RESUMO
A new complex of indium(III)chloride with etioporphyrin-I was synthesized and characterized. As with naturally occurring extraligated etioporphyrins, the InCl-EtioP-I spectrum in solution has a very strong B-band and a more than an order of magnitude weaker Q-band, but this difference diminishes in solid films of InCl-EtioP-I obtained by thermal evaporation in vacuum. In a solid, molecules have a tight convex-convex arrangement in a 2D double layered structure with interplane distance of 3.066â Å. The conductivity of films can easily be activated by the action of temperature or light. In the cells with symmetrical lateral contacts the photocurrent exceeds the dark current by about three orders of magnitude, with the contribution of photons in the Q-band range being greater than expected from the experimental or calculated absorption spectrum. The Q-bands contribute significantly to the photovoltaic effect in the ITO/InCl-EtioP-I/Al sandwich cells. Such cells show an untypically strong signal in the photodiode regime, which yields the spectral detectivity of 10^12 Jones.
RESUMO
A new method for creating nanomaterials based on gallium oxide by ion-beam synthesis of nanocrystals of this compound in a SiO2/Si dielectric matrix has been proposed. The influence of the order of irradiation with ions of phase-forming elements (gallium and oxygen) on the chemical composition of implanted layers is reported. The separation of gallium profiles in the elemental and oxidized states is shown, even in the absence of post-implantation annealing. As a result of annealing, blue photoluminescence, associated with the recombination of donor-acceptor pairs (DAP) in Ga2O3 nanocrystals, appears in the spectrum. The structural characterization by transmission electron microscopy confirms the formation of ß-Ga2O3 nanocrystals. The obtained results open up the possibility of using nanocrystalline gallium oxide inclusions in traditional CMOS technology.
RESUMO
In periodic W/Be multilayers, thickness-dependent microstructural and phase modifications were investigated in W and Be layers. In X-ray diffraction, α-W was predominant for the ultrathin layer of W, while ß-W evolved along with the α-W phase for higher film thickness. For the thicker layers, the thermodynamically metastable ß-W vanished and a single well-defined preferably oriented stable α-W phase was observed. The lattice spacing revealed that these phases exist in the tensile stressed condition. With the increase in thickness of Be layers, the blueshift and narrow linewidth of the transverse optical (TO) phonon mode was observed in Raman scattering studies. However, the TO mode was redshifted and the linewidth was further narrowed consistently with an increase in the thermal annealing temperature of the multilayers. The investigation has quantified an increase in compressive strain and reduction of defects with an increase in thickness of the Be layers. However, for thermally annealed samples, the compressive strain in the Be layers was relaxed and crystalline quality was improved.
RESUMO
The distribution of magnetic impurities (Mn) across a GaAs/Zn(Mn)Se heterovalent interface is investigated combining three experimental techniques: Cross-Section Scanning Tunnel Microscopy (X-STM), Atom Probe Tomography (APT), and Secondary Ions Mass Spectroscopy (SIMS). This unique combination allowed us to probe the Mn distribution with excellent sensitivity and sub-nanometer resolution. Our results show that the diffusion of Mn impurities in GaAs is strongly suppressed; conversely, Mn atoms are subject to a substantial redistribution in the ZnSe layer, which is affected by the growth conditions and the presence of an annealing step. These results show that it is possible to fabricate a sharp interface between a magnetic semiconductor (Zn(Mn)Se) and high quality GaAs, with low dopant concentration and good optical properties.
