S.V. Mamykin

Morphology and interfacial properties of microrelief metal–semiconductor interface

Abstract The effect of the morphology of Au/GaAs interface microrelief, prepared by chemical anisotropic etching, on current flow mechanism, electronic and recombination properties of interface has been investigated. Simulation of I – V curves and optical transmittance of light into semiconductor was made on the basis of the developed theories taking into account the barrier height distribution and the effect of scattering of light by low microrelief.

Modeling and measurement of optical response of 1D array of metallic nanowires for sensing and detection application

We have investigated 1D nanosized metallic wires with subwavelength dimensions in which localized surface plasmon (LSP) and surface plasmon polariton (SPP) can exist. Elaboration of the localized surface plasmon resonance (LSPR) based device for scaling down to nanometric dimensions, which provide significant flexible design is the aim of this paper. Modeling of the interaction of the incident light with the periodic system of nanowires (differential formalism) and measurements of the optical (transmittance, extinction) properties of the structures under consideration were performed to reveal the general trends in the design of the gold nanostructure geometry to optimize sensitivity of sensor system.

Texturized interface as a basis of surface-barrier heterostructure for solar cells application

Simulation of the photocurrent of surface-barrier structures (SBS) with texturized interface has been performed on the basis of obtained theoretical expression for internal quantum efficiency of homogeneous SBS and the model of parallelly connected diodes. The role of various sources of recombination losses (in the semiconductor, at the interface and due to the emission of majority carriers into the metal) in solar energy convertors has been analyzed. The complex method of characterization of SBS with texturized interface is proposed that includes an analysis of optical, electric and photoelectric characteristics. The possibility to increase the photosensitivity of the Au/GaAs SBS due to texturization and sulfur passivation of the interface for two types of microrelief (dendritic and quasigrating) obtained by wet anisotropic etching has been investigated. The morphology and statistical geometric characteristics of the interface were investigated by atomic force microscopy (AFM). The obtained results allowed to determine the change of optical and electronic (recombination) parameters of the interface caused by the used processing (texturization, passivation).

Metal nanoparticle-enhanced photocurrent in GaAs photovoltaic structures with microtextured interfaces

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.

Gilded nanoparticles for plasmonically enhanced fluorescence in TiO2:Sm3+ sol-gel films

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.PACS78; 78.67.-n; 78.67.Bf

New advanced polaritonic photodetector on base of surface barrier structure

The paper is devoted to elaboration of an advanced polaritonic photodetector based on the metal (Au or Al)/semiconductor (GaAs or InP) surface barrier heterostructures (SBH). A basic principle underlying the device operation is surface plasmon resonance (SPR) in a SBH with the microrelief (quasigrating, grating and bigrating) at the interface. Influence of the microstructure of continuous metal films and of island films on the efficiency of photodetectors is also investigated.

Enhanced Dielectric Environment Sensitivity of Surface Plasmon-Polariton in the Surface-Barrier Heterostructures Based on Corrugated Thin Metal Films with Quasi-Anticorrelated Interfaces

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 (Tp/Ts) 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.

Hybridization of Surface Plasmon Polariton and Photonic Crystal Modes in Bragg Mirror with Periodically Profiled Metal Film.

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.

Effect of gamma irradiation on photoconversion characteristics of metal/gallium arsenide barrier structures with textured interface

The effect of 60Co gamma irradiation at doses of 103-2×105 Gy on the photoconversion and dark I-V characteristics of Au/GaAs surface-barrier solar cells (SCs) is studied. The morphology of the interface microrelief is varied to reach the highest photoconversion efficiency. Of the two types of microrelief morphology (dendritic and quasi-grating) obtained by the chemical anisotropic etching of n-(100)GaAs, the latter is more promising, particularly for SCs designed for space application, since the associated SCs offer higher efficiency and radiation resistance.

Gold micro- and nano-particles for surface enhanced vibrational spectroscopy of pyridostigmine bromide

Abstract Triangular gold microprisms and spherical silica nanoparticles with attached gold nano-islands were examined as an active nanostructures for the surface enhanced Raman and infrared spectroscopy. These particles were probed for the detection of pyridostigmine bromide as a safe analog of military compound sarin. Raman and infrared spectral bands of the pyridostigmine bromide were measured. Detailed correlation of obtained spectral bands with specific vibrations in pyridostigmine bromide was done. Silica nanoparticles with attached gold nano-islands showed more essential enhancement of the Raman signal than gold microcrystals. The reasons of such behaviour are discussed.