The synthesis of ZnO nano-needles using unbalanced magnetron
sputtering is reported. A multilayer structure comprised of
ZnO(50 nm)/Zn(20 nm)/ZnO(2 µm) was grown on a stainless steel substrate without substrate heating. The growth of ZnO nano-needles
was observed on the surface of the multilayer structure after post-annealing treatment at
300–400 °C. The nano-needles were distributed randomly over the entire surface
and had an average diameter of 20 nm; their length varied from 2 to
5 µm. The ultra-thin Zn layer (20 nm) in the multilayer structure is attributed to act as a
nucleating centre and it activates the coalescence process for the growth of ZnO
nano-needles. The ZnO nano-needles showed enhanced ultraviolet photoresponse with an
initial fast rise and decay. The origin of the photoconductivity is due to the bulk related
process. Results show the myriad application of ZnO nano-needles in ultraviolet light
detection.
We have investigated electron transport in a quasi-one dimensional (quasi-1D)
electron gas as a function of the confinement potential. At a particular
potential configuration, and electron concentration, the ground state of a 1D
quantum wire splits into two rows to form an incipient Wigner lattice. It was
found that application of a transverse magnetic field can transform a
double-row electron configuration into a single-row due to magnetic enhancement
of the confinement potential. The movements of the energy levels have been
monitored under varying conditions of confinement potential and in-plane
magnetic field. It is also shown that when the confinement is weak, electron
occupation drives a reordering of the levels such that the normal ground state
passes through the higher levels. The results show that the levels can be
manipulated by utilising their different dependence on spatial confinement and
electron concentration, thus enhancing the understanding of many body
interactions in mesoscopic 1D quantum wires.Comment: 14 pages, 3 figure
The conducting polymer composite material is desired to have a high dielectric constant and high dissipation factor in low and high frequency ranges, so that it can be used in charge storing devices, decoupling capacitors, and electromagnetic interference (EMI) shielding applications. Currently, on-going research is trying to enhance the dielectric constant of ceramic powder-polymer, metal powder-polymer, and nanotube-polymer composites in the low frequency region. In this article, we present the dielectric properties of polypropylene (PP)-graphite (Gr) composites in low and radio frequency ranges. Furthermore, the EMI shielding properties of these composites are examined in the radio frequency range. The PP-Gr composites were prepared by mixing and the hot compression mold technique. The electrical conductivity and dielectric constant of PP-Gr composites with graphite volume fraction follow the power law model of percolation theory. The percolation threshold of the composites is estimated to be 0.0257 ($ 5wt % of Gr). The current of PP-Gr composites as a function of voltage shows a nearly ohmic behavior above the percolation threshold. Shore-D hardness of the composites is decreased with the addition of conducting filler. The PPGr composites exhibit a high dielectric constant and high dissipation factor with the addition of graphite in low frequency and radio frequency regions, so they can be used in the proposed applications.
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