Search results for "thin film"
showing 10 items of 1200 documents
A DC and small signal AC model for organic thin film transistors including contact effects and non quasi static regime
2017
Abstract We present a compact model for the DC and small signal AC analysis of Organic Thin Film Transistors (OTFTs). The DC part of the model assumes that the electrical current injected in the OTFT is limited by the presence of a metal/organic semiconductor junction that, at source, acts as a reverse biased Schottky junction. By including this junction, modeled as a reverse biased gated diode at source, the DC model is able to reproduce the scaling of the electrical characteristics even for short channel devices. The small signal AC part of the model uses a transmission line approach in order to compute the impedances of the channel and parasitic regions of the device. The overlap capacit…
A liquid alkoxide precursor for the atomic layer deposition of aluminum oxide films
2020
For large-scale atomic layer deposition (ALD) of alumina, the most commonly used alkyl precursor trimethylaluminum poses safety issues due to its pyrophoric nature. In this work, the authors have investigated a liquid alkoxide, aluminum tri-sec-butoxide (ATSB), as a precursor for ALD deposition of alumina. ATSB is thermally stable and the liquid nature facilitates handling in a bubbler and potentially enables liquid injection toward upscaling. Both thermal and plasma enhanced ALD processes are investigated in a vacuum type reactor by using water, oxygen plasma, and water plasma as coreactants. All processes achieved ALD deposition at a growth rate of 1-1.4 angstrom/cycle for substrate tempe…
Role of photoactive layer morphology in high fill factor all-polymer bulk heterojunction solar cells
2011
We report on the realization of all-polymer solar cells based on blends of poly(3-hexylthiophene-2,5-diyl) (P3HT) as a donor and poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)) as an acceptor. High fill factors are demonstrated for the first time in this class of devices suggesting high dissociation efficiency for the bounded electron-hole pairs and balanced electron and hole mobility along the thin films. The use of the high-mobility n-type P(NDI2OD-T2) polymer enables us to overcome one of the problems limiting the efficiency of all-polymer solar cells, resulting in fill factors comparable with those reported for …
Ac field dependence of the susceptibility of Bi2Sr2CaCu2O8 thin films at low dc fields
1996
We have measured the ac field dependence of the ac susceptibility of 400 nm thick Bi2212 thin films at low dc fields 0 ≤μ0Ha ≤ 1 mT in transverse geometry. We show that at reduced temperaturest≤0.85 the ac field dependence can be described by the non-linear Bean model after Brandt as in Y123 thin films. Att>0.85, however, we observe a decrease of the energy dissipation and shielding capability. The critical current density at zero dc field is given byjc−4×1010(1−(T/Tc))2.8±0.1 A/m2.
Complex Ordering in Thin Films of Di- and Trifunctionalized Hexaalkoxytriphenylene Derivatives
1997
We have used pressure−area isotherms, X-ray diffraction, atomic force microscopy, and infrared dichroism to study Langmuir and Langmuir−Blodgett films of 2,3,6,7,10,11-hexaalkoxytriphenylenes which...
Structure determination of thin CoFe films by anomalous x-ray diffraction
2012
This work reports on the investigation of structure-property relationships in thin CoFe films grown on MgO. Because of the very similar scattering factors of Fe and Co, it is not possible to distinguish the random A2 (W-type) structure from the ordered B2 (CsCl-type) structure with commonly used x-ray sources. Synchrotron radiation based anomalous x-ray diffraction overcomes this problem. It is shown that as grown thin films and 300 K post annealed films exhibit the A2 structure with a random distribution of Co and Fe. In contrast, films annealed at 400 K adopt the ordered B2 structure.
X‐ray characterization of CdO thin films grown on a ‐, c ‐, r ‐ and m ‐plane sapphire by metalorganic vapour phase‐epitaxy
2005
CdO thin films have been grown on a-plane (110), c-plane (0001), r-plane (012) and m-plane (100) sapphire substrates by metalorganic vapour-phase epitaxy (MOVPE). The effects of different substrate orientations on the structural properties of the films have been analyzed by means of X-ray diffraction, including θ-2θ scans, pole figures and rocking curves. (111), (001) and (110) orientations are found on a-, r-, and m-sapphire respectively, while films deposited on c-plane exhibit an orientation in which no low-index crystal plane is parallel to the sample surface. The recorded pole figures have allowed determining the epitaxial relationships between films and substrates, as well as the pres…
Photoluminescence in Carborane–Stilbene Triads : A Structural, Spectroscopic, and Computational Study
2016
A set of triads in which o- and m-carborane clusters are bonded to two stilbene units through Ccluster -CH2 bonds was synthesized, and their structures were confirmed by X-ray diffraction. A study on the influence of the o- and m- isomers on the absorption and photoluminescence properties of the stilbene units in solution revealed no charge-transfer contributions in the lowest excited state, as confirmed by (TD)DFT calculations. The presence of one or two B-I groups in m-carborane derivatives does not affect the emission properties of the stilbenes in solution, probably due to the rather large distance between the iodo substituents and the fluorophore. Nevertheless, a significant redshift o…
A comparative study of heterostructured CuO/CuWO4 nanowires and thin films
2017
Authors are grateful to Reinis Ignatans for XRD measurements.
Holographic recording optimization in amorphous As-Se-S films
2003
The holographic recording parameters of amorphous chalcogenide semiconductor (AChS) thin films under optimization depend on hologram type. So, using self-enhancement effect during recording and wet etching after recording enable possibility to decrease recording energy and increase of signal/noise ratio for embossed holograms. Choosing the appropriate light exposure permit us to achieve equal values of diffraction efficiency (DE) for different diffraction orders during fabrication of light splitting holographic optical elements (HOE). Changing film thickness and recording wavelength it is possible to find optimal conditions for high DE holographic gratings readable at infrared region of lig…