Browsing by Subject "Chemical-vapor-deposition"
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Item Open Access Band alignment issues related to HfO2/SiO2/p-Si gate stacks(American Institute of Physics, 2004-12-15) Sayan, S.; Emge, T.; Garfunkel, E.; Zhao, X.; Wielunski, L.; Bartynski, R. A.; Vanderbilt, D.; Suehle, J. S.; Süzer, Şefik; Banaszak Holl, M.The valence and conduction band densities of states for the HfO2/SiO2/Si structure are determined by soft x-ray photoemission and inverse photoemission. First principles calculations are used to help in assigning valence band maxima and conduction band minima. The energies of defect states at the band edges are estimated by comparing the theoretical and experimental results. Determinations of the local surface potentials before and after a forming gas anneal are used to help determine the possible location of the charge in the film.Item Open Access Enhancement and inhibition of photoluminescence in hydrogenated amorphous silicon nitride microcavities(Optical Society of America, 1997-09-01) Serpenguzel, A.; Aydınlı, Atilla; Bek, A.A Fabry-Perot microcavity is used for the enhancement and inhibition of photoluminescence in hydrogenated amorphous silicon nitride. The amplitude of the photoluminescence is enhanced 4 times, while its linewidth is reduced 8 times with respect to the bulk hydrogenated amorphous silicon nitride. The transmittance, reflectance, and absorptance spectra of the microcavity were also measured and calculated. The calculated spectra agree well with the experimental ones. (C) 1997 Optical Society of AmericaItem Open Access Low dielectric constant Parylene-F-like films for intermetal dielectric applications(American Institute of Physics, 1999) Hanyaloglu, B.; Aydınlı, Atilla; Oye, M.; Aydi, E. S.We report on the dielectric properties and thermal stability of thin polymer films that art: suitable candidates for replacing silicon dioxide as the intermetal dielectric material in integrated circuits. Parylene-F-Iike films, (-CF2-C6H4-CF2-)(n), were produced by plasma deposition from a mixture of Ar and 1,4-bis(trifluoromethyl)benzene (CF3-C6H4-CF3) discharges and characterized using infrared absorption spectroscopy, spectroscopic ellipsometry, and capacitance measurements. The dielectric constant and the magnitude of the electronic and ionic contributions to the dielectric constant were determined through capacitance measurements and Kramers-Kronig analysis of the infrared absorption data. The film's dielectric constant ranges between 2 and 2.6 depending on the deposition conditions and the largest contribution to the dielectric constant is electronic. The films deposited at 300 degrees C are stable above 400 degrees C and further optimization could push this limit to as high as 500 degrees C. (C) 1999 American Institute of Physics.Item Open Access Low-Temperature Deposition of Hexagonal Boron Nitride via Sequential Injection of Triethylboron and N2/H2 Plasma(Wiley-Blackwell Publishing, Inc., 2014) Haider A.; Ozgit Akgun, C.; Goldenberg, E.; Okyay, Ali Kemal; Bıyıklı, NecmiHexagonal boron nitride (hBN) thin films were deposited on silicon and quartz substrates using sequential exposures of triethylboron and N 2 /H 2 plasma in a hollow-cathode plasma- assisted atomic layer deposition reactor at low temperatures ( ≤ 450 ° C). A non-saturating film deposition rate was observed for substrate temperatures above 250 ° C. BN films were charac- terized for their chemical composition, crystallinity, surface morphology, and optical properties. X-ray photoelectron spec- troscopy (XPS) depicted the peaks of boron, nitrogen, carbon, and oxygen at the film surface. B 1s and N 1s high-resolution XPS spectra confirmed the presence of BN with peaks located at 190.8 and 398.3 eV, respectively. As deposited films were polycrystalline, single-phase hBN irrespective of the deposition temperature. Absorption spectra exhibited an optical band edge at ~ 5.25 eV and an optical transmittance greater than 90% in the visible region of the spectrum. Refractive index of the hBN film deposited at 450 ° C was 1.60 at 550 nm, which increased to 1.64 after postdeposition annealing at 800 ° C for 30 min. These results represent the first demonstration of hBN deposi- tion using low-temperature hollow-cathode plasma-assisted sequential deposition technique. © 2014 The American Ceramic Society.Item Open Access Microstructural defect properties of InGaN/GaN blue light emitting diode structures(Springer US, 2014-06-28) Bas, Y.; Demirel, P.; Akin, N.; Başköse, C.; Özen, Y.; Kınacı, B.; Öztürk, M. K.; Özcelik, S.; Özbay, EkmelIn this paper, we study structural and morphological properties of metal-organic chemical vapour deposition-grown InGaN/GaN light emitting diode (LED) structures with different indium (In) content by means of high-resolution X-ray diffraction, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL) and current-voltage characteristic (I-V). We have found out that the tilt and twist angles, lateral and vertical coherence lengths of mosaic blocks, grain size, screw and edge dislocation densities of GaN and InGaN layers, and surface roughness monotonically vary with In content. Mosaic defects obtained due to temperature using reciprocal lattice space map has revealed optimized growth temperature for active InGaN layer of MQW LED. It has been observed in this growth temperature that according to AFM result, LED structure has high crystal dimension, and is rough whereas according to PL and FTIR results, bandgap energy shifted to blue, and energy peak half-width decreased at high values. According to I-V measurements, it was observed that LED reacted against light at optimized temperature. In conclusion, we have seen that InGaN MQW structure's structural, optical and electrical results supported one another.