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Öğe Laws doku enerji ölçümü tabanli k-NN siniflandirici modeli ile iris tanima sistemi(IEEE, 20013-06-13) Acar, Emrullah; Özerdem, Mehmet SiraçBiyometrik tanıma teknolojisi genellikle çok pahallı ve son derece önemli güvenlik uygulamaları ile ilişkili olmuştur.İris tanıma sistemi, etkili biyometrik tanımasistemlerinden biridir. Bu çalışmada, farklı insanlardan elde edilen gözimgelerininiçerdiği irisdokuözelliklerinegörekişilerin tanınmasıamaçlanmıştır. İmgeler CASIAiris veritabanındanelde edilmiştir. İmge dokusuna duyarlı yeni yöntemlerdenbiri olanLawsDoku Enerji Ölçümü (Laws TEM) kullanılarak, iris dokusunun belirli yerelalanlarındanöznitelik vektörleri elde edilmiştir. kEn Yakın Komşu (k-NN) sınıflandırıcıparametrelerinden komşu sayısı(k) farklı değerlerde alınarak, elde edilen öznitelik vektörleri k-NN sınıflandırıcısı ile ayrıştırılmıştır. Farklı komşu sayılarına göre sisteminperformans değerlerikarşılaştırılmıştır. Sonuç olarak en yüksek ortalama performans,k-NNsınıflandırıcısınınk=1ve 2komşularıyapısında % 80.74olarak gözlemlenmiştir.Öğe Electrical properties of organic–ınorganic semiconductor device based on rhodamine-101(SpringerLink, 2009-05) Güllü, Ömer; Turut, Abdulmecit; Yıldırım, Nezir; Çakar, MuzafferRhodamine-101 (Rh101) thin films on n-type Si substrates have been formed by means of evaporation, thus Sn/Rh101/n-Si heterojunctions have been fabricated. The Sn/Rh101/n-Si devices are rectifying. The optical energy gaps have been determined from the absorption spectra in the wavelength range of 400 nm to 700 nm. Rh101 has been characterized by direct optical absorption with an optical edge at 2.05 ± 0.05 eV and by indirect optical absorption with␣an optical edge at 1.80 ± 0.05 eV. It was demonstrated that trap-charge-limited current is the dominant transport mechanism at large forward bias. A␣mobility value of μ = 7.31 × 10−6 cm2 V−1 s−1 for Rh101 has been obtained from the forward-bias current–voltage characteristics.Öğe Electrical analysis of organic interlayer based metal/interlayer/semiconductor diode structures(Journal of Applied Physics, 2009-01) Güllü, Ömer; Turut, AbdulmecitIn this work, metal/interlayer/semiconductor (MIS) diodes formed by coating of an organic film to p-Si semiconductor substrate were prepared. Metal(Al)/interlayer (phenolsulfonphthalein=PSP)/semiconductor(p-Si) MIS device had a good rectifying behavior. By using the forward bias I-V characteristics, the values of ideality factor (n) and barrier height (Phi(b)) for the Al/PSP/p-Si MIS diode were obtained as 1.45 and 0.81 eV, respectively. It was seen that the Phi(b) value of 0.81 eV calculated for the Al/PSP/p-Si MIS diode was significantly larger than value of 0.50 eV of conventional Al/p-Si Schottky diodes. Modification of the interfacial potential barrier of Al/p-Si diode was achieved by using a thin interlayer of the PSP organic material. This has been attributed to the fact that the PSP organic interlayer increases the effective barrier height by influencing the space-charge region of Si. The interface-state density of the MIS diode was determined, and the interface-state density was found to vary from 3.00 x 10(13) to 2.99 x 10(12) eV(-1) cm(-2). (C) 2009 American Institute of Physics.Öğe Electrical characteristics of Co/n-Si schottky barrier diodes using I – V and C – V measurements electrical characteristics of Co/n-Si schottky barrier diodes using I – V and C – V measurements(Chinese Physics Letters, 2009-06) Güllü, Ömer; Güler, Gülşen; Karataş, Şükrü; Bakkaloğlu, Ömer FarukElectrical characteristics of Co/n-Si Schottky barrier diodes are analysed by current-voltage (I – V) and capacitance-voltage (C – V) techniques at room temperature. The electronic parameters such as ideality factor, barrier height and average series resistance are determined. The barrier height 0.76eV obtained from the C – V measurements is higher than that of the value 0.70eV obtained from the I – V measurements. The series resistance RS and the ideality factor n are determined from the d ln(I)/dV plot and are found to be 193.62Ω, and 1.34, respectively. The barrier height and the RS value are calculated from the H(I) – I plot and are found to be 0.71 eV and 205.95Ω. Furthermore, the energy distribution of the interface state density is determined from the forward bias I – V characteristics by taking into account the bias dependence of the effective barrier height. The interface state density Nss ranges from 6.484 × 1011 cm−2eV−1 in (EC – 0.446) eV to 2.801 × 1010 cm−2eV−1 in (EC – 0.631) eV, of the Co/n-Si Schottky barrier diode. The results show the presence of a thin interfacial layer between the metal and the semiconductor.