Physics Group

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Now showing 1 - 5 of 24
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    A study on the dark and illuminated operation of Al/Si3N4/p‑Si Schottky photodiodes: optoelectronic insights
    (Applied Physics A, 2024-01-28) Sürücü, Özge ; Yıldız, Dilber Esra ; Yıldırım, Murat
    This work extensively investigates the operation of an Al/ Si3N4/p-Si Schottky-type photodiode under dark and varying illumination intensities. The photodiode is fabricated by employing the metal–organic chemical vapor deposition (MOCVD) method. A thorough electrical characterization is performed at room temperature, encompassing measurements of cur- rent–voltage (I–V), current–time (I–t), capacitance–time (C–t), and conductance time (G–t). The photodiode’s rectification factor and reverse bias area increased under illumination. The relationship between light power density, barrier height, and diode ideality factor is found. The study also found a strong correlation between light intensity and applied voltage on series resistance (Rs) and shunt resistance (Rsh). Rs values are calculated using Cheung’s functions, revealing the diode’s resistance behavior. The study also examines the photodiode’s photoconductivity and photoconductance, finding a non-linear relation- ship between photocurrent and illumination intensity, suggesting bimolecular recombination. Calculated photosensitivity (K), responsivity (R), and detectivity (D*) values show the device’s light response effectiveness, but efficiency decreases at higher illumination intensities. Transient experiments indicate stable and reproducible photocurrent characteristics, reveal- ing photogenerated charge temporal evolution. This study provides a complete understanding of the Al/Si3N4/p-Si Schottky photodiode’s behavior under different illumination intensities. The findings advance optoelectronic device knowledge and enable their use in advanced technologies.
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    Nanowire geometry effects on devices and transport mechanisms: SnS2/SiNW heterojunction
    (Journal of Materials Science, 2023-10-04) Coskun, Emre ; Emir, Cansu ; Terlemezoğlu, Makbule ; Parlak, Mehmet
    The semiconductor nanowire technology has become essential in developing more complex and efficient devices. In this study, the Si nanowire (SiNW) heterojunction structure with a two-dimensional SnS2 thin film was investigated. The SiNW array was created by the metal-assisted etching method because of length control and production over large areas of nanowires. The created SiNW has more diminishing reflectivity compared with Si planar substrate. The diode characteristics of SnS2/SiNW and SnS2/Si planar heterojunctions were investigated by dark current analysis at room temperature, and the improving diode characteristics by the three-dimensional interface between SiNW and SnS2 thin film were discussed. Transport mechanisms of the SiNW heterojunction were also studied for various methods. Thermionic emission and thermally assisted tunneling models are the dominant mechanisms for low voltages (0.02–0.20 V), and the space charge limiting current mechanism dominates the current for comparingly high voltages (0.20–0.40 V). All the values reveal the significant impact of the SiNW on heterojunctions for improving efficiency.
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    A new method to determine the continuous refractive index of an absorbing film by Generalized Stockwell Transform
    (Optics and Laser Technology, 2023-12) Coşkun, Emre ; Emir, Cansu ; Selamet, Semanur ; Parlak, Mehmet ; Özder, Serhat
    Generalized Stockwell Transform (GST) was adapted to analyze a transmittance signal to continuously determine the refractive index and extinction coefficient. The process is built by analyzing oscillation frequencies of the transmission signal where oscillations exist. The simulation studies clearly show the advantage of the locally referenced phase property of the presented method. The validity of the method was checked for a CdS thin film. The results determined by the GST method are consistent with the results determined by envelope and other signal analyzing methods, and the literature. The noise and relative error analysis of the method was also discussed.
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    Investigation of a candidate spin-$\frac{1}{2}$ hidden-charm triple strange pentaquark state $P_{csss}$
    (Physical Review D, 2023-01-10) Azizi, Kazım ; Saraç, Yasemin ; Sundu, Hayriye
    A candidate triple strange pentaquark state, $P_{csss}$, is investigated through its strong decay channel $P_{csss} \rightarrow \Omega^-J/\psi $. To calculate the relevant strong coupling constants, two possible interpolating currents with spin-parity $J^P=\frac{1}{2}^{-}$ are used. Though the chosen currents for the state under consideration have spin-parity quantum numbers $J^P=\frac{1}{2}^{-}$, they couple to both the positive and negative parity states simultaneously and the corresponding decay widths are obtained for both parities. These widths are obtained as $\Gamma(P_{csss} \rightarrow J/\psi \Omega^-)=201.4\pm 82.5~\mathrm{MeV}$ for the negative and $\Gamma(\widetilde{P}_{csss} \rightarrow J/\psi \Omega^-)=316.4\pm 107.8~\mathrm{MeV}$ for the positive parity state when the first current is used. For the second current, we obtain $\Gamma(P_{csss} \rightarrow J/\psi \Omega^-)=252.5\pm 116.7~\mathrm{MeV}$ for the negative and $\Gamma(\widetilde{P}_{csss} \rightarrow J/\psi \Omega^-)=361.1\pm 98.4~\mathrm{MeV}$ for the positive parity state. These results may provide insights into future experimental observations of such candidate states and help to distinguish and fix their properties.
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    Investigation of the strange pentaquark candidate P_{\psi s}(4338)^0 recently observed by LHCb
    (Physical Review D., 2023-10-01) Azizi, Kazım ; Saraç, Yasemin ; Sundu, Hayriye
    The recently observed strange pentaquark candidate, PΛψs(4338)0, is investigated to provide information about its nature and substructure. To this end, its mass and width through the decay channels PΛψs(4338)0→J/ψΛ and PΛψs(4338)0→ηcΛ are calculated by applying two- and three-point QCD sum rules, respectively. The state is considered as a Ξc¯D meson-baryon molecular structure with spin-parity quantum numbers JP=12−. The obtained mass, mPΛψs(4338)0=4338±130  MeV, and width, ΓPΛψs(4338)0=10.40±1.93  MeV, are consistent with the experimental data within the presented uncertainties. This allows us to assign a Ξc¯D molecular structure of JP=12− for the PΛψs(4338)0 state.