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Polycrystalline Films (polycrystalline + film)
Selected AbstractsAir-Operable, High-Mobility Organic Transistors with Semifluorinated Side Chains and Unsubstituted Naphthalenetetracarboxylic Diimide Cores: High Mobility and Environmental and Bias Stress Stability from the Perfluorooctylpropyl Side ChainADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Byung Jun Jung Abstract N,N,-bis(3-(perfluoroctyl)propyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (8,3-NTCDI) was newly synthesized, as were related fluorooctylalkyl-NTCDIs and alkyl-NTCDIs. The 8,3-NTCDI-based organic thin-film transistor (OTFT) on an octadecyltrimethoxysilane (OTS)-treated Si/SiO2 substrate shows apparent electron mobility approaching 0.7 cm2 V -1s -1 in air. The fluorooctylethyl-NTCDI (8,2-NTCDI) and fluorooctylbutyl-NTCDI (8,4-NTCDI) had significantly inferior properties even though their chemical structures are only slightly different, and nonfluorinated decyl and undecyl NTCDIs did not operate predictably in air. From atomic force microscopy, the 8,3-NTCDI active layer deposited with the substrate at 120 °C forms a polycrystalline film with grain sizes >4,m. Mobilities were stable in air for one week. After 100 days in air, the average mobility of three OTFTs decreased from 0.62 to 0.12 cm2 V -1s -1, but stabilized thereafter. The threshold voltage (VT) increased by 15 V in air, but only by 3 V under nitrogen, after one week. On/off ratios were stable in air throughout. We also investigated transistor stability to gate bias stress. The transistor on hexamethlydisilazane (HMDS) is more stable than that on OTS with mobility comparable to amorphous Si TFTs. VT shifts caused by ON (30 V) and OFF (,20 V) gate bias stress for the HMDS samples for 1 hour were 1.79 V and 1.27 V under N2, respectively, and relaxation times of 106 and 107 s were obtained using the stretched exponential model. These performances are promising for use in transparent display backplanes. [source] Nanowire,quantum-dot,polymer solar cellPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2008A. Nadarajah Abstract We report first results on a new solar cell structure which incorporates n-type ZnO nanowires, an undoped CdSe layer, obtained from quantum dot precursors, and a p-type polymer layer as the main components. In the fabrication process the quantum dot layer is converted to a conformal ,30 nm thick polycrystalline film. The fabrication of the cell occurs in lab air at temperatures below 100 °C. Several intermittent annealing steps raise the energy conversion efficiency to approximately 1%. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth of lead bromide polycrystalline filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2004M. Giles Abstract Lead bromide polycrystalline films were grown by the physical vapor deposition method (PVD). Glass 1,x1, in size, uncoated, and coated with Indium Tin Oxide (ITO), was used as substrate and rear contact. The starting material was evaporated at temperatures from 395°C to 530°C under high vacuum atmosphere (6 x 10 -3 Pa) and during 8 days. The substrate temperature was prefixed from 190°C to 220°C. Film thickness yielded values from 40 to 90 ,m. Optical microscopy and scanning electron microscopy (SEM) were performed on the films. Grain size resulted to be from 1.0 to 3.5 ,m. SEM and X-ray diffraction indicate that films grow with a preferred orientation with the (0 0 l) planes parallel to the substrate. The Texture Coefficient (TC) related to the plane (0 0 6) was 7.3. Resistivity values in the order of 1012 ,cm were obtained for the oriented samples, but a strong polarization indicates severe charge transport problems in the films. Film properties were correlated with the growth temperature and with previous results for films of other halides. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Modelling of diffraction from fibre texture gradients in thin polycrystalline filmsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2007M. Birkholz Crystallographic textures in thin polycrystalline films typically exhibit a rotational symmetry, i.e. they occur as a fibre texture with the texture pole being orientated in the direction of the substrate normal. As a further characteristic of thin-film textures, it was often observed that the degree of preferred orientation increases with increasing thickness. It is shown in this work how a fibre texture gradient may be modelled in kinematical X-ray diffraction and which effects it has on the intensity mapping of the IHKL reflection, when the HKL pole is the fibre axis. A general expression for IHKL is derived for a depth-dependent fibre texture that is based on the finite Laplace transform of the texture distribution. The concept is outlined for the cosn, function to model the tilt-angle dependence of intensity, with the parameter n denoting the degree of texture. It is found that the measured intensity distribution sensitively depends on the ratio of texture gradient over X-ray attenuation coefficient. For particular cases, it is found that the maximum intensity may occur for non-zero tilt angles and thus arise at a different tilt angle from the pole of the fibre texture. [source] Quantitative microstructural and texture characterization by X-ray diffraction of polycrystalline ferroelectric thin filmsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2004Jesús Ricote Texture becomes an important issue in ferroelectric materials as it greatly influences the physical properties of polycrystalline films. The use of advanced methods of analysis of the X-ray diffraction profiles, namely quantitative texture analysis or the recently developed combined approach, allows access to quantitative information on the different components of the global texture and to more accurate values of structural and microstructural parameters of both the ferroelectric film and the substrate, not available by more conventional methods of analysis. The results obtained allow important conclusions to be