Evolution of the UV-induced absorption within the polymer matrix possessing a highly soluble CdS precursor is studied. The initially optically transparent (polymethylmethacrylate based) samples are irradiated by a light-emitting diode operated at 365 nm for different intensities and different temperatures. In situ monitoring of the process is performed at a wavelength of 405 nm where the samples are initially transparent. The study shows that the increase in absorbance is temperature dependent, and at a fixed temperature it is determined by UV exposure rather than the intensity or irradiation time separately. TEM, HR TEM data, as well as data on absorption and luminescent spectra, allow the relation of the optical absorption evolution to the CdS nanoparticles growth process. This provides new valuable information on the kinetics of this phenomenon in UV irradiated polymer films with a soluble precursor.
1 October 2012 in Journal of Experimental and Theoretical Physics
It is shown that the elastic scattering of unpolarized neutrons by systems with the noncoplanar spatial magnetic induction distribution in nonreciprocal. Two systems with the noncoplanar distribution of the magnetic field are proposed and calculated, i.e., a nanoparticle with vortex magnetization and a system of three magnetic mirrors. It is shown that, under certain conditions, the nonreciprocity is rather large and can be observed experimentally.
HgTe/CdHgTe quantum well (QW) heterostructures have attracted a lot of interest recently due to insights they provided towards the physics of topological insulators and massless Dirac fermions. Our work focuses on HgCdTe QWs with the energy spectrum close to the graphene-like relativistic dispersion that is supposed to suppress the non-radiative Auger recombination. We combine various methods such as photoconductivity, photoluminescence and magneto-optical measurements as well as transmission electron microscopy to retrofit growth parameters in multi-QW waveguide structures, designed for long wavelengths lasing in the range of 10–22 μm. The results reveal that the attainable operating temperatures and wavelengths are strongly dependent on Cd content in the QW, since it alters the dominating recombination mechanism of the carriers.
It is demonstrated that UV (LED at 365 nm) irradiation with subsequent heating (90–110 °C) of the polystyrene matrix containing a soluble Au(I) compound ((Ph3P)Au(n-Bu)) results in the growth of gold nanoparticles within the sample bulk, as confirmed by UV-vis spectroscopy and TEM electron microscopy. Pure heating of the samples without previous UV irradiation does not provide gold nanoparticles, thereby facilitating optical image printing. Comparing the nanoparticles’ growth kinetics in samples with different precursor content suggests the nanoparticle growth mechanism through Au(I) autocatalytic reduction at the surface of a gold nanoparticle. Within the polymer matrix, this mechanism is suggested for the first time.
This paper presents the results of investigating the crystal structure of thin films of the Co40Fe60 composition obtained by magnetron sputtering on their magnetic properties and properties of ferromagnetic nanostructures formed from these films using the optical and electron lithography. It has been found experimentally that magnetic properties of the structures depend on the crystalline-grain sizes, which can be controlled by means of deposition of additional buffer layers of various materials ∼1 nm thick on the substrate under the ferromagnetic film. It has been shown that the crystallite size can be the main factor that determines the minimal lateral sizes of the structures with specified magnetic properties, which are formed from thin ferromagnetic films.