The investigation of temperature and radiation dependent electrical characteristics of au/pva:zn/n-si (mps) schottky barrier diodes

Çinko asetat [Zn(CH3COO)2.2H2O] katkılı PVA arayüzey tabakalı (PVA:Zn) Au/n-Si Schottky engel diyodun (SBDs) doğru ve ters ön-gerilim akım-voltaj (I-V), kapasitans-voltaj (C-V) ve kondüktans-voltaj (G/-V) karakteristikleri geniş bir sıcaklık aralığında (80-400 K) incelendi. Doğru ön-gerilim ln I-V eğrilerinde görülen kesişme davranışı beklenmeyen bir durum olup akım iletiminin termoiyonik teorisine zıt düşmektedir. Diyodun I-V karakteristiklerindeki bu anormal davranış engel yüksekliklerinin uzaysal dağılımına atfedildi. Termoiyonik Emisyon (TE) teorisinin temeline dayanarak deneysel I-V verilerinin analizi, yüksek ve düşük sıcaklık bölgesi için (200-400 K ve 80-170 K) sırasıyla 0,110 ve 0,087 V standart sapma değerleri ve 1,06 eV ve 0,86 eV ortalama engel yükseklikleri ile ikili Gaussian dağılımını ortaya çıkardı. Sonuç olarak ln(Io/T2)-(q)2/2(kT)2q/kT eğrisi düzeltilerek yine yüksek ve düşük sıcaklık bölgesi için (200-400 K ve 80-170 K) sırasıyla 1,06 eV ve 0,85 eV olmak üzere yeni ortalama engel yüksekliği değerleri ile 121 ve 80,4 A/cm2K2 olmak üzere Richardson sabiti (A*) değerleri elde edildi. Elde edilen A*=121 A/cm2K2 Richardson sabiti değeri silisyum için bilinen teorik Richardson sabiti olan 120 A/cm2K2 değerine oldukça yakındır. Deneysel sonuçlar seri direnç ve arayüzey durumlarının sıcaklığa güçlü bir şekilde bağlı olduğunu göstermiştir. Aynı zamanda C-V eğrilerinde görülen anormal pikler seri direnç etkisi ve arayüzey durumlarının sıcaklık ile yeniden yapılanıp düzenlenmesine atfedilebilir. Sıcaklığa bağlı Nss değerleri hem enerjinin bir fonksiyonu olarak I-V verilerinden hemde C-V ve G/-V karakteristikleri kullanılarak Hill-Coleman metodundan elde edildi. Bunların yanı sıra, radyasyonun Au/PVA:Zn/n-Si SBD üzerinde etkisini görmek amacıyla, numune Co60ışını kaynağına 20 kGy doza maruz bırakıldı. Radyasyondan sonra I-V karakteristiklerinden hesaplanan engel yüksekliği ve idealite faktörü değerlerinin azalırken, seri direnç ve doyum akımı değerlerinin arttığı görüldü. Aynı zamanda diyodun taşıyıcı konsantrasyonu, kapasitans ve iletkenlik değerlerinin de uygulanan radyasyon dozu ile azaldığı gözlendi.The forward and reverse bias current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/-V) characteristics of Au/n-Si Schottky barrier diodes (SBDs) with Zinc acetate [Zn(CH3COO)2.2H2O] doped poly(vinyl alcohol) (PVA:Zn) interfacial layer have been investigated in the wide temperature range of 80-400 K. The crossing of the experimental forward bias semi-logarithmic ln I-V plots is rather unexpected and seems to be in contradiction with thermionic concept of current transport. The abnormal behavior of current-voltage characteristics of SBD has been attributed to spatial variation of barrier height. The analysis of I-V data based on thermionic emission (TE) of the Au/PVA:Zn/n-Si SBDs has revealed the existence of double Gaussian distribution (GD) with mean barrier height (BH) values ( B0  ) of 1,06 and 0,86 eV with standard deviation (σ) of 0,110 and 0,087 V, respectively. Thus, we modified ln(Io/T2)-(q)2/2(kT)2 vs q/kT plot for two temperature regions (200-400 K and 80-170 K) and it gives renewed mean barrier heights B0  values as 1,06 and 0,85 eV with Richardson constant (A*) values 121 and 80,4 A/cm2K2, respectively. This obtained value of A*=121 A/cm2K2 is very close to the known theoretical value of 120 A/cm2K2 for n-type Si. Our experimental results show that both series resistance (Rs) and interface states (Nss) were vii strongly functional with temperature. It was observed that C-V and G/-V plots exhibited anomalous peak at forward bias because of Rs and thermal restructuring and reordering of Nss. The density of Nss depending on temperature was determined both by I-V data as a function of energy and Hill-Coleman method using C-V and G/-V characteristics. In addition, to see gamma-ray irradiation effect on electrical characteristics of Au/PVA:Zn/n-Si SBD, the sample was exposed to 60Co -ray source at 20 kGy. It was seen that the barrier height and ideality factor calculated from I-V characteristics decreased after the applied radiation, while the saturation current and series resistance values increased. It was also seen that the carrier concentration, the capacitance and conductance of device decreased with radiation dose

