DIODE PROPERTY OF n-ZnO/p-Si HETEROJUNCTION STRUCTURE IN THE DARK AND ILLUMINATION CONDITION

DIODE PROPERTY OF n-ZnO/p-Si HETEROJUNCTION STRUCTURE IN THE DARK AND ILLUMINATION CONDITIONAbstractIn this study, Zinc Oxide (ZnO) thin film was deposited on the Silicon (Si) wafer by Pulsed Laser Deposition (PLD) to form n-ZnO/p-Si heterojunction.  The morphological and the crystal structure of ZnO thin film was analysed and interpreted by Atomic Force Microscopy (AFM) and X-Ray Diffraction (XRD), respectively.  The absorption spectrum was obtained by using the UV-Vis spectra and the band gap (Eg) was found by using Tauc Law.  The current density-Voltage (J-V) plot was obtained at room temperature (RT) in the dark and under illumination.  The barrier height (BH) and ideality factor were found about 0.46 eV and 1.35, respectively.  The largest values of open circuit voltage (Voc) and short-circuit current (Jsc) were about 100 mV and 3×10-2 mA/cm2, respectively.  It has been measured that ZnO/Si heterojunction diode behaves a solar cell like device under the illumination conditions.Keywords: Heterojunction, open circuit voltage, short circuit current, barrier height, ideality factorKARANLIK ve AYDINLIK ŞARTLARDA n-ZnO/p-Si HETEROEKLEM YAPISININ DİYOT ÖZELLİĞİÖzetBu çalışmada, n-ZnO/p-Si heteroeklem oluşturmak için Silikon (Si) wafer üzerine Çinko Oksit (ZnO) ince film Puls Lazer Deposizasyon (PLD) ile depozit edilmiştir. ZnO ince filmin morfolojik ve kristal yapısı, sırasıyla Atomik Kuvvet Mikroskopu (AFM) ve X-Ray Kırınımı (XRD) ile analiz edilmiş ve yorumlanmıştır. Soğurma spektrumu UV-Vis spektrumu kullanılarak elde edilmiş ve bant aralığı (Eg) Tauc yasası kullanılarak bulunmuştur. Akım yoğunluğu-Gerilim (J-V) grafiği, oda sıcaklığında (RT) karanlıkta ortamda ve ışık altında elde edilmiştir. Bariyer yüksekliği (BH) ve idealite faktörü sırasıyla yaklaşık 0.46 eV ve 1.35 bulunmuştur. Açık devre voltajının (Voc) ve kısa devre akım yoğunluğunun (Jsc) en büyük değerleri sırasıyla 100 mV ve 3x10-2 mA/cm2’dir. ZnO/Si heteroeklem diyotunun ışık altında güneş piline benzer bir cihaz gibi davrandığı gözlemlenmiştir.Anahtar Kelimeler: Heteroeklem, açık devre voltajı, kısa devre akımı, bariyer yüksekliği, idealite faktör