drawn regarding the mechanisms that lead to the development of preferred orientations in thin films and, also, the correlation between them and the ferroelectric behaviour. For example, it is observed that the inducement of a strong ,111, texture component does not mean the complete disappearance of the so-called `natural' ,100,, ,001, components, and that the ratio between the contributions to the global texture of these two components can be changed by the presence of tensile or compressive stress during crystallization of the films. The relative contributions of these texture components are also related to the final properties of the ferroelectric films. [source] Pyroelectric coupling in thin film photovoltaicsPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 4 2007Victor G. Karpov Abstract We propose a theory of thin film photovoltaics in which one of the polycrystalline films is made of a pyroelectric material grains such as CdS. That film is shown to generate strong polarization improving the device open circuit voltage. Implications and supporting facts for the major photovoltaic types based on CdTe and CuIn(Ga)Se2 absorber layers are discussed. Band diagram of a pyroelectric (CdS) based PV junction. Arrows represent the charge carrier photo-generation. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of boron concentration on the XPS spectra of the (100) surface of homoepitaxial boron-doped diamond filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2006S. Ghodbane Abstract As-grown (100) homoepitaxial diamond films with boron concentrations [B] from 4.6 × 1016 to 1.5 × 1021 cm,3 have been analysed using X-ray photoelectron spectroscopy (XPS). Their C 1s core levels contain a dominant component around 284.17 ± 0.2 eV ascribed to sp3 C and a main secondary component around 284.88 ± 0.2 eV ascribed to CHx (x , 2) on surface defects. Their relative concentration decreases and increases, respectively, as [B] increases. A significant component around 286.4 ± 0.2 eV ascribed to ether group (C,O,C) remains nearly constant up to [B] , 3 × 1020 cm,3, then increases for greater boron concentrations. Other components around 283.0 ± 0.2, 287.69 ± 0.2 and 288.76 ± 0.2 eV ascribed, respectively, to sp2 C, carbonyl (C=O) and carboxyl (HO,C=O) on surface defects remain with low concentrations. The occurrence of these XPS components, their assignments and their relative concentrations are satisfactorily compared to those previously found for IIb crystals with (100) surface and for polycrystalline films with [B] around 1019 and 7 × 1020 cm,3. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Polycrystalline silicon thin films on glass obtained by nickel-induced crystallization of amorphous siliconPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010J. A. Schmidt Abstract In this work, we use the nickel-induced crystallization process to crystallize a-Si:H thin films at temperatures compatible with the utilization of glass substrates. Hydrogenated amorphous silicon films are deposited on planar float glass (Schott AF37) by plasma-enhanced chemical vapour deposition. The films, between 400 and 1400 nm thick, are grown intrinsic, slightly p-doped (p - ) or with a combined structure of heavily p-doped / slightly p-doped (p+/p - ) layers. On these films we sputter nickel with concentrations between 2.5×1014 and 3×1015 at./cm2, and then we anneal the samples in a standard nitrogen-purged tube furnace. The process evolves through the formation of the nickel silicide NiSi2, which has a lattice constant very similar to that of c-Si and acts as a nucleation centre. As a result of this thermal treatment we obtain thin polycrystalline films with a grain size over 100 ,m. The high crystallinity of the samples is confirmed through optical and electron microscopy observations, X-rays diffraction and Raman spectroscopy. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fabrication of a n -type ZnO/p -type Cu,Al,O heterojunction diode by sputtering deposition methodsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009Satoru Takahata Abstract CuAlO2 polycrystalline films were deposited by the helicon-wave-excited plasma sputtering (HWPS) method at 700 °C. The best full-width at half-maximum value of the (006) CuAlO2 X-ray diffraction peak was 0.19 degrees, which was similar to those reported previously using other deposition methods. While, noncrystalline Cu,Al,O films were deposited by a conventional RF sputtering method. Using this p -type transparent conducting oxide (TCO) film and an n -type ZnO film deposited by HWPS, a n -type ZnO/p -type Cu,Al,O heterojunction diode was fabricated. Optical transmittance of the device was approximately 80% in the near infrared region. The rectifying current,voltage characteristics with a threshold forward voltage approximately 1.4 V were obtained. These results are the first step toward realizing an electrical/optical device using p -type CuAlO2 or Cu-Al-O films. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of a polymeric solution buffer layer on the chemical bath deposition of polycrystalline PbS filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2005Y. González-Alfaro Abstract Polycrystalline thin films of PbS grown on glass substrates previously coated with PbS colloidal particles in a polyvinyl alcohol solution were obtained by chemical bath deposition (CBD). The X-ray diffraction procedures showed evidence of polycrystalline films of cubic PbS with a preferred normal orientation of the planes [100] with the growth direction. The film texture showed a strong influence of the initial conditions of the surface. Moreover, changes in colour, morphology and grain size of the films were observed by optic and atomic force microscopy (AFM). Rutherford backscattering spectrometry (RBS) showed a dependence of the thickness and roughness of the PbS films with the growth initial conditions. A kinetic growth model is proposed to explain the changes in the structure and morphology of the PbS. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||