Frequency, voltage and illumination interaction with the electrical characteristics of the CdZnO interlayered Schottky structure

Taşçıoğlu, İlke (Arel Author)cadmium-zincoxide (CdZnO) interlayered metal-semiconductor structure was examined by capacitance and conductance versus voltage data in dark and under 250W illumination at 100kHz, 500kHz and 1MHz frequencies, respectively. The effectuality of the frequency, applied voltage, illumination, and series resistance on the electrical parameters was discussed in detail. The increase in the frequency led to the decrement in capacitance and conductance and the increment in the illumination generally led to the increment in capacitance and conductance. An abnormal behavior was detected in the accumulation region of the C-V plots at 500kHz and 1MHz due to the inductive phenomenon of device. The effect of illumination intensity reduces the R-i values in the inversion region while enhances them in the depletion and accumulation region for 1MHz. Additionally, the series resistance values decrease with increasing frequency due to the specific dispersion of localized interface states. As a consequence of the experimental results, a remarkable interaction was realized between the electrical parameters and the illumination, frequency and applied biases

Illumination dependent admittance characteristics of Au/Zinc acetate doped polyvinyl alcohol (PVA:Zn)/n-Si Schottky barrier diodes (SBDs)

1st International Congress on Advances in Applied Physics and Materials Science (APMAS) -- MAY 12-15, 2011 -- Antalya, TURKEYWOS: 000301042000058This study presents the effect of illumination on main electrical parameters of Schottky barrier diode (SBD). The admittance (capacitance-voltage (C-V) and conductance-voltage (G/omega-V)) characteristics of Au/Zinc acetate doped polyvinyl alcohol (PVA:Zn)/n-Si SBD were investigated in dark and under various illumination intensities. Experimental results demonstrate that the C-V plots give a peak due to the illumination induced interface states or electron-hole pairs at metal/semiconductor (M/S) interface. The C-2-V plots were also drawn to determine main electrical parameters such as doping concentration (N-D), depletion layer width (W-D) and barrier height (Phi(B)(C-V)) of device. In addition, the voltage dependence R-s values were obtained from C-V and G/omega-V data by using Nicollian and Brews method. In order to obtain the real diode capacitance and conductance, the high frequency (1 MHz) C-m and G(m)/w values were corrected for the effect of series resistance. All these observations confirm that both C-V and G/w-V characteristics were strongly affected by illumination.Istanbul Kultur Univ, Gebze Inst Technol, Doga Nanobiotech Inc, Terra Lab Inc, LOT Oriel Grp, PHYWE, Delta Elekt In

Effectuality of Barrier Height Inhomogeneity on the Current-Voltage-Temperature Characteristics of Metal Semiconductor Structures with CdZnO Interlayer