FEMTOSANİYE LASER Z-SCAN TEKNİĞİ İLE MALZEMELERİN NONLİNEER OPTİK KARAKTERİZASYONU

FEMTOSANİYE LASER Z-SCAN TEKNİĞİ İLE MALZEMELERİN NONLİNEER OPTİK KARAKTERİZASYONUÖzetFarklı yapıdaki sıvı kristallerin, organik malzemelerin ve saydam optik malzemelerin; lineer olmayan soğurma (NLA) ve lineer olmayan kırılma (NLR) gibi optik özelliklerinin belirlenmesi amacıyla geniş çaplı uygulamalar ve güvenilir yöntemler geliştirilmiştir.  Z-tarama metodu, yoğunlaşmış ışık demeti boyunca incelenecek malzemeyi yatay bir düzlemde (optik eksen boyunca) ve odak noktasından geçecek şekilde hareket ettirerek farklı şiddetlerle etkileşmesi üzerine dayanan bir tarama yöntemidir. Z-tarama tekniği puls laserler kullanılarak da malzemenin optiksel lineer olmayan özelliklerinin belirlenmesinde kullanılmaktadır.  Bu yöntem ile lineer olmayan soğurma katsayısı ve lineer olmayan kırılma indisi bağıntıları belirlenerek malzeme için ayırt edici bazı özellikler yapılan hesaplamalar ile saptanabilmektedir. Bu çalışma kapsamında z-tarama sistemi femtosaniye (fs)  laser ile birlikte kullanılarak sıvı içerisinde puls laser ablasyon ile elde edilmiş olan PMMA, altın (Au) ve bakır (Cu) nanoparçacıkların lineer olmayan optik parametreleri elde edilmiştir.  Aynı zamanda z-tarama deney düzeneğinde referans çalışması olarak CS2 molekülünün analizleri de yapılmıştır ve sonuçların literatür ile uyumlu olduğu gösterilmektedir.Anahtar Kelimeler: Laserler, Femtosaniye Laser, Z-tarama, Lineer Olmayan OptikTHE OPTICAL CHARACTERIZATION OF THE MATERIALS WITH FEMTOSECOND LASER Z-SCAN TECHNIQUEAbstractA wide range of applications and reliable methods have been developed to determine the optical properties such as nonlinear absorption (NLA) and nonlinear refraction (NLR) of the different types of liquid crystals, organic materials and optically transparent materials. The z-scan method is accepted as a method based on material interaction with different laser intensity by moving in a horizontal plane along the intensive laser beam. The z-scan technique with femtosecond lasers is used to determine the nonlinear optical properties of the material. With this method, the nonlinear absorption coefficient and nonlinear refractive index can be calculated to determine the distinguishing feature of the materials. In this study, a z-scan system used with femtosecond laser system which has been obtained nonlinear optical parameters rhenium, gold and copper nanoparticles achieved by pulse laser ablation method and also z-scan experimental setup was performed for CS2 molecule as a reference study and results have been shown to be consistent with the literature.Keywords: Lasers, Femtosecond Laser, Z-scan, Nonlinear Optic

PULSLU LASER DEPOZİSYON (PLD) YÖNTEMİ İLE ÜRETİLEN FTO ve ZnO İNCE FİLMLERİN MORFOLOJİK VE OPTİK ÖZELLİKLERİ

PULSLU LASER DEPOZİSYON (PLD) YÖNTEMİ İLE ÜRETİLEN FTO ve ZnO İNCE FİLMLERİN MORFOLOJİK VE OPTİK ÖZELLİKLERİ  ÖzetBu çalışmada, PLD tekniği ile oda sıcaklığında (RT) soda lime cam (SLG) alt tabaka üzerine büyütülen Flor (F) katkılı SnO2 (FTO) ve ZnO ince filmlerin üretiminde; laser enerjisinin, filmlerin optik ve morfolojik özellikleri üzerine etkileri incelenmiştir.  Bununla birlikte, faklı O2 gaz basıncında ZnO ince filmleri büyütülmüş ve bir ZnO ince film 300 oC sıcaklıkta tavlanmıştır.  İnce filmlerin, morfolojik yapısı Atomik Kuvvet Mikroskop (AFM) yöntemi, kristal yapısı ise X-ışını kırınımı  (XRD) yöntemi ile analiz edilmiştir.  FTO ve ZnO ince filmleri genel olarak gözenekli yapıdadır.  PLD ile oda sıcaklığındaki SLG üzerine büyütülen FTO ve ZnO ince filmler polikristal yapıya sahiptirler.  İnce filmler spektrumun görünür bölgesinde şeffaftırlar ve 3.75 eV (FTO), 3.50 eV (ZnO), 3.30 eV (tavlanmış ZnO) bant aralıklarına (Eg) sahiptirler. Çalışmada, laser enerjisi (FTO ve ZnO ince filmlerinin), O2 gaz basıncı ve tavlama sıcaklığı değerlerinin (sadece ZnO ince filminin) üretilen ince filmlerin morfolojik ve kristal yapıları ile optik özellikleri üzerine etkileri ayrıntılı olarak incelenmiş ve yorumlanmıştır.Anahtar Kelimeler: Pulslu Laser Depozisyon, ZnO, FTO, laser, bant aralığı, ince film, polikristal.MORPHOLOGICAL AND OPTICAL PROPERTIES OF FTO AND ZnO THIN FILMS PRODUCED BY PULSED LASER DEPOSITION (PLD) METHODAbstractIn this study, in the production of Fluorine (F) doped SnO2 (FTO) and ZnO thin films grown on soda lime glass (SLG) substrate by PLD technique at room temperature (RT); the effects of laser energy on optical and morphological properties of films have been investigated.  However, ZnO thin films were grown in a different O2 gas pressure and a ZnO thin film was annealed at 300 oC.  The morphological structure of thin films was analysed by Atomic Force Microscopy (AFM) method and the crystal structure by X-ray diffraction (XRD) method.  FTO and ZnO thin films are generally porous. FTO and ZnO thin films grown on PLD at room temperature on SLG substrate have polycrystalline structure. Thin films are transparent in the visible region of the spectrum and have the band gaps (Eg) of 3,75 eV (FTO), 3.50 eV (ZnO), 3.30 eV (annealed ZnO).  In the study, the effects of laser energy (FTO and ZnO thin films), O2 gas pressures and annealing temperature values (only ZnO thin film) on the morphological, crystal structures and optical properties of thin films were examined and interpreted in detail.Keywords: Pulsed Laser Deposition, ZnO, FTO, laser, band gap, thin film, polycrystalline

