Igor I. Shaganov

Spectroscopic characteristics of SiO and SiO2 solid films: Assignment and local field effect influence

A number of thin SiOx (x=1, 2) films formed on silicon and reflection-absorption substrates were investigated using infrared transmission and aluminized glass techniques. The application of these techniques to SiO and SiO2 films at normal and oblique incidence of light allows the observation of both the longitudinal and transverse optical phonons. The longitudinal-transverse optical phonon splitting is analyzed in terms of a dispersive local field effect.

Comparative investigations of the bolometric properties of thin film structures based on vanadium dioxide and amorphous hydrated silicon

A choice of sensitive element material for uncooled microbolometric array dependents on the ultimate array parameters to a great extent. This paper presents the results of studies of sandwich and planar bolometric structures based on aSi:H and VO2 films accordingly. The aSi:H films were fabricated by plasmachemical vapor-phase deposition and VO2 films were prepared by reactive magnetron ion-plasma sputtering. Sandwich structures with area 100 X 100 micrometers have a resistance of 20 k(Omega) and temperature coefficient of resistance (TCR) of approximately equals 2%/K at 25 degree(s)C. Planar structures with operating section dimensions of 100 X 70 micrometers have TCR of 2.9%/K at the same resistance. The methods of contact noise reduction are found for both type structures. Sandwiches constructed to act as an optical cavity absorb 80% of radiation at 8 micrometers wavelength. It is shown that the planar structures absorption of 50 - 80% can be reached in the 8.5 - 10 micrometers band.

Study of Structure and Quality of Different Silicon Oxides Using FTIR and Raman Microscopy

In this work, SiO2 and fluorine and phosphorous doped SiO2 thin films are investigated using FTIR and Raman techniques. FTIR spectroscopy was performed at normal and oblique incidence of the probe beam in transmission and reflection modes. The effect of polarisation and angle of incidence of the probe beam is examined for the case of reflection mode. Infrared spectra taken from doped oxides show that the structure changes with the passage of time. Alternate methods to calculate the thickness of the doped film are therefore discussed. Infrared spectra of electron beam evaporated oxides give valuable information on their structure and water content. The porosity is calculated for these samples. Finally, micro-Raman spectroscopy is used to measure the fluorine content in a device structure.

Local field effect on infrared phonon frequencies of thin dielectric films

A number of thin dielectric films deposited onto aluminated glass substrates and onto the materials transparent in the IR range (silicon, KRS-5 and CsI) were investigated using infrared transmission and reflection-absorption techniques. The application of these techniques to thin dielectric films at normal and oblique incidence of light allows the observation of both the longitudinal and transverse optical phonons. The longitudinal (LO)-transverse (TO) optical phonons splitting is analysed in terms of a dispersive local field effect. It has been shown that the results of LO-TO splitting obtained from dispersive local field effect are in a good agreement with the results obtained from the dynamical theory of crystalline lattices.

Spectroscopic characteristics of nanocomposite structures in 3D, 2D, and 1D size confinements

Based on the relationship between spectrum of Einstein coefficient B(v) and optical response ε2 meso for nanostructural materials with different types of size confinement (nanospheres, nanowires and nanowalls) we perform the numerical calculation and analysis of ε2 meso and B(v) functions using dispersive effective field approach for a number of harmonic oscillators with different dispersive parameters (oscillator strength, decay factor and peak frequency). It has been shown that the spectral properties (peak position, peak intensity and half width) of ε2 meso strongly depend upon the type of size confinement. In contrast, the spectrum B(v) is the same for all cases of composite media and therefore has a fundamental meaning. Differences in dielectric functions observed for all studied cases arise as a result of the variation in the local field factor for 3D, 2D and 1D size confinements.

Effect of diode–diode interactions on the characteristics of the absorption spectra of granular films and colloidal suspensions of gold and silver nanoparticles

This paper discusses the possibility of using the concepts of intermolecular-interaction theory and the effective-field-dispersion method to model how resonance and inductive-resonance dipole–dipole interactions affect the frequencies of the plasmon-absorption bands of granular films and colloidal suspensions of gold and silver nanoparticles. It is shown that the results of theoretical calculations carried out in terms of the quasi-static approximation agree well with the available experimental data.

The Effect of Local Field Dispersion on the Spectral Characteristics of Nanosized Particles and their Composites

Infrared (IR) spectroscopy of microand nanosized particles and their composites is currently one of the most important enabling technologies in the development of microand nanostructures and their application to various areas of science and technology. Decreasing the characteristic size of metallic, dielectric and semiconductor materials results in a dramatic alteration to their optical, electrical and mechanical properties, allowing the fabrication of new materials with unique physical properties (Lamberti, 2008; Cao, 2004). These alterations in the optical properties are related to a quantum confinement effect, as well as to a dielectric, or electrostatic, confinement effect (Cahay et al., 2001; Chemla & Miller, 1986). The effect of quantum confinement is most pronounced in semiconductor materials, where the transition from the bulk state to the microcrystalline state causes a substantial change in the band structure and an enhancement of the non-linear electrooptical properties. Dielectric, or polarisation, confinement has a wider impact, since it influences the frequencies and intensities of absorption bands in the spectra of any condensed matter, including crystalline and amorphous solids, as well as liquids. This is because considerable changes in the polarisation of micro/nanoparticles occur, depending on their form and orientation with respect to the external electromagnetic field and the details of the spatial restriction. So, the dielectric confinement effect is due to abrupt changes in the intensity of the internal (Ein(ν)), local electric field Eloc(ν), causing significant changes in the spectroscopic characteristics, depending on the direction of the external field Е(ν), and the size and shape of the submicron sized particles, or micro-objects. Dielectric confinement occurs when the absorbing material consists of micro-particles with characteristic sizes significantly smaller than the wavelength of the probe beam. These particles are generally embedded in a transparent dielectric matrix, or deposited on a transparent substrate as an ultra-thin film (Fig. 1). A good analogy to these systems is that of an aerosol suspended in air or stained glass, that is, glass doped with small metal particles (Gehr & Boyd, 1996). In the long wavelength limit, d << λ, for the determination of the spectroscopic characteristics of micro-

Synthesizing film-forming materials from vanadium oxides and investigating the possibilities of producing optical coatings based on them

This paper discusses questions of synthesizing and pressing vanadium oxides to create film-forming materials that can be used in producing optical coatings. Based on the film-forming materials thus created, technological processes have been developed for fabricating coatings from vanadium dioxide by two methods of producing thin films: vacuum evaporation and magnetron sputtering. Questions of using films made from vanadium oxide in optical instrumentation are considered.

Development of 65 X 1 uncooled membrane-type microbolometer array

This paper presents the structure and technology of 65- elements linear array of membrane type microbolometers, and the research results of its properties. DC biased microbolometers with VOx thermosensitive layer have detectivity of 5x107 cm/Hz1/2W at 12.5 Hz at 12.5 Hz frequency, and response time of 3 ms. The ways of improvement of developed linear array sensitivity are planed.

Interference systems for wideband mid-IR VO2 mirrors

We performed the analyze of principles of wide-band VO2- mirrors creation for mid-IR (2.5 - 12 micrometers ) laser radiation control. It was shown, that the choice of interference system of VO2-mirror makes possible to extend region of maximum reflection change up to 1 - 2 (mu) . Calculations and experimental results are presented for mirrors with dR/d>0 and <0 with the change of reflection coefficient from 0.1 up to 94 - 98%.