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  • Küçük Resim
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    Friction and wear characteristics of bismuth selenide topological insulator
    (Elsevier, 2023) Uzun, Utku; Lamuta, Caterina; Yetmez, Mehmet
    Single crystal Bi2Se3 was grown using the novel Bridgeman-Stockbarger method. Surface characteristics in terms of wear rate (W), wear coefficient (K), coefficient of friction (COF), and strain hardening exponent (n) were investigated using nanoindentation and nano scratch techniques. Our results revealed that the remarkable wear properties of single-crystal Bi2Se3 are promising for nanoscale design of topological insulators.
  • Küçük Resim
    Öğe
    Nanoindentation Creep Behavior of Single-Crystal Bi2Se3 Topological Insulator
    (Wiley, 2022) Uzun, Utku; Lamuta, Caterina; Yetmez, Mehmet
    A single-crystal Bi2Se3 topological insulator is fabricated using the Bridgman-Stockbarger method. The crystal structure and atomic lattice parameters are identified by X-ray diffraction analysis. The nanoindentation size effect on creep displacement, activation volume, and strain rate sensitivity (SRS) with different maximum holding loads between 1000 and 5000 mu N is investigated using depth-sensing nanoindentation. Furthermore, the effect of the loading rate on the steady-state creep displacement and SRS is analyzed and discussed. Results show Bi2Se3's low resistance to plastic deformation and a significant increase of creep displacement with increasing holding load and holding rate. Additionally, creep strain rate, activation volume, and SRS are also calculated from the secondary stage creep, and results are compared with those of other flexible electronic materials.
  • [ X ]
    Öğe
    Nanomechanical properties and wear resistance of Palladium diselenide (PdSe2 ) for flexible electronics
    (Elsevier, 2024) Uzun, Utku; Kotak, Parth; Shakib, Mahmudul Alam; Mamman, Rabiu Onoruoiza; Daws, Sawsan; Kuo, Chia-Nung; Lue, Chin Shan
    Palladium diselenide (PdSe 2 ), a transition -metal dichalcogenide (TMDC), has received interest for its intriguing optical and electrical characteristics. Despite its relevance for flexible electronics, its mechanical properties have been only scarcely investigated. In this work, we examined time -dependent mechanical response, wear, and nanoductility of PdSe 2 grown using chemical vapor transport. Specifically, we measured hardness, elastic modulus, creep characteristics, activation volume, strain rate sensitivity, and wear resistance using nanoindentation and nanoscratch experiments. The obtained values of Young ' s modulus and hardness are promising for flexible electronic applications. Due to its strain hardening and strain -rate sensitivity, PdSe 2 is ductile like aluminum and could endure significant deformation without losing structural integrity. The investigation of the creep behavior showed its size -dependent mechanical endurance under steady load, which is important for device dependability. Additionally, activation volume calculations indicate dislocation dynamics and processes during deformation, revealing the material ' s reaction to different mechanical loading conditions. Our nanoscratch experiments showed resilience to surface wear, confirming its suitability for durable flexible electronic devices. The significant elasticity of PdSe 2 , facilitating substantial recovery after deformation, renders it well -suited for flexible and wearable electronic devices requiring the maintenance of electrical continuity even under mechanical stress. The results of our mechanical characterization will open the door to the design and manufacturing of next generation PdSe 2 -based flexible electronic devices.
  • [ X ]
    Öğe
    Simple and solvent-free procedure for fabricating Ag/Bi-based halide double perovskite polycrystalline wafers and investigating their photodetector properties
    (Academic Press Inc Elsevier Science, 2024) Oktay, Ozge; Uzun, Utku; Kaya, Ismail Cihan
    Herein, a solvent-free and simple solid-state method was used to synthesize Cs2AgBiBr6 wafers. Cs2AgBiBr6 particles were successfully synthesized in two steps, namely grinding and annealing. Phase-pure Cs2AgBiBr6 was produced in a very short time, such as 4 h, by stepwise heat treatment at 205 degrees C for 2 h and 250 degrees C for 2 h after grinding bromide powders for 20 min in an agate mortar. Another grinding step for 20 min, following the phasepure synthesis of Cs2AgBiBr6, facilitated the formation of larger perovskite grains through sintering at 350 degrees C. Increasing the sintering time from 4 h to 20 h also contributed to the formation of larger and more compact perovskite grains. This study demonstrated that the formation of larger and more compact grains through sintering at 350 degrees C for 20 h contributes to better detectivity and responsivity values for solvent-free produced Cs2AgBiBr6 wafers. Additionally, the structural strength of the material was examined through hardness tests using the nanoindentation method, resulting in a value of 0.0923 MPa. The simple and solvent-free method employed in this study may create opportunities to fabricate emerging double perovskites for detector applications.