Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4719
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Article Citation - WoS: 2Citation - Scopus: 2Electronic Structure of Cyanocobalamin: Dft+qmc Study(Springer Verlag, 2017) Mayda, Selma; Kandemir, Zafer; Kandemir, Zafer; Mayda, Selma; Bulut, Nejat; 01. Izmir Institute of Technology; 04.05. Department of Pyhsics; 04. Faculty of ScienceWe study the electronic structure and the magnetic correlations of cyanocobalamin (C63H88CoN14O14P) by using the framework of the multi-orbital single-impurity Haldane-Anderson model of a transition metal impurity in a semiconductor host. Here, we first determine the parameters of the Anderson Hamiltonian by performing density functional theory (DFT) calculations. Then, we use the quantum Monte Carlo (QMC) technique to obtain the electronic structure and the magnetic correlation functions for this effective model. We find that new electronic states, which correspond to impurity bound states, form above the lowest unoccupied level of the host semiconductor. These new states derive from the atomic orbitals at the cobalt site and the rest of the molecule. We observe that magnetic moments develop at the Co(3dν) orbitals and over the surrounding sites. We also observe that antiferromagnetic correlations exist between the Co (3dν) orbitals and the surrounding atoms. These antiferromagnetic correlations depend on the filling of the impurity bound states.Article Fabrication of Bi2212 Single Crystal Bolometer for Detection of Terahertz Waves(Springer Verlag, 2017) Semerci, Tuğçe; Demirhan, Yasemin; Demirhan, Yasemin; Wang, Huabing; Özyüzer, Lütfi; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyTerahertz (THz) radiation is in powerful region of electromagnetic spectrum because of prosperous application areas yet deficiency still exists about sources and detectors in despite of improvements of the research field in this range. This gap can be filled by focusing on development of THz detectors. Therefore, bolometers were preferred through many detectors due to detection sensitivity above 1 THz. In this study, Bi2Sr2CaCu2O8+δ (Bi2212) single crystals were used to fabricate THz bolometric detector. Bi2212 single crystals were transferred on sapphire substrate by cleavage process and e-beam lithography and ion beam etching were used to fabricate the microchip clean room facilities. Customdesigned cryogenic cryostat was used for a-b axis electrical and THz response measurements with liquid nitrogen cooled system. After electrical measurements, Bi2212 microchips detected the signals using Stefan-Boltzmann Lamp and response time were calculated. This study have shown with our experimental results that Bi2212 single crystals are potential candidates for THz bolometric detectors.Article Citation - WoS: 2Citation - Scopus: 2Electronic Structure and Correlations of Vitamin B12 Studied Within the Haldane-Anderson Impurity Model(Springer Verlag, 2016) Kandemir, Zafer; Mayda, Selma; Mayda, Selma; Kandemir, Zafer; Bulut, Nejat; 01. Izmir Institute of Technology; 04.05. Department of Pyhsics; 04. Faculty of ScienceWe study the electronic structure and correlations of vitamin B12 (cyanocobalamine) by using theframework of the multi-orbital single-impurity Haldane-Anderson model of atransition-metal impurity in a semiconductor host. The parameters of the effectiveHaldane-Anderson model are obtained within the Hartree-Fock (HF) approximation. Thequantum Monte Carlo (QMC) technique is then used to calculate the one-electron andmagnetic correlation functions of this effective model. We observe that new states forminside the semiconductor gap found by HF due to the intra-orbital Coulomb interaction atthe impurity 3d orbitals. In particular, the lowest unoccupiedstates correspond to an impurity bound state, which consists of states from mainly the CNaxial ligand and the corrin ring as well as the Co eg-like orbitals. We alsoobserve that the Co (3d) orbitals can develop antiferromagneticcorrelations with the surrounding atoms depending on the filling of the impurity boundstates. In addition, we make comparisons of the HF+QMC data with the density functionaltheory calculations. We also discuss the photoabsorption spectrum of cyanocobalamine.Other Erratum To: Mbe-Grown Cdte Layers on Gaas With In-Assisted Thermal Deoxidation(Springer Verlag, 2016) Arı, Ozan; Bilgilisoy, Elif; Selamet, Yusuf; Selamet, Yusuf; Arı, Ozan; Bilgilisoy, Elif; 01. Izmir Institute of Technology; 04.05. Department of Pyhsics; 04. Faculty of ScienceArticle Citation - WoS: 6Citation - Scopus: 5Mbe-Grown Cdte Layers on Gaas With In-Assisted Thermal Deoxidation(Springer Verlag, 2016) Arı, Ozan; Bilgilisoy, Elif; Selamet, Yusuf; Selamet, Yusuf; Arı, Ozan; Bilgilisoy, Elif; 01. Izmir Institute of Technology; 04.05. Department of Pyhsics; 04. Faculty of ScienceMolecular beam epitaxy (MBE) growth of thin (∼2 μm) CdTe layers characterized by high crystal quality and low defect density on lattice mismatched substrates, such as GaAs and Si, has thus far been difficult to achieve. In this work, we report the effects of in situ thermal deoxidation under In and As4 overpressure prior to the CdTe growth on epiready GaAs(211)B wafers, aiming to enhance CdTe crystal quality. Thermally deoxidized GaAs samples were analyzed using in situ reflection high energy electron diffraction, along with ex situ x-ray photo-electron spectroscopy (XPS) and atomic force microscopy. MBE-grown CdTe layers were characterized using x-ray diffraction (XRD) and Everson-type wet chemical defect decoration etching. We found that In-assisted desorption allowed for easier surface preparation and resulted in a smoother surface compared to As-assisted surface preparation. By applying In-assisted thermal deoxidation to GaAs substrates prior to the CdTe growth, we have obtained single crystal CdTe films with a CdTe(422) XRD rocking curve with a full-width half-maximum value of 130.8 arc-s and etch pit density of 4 × 106 cm−2 for 2.54 μm thickness. We confirmed, by XPS analysis, no In contamination on the thermally deoxidized surface.