Taşçıoğlu, İlke (Arel Author)Current-conduction/transport mechanisms (CCMs or CTMs) through barrier and barrier height (BH) formation in the Al/(CdZnO)/p-Si/Al diodes, which were prepared by the sol-gel method, were examined in the range of 110-380 K. The decrease of zero-bias BH (Phi(Bo)) and increase of ideality factor (n) with decreasing temperature were observed. The classic Richardson plot indicated two distinct linear regions that correspond to low and high temperature range (LTR and HTR), respectively. Contrary to this, the acquired Richardson constant value (A*) was much lower than its theoretical value (32 A cm(-2) K-2). Such abnormal behavior of the Phi(Bo), n and A* was attributed to the evidence of the barrier inhomogeneities, especially at low temperature. Therefore, the Phi(Bo-)n, Phi(Bo) and (n(-1) - n) versus q/2kT plots were sketched to acquire significant clues for the Gaussian distribution (GD) of the BHs at rectifier contact area with the mean BH ((Phi) over bar (Bo)) and standard deviation (sigma(so)), which also have two linear parts with distinct slopes. (Phi) over bar and sigma(so) were calculated from the slope and intercept of Phi(Bo) versus q/2kT plot as 0.802 eV and 0.066 V for LTR, 1.043 eV and 0.106 V for HTR, respectively. The (Phi) over bar (Bo) and A* were acquired by utilizing the sigma(so) values and using the Richardson plot as 0.626 eV and 14.26 A cm(-2) K-2 for LTR and 1.021 eV and 32.53 A cm(-2) K-2 for HTR, respectively. Thus, the I-V-T characteristics of the Al/(CdZnO)/p-Si/Al diodes at forward biases were successfully elucidated by the double-GD of BHs with mean BHs of 0.626 eV and 1.021 eV, respectively

Frequency-Dependent Admittance Analysis of Au/n-Si Structure with CoSO4-PVP Interfacial Layer

A film of cobalt sulfate (CoSO4)-doped polyvinylpyrrolidone (PVP) blend was spin-coated on n-Si. Electrical measurements were conducted on the Au/n-Si structure with the CoSO4-PVP film sandwiched between them. The frequency dispersion of the main electrical and dielectric parameters and the corresponding mechanisms were evaluated. The extra capacitance originating from the contribution of interface states (N-ss) resulted in a fairly large frequency dispersion in C-V plots. These states also influence the carrier transport and conduction mechanism, thus the determination of real N-ss values is crucial to evaluate the nonideal behavior of such plots. The values of N-ss were calculated using the Hill-Coleman method. The dielectric constant (epsilon ') and dielectric loss (epsilon '') exhibited higher values in the low-frequency region as a result of interface and dipole polarization, while the alternating-current (AC) electrical conductivity (sigma(ac)) generally decreased. The variation of the loss tangent with increasing frequency of the applied field confirmed the effect of some internal field within the CoSO4-PVP film accompanied by the external AC field

Frequency Dependent Electrical and Dielectric Properties of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky Barrier Diode

Tascioglu, Ilke/0000-0001-9563-4396WOS: 000395454400057In this study, poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (P3HT:PCBM:F4-TCNQ) organic film was deposited on n-type silicon (n-Si) substrate by spin coating method. The electrical and dielectric analysis of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky barrier diode was conducted by means of capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements in the frequency range of 10 kHz-2 MHz. The C-V-f plots exhibit fairly large frequency dispersion due to excess capacitance caused by the presence of interface states (N (ss)). The values of N (ss) located in semiconductor bandgap at the organic film/semiconductor interface were calculated by Hill-Coleman method. Experimental results show that dielectric constant (epsilon') and dielectric loss (epsilon aEuro(3)) decrease with increasing frequency, whereas loss tangent (tan delta) remains nearly the same. The decrease in epsilon' and epsilon aEuro(3) was interpreted by the theory of dielectric relaxation due to interfacial polarization. It is also observed that ac electrical conductivity (sigma (ac)) and electric modulus (M' and MaEuro(3)) increase with increasing frequency

Examination of dielectric response of Au/HgS-PVA/n-Si (MPS) structure by impedance spectroscopy method

