Search results for " Devices"
showing 10 items of 517 documents
Donor–Acceptor Interfaces by Engineered Nanoparticles Assemblies for Enhanced Efficiency in Plastic Planar Heterojunction Solar Cells
2016
Precisely positioning functionalized gold nanoparticles assemblies at planar donor-acceptor interfaces results in 14-fold enhancement of power conversion efficiency in P3HT/PCBM organic solar cells on plastic (ITO/PET) substrates. This result has been achieved by employing naphthalenethiol-capped gold nanoparticles (NT-Au-NPs) produced by laser ablation in liquid and size varied in the 10-30 nm range. Upon surface functionalization with the aromatic thiol, these particles self-assemble in submicrometer aggregates, which give increased light scattering. When these aggregates are deposited in the planar heterojunction between the donor and the acceptor systems, the localized scattering leads …
Surface plasmon effects on carbon nanotube field effect transistors
2011
Herein, we experimentally demonstrate surface plasmon polariton (SPP) induced changes in the conductivity of a carbon nanotube field effect transistor (CNT FET). SPP excitation is done via Kretschmann configuration while the measured CNT FET is situated on the opposite side of the metal layer away from the laser, but within reach of the launched SPPs. We observe a shift of 0.4 V in effective gate voltage. SPP-intermediated desorption of physisorbed oxygen from the device is discussed as a likely explanation of the observed effect. This effect is visible even at low SPP intensities and within a near-infrared range. peerReviewed
Toward Photopatternable Thin Film Optical Sensors Utilizing Reactive Polyphenylacetylenes
2013
Substituted polyphenylacetylenes featuring reactive pentafluorophenyl (PFP) ester moieties are synthesized. Parts of the reactive PFP groups are then converted with a mono ortho-nitrobenzyl-protected diamine in variable ratios. Thin films are prepared from these copolymers and irradiated with UV light (λ = 365 nm), resulting in crosslinking of the irradiated areas and hence enabling a photopatterning. We found that during the photocrosslinking process, the excess of PFP ester moieties is stable and remained intact, enabling a subsequent post-polymerization modification step with amines. Noteworthy, this subsequent modification with amines results in a dramatically shift in the UV-vis absorp…
Electrochromic Devices Incorporating Cr Oxide And Ni Oxide Films:
2000
Abstract Transparent films of Cr oxide and Ni oxide were made by reactive DC magnetron sputtering in Ar+O2+H2. They displayed anodic electrochromism with charge capacities similar to that of W oxide. Cr oxide was stable in acidic environments, while Ni oxide was stable in basic environments. Electrochromic devices were made with pristine Cr oxide or Ni oxide films operating in conjunction with W oxide and a proton conducting electrolyte. Of the two oxides, Cr oxide film allowed device operation at a lower voltage span, while the device with Ni oxide film yielded a higher transmittance in the bleached state, a larger absorptance modulation, and a more neutral color.
Analysis of multipactor RF breakdown in a waveguide containing a transversely magnetized ferrite
2016
In this paper, the multipactor RF breakdown in a parallel-plate waveguide partially filled with a ferrite slab magnetized normal to the metallic plates is studied. An external magnetic field is applied along the vertical direction between the plates in order to magnetize the ferrite. Numerical simulations using an in-house 3-D code are carried out to obtain the multipactor RF voltage threshold in this kind of structures. The presented results show that the multipactor RF voltage threshold at certain frequencies becomes considerably lower than for the corresponding classical metallic parallel-plate waveguide with the same vacuum gap
Growth kinetics of colloidal Ge nanocrystals for light harvesters
2016
Colloidal Ge nanocrystals (NCs) are gaining increased interest because of their potential application in low-cost optoelectronic and light harvesting devices. However, reliable control of colloidal NC synthesis is often an issue and a deeper understanding of the key-role parameters governing NC growth is highly required. Here we report an extended investigation on the growth of colloidal Ge NCs synthesized from a one-pot solution based approach. A systematic study of the effects of synthesis time, temperature and precursor concentration is elucidated in detail. X-ray diffraction (XRD) analysis reveals the presence of crystalline Ge NCs with a mean size (from 5 to 35 nm) decreasing with the …
Incident angle effect on heavy ion induced reverse leakage current in SiC Schottky diodes
2016
Heavy-ion induced degradation in the reverse leakage current of SiC Schottky power diodes shows distinct dependence on the angle of incidence. TCAD simulations have been used to study the physical mechanisms involved.
Mechanical cleaning of graphene using in situ electron microscopy
2020
Avoiding and removing surface contamination is a crucial task when handling specimens in any scientific experiment. This is especially true for two-dimensional materials such as graphene, which are extraordinarily affected by contamination due to their large surface area. While many efforts have been made to reduce and remove contamination from such surfaces, the issue is far from resolved. Here we report on an in situ mechanical cleaning method that enables the site-specific removal of contamination from both sides of two dimensional membranes down to atomic-scale cleanliness. Further, mechanisms of re-contamination are discussed, finding surface-diffusion to be the major factor for contam…
Carrier-induced quenching processes on the erbium luminescence in silicon nanocluster devices
2006
The luminescence-quenching processes limiting quantum efficiency in Er-doped silicon nanocluster light-emitting devices are investigated and identified. It is found that carrier injection, while needed to excite Er ions through electron-hole recombination, at the same time produces an efficient nonradiative Auger deexcitation with trapped carriers. This phenomenon is studied in detail and, on the basis of its understanding, we propose device structures in which sequential injection of electrons and holes can improve quantum efficiency by avoiding Auger processes. © 2006 The American Physical Society.
Effects of partial self-ordering of Si dots formed by chemical vapor deposition on the threshold voltage window distribution of Si nanocrystal memori…
2006
We study the role that the denuded zone around Si nanocrystals obtained by chemical vapor deposition plays on the fluctuations of the dot surface coverage. In fact, the capture mechanism of the silicon adatoms in the proximity of existing dots restricts the number of possible nucleation sites, the final dot size, and the dot position, thus driving the process toward partial self-order. We numerically evaluate the relative dispersion of surface coverage for several gate areas and compare the results to the fully random case. The coverage dispersion is related to the fluctuations from bit to bit of the threshold voltage window (Δ Vth) distribution of nanocrystal memories. The evaluations, com…