics. XRD analysis showed that TbFeCo films without the CoPt layer were only crystalline in the Pt(111) and Pt(222) directions. Conversely, films that were buffered with a CoPt layer developed the L11-ordered CoPt phase, especially in the CoPt(222) and CoPt(444) directions. This issue was linked to an increase in the CoPt unit cell parameter, indicating bulk-like crystallinity, particularly in the 20 nm CoPt layer, while the TbFeCo layer remained amorphous. The FIB-SEM showed that the layers were all gathered the thickness of 20 nm for Pt, 10 or 20 nm for CoPt, and 200 nm for TbFeCo with homogeneous distributed the elements in the Tb46Fe41Co13 composition matrix. Magnetic characterization from VSM measurements ranged from 5 to 350 K and revealed significant differences based on CoPt thickness. At 300 K, the coercive field (HC) got stronger as the thickness of the CoPt layer risen up. For 0, 10, and 20 nm CoPt, the HC was 2.8, 3.3, and 4.1 kOe, and the MS values were about 205, 229, and 234 emu/cm³, respectively. The L11-ordered CoPt underlayer facilitated strong exchange coupling at the TbFeCo/CoPt interface, which is responsible for these improvements. AFM and MFM measurements indicated that surface roughness, and hence magnetic pinning sites, increased dramatically with CoPt thickness. These pinning sites inhibited magnetic domain wall motion, increasing HC values in the out-of-plane direction. This kind of magnetic stability leads to excellent qualities, like higher HC and better thermal stability up to 350 K, that make these films interesting for use in spintronics and data storage, where HC and thermal resilience are important.

  AtıfScopus3·WoS3·OpenAlex3

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• MakaleYalnız künye2025Scopus SJRQ1/r/munzur/1088
  Evaluation of TiO2/ZnO/SnO2 multilayer thin films on Si(100) as triboelectric friction layer

  Yüzüak, G. Durak; Yüzüak, E.

  This study presents a novel multilayer-semiconductor triboelectric nanogenerator (MLSC-TENG) that enhances charge transfer and initial charge density to overcome the limitations of conventional TENGs by multilayer thin films composed of TiO2, ZnO, and SnO2. The device operates through contact electrification and electrostatic induction, featuring two distinct electrodes. The active negative layer is deposited on Si substrates with an Ag seed layer using magnetron sputtering, employing a PET/ITO counter-electrode. The system attains a maximum power density of 400 mW/m2 with a 100 MΩ load, a short-circuit current of 20 μA at 10 Hz, and an open-circuit voltage of ±55 V. Additionally, it powers 156 LEDs and exhibits an energy storage capacity of 16.9 μJ at 52 μF, highlighting its applicability for wearable electronics. This scalable and cost-effective approach highlights the significant role of semiconductor (SC) band structures in enhancing TENG performance and presents a viable pathway for sustainable energy harvesting. The demonstrated strategy has the potential to meaningfully influence the application of TENGs in energy harvesting systems, providing a cost-effective solution for powering wearable electronics. The study facilitates progress in sustainable energy solutions for future wearable technologies by tackling critical issues in energy conversion efficiency.

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  AtıfScopus2·WoS3·OpenAlex3

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• BildiriYalnız künye2024/r/munzur/2312
  Exploring Triboelectric Properties in Sputtered Si(100)/SiO2/Cr/ZnO Thin Films - Ag/FEP Using Contact Speration Technique for Renewable Energy Harvesting

  Yüzüak, Gizem Durak

  Currently, there is an ongoing inquiry into triboelectric nanogenerators (TENG), which use the triboelectric phenomenon to capture electrical energy from mechanical vibrations. The work aims to figure out the magnetron sputtered Cr/ZnO-based films on SiO2/Si(100) substrates with the construction of a Cr/ZnO-Ag/FEP tribo-based nanogenerator (TENG) and a specific emphasis on measuring TENG properties. The structural investigation of these films was conducted using X-ray diffraction (XRD) photoluminescence (PL), attenuated total reflectance fourier-transform infrared spectroscopy (AT-FTIR), and current - voltage (I-V) analysis in contact-separation mode (CSM). The Cr/ZnO-Ag/FEP TENG has a notable instantaneous maximum output voltage of around 63 V and a current density of 7 μA/cm2 when compared to other nanogenerators based on semiconductors, as determined by a comparative analysis. The results of this study provide useful information on the possible application of optimized magnetron sputtered Cr/ZnO-based films in triboelectric and energy harvesting systems, which might contribute to the progress of sustainable and renewable energy technologies.

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