Person: KAHRAMAN, AYŞEGÜL
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KAHRAMAN
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AYŞEGÜL
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Publication Effects of the oxide/interface traps on the electrical characteristics in Al/Yb₂O₃/SiO₂/n-Si/Al MOS capacitors(Springer, 2021-02-20) Morkoç, Berk; Kahraman, Ayşegül; Yılmaz, Ercan; KAHRAMAN, AYŞEGÜL; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-1836-7033; AAH-6441-2021In the present work, we examine the effect of structural modifications occurring during the fabrication of Al/Yb₂O₃/SiO₂/n-Si/Al MOS capacitors under different annealing temperatures on the electrical characteristics of the capacitors. The structural properties depending on post-deposition annealing (PDA) were evaluated based on the crystal properties, elemental compositions, and bonding structures of Yb₂O₃/SiO₂ films, while the electrical characteristics were determined by capacitance-voltage (C-V) measurements. The smallest particle size was found in the film annealed at the highest PDA temperature. In all films, the Yb atom concentration was determined higher than the others. The non-stoichiometric silicate (YbSixOy) layer was detected in film structure annealed at 400 degrees C. The Yb 4d and O 1s spectra shifted toward higher binding energies with increasing depth in the films. The density of bonded oxygen species decreased with increasing PDA temperature. It was obtained that capacitance in accumulation region (C-acc), dielectric constant (epsilon(k)), and series resistance (R-s) values tend to decrease with both increasing frequency and PDA temperature. The highest and lowest interface state density (N-it) was found for capacitors obtained from as-deposited and annealed at 400 degrees C structures, respectively. The effective oxide charge density (Q(eff)), which expresses the net charge trapped in the oxide layer, is at the 10(11) level. The barrier heights (phi(B)), which generally tend to increase, have shown that acceptor-type interface states are active on electrical characteristics.Publication The relationship between structural and electrical properties of the post-deposition annealed Er₂O₃/n-Si hetero-structures(Elsevier, 2021-08-01) Kahraman, Ayşegül; Morkoç, Berk; Yılmaz, Ercan; KAHRAMAN, AYŞEGÜL; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-1836-7033; AAH-6441-2021This study presents comprehensive results on the structural modifications of Er₂O₃/n-Si hetero-structures under post-deposition annealing (PDA) and the effects of these changes on the electrical characteristics of the Al/Er₂O₃/n-Si/Al MOS capacitors. The Er₂O₃ films were grown on n-Si substrate with RF magnetron sputtering and annealed under nitrogen at RT, 300 degrees C, 500 degrees C, 600 degrees C, 700 degrees C. The increasing grain size of the films up to 300 degrees C did not show a significant change in other annealing temperatures. The erbium silicate content in the RT and 600 degrees C-Er₂O₃/n-Si interface is quite higher than those of 500 degrees C and 700 degrees C, while a silicate-like layer was not found at 300 degrees C. The highest dielectric constant (epsilon) value was obtained from the 500 degrees C-Er₂O₃ MOS capacitor due to the lowest oxygen deficient bond content. It was found that Q(eff) values tend to increase as the oxygen concentration decreases in the film. It was determined that Er-Er oxygen deficient bonds may have acted as negative charge trap centers. Although the Er-M content in the 700 degrees C-Er₂O₃/n-Si is higher than that of 500 degrees C, lower Q(eff) values were obtained from the 700 degrees C-Er₂O₃ MOS capacitor due to the higher Si-Si oxygen deficient bond content, which is most likely act as a positive charge trap center. It was concluded that the contributions of oxide trap and interface trap charges should be evaluated together in establishing a link between electrical characteristics and structural analyses.Publication Effect of oxide and interface traps on electrical characteristics of post-deposition annealed HfSiO₄/n-Si structures(Iop Publishing, 2021-04-01) Kahraman, Ayşegül; Yılmaz, Ercan; KAHRAMAN, AYŞEGÜL; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-1836-7033; AAH-6441-2021This