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  • Küçük Resim
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    Arayüzey tabakalı ve arayüzey tabakasız Au-Sb/n-Si/Au schottky diyodların karakteristik parametrelerinin teorik ve deneysel karşılaştırılması
    (2018) Asubay, Sezai; Kılıçoğlu, Tahsin
    Bu çalışmada <111> doğrultulu n-tip Silisyum dilimleri taban alınarak, arayüzey tabakalı ve arayüzey tabakasız Au-Sb/n-Si/Au diyodlan imal edildi. Bunların I-V ve C-V ölçümlerinden elde edilen karakteristik parametreleri deneysel ve teorik olarak karşılaştırıldı. idealite faktörü değerine bağlı olarak Dİ diyodunun ideal bir diyod, D2 ve D3'ün ideal olmayan diyodlar olduğu görüldü. Bu ideal olmayış arayüzey hallerine ve arayüzey tabakasına atfedildi. Bu diyodlar için elde edilen engel yüksekliğinin değerleri, I-V karakteristiklerinden C-V karakteristiklerinden elde edilen değere hemen hemen eşit olduğu görüldü. Arayüzey tabakasız Dİ diyodunun iki noktası için doğru ve ters beslem I-V karakteristiklerinden elde edilen engel yüksekliklerinin değerlerinin eşit, ideal olmayan D2 ve D3 diyodların ters beslem I-V den elde edilen engel yüksekliği değerleri doğru beslem I-V'den elde edilen değerlerden küçük olduğu görüldü. Doğru beslem I-V karakteristiklerinin deneysel değerlerini kullanarak çizdiğimiz yüzey potansiyeli - gerilim (\|/s - V) grafiklerinden de engel vükseklikeri hesaplandı. Bu değerlerin diğer metodlarla elde edilen değerlerle yakın bir uyum içinde olduğu görüldü. Arayüzey tabakalı Schottky diyodlarının C2 - V grafiklerinin kesişim voltajı daima ideal Schottky diyodlarınkinden büyük olduğu görüldü. Diyodlarm arayüzey hal enerji dağılım eğrileri çizilerek karşılaştırıldı. Arayüzey tabakalı diyodların arayüzey hal yoğunluk değerlerinin daha düşük olduğu görüldü. Bu durum, arayüzey oksit tabakası tarafından doymamış bağların doymasına bağlandı.
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    Öğe
    THE CHARACTERISTIC DIODE PARAMETERS IN Ti/p-InP CONTACTS PREPARED BY DC SPUTTERING AND EVAPORATION PROCESSES OVER A WIDE MEASUREMENT TEMPERATURE
    (World Scientific Publ Co Pte Ltd, 2017) Ejderha, Kadir; Asubay, Sezai; Yildirim, Nezir; Gullu, Omer; Turut, Abdulmecit; Abay, Bahattin
    The titanium/p-indium phosphide (Ti/p-InP) Schottky diodes (SDs) have been prepared by thermal evaporation and DC magnetron sputtering deposition. Then, their current-voltage (I-V) characteristics have been measured in the sample temperature range of 100-400K with steps of 20 K. The characteristic parameters of both Ti/ p-InP SDs have been compared with each other. The barrier height (BH) values of 0.824 and 0.847 at 300K have been obtained for the sputtered and the evaporated SDs, respectively. This low BH value for the sputtered SD has been attributed to some defects introduced by the sputtered deposition technique over a limited depth in to the p-type substrate. The BH of the evaporated and sputtered diodes has decreased with the standard deviations of 58 and 64mV obeying to double-Gaussian distribution (GD) in 220-400K range, respectively, and it has seen a more sharper reduction for the BHs with the standard deviations of 93 and 106 mV in 100-220K range. The Richardson constant values of 89.72 and 53.24 A(Kcm)(-2) (in 220-400K range) for the evaporated and sputtered samples, respectively, were calculated from the modiified ln(I-0/T-2) - q(2)sigma(2)(s)/2k(2)T(2) vs (kT)(-1) curves by GD of the BHs. The value 53.24A (Kcm)(-2) for the sputtered sample in high temperatures range is almost the same as the known Richardson constant value of 60 A(Kcm)(-2) for p-type InP.