Taşçıoğlu, İlke (Arel Author)HgS-PVA nanoparticles were obtained via a simple ultrasound-assisted method. The structural and morphological characteristics of the products were analyzed by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The optical properties were also analyzed by UV-Vis spectroscopy, and Fourier transform infrared (FTIR). The XRD pattern demonstrated that the samples were high purity and no impurity other peaks were detected. The optical band gap was calculated by Tauc plot measured as 2.4 eV and a blue shift of about 0.3 eV due to the quantum confinement of charge carriers in a small nanostructure was observed. The surface of the samples consisting of nano-sized particles and the energy between the functional group were proved by SEM measurement and FTIR analysis techniques, respectively. Dielectric behavior was examined in the frequency range of 1 kHz-5MHz by using admittance (C-V and G/omega-V) measurements. The effect of surface states (N-ss) and polarization processes are dominant especially at low frequencies which lead to large discrepancies in C and G values. The dielectric constant value epsilon' reduces with the frequency increments, whereas the ac electrical conductivity sigma(ac) increases, depending on the nature of reducing polarization and series resistance (R-s) effect. The epsilon ''-V and tan delta-V plots give a peak in the inversion region and the magnitude of this peak reduces with the frequency increments, shifting towards the accumulation region that can be ascribed to a frequency dependent dielectric relaxation

Frequency Dependent Electrical and Dielectric Properties of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky Barrier Diode

Taşçıoğlu, İlke (Arel Author)In this study, poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (P3HT:PCBM:F4-TCNQ) organic film was deposited on n-type silicon (n-Si) substrate by spin coating method. The electrical and dielectric analysis of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky barrier diode was conducted by means of capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements in the frequency range of 10 kHz-2 MHz. The C-V-f plots exhibit fairly large frequency dispersion due to excess capacitance caused by the presence of interface states (N (ss)). The values of N (ss) located in semiconductor bandgap at the organic film/semiconductor interface were calculated by Hill-Coleman method. Experimental results show that dielectric constant (epsilon') and dielectric loss (epsilon aEuro(3)) decrease with increasing frequency, whereas loss tangent (tan delta) remains nearly the same. The decrease in epsilon' and epsilon aEuro(3) was interpreted by the theory of dielectric relaxation due to interfacial polarization. It is also observed that ac electrical conductivity (sigma (ac)) and electric modulus (M' and MaEuro(3)) increase with increasing frequency

Illumination Dependent Electrical Data Identification of the CdZnO Interlayered Metal-Semiconductor Structures

Electrical data of the Schottky structure with CdZnO interlayer have been evaluated for different illumination intensities. Considering such parameters as, the ideality factor (n), reverse saturation current (I-o), zero bias barrier height (phi(Bo)), series and shunt resistances (R-s and R-sh) and surface states (N-ss), we concluded that these parameters extremely depend on the illumination power and applied bias voltage. In consequence of the Ohm's law and Norde's method used for R-s determination, the R-s values decreased with increasing illumination intensity. The energy distribution of the N-ss and voltage dependent profile of resistance (R-i) of the structure were extracted from the forward bias current-voltage (I-V) data. The fabricated CdZnO interlayered metal-semiconductor structure appears to have photodiode behavior. Accordingly, the alteration in the basic electrical parameters by the increment in illumination levels indicates that, the carrier generation takes place in the depletion layer and the conductivity of the CdZnO interlayered structure is improved

Si tabanlı nano-malzemelerin geliştirilerek güneş gözesi ve optoelektronik aygıtlara uygulanması