study presents detailed results on the modifications in chemical composition, defective bonds, crystal properties based on x-ray photoelectron spectroscopy (XPS) depth profiles and x-ray diffraction of post-deposition annealed HfSiO₄/Si structure. It also leads to a link to defect centers and their effect on the electrical characteristics of MOS capacitors. The HfSiO₄ films were deposited on n-Si wafers by RF magnetron sputtering and annealed at room temperature (RT), 300 degrees C, 700 degrees C, 900 degrees C, 1100 degrees C under N-2 ambient. That the atomic concentration values of each element in the oxide did not change significantly depending on the annealing temperature showed that the film was deposited with high homogeneity. It was determined that the shift direction of the binding energies of Hf 4f and O 1s XPS spectra were related to the bonding preference of oxygen rather than its concentration. The increase in Hf-M and Hf-Si oxygen defective bonds decreased the binding energy of the XPS spectra. It was determined from the XPS analyses of amorphous films that Hf-Si and Si-Si oxygen defective bonds may cause the positive charge trapping, resulting in the highest negative charge trapping/positive effective oxide charge density (Q(eff) ) in the 300 degrees C-MOS capacitor. It was determined that Hf-Hf oxygen defective bonds may be the precursors of negative charge trapping. Interface states only contributed to the dielectric constant (k) in the RT-MOS capacitor. The Phi(B) (barrier height) values showed that the efficiency of acceptor-like and donor-like interface states changes depending on the frequency.Publication Stereotactic body radiotherapy for primary and metastatic lung cancer, cyberknife-m6 experience(Elsevier Science Inc, 2022-09-01) Sarıhan, S.; SARIHAN, SÜREYYA; Tunç, S. G.; İrem, Z. K.; ÇELİK UZUNÇAKMAK, ZEYNEP İREM; Kahraman, A.; KAHRAMAN, AYŞEGÜL; Bursa Uludağ Üniversitesi/Tıp Fakültesi; 0000-0002-2597-1001Publication Post-deposition annealing effect on the structural and electrical properties of ytterbium oxide as an alternative gate dielectric(Elsevier Science Sa, 2022-10-12) Morkoç, Berk; Yılmaz, Ercan; KAHRAMAN, AYŞEGÜL; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Anabilim Dalı.The possibility of ytterbium(III) oxide, one of the rare earth oxides, to replace silicon dioxide used as the gate dielectric is discussed in this article. For such a replacement, it is primarily necessary to understand the physical and chemical characteristics of ytterbium(II) oxide as a candidate, such as bond structure, electronic structure, band offsets with Si, dielectric constant, interfacial states and defect behavior. The effects of structural and electrical features of ytterbium(III) oxide-based MOS capacitors on device performance are investigated. The electron beam physical vapor deposition (EBPVD) technique was used for the deposition of ytterbium(III) oxide thin films. The 122 nm thick Yb2O3 thin film was annealed at four different temperatures (200 degrees C, 400 degrees C, 600 degrees C, and 800 degrees C) in nitrogen environment. The crystallite size determined from the as-deposited sample as 15 nm is the lowest. As expected, crystallite sizes increased as a result of increasing annealing temperature. The presence of Yb2+ oxidation states increased in the region close to the interface or at the interface. The binding energies of the Yb 4d and O 1s spectra increased with increasing depth into the films. In the O 1s spectra, the organic bonds on the surface first decreased and then increased with increasing annealing temperature. Silicate formation at the interface was determined for the annealed samples. This affected the electrical performance of the capacitors. The calculated dielectric values range from 12.1 to 15.8. Interface level densities were found in the order of 10(12) cm(-2) and it did not exhibit frequency-dependent behavior. The calculated values for the effective charge densities varied between -24.19x10(11) - 7.03x10(11) cm(-2). It has been determined that mostly negative charges are trapped more for different capacitors. Finally, Fermi energy level, dopant concentration, diffusion potential and barrier heights were calculated.