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    Deposition and Characterization of Si Substituted Cu2ZnSnS4 Thin Films
    (Springer, 2023) Ava, Canan Aytug; Ocak, Yusuf Selim; Celik, Omer; Asubay, Sezai
    The influence of the Si substitution ratio on the structural, morphological, and optical properties of Cu2ZnSnS4 (CZTS) thin films was examined. The Cu2Zn(SixSn1-x)S-4 thin films (x = 0, 0.25, 0.50, 0.75, and 1) were deposited on soda-lime glasses by spin coating technique and annealed in a quartz tube at 550 degrees C under H2S:Ar (1:9) flows. The X-ray diffraction (XRD) patterns showed that the crystal sizes of CZTS thin film decreased rapidly from 30 nm to 19 nm after the substitution of 25% Si to the Sn sites (Cu2Zn(Si0.25Sn0.75)S-4 thin films) and increased to the same range after increasing the Si substitution ratio. It was attributed to the highest dislocation density and strain values of the film after partial Si substitution to the structure. It was also reported that the Si substitution for Cu2ZnSnS4 (CZTS) structure shifted both main XRD (from 28.51 to 28.62 degrees) and Raman peaks (from 332 to 334 cm(-1)). Furthermore, the strong influence of Si addition on the optical properties of the films was examined. It was seen that the optical band gap of CZTS increases from 1.51 to 3.22 eV with the increase in Si ratio.
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    Öğe
    Determination of Proton Relaxivities of Mn(II), Cu(II) and Cr(III) added to Solutions of Serum Proteins
    (Mdpi, 2009) Koylu, Mehmet Zafer; Asubay, Sezai; Yilmaz, Ali
    Relaxometric studies are still of scientific interest due to their use in medicine and biology. In this study, proton T-1 and T-2 relaxivities of Mn(II), Cu(II) and Cr(III) in water were determined in the presence and absence of various proteins (albumin, alpha-globulin, gamma-globulin, lysozyme, fibrinogen). The 1/T-1 and 1/T-2 in all solutions are linearly proportional to the concentration of the paramagnetic ions. Mn(II) has the great influence to alter relaxations in all protein solutions, while Cu(II) and Cr(III) have a poor influence on the relaxations. In addition, Mn(II) and Cu(II) are bound to each protein, but Cr(III) is not bound to any protein.
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    The electrical characteristics of Al/p-InP Schottky contacts
    (Elsevier Science Bv, 2011) Asubay, Sezai
    In this study, it has been investigated the electrical characteristics of identically prepared Al/p-InP Schottky diodes. The barrier heights (BHs) and ideality factors of all devices have been calculated from the electrical characteristics. Although the diodes were all identically prepared, there was a diode-to-diode variation: the effective barrier heights ranged from 0.83 +/- 0.01 to 0.87 +/- 0.01 eV, and the ideality factors ranged from 1.13 +/- 0.02 to 1.21 +/- 0.02. The barrier height vs. ideality factor plot has been plotted for the devices. Lateral homogeneous BH was calculated as a value of 0.86 eV from the observed linear correlation between BH and ideality factor, which can be explained by laterally inhomogeneities of BHs. The values of barrier height and free carrier concentration yielded from the reverse bias capacitance-voltage (C-V) measurements ranged from 0.86 +/- 0.04 to 1.00 +/- 0.04 eV and from (3.47 +/- 0.39) x 10(17) to (4.90 +/- 0.39) x 10(17) cm(-3), respectively. The mean barrier height and mean acceptor doping concentration from C-V characteristics have been calculated as 0.91 eV and 3.99 x 10(17) cm(-3), respectively. (C) 2010 Elsevier B.V. All rights reserved.
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    Electrical parameters of a DC sputtered Mo/n-type 6H-SiC Schottky barrier diode
    (Elsevier Sci Ltd, 2014) Asubay, Sezai; Genisel, Mustafa Fatih; Ocak, Yusuf Selim
    A Mo/n-type 6H-SiC/Ni Schottky barrier diode (SBD) was fabricated by sputtering Mo metal on n-type 6H-SiC semiconductor. Before the formation of Mo/n-type 6H-SiC SBD, an ohmic contact was formed by thermal evaporation of Ni on n-type 6H-SiC and annealing at 950 degrees C for 10 min. It was seen that the structure had excellent rectification. The electrical parameters were extracted using its current-voltage (I-V) and capacitance-voltage (C-V) measurements carried out at room temperature. Very high (1.10 eV) barrier height and 1.635 ideality factor values were reported for Mo/n-type 6H-SiC using In plot. The barrier height and series resistance values of the diode were also calculated as 1413 eV and 69 Omega from Norde's functions, respectively. Furthermore, 1.938 eV barrier height value of Mo/n-type 6H-SiC SBD calculated from C-V measurements was larger than the one obtained from I-V data. (C) 2014 Elsevier Ltd. All rights reserved.
