Zinc oxide (ZnO) nanopowder-based nanoparticles (NPs) with a mean diameter of less than 100 nm were mixed with synthesized electrophoretic deposition (EPD) solutions under different concentrations and deposited onto silicon (Si), 3-Aminopropyl-Triethoxysilane (APTES) functionalized silicon (APTES-Si), and aluminum (Al) substrates. The wavelength ranges and intensity of each structure's emission spectrum are determined using fluorescence spectroscopy. We will describe our findings considering our hypothesis that the underlying substrate conductivity and concentrations of ZnO nanoparticles in the electrophoretic deposition solutions are significant components in achieving higher intensity fluorescence of ZnO thin films required for devices. This study shows that ZnO NPs with higher concentrations deposited on a conductive substrate emit higher emission intensity. The presence of visible emission spectra for ZnO NPs deposited on all three substrate types show potential for future optical device applications employing the next generation of nanoscale electronic materials.
The scattering effects (specifically LO-phonon scattering) in a 45 Å AlAs/80 Å GaAs/33 Å AlAs asymmetric double barrier resonant tunneling (ADBRT) structure with a short period GaAS/Al0.3Ga0.7As superlattice incorporated on one side of the double barrier have been studied and characterized. Enhanced levels of current conduction were produced in the ADBRT due to the superlattice miniband electron transport under forward bias. And the effect of the said superlattice on the phonon scattering phenomena exhibited by the entire device was subsequently examined. Magnetic field fan diagrams at 4.2 K under reverse bias showed a new feature at an energy of 22 meV that could be explained on the basis of previously unreported GaAs LO-phonon scattering processes from the first excited emitter level. Finally, quenching of phonon-assisted tunneling in reverse bias on decreasing the period of the superlattice was also observed.
This paper reports a new low cost technique for fabricating Surface Enhanced Raman Spectroscopy substrates. A Gold (Au) nano-metallic structure for surface enhancement is created by depositing Au nanoparticles on a Multi-wall Carbon Nanotube layer previously deposited on the etched Aluminum foil. A low cost, simple method is used to deposit the nanotubes. Huge enhancements have been observed in both in vitro and in vivo measurements.
Abstract This communication focuses on the Raman spectroscopic characterization of a voltage‐controlled electrospray deposition (VCED) of multiwalled carbon nanotubes (MWCNTs) dispersed from acid refluxed and SDBS (sodium dodecyl benzene sulfonate) assisted carbon nanotube (CNT) dispersion techniques. This versatile method resulted in the direct deposition of CNT films on the surface functionalized target substrates, that is—APTES (3‐aminopropyl‐triethoxysilane) treated metal (aluminum foil), semiconducting (bare Si), and insulators (microscopy grade glass, silicon dioxide, and polymethyl methacrylate or PMMA)—used in this study. During the voltage‐controlled deposition process itself, the spray area and thickness of the MWCNT films on a substrate can be easily manipulated. In this work, CNT thin films of 40‐70 nm to 3‐7 μm were produced as a function of deposition time, with excellent packing density and surface coverage. The precise thickness control of the CNT deposits on each target substrate was achieved by meticulously calibrating the mechanics of the voltage‐controlled spray system, for example, inter‐electrode distance between the target surface and the nozzle, electric field, and flow rate of the CNT solution feed, in addition to the concentration of the CNT solution and the deposition time. These overall experimental results bode well for use of this technique in a wider range of applications where CNTs films with controlled thicknesses are required.
High-density InAs nanowires embedded in an In0.52Al0.48As matrix are fabricated in situ by molecular beam epitaxy on (100) InP. The average cross section of the nanowires is 4.5×10 nm2. The linear density is as high as 70 wires/μm. The spatial alignment of the multilayer arrays exhibit strong anticorrelation in the growth direction. Large polarization anisotropic effect is observed in polarized photoluminescence measurements.
Conventional Raman scattering is a workhorse technique for detecting and identifying complex molecular samples. In surface enhanced Raman scattering, a nanorough metallic surface close to the sample enhances the Raman signal enormously. In this work, the surface is on a clear epoxy substrate. The epoxy is cast on a silicon wafer, using 20 nm of gold as a mold release. This single step process already produces useful enhanced Raman signals. However, the Raman signal is further enhanced by (1) depositing additional gold on the epoxy substrate and (2) by using a combination of wet and dry etches to roughen the silicon substrate before casting the epoxy. The advantage of a clear substrate is that the Raman signal may be obtained by passing light through the substrate, with opaque samples simply placed against the surface. Results were obtained with solutions of Rhodamine 6G in deionized water over a range of concentrations from 1 nM to 1 mM. In all cases, the signal to noise ratio was greater than 10:1.
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