ABSTRACT
The influence of the addition of Bi to the dilute ferromagnetic semiconductor (Ga,Mn)As on its electronic structure as well as on its magnetic and structural properties has been studied. Epitaxial (Ga,Mn)(Bi,As) layers of high structural perfection have been grown using low-temperature molecular-beam epitaxy. Post-growth annealing of the samples improves their structural and magnetic properties and increases the hole concentration in the layers. Hard X-ray angle-resolved photoemission spectroscopy reveals a strongly dispersing band in the Mn-doped layers, which crosses the Fermi energy and is caused by the high concentration of Mn-induced itinerant holes located in the valence band. An increased density of states near the Fermi level is attributed to additional localized Mn states. In addition to a decrease in the chemical potential with increasing Mn doping, we find significant changes in the valence band caused by the incorporation of a small atomic fraction of Bi atoms. The spin-orbit split-off band is shifted to higher binding energies, which is inconsistent with the impurity band model of the band structure in (Ga,Mn)As. Spectroscopic ellipsometry and modulation photoreflectance spectroscopy results confirm the valence band modifications in the investigated layers.
ABSTRACT
The surface plasmon resonance properties of highly regular laser-induced periodic surface structures (HR-LIPSSs) on Si, functionalized with Au nanoparticles (NPs), were investigated. In particular, the spectral dependencies of polarized light reflectance at various angles of incidence were measured and discussed. It is found that the deposition of Au NPs on such periodically textured substrates leads to significant enhancement of the plasmon resonance properties, compared to that measured on planar ones. This effect can be used to improve the efficiency of localized-plasmon-resonance-based sensors.
ABSTRACT
A new approach to the formation of a 1D planar periodicity on the front of a plasmonic photodetector based on Schottky barrier is proposed. It allows forming a 1D planar periodicity with corrugation at the "metal/environment" interface by laser interference lithography using embedded chalcogenide wires, whereas the "metal/semiconductor" interface is flat that leads to reducing of surface recombination losses at Shottky barrier in contrary to the conventional technology for forming corrugated metal films on the semiconductor surface requiring chemical etching of the semiconductor substrate. In this case, the metal film interfaces are quasi-anticorrelated as opposed to correlated ones in the conventional technology. It has been theoretically predicted that the polarization sensitivity (T p /T s ) strongly depends on the cross-sectional shape of chalcogenide wires and reaches a value of 8. Furthermore, it was theoretically found that the maximum sensitivity of the signal intensity on the environment refractive index is three times larger than for an equivalent structure obtained by conventional technology. Comparison of experimental data for the photocurrent in the case of two types of correlation between metal film interfaces demonstrates good agreement with numerical simulations.
ABSTRACT
Schottky barrier structures based on nanoporous InP with inclusion of Au nanoparticles and evaporated semitransparent Au film have been made. The spectra of short-circuit photocurrent in the visible range and current-voltage characteristics have been measured. Prepared structures are characterized by increased photocurrent due to the microrelief interface and surface plasmon excitation in gold nanoparticles as well as increased surface recombination especially in the short wavelength region.
ABSTRACT
The hybridization of the plasmonic and guided modes in the case of one-dimension photonic crystal based on Bragg mirror terminated by a corrugated metal film has been demonstrated theoretically. The simulations have showed that the hybrid plasmonic-photonic mode is characterized by low broadening due to redistribution of the electric field intensity between photonic mode and surface plasmon polariton. It was found that the Q-factor and the polarisation sensitivity of these modes are about 144 and 25, respectively, that is 3 times greater than for surface plasmon polariton exciting in similar structure without Bragg mirror.
ABSTRACT
This study reports on the employment of the interference lithography (IL) technique, using photoresist based on the chalcogenide glass (ChG) films, for fabrication of one-dimensional (gratings) and two-dimensional (arrays) periodic plasmonic structures on the surface of glass plates. The IL technique was optimized for patterning of the Au and Al layers and formation of gratings and arrays with a spatial frequency of 2000 mm(-1). Optical properties of obtained structures were studied using measurements of spectral and angular dependence of transmission and reflection of polarized light. It was shown that the spectral and angular position of the surface plasmon polariton and local surface plasmon resonance, which are observed in these samples, can be adjusted over a wide range by selecting the geometric parameters of structures and technological modes of their manufacturing.
ABSTRACT
The photocurrent enhancement effect caused by Au and Ag nanoparticles for GaAs-based photovoltaic structures of surface barrier or p-n junction type with microtextured interfaces has been investigated in dependence on the conditions of nanoparticles deposition and, respectively, on the shape and local dielectric environment of obtained nanoparticle arrays. Three nanoparticle deposition methods have been checked: 1) photoinduced chemical deposition of Au from aqueous AuCl3 solution forming nanowires on the ridges of quasigrating-type surface microrelief, 2) deposition of Ag nanoparticles from colloidal suspension on the GaAs substrate covered with poly(vinylpyridine), and 3) drop and dry deposition of Au/SiO2 core-shell nanoparticles from aqueous colloid solution. The comprehensive investigation of optical reflectance, photoelectric, and electrical characteristics of the fabricated barrier structures has shown the highest photovoltaic parameters for surface microrelief of quasigrating-type and electroless Au nanoparticle deposition. The analysis of characteristics obtained allowed us also to define the mechanisms of the total photocurrent enhancement.
ABSTRACT
Silica-gold core-shell nanoparticles were used for plasmonic enhancement of rare earth fluorescence in sol-gel-derived TiO2:Sm3+ films. Local enhancement of Sm3+ fluorescence in the vicinity of separate gilded nanoparticles was revealed by a combination of dark field microscopy and fluorescence spectroscopy techniques. An intensity enhancement of Sm3+ fluorescence varies from 2.5 to 10 times depending on the used direct (visible) or indirect (ultraviolet) excitations. Analysis of fluorescence lifetimes suggests that the locally stronger fluorescence occurs because of higher plasmon-coupled direct absorption of exciting light by the Sm3+ ions or due to plasmon-assisted non-radiative energy transfer from the excitons of TiO2 host to the rare earth ions. PACS: 78; 78.67.-n; 78.67.Bf.