Structural and Electronic Characterization of m-Fluoroaniline and m-Iodoaniline: A Density Functional Theory Study

This study aimed to investigate the electronic and structural characteristics of m-fluoroaniline (MFA) and m-iodoaniline (MIA). Density functional theory (DFT) and CAM-B3LYP/LanL2DZ methods were employed to determine various properties such as the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, chemical reactivity descriptors, nonlinear optical properties, Mulliken population analysis, molecular electrostatic potential map, thermodynamic properties, and UV-Vis spectral analysis. In addition, the research explored the vertical and adiabatic ionization energy parameters of these molecules by constructing singly charged cation radicals using the same level theory. The obtained results were compared with experimental data from the literature

Ag/AgCl electrodes in the EEG/fMRI method in 3T MRI scanner

This study focuses on the comparison of two different types of EEG electrodes (the first B10-S-150 Ag/AgCl sintered ring electrode with 1, 5 mm touch proof safety socket and 150 cm heavy-duty lead wire and the second, B12-LS-100 Ag/AgCl sintered FE-electrode with 100 cm light-duty lead wire and 1, 5 mm touch proof safety socket with 5 kΩ resistor near sensor) used in the EEG/fMRI method in 3T MRI scanner. We compared these electrodes by their specific absorption rate (SAR) simulation values and the temperature change calculated by PRF method. The experimental setup of the study is described as follows: a phantom is prepared and the electrodes are placed on it. Then, a simulation for SAR values is realized. The temperature change is calculated by MR thermometer. As a result of this study, Ag/AgCl pin electrode is better to be use in EEG/fMRI; because the measured temperature change is expected to be low

Rapid and efficient ambient temperature X-ray crystal structure determination at Turkish Light Source

High-resolution biomacromolecular structure determination is essential to better understand protein function and dynamics. Serial crystallography is an emerging structural biology technique which has fundamental limitations due to either sample volume requirements or immediate access to the competitive X-ray beamtime. Obtaining a high volume of well-diffracting, sufficient-size crystals while mitigating radiation damage remains a critical bottleneck of serial crystallography. As an alternative, we introduce the plate-reader module adapted for using a 72-well Terasaki plate for biomacromolecule structure determination at a convenience of a home X-ray source. We also present the first ambient temperature lysozyme structure determined at the Turkish light source (Turkish DeLight). The complete dataset was collected in 18.5 min with resolution extending to 2.39 Å and 100% completeness. Combined with our previous cryogenic structure (PDB ID: 7Y6A), the ambient temperature structure provides invaluable information about the structural dynamics of the lysozyme. Turkish DeLight provides robust and rapid ambient temperature biomacromolecular structure determination with limited radiation damage

Cryogenic X-ray crystallographic studies of biomacromolecules at Turkish Light Source “Turkish DeLight”

X-ray crystallography is a robust and powerful structural biology technique that provides high-resolution atomic structures of biomacromolecules. Scientists use this technique to unravel mechanistic and structural details of biological macromolecules (e.g., proteins, nucleic acids, protein complexes, protein-nucleic acid complexes, or large biological compartments). Since its inception, single-crystal cryocrystallography has never been performed in Türkiye due to the lack of a single-crystal X-ray diffractometer. The X-ray diffraction facility recently established at the University of Health Sciences, İstanbul, Türkiye will enable Turkish and international researchers to easily perform high-resolution structural analysis of biomacromolecules from single crystals. Here, we describe the technical and practical outlook of a state-of-the-art home-source X-ray, using lysozyme as a model protein. The methods and practice described in this article can be applied to any biological sample for structural studies. Therefore, this article will be a valuable practical guide from sample preparation to data analysis