TÜBİTAK MFAG01.02.2015TÜBİTAK ile ABD Ulusal Bilim Vakfı (NSF) arasındaki işbirliği çerçevesinde, silisyum nanoteller metal yardımlı aşındırma yöntemiyle elde edilerek güneş gözesi ve Li-iyon pil üretiminde kullanılmıştır. Bu projedeki temel amacımız yüzey yapılarının şeklini, boyutunu, dağılım ve yoğunluğunu kontrol edecek yeni yöntemler geliştirmek ve farklı yapılar için reçeteler üretmektir. Bu kapsamda ışıkla modüle edilmiş metal yardımlı aşındırma prosesinde Si nanotellerin oluşumu yeni bir metot olarak incelenmiştir. Bunun yanı sıra Si alttaşların yüzey yapısı üzerine farklı kimyasalların etkisi morfolojik analizlerle ve optik ölçümlerle incelenmiştir. Deneysel sonuçlar, Si nanotellerde kümelenme ve eğimli olma durumunun temel kaynağının nanotellerin dibindeki reaksiyon cephesinde enine hareket olduğunu göstermiştir. Bu olay Si yüzeyindeki farklı bölgelerde ışıkla üretilmiş elektron-hol çiftinin homojen olmayan dağılımını ortaya koymaktadır. Nanoteller endüstriyel boyutta tek kristal Si güneş pilleri (156 mm × 156 mm) güneş pillerine uygulanmıştır. Mavi-mor bölgeyi de içine alan bütün görünür bölgede yüzeyden yansıma 5%'den daha az bir değere düşmüştür. Güneş gözelerini üretmek için Si nanoteller oluşturularak standart güneş gözesi üretim işlemleri uygulanmıştır. Önerilen fikrin potansiyelini ortaya çıkaran sonuçlar nanotellere sahip güneş gözelerinin verimlerinin standart piramit desenli gözelere yakın olduğunu göstermiştir. Si nanoteller aynı zamanda sonikasyon yöntemi ile alttaşlardan koparılıp Li-iyon pillere uygulanmıştır. n-tipi Si nanotellere sahip piller p-tipinden elde edilenlere kıyasla daha iyi bir pil performansı göstermiştir. n tipi nanotellerden oluşturulan piller 1500 mAh/g üzerine çıkan yüksek kapasite ve yaklaşık %97 coulomb verimi göstermiştir. Bu proje Si nanotel oluşum mekanizmasının temel yönlerini açığa kavuşturmakla birlikte üzerine yapılabilecek olası uygulamaları ve nano-yapılı malzeme üretim prosesi için yeni yollar ortaya koymaktadır. Oldukça umut verici sonuçlar veren bu tür aygıtların daha da geliştirilmesi için yeni çalışmaların yürütülmesi gerekmektedir. Proje önerisi 12 ay gibi nisbeten kısa bir sürede çok sayıda iş yapmayı hedefleyen bir proje olarak sunulmuştur. Uluslararası bir organizasonu da içeren zorlu bir programı olan proje hedeflerine büyük ölçüde ulaşmıştır. Çok sayıda deney ve çalışma yürütülmüştür. Bu çalışmaların bir özeti bu sonuç raporunda sunulmuştur.As part of the bilatereal cooperation project between TUBITAK and National Science Foundation (NSF), silicon nanowires (Si NWs) fabricated by metal assisted etching (MAE) method have been used to fabricate solar cell and Li-ion batteries. Our main aim in this project is to develop methodologies to control the shape, size, and the distribution of the surface structures and density, and generate recipes for different structures. In this context, a novel method to manipulate Si NWs with a light-modulated MAE process has been investigated. In addition to this, the effect of different chemicals of etching process on the surface structure of silicon wafers have been studied through morphology analysis and optical measurements. Experimental results for the Si nanowires has shown that the main origin of the nanowire inclination and clustering is preferential lateral movement of the reaction fronts at the bottom of the SiNWs. Evidence suggests a relationship of this phenomenon to the inhomogeneous distribution of photo-generated electron–hole pairs at the Si surface in different areas. Nanowires were applied to industrial size (156 mm × 156 mm) monocyrstalline Si solar cells. The reflectivity from the device surface was reduced to less than 5% for the entire visible spectrum (350–750 nm), including the blue–violet region. Standard solar cell fabrication procedures were employed to fabricate cells with and without Si nanowires, and the results showed that the efficiencies of solar cells with nanowires were similar to those of standard pyramid- textured cells, revealing the potential of the proposed concept. Si NWs were also applied to Li-ion batteries after detaching from the silicon wafer substrates by sonication. Batteries with n-type Si NWs showed better performance in comparison with the p-type ones. n-type nanowire batteries exhibited high capacities, over 1500 mAh/g, with nearly 97% Coulombic efficiency. This project not only elucidated fundamental aspects of the mechanism of SiNW formation, but also provided prospective applications and new routes for modulation in other noble metal etching systems and similar nanostructure fabrication processes. All results have shown some promising features. However, they need to be studied and optimized for an actual application. It was submitted as an ambitious study to be performed in a relatively short time. In addition to its scientific and technical program, it also included international oragnization tasks, which sometimes slows down the project execution. In spite of these difficulties, and the heavy content, we have achived most of the goals through extensive experiments and studies. Below, we present a summary of our project acitivities and the results obtained from these studies