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  • Küçük Resim
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    Current-voltage characteristics of nano whisker ZnO/Si heterojunction under UV exposition
    (Elsevier Science Sa, 2022) Koç, Nevin Soylu; Altıntaş, Sevgi Polat; Gökçen, Muharrem; Doğruer, Musa; Altuğ, Cevher; Varilci, Ahmet
    In/ZnO/p-Si heterojunction diode was produced to investigate the photo-responsivity and electrical features under ultraviolet (UV) light. A hydrothermal synthesis technique was used to coat the ZnO layer on the p-Si single crystal as nanowhisker/rods. The formation of surface and nanowhisker properties of the ZnO layer were investigated by scanning electron microscope (SEM). The I-V (current-voltage) analysis of the In/ZnO/p-Si diode was realized in dark and under UV (290-400 nm) illumination. Further, the main electrical parameters of the diode; such as reverse bias saturation current (I-V), ideality factor (n), zero bias barrier height (Phi(Bo)), resistance (R) and interface state density (N-ss) were obtained from the experimental I-V measurements by thermionic emission (TE) and Card and Rhoderick's function. Also, the power law of the photocurrents (I-PC), photoresponsivity (PR) and response time were extracted. Photo-responsivity and response time values of In/ZnO/p-Si heterojunction diode were obtained as 2.0 A/W and (rise/decay) 160/200 ms, respectively.
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    Investigation of frequency-dependent dielectric properties of ZnO nanorods grown on Si wafer: In/ZnO/p-Si heterostructure
    (Springer, 2022) Al-Khafaji, A.; Soylu-Koç, N.; Altıntaş, Sevgi Polat; Doğruer, Musa; Altuğ, Cevher; Gökçen, Muharrem; Varilci, Ahmet
    We report the result of an in-depth study of growth, structural properties and frequency-dependent dielectric function of ZnO nanorods (NRs) grown on p-Si as well as the In/ZnO/p-Si heterostructures. The NRs were produced by hydrothermal method on the Si substrate in a Teflon-lined stainless-steel cover at 90 degrees C. Scanning electron microscopy analysis indicates nanorod morphology while LeBail refinement of XRD data showed that the ZnO NRs crystallize in hexagonal wurtzile structure with (002) orientation (space group P6(3)mc). The dielectric properties of the In/ZnO/p-Si heterostructure were calculated with the help of experimental admittance measurements performed in the +/- 5 V voltage range and 1 kHz/1 MHz frequency range under ambient conditions. The real part of the complex relative permittivity (epsilon '), the imaginary part of complex relative permittivity (epsilon '') and loss tangent (tan delta) were obtained. Also, real (M ') and imaginary (M '') parts of the complex electric modulus (M*) were extracted. Frequency dependence in the epsilon ', epsilon '' and tan delta was attributed to the frequency dependence of the space charge polarization. The real part of electrical modulus was found to be nearly independent of frequency and voltage for positive voltages.
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    Morphological, microstructural and electrical examinations on ZnO film on p-Si wafer
    (Springer, 2012) Gökçen, Muharrem; Bal, S.; Yıldırım, Gürcan; Gülen, Mahir; Varilci, Ahmet
    This study reports not only main electrical and dielectric characteristics of Ag/ZnO/p-Si heterostructure with the aid of the experimental admittance measurements at room temperature and theoretical approaches but also the microstructure and surface morphology of the heterostructure by means of X-ray diffraction, scanning electron microscopy and atomic force microscopy measurements. The results obtained show that the sample, obtaining Wurtzite structure with the (002) preferred orientation, has a fine crystalline microstructure consisting of micro-sized hexagonal rods growing uniformly in large scale on the film surface. When the diameters of the rods are found to vary from 0.5 mu m to 1.5 mu m, thickness values are observed to be about 2 mu m. Further, series resistance (R-s) and some other electronic parameters of the heterostructure are obtained by the capacitance-voltage (C-V), conductance-voltage (G-V) and C-2-V measurements. Moreover, voltage (V) and frequency (f) dependence of dielectric parameters such as dielectric constant (epsilon'), dielectric loss (epsilon aEuro(3)), dielectric loss tangent (tan delta), real and imaginary parts of electric modulus (IeaEuro(2) and IeaEuro(3)) are determined and discussed. It is found that both electrical and dielectric parameters of the heterostructure prepared in this work depend strongly on the applied bias voltage and frequency.