Öğe Analysis of the series resistance and interface state densities in metal semiconductor structures(Journal of Physics: Conference Series, 2009-03) Güllü, Ömer; Karataş, Şükrü; Güler, Gülşen; Bakkaloğlu, Ömer FarukThe electrical properties of Co/n-Si metal-semiconductor (MS) Schottky structure investigated at room temperature using current-voltage (I-V) characteristics. The characteristic parameters of the structure such as barrier height, ideality factor and series resistance have been determined from the I-V measurements. The values of barrier height obtained from Norde’s function were compared with those from Cheung functions, and it was seen that there was a good agreement between barrier heights from both methods. The series resistance values calculated with Cheung’s two methods were compared and seen that there was an agreement with each other. However, the values of series resistance obtained from Cheung functions and Norde’s functions are not agreeing with each other. Because, Cheung functions are only applied to the non-linear region (high voltage region) of the forward bias I–V characteristics. Furthermore, the energy distribution of interface state density was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. The results show that the presence of thin interfacial layer between the metal and semiconductorÖğe The analysis of lateral distribution of barrier height in identically prepared Co/n-Si Schottky diodes(Elsevier, 2009-11-03) Güllü, Ömer; Karataş, Şükrü; Güler, Gülşen; Bakkaloğlu, Ömer FarukWe have studied the experimental linear relationship between ideality factors and barrier heights (BHs) for Co/n-Si metal–semiconductor (MS) structures with a doping density of about 1015 cm−3. The barrier heights for the Co/n-type Si metal–semiconductor structures from the current–voltage (I–V) characteristics varied from 0.64 to 0.70 eV, the ideality factor n varied from 1.18 to 1.26, and from reverse bias capacitance–voltage (C−2–V) characteristics the barrier height varied from 0.68 to 0.81 eV. The experimental barrier height distributions obtained from the I–V and C−2–V characteristics were fitted by a Gaussian distribution function, and their mean values were found to be 0.67 and 0.75 eV, respectively. Furthermore, the lateral homogeneous BH value of approximately 0.81 eV for Co/n-Si metal–semiconductor structures was obtained from the linear relationship between experimental effective BHs and ideality factors.Öğe Determination of the laterally homogeneous barrier height of thermally annealed and unannealed Au/p-InP/Zn-Au Schottky barrier diodes(Elsevier, 2008-03-25) Güllü, Ömer; Turut, Abdulmecit; Asubay, SezaiWe have identically prepared Au/p-InP Schottky barrier diodes (SBDs). The diodes were annealed up to 400 °C thermally. The barrier height (BH) for the as-deposited Au/p-InP/Zn-Au SBDs from the current–voltage characteristics have varied from 0.58 to 0.72 eV, and ideality factor n from 1.14 to 1.47. The BH for the annealed SBDs from the current–voltage characteristics have varied from 0.76 to 0.82 eV, and ideality factor n from 1.17 to 1.39. As a result of the thermal annealing, it has been seen that the BH values of the annealed SBDs are larger than those of the as-deposited SBDs. We have determined a lateral homogeneous BH value of 0.72 eV for the as-deposited Au/p-InP SBD from the experimental linear relationship between barrier heights and ideality factors, and a value of 0.85 eV for the annealed Au/p-InP SBD. The increase of 0.13 eV in the BH value by means of 400 °C annealing has been ascribed to the formation of the excess charges that electrically actives on the semiconductor surface.
