Papers by Keyword: Optical Transmission

Paper TitlePage

Authors: Rajendra Deshmukh, Manoj Malik, Sanmesh Parab
Abstract: The electro-optical characteristics of dye-doped polymer dispersed liquid crystals (PDLCs) have been investigated for display applications. The PDLC samples were obtained by polymerization induced phase separation of the nematic liquid crystal (LC)-dye-prepolymer mixtures under UV illumination with a constant intensity. The optimum conditions for the scattering characteristics of the dye-doped PDLC films as function of the dye concentration have been examined. It was seen that the phase separation and segregation of LC droplets is dependent on the amount of dye used. LC droplets in dye-doped PDLC films exhibit various configurations at lower and higher applied electric field when observed in situ under polarizing optical microscope. The effects of morphology on the electro-optical properties were examined. Experimental results indicate that the driving voltage and contrast ratio were affected considerably by the amount of dye. UV-VIS spectroscopy results showed that the molecular orientation of dye in LC droplets can be controlled to induce nonlinearity in these materials. The results showed that the dye concentration can be optimized to obtain promising electronic materials with minimum threshold and high contrast for display applications.
Authors: Patthamapun Boonprakom, Watcharee Rattanasakulthong
Abstract: Transparent conductive Al-doped zinc oxide (ZnO:Al) films with different sputtering power were prepared on glass substrate using an RF sputtering technique. Two main peaks of the hexagonal wurtzite structure in the (002) and (004) direction were observed in every deposited ZnO:Al film. Intensities of these peaks were increased with the increasing sputtering power. Moreover, the surface roughness tended to increase with increasing sputtering power whereas the electrical resistance decreased with increasing sputtering power. The ZnO:Al film deposited at 150 and 200 W showed maximum optical transmittance of over 80% in the visible wavelength range. All results confirmed that the sputtering power directly affected film thickness because the higher sputtering power gave rise to a higher deposition rate; the surface morphology of the deposited films was dependent on the sputtering power and the optical properties were indirectly affected by the power of the deposition process.
Authors: Yong Ge Cao, Lei Miao, Sakae Tanemura, Yasuhiko Hayashi, Masaki Tanemura
Abstract: Transparent indium-doped ZnO (IZO) films with low In content (<6at%) were fabricated through radio-frequency (rf) helicon magnetron sputtering. Formation of In-Zn-O solid solution was confirmed by X-ray diffraction (XRD) patterns. Incorporation of indium into ZnO films enhances the optical transmission in the visible wavelength. The optical band-gaps slightly increase from 3.25eV (ZnO) to 3.28eV (In0.04Zn0.96O) and to 3.30eV (In0.06Zn0.94O) due to Burstain-Moss effect. The Urbach tail parameter E0, which is believed to be a function of structural disorder, increases from 79meV (ZnO), to 146meV (In0.04Zn0.96O), and to 173meV (In0.06Zn0.94O), which is consistent with increase of Full-Width Half-Maximum (FWHM) in corresponding XRD patterns. Decreasing in crystal quality with increasing indium concentration is also confirmed by photoluminescence spectra.
Authors: Barış Demirbay, Şaziye Uğur
Abstract: Electrical characteristics and morphology of nanocomposite films composed of two different polystyrene (PS) latexes impregnated with multi-walled carbon nanotubes (MWCNT) in the range between 0 wt% and 20 wt% were assessed by considering photon transmission (UV-Vis) technique and electrical conductivity measurements. Emulsion polymerization technique was employed both to synthesize very fine PS particles dispersed in water and to tailor the sizes of the PS particles as 382 nm and 560 nm, respectively. PS/MWCNT nanocomposite films were obtained from the liquid form on glass substrates via drop-casting method and all they dried at 40 QUOTE C. Each dried sample was then annealed at varying temperatures between 100 QUOTE C and 250 QUOTE C for 10 min. The surface conductivity QUOTE of each annealed film at 250 QUOTE C was measured and was found to increase dramatically above a certain mass fraction of MWCNT content, QUOTE . Each set of PS/MWCNT nanocomposite film had a similar electrical percolation threshold of QUOTE =1.5 wt% as the MWCNT content and critical exponents of QUOTE were found to be 2.64 and 1.19 for 382 nm and 560 nm PS latex systems, respectively.
Authors: Arif M. Pashaev, Omar I. Davarashvili, Megi I. Enukashvili, Zaira G. Akhvlediani, Revaz G. Gulyaev, Vladimir P. Zlomanov
Abstract: The article deals with the peculiarities of creation of effective negative pressure and the increase in the forbidden gap width in PbSe nanolayers. The dielectric state that maybe realized under these conditions and their appropriate doping can be considered as a new resource in lead selenide nanolayers. The increasing of the tangential lattice constant with higher growth temperature and layer growth rate confirms this consideration. When determining the forbidden gap width, the optical transmission spectra were processed by a model of the Fabry-Perot interferometer, and, at high concentration of free current carriers, the absorption on them and their degeneracy were taken into consideration.
Authors: Arif M. Pashaev, Omar I. Davarashvili, Megi I. Enukashvili, Zaira G. Akhvlediani, Larisa P. Bychkova, Revaz G. Gulyaev
Abstract: It was revealed that, according to the analysis by the half-width of the X-ray lines of reflection planes (200) and (600), the sizes of subgrains in the lead selenide nanolayer ~70 nm thick made up 30-45 nm. Disorientation between the subgrains of the order of the ten thousandth of a minute and the deformation (strain) in the layer was determined by the mismatch between the layer and the substrate. It is shown that the forbidden gap width Eg of the same PbSe nanolayer determined by analyzing the optical transmission spectra by two types of straightening f (hν) and (hν)2=f (hν) coincided and made up 0.445 eV, which exceeded Eg of the unstrained PbSe layer by 0.16 eV. The total contribution of quantum effects at the given subgrain sizes and degeneracy of current carriers is less than 0.03 eV, and generally the change in the forbidden gap width was associated with deformation. Key words: dispersion, deformation, disorientation between subgrains, optical transmission, forbidden gap width.
Authors: V. Augelli, T. Ligonzo, A. Pizzichetti, F. Quaranta, L. Schiavulli, A. Valentini
Authors: Zhe Chuan Feng, Feng Yan, W.Y. Chang, Jian Hui Zhao, Jian Yi Lin
Authors: Zhe Chuan Feng, J.W. Yu, J.B. Wang, R. Varatharajan, B. Nemeth, J. Nause, Ian T. Ferguson, Wei Jie Lu, W.E. Collins
Abstract: ZnO bulk crystal wafers, undoped and doped with various impurities of Ga, Er, Co, Ho, Fe, Mn, and co-doped Mg-Li, have been prepared by a modified melt growth method, and characterized by optical techniques of Raman scattering, photoluminescence and UV-visible transmission. Their wurtzite structures were confirmed, with a small degree of crystalline imperfection. It is shown that with some dopants, such as, Co and Fe, the electronic energy gap is affected much less than the optical absorption gap. Computer analysis has helped greatly in obtaining useful information of the optical properties of the ZnO bulk materials.
Showing 1 to 10 of 13 Paper Titles