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    Fabrication and electrical properties of an organic-inorganic device based on Coumarin 30 dye
    (Elsevier Sci Ltd, 2014) Tombak, Ahmet; Ocak, Yusuf Selim; Asubay, Sezai; Kilicoglu, Tahsin; Ozkahraman, Fatma
    A Coumarin 30/p-Si organic-inorganic device was fabricated by forming a Coumarin 30 thin film on a p-Si semiconductor. The resulting structure had excellent rectifying properties. Electrical parameters of the structure were determined from current-voltage (I-V) measurements in the temperature range 300-380 K. While the barrier height (phi(b)) increased with increasing temperature, the ideality factor and series resistance of the diode decreased. I-V measurements of the structure were also performed under a solar simulator with AM1.5 filter and 100 mW/cm(2) illumination intensity. The structure had 59 mu A short-circuit current and 337 mV open-circuit voltage. Furthermore, capacitance-voltage (C-V) measurements of an Al/Coumarin 30/p-Si diode were carried out at various frequencies. The phi(b), value obtained by using C-V values was compared with that obtained by using I-V data. (C) 2014 Elsevier Ltd. All rights reserved.
  • Küçük Resim
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    The influence of Ge substitution and H2S annealing on Cu2ZnSnS4 thin films
    (Elsevier, 2021) Ava, Canan Aytuğ; Ocak, Yusuf Selim; Asubay, Sezai; Çelik, Ömer
    Cu2Zn(Sn1-xGex)S-4 thin films (where x = 0, 0.25, 0.50, 0.75, and 1) were deposited by spin coating technique and annealed under 30 and 40 ccm H2S:Ar (1:9) flows to understand the influence of Ge atom content ratio and H2S flow rate during the annealing of thin films on morphological, structural and optical properties of Cu2Zn(Sn1- x Ge-x)S-4 thin films. It was seen that the Ge content has a strong influence on the structural and optical properties of the films. The crystal size of the films decreased sharply for Cu2Zn(Sn0.75Ge0.25)S-4 thin film and started to increase slowly owing to the formation of high dislocation density and strain in the structures. The Raman spectra show the formation of kesterite thin films and blue Raman shift with Ge substitution to the content. The films obtained under 40 ccm H2S:Ar (1:9) flows have weak secondary peaks associated with ZnS formation. The UV-Vis data showed the increase of optical bandgap from 1.52 to 2.05 eV with a rise in Ge ratio in the structures.
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    Influence of Temperature And Light Intensity on Ru(II) Complex Based Organic-Inorganic Device
    (Amer Inst Physics, 2016) Asubay, Sezai; Durap, Feyyaz; Aydemir, Murat; Ocak, Yusuf Selim; Tombak, Ahmet; Baysal, Akin
    An organic-inorganic junction was fabricated by forming [Ru(Cy2PNHCH2-C4H3O)(eta(6)-p-cymene)Cl-2] complex thin film using spin coating technique on n-Si and evaporating Au metal on the film. It was seen that the structure had perfect rectification property. Current-voltage (I-V) measurements were carried out in dark and under various illumination conditions (between 50-100 mW/cm(2)) and with the temperature range from 303 to 380 K. The structure showed unusually forward and reverse bias temperature and light sensing behaviors. It was seen that the current both in forward and reverse bias increased with the increase in light intensity and temperature.
  • Küçük Resim
    Öğe
    Metal/p-InP/metal Schottky kontakların akım-kapasite-gerilim karakteristiklerinin metal iş fonksiyonuna bağımlılığının incelenmesi
    (2017) Asubay, Sezai; Türüt, Abdülmecit; Yılmaz, Ali
    Bu çalışmada, (100) doğrultusunda büyütülmüş, 400 ?m kalınlıklı ve direnci 5– 10 ?.cm arasında olan n ve p-tipi Silisyum kullanıldı. Çalışmadaki amacımız, engel yüksekliğinin uzaysal inhomojenliğinin neden olduğu etkin engel yüksekliği ile idealite faktörleri arasındaki lineer ilişkiyi deneysel olarak göstermektir. Bu amaç için, ince arayüzey doğal oksit tabakalı ve tabakasız Sn/n-Si ve Sn/pSi (n-MS, n-MIS, p-MS ve p-MIS) diyotlarını kendi araştırma laboratuvarımızda imal ettik. Diyotların karakteristik parametreleri, akım-gerilim (I-V), kapasite-gerilim (CV) ve iletkenlik gerilim (G-V) ölçümlerinden belirlendi. İnce arayüzey doğal oksit tabakasız, n-MS için engel yüksekliği 0.60 eV ile 0.67 eV arasında ve idealite faktörleri 1.35 ile 2.56 arasında, ince arayüzey doğal oksit tabakalı, n-MIS için ise engel yükseklikleri 0.56 eV ile 0.65 eV arasında idealite faktörleri ise 1.381 ile 2.777 arasında sıralandı. İnce arayüzey doğal oksit tabakasız p-MS için engel yüksekliği 0.70 eV ile 0.73 eV ile arasında ve idealite faktörleri 1.002 ile 1.189 arasında, p-MIS için ise engel yükseklikleri 0.77 eV ile 0.80 eV arasında idealite faktörleri ise 1.051 ile 1.199 eV arasında sıralandı. Bunun yanı sıra, deneysel engel yüksekliklerine karşı çizilen doğrusal grafiklerinin ekstrapolasyonuyla, imaj kuvvet azaltma değeri eklenerek, uzaysal homojen engel yüksekliklerini sırasıyla ince arayüzey tabakalı ve tabakasız n-MS için yaklaşık olarak 0.665eV ve 0.692 eV olarak bulundu.
