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    Dark and illuminated electrical characteristics of Si-based photodiode interlayered with CuCo5S8 nanocrystals
    (Springer, 2020) Yildiz D.E.; Gullu H.H.; Sarilmaz A.; Ozel F.; Kocyigit A.; Yildirim M.
    Derived from the traditional dichalcogenide CuS structure, ternary transition metal chalcogenide nanoparticles in the form of CuCo5S8 are investigated under the aim of photodiode application. In addition to the detailed analysis on material characteristics of CuCo5S8 thin-film layer, the work is focused on the electrical characteristics of Au/CuCo5S8/Si diode to investigate its current–voltage, capacitance–voltage, and conductance–voltage characteristics under dark and illuminated conditions. CuCo5S8 nanocrystals with an average size of 5 nm are obtained using hot-injection method, and they are used to form thin-film interfacial layer between metal (Au) and semiconductor (Si). Under dark conditions, the diodes show about four orders in magnitude rectification rate and diode illumination results in efficient rectification with increase in intensity. The analysis of current–voltage curve results in non-ideal diode characteristics according to the thermionic emission model due to the existence of series resistances and interface states with interface layer. The measured current–voltage values are used to extract the main diode parameters under dark and illumination conditions. Under illumination, photogenerated carriers contribute to the current flow and linear photoconductivity behavior in photocurrent measurements with illumination shows the possible use of CuCo5S8 layer in Si-based photodiodes. This characteristic is also observed from the typical on/off illumination switching behavior for the photodiodes in transient photocurrent, photocapacitance, and photoconductance measurements with a quick response to the illumination. The deviations from ideality are also discussed by means of distribution of interface states and series resistance depending on the applied frequency and bias voltage. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
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    Facile preparation of amorphous NiWSex and CoWSex nanoparticles for the electrocatalytic hydrogen evolution reaction in alkaline condition
    (Elsevier B.V., 2020) Aslan E.; Sarilmaz A.; Yanalak G.; Chang C.S.; Cinar I.; Ozel F.; Patir I.H.
    The development of catalysts as an alternative to platinum group metals (PGMs) has great importance to improve the efficiency of hydrogen evolution reaction (HER). Herein, the novel amorphous ternary refractory metal selenides (MWSex; M = Co and Ni), which were synthesized by hot-injection approach, were firstly investigated on the electrocatalytic HER in alkaline media. Optical, electrochemical and magnetic properties of the electrocatalysts were explored, as well as the chemical structures and morphologies. These results clearly show that the obtained materials are having the amorphous crystal structure and are shaped as spherical and rod-like structures. Moreover, the addition of Ni and Co metals into the WSex structure were raised the catalytic activity of HER comparing to that of only WSex. This work paves the way for the exploration of copper-based amorphous selenides as electrocatalysts for the hydrogen evolution in order to replace noble metal Pt. © 2019 Elsevier B.V.