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    Temperature dependent electrical characterization of RF sputtered MoS2/n-Si heterojunction
    (Elsevier Gmbh, 2017) Ocak, Yusuf Selim; Bozkaplan, Cihat; Ahmed, Honar Salah; Tombak, Ahmet; Genisel, Mustafa Fatih; Asubay, Sezai
    MoS2 is one of the most promising materials due to its exciting properties. Al/MoS2/n-Si heterojunction diode was acquired via the formation of a MoS2 thin film on n-Si semiconductor using radio frequency (RF) sputtering technique and an evaporation of Al metal on MoS2/n-Si structure. The morphological and optical properties of the RF sputtered MoS2 thin film were examined using atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV-vis data. The electrical parameters of Al/MoS2/n-Si heterojunction on temperature were investigated using its current-voltage (I-V) measurements within 150-400 K in the dark. The results showed that while the ideality factor and series resistance values of the junction decreased, the barrier height values increased with the increase in temperature. The linear correlation between ideality factor and barrier height values was also reported for Al/MoS2/n-Si heterojunction. (C) 2017 Elsevier GmbH. All rights reserved.
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    Temperature-dependent behavior of Ti/p-InP/ZnAu schottky barrier diodes
    (Iop Publishing Ltd, 2008) Asubay, Sezai; Gullu, Omer; Abay, Bahattin; Turut, Abdulmecit; Yilmaz, Ali
    The current-voltage ( I-V) characteristics of Ti/p-InP Schottky diodes have been measured in a wide temperature range with a temperature step of 20 K. An experimental barrier height ( BH) Phi(ap) value of about 0.85 eV was obtained for the Ti/p-InP Schottky diode at 300 K. A decrease in the experimental BH Phi(ap) and an increase in the ideality factor n with a decrease in temperature have been explained on the basis of a thermionic emission mechanism with the Gaussian distribution of the barrier heights due to the BH inhomogeneities at the metal semiconductor interface. (Phi) over bar (b) and A* as 1.01 eV, and 138 A cm(-2) K-2, respectively, have been calculated from a modified ln( I-0/T-2) - q(2)sigma(2)(s)/2k(2)T(2) versus 1/T plot. This BH value is in close agreement with the values of 0.99 eV obtained from the Phi(ap) versus 1/T and ln( I-0/T-2) versus 1/nT plots.
  • Küçük Resim
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    A useful model to interpret the experimental I-V-T and C-V-T data of spatially inhomogeneous metal-semiconductor rectifying contacts
    (Taylor and Francis Ltd., 2020) Asubay, Sezai; Türüt, Abdülmecit
    The temperature-dependent capacitance-voltage (C-V) and current-voltage (I–V) characteristics of the Ti/p-InP/ZnAu Schottky contacts were investigated in this study. The current across a metal-semiconductor Schottky contact can vary sensitively with the change of the Schottky barrier heights (SBHs) and sample temperature. Thereby, the value of the C-V barrier height (Formula presented.) increased and the value of the I–V barrier height (Formula presented.) decreased with a decrease in temperature. Such a change was ascribed to a Gaussian distribution of the spatial inhomogeneity of the SBHs over whole range of the measurement temperatures. Thus, the temperature dependences of the I–V and C-V characteristics were interpreted by a quantitative analysis of spatial distribution (Gaussian distribution) of the SBHs presented as a useful model. Thus, this quantitative analysis was determined from the change of (Formula presented.) values with (2kT ?1).