The optical properties of emulsion nanocomposite materials based on powder silicon are studied. The method of creation of a new type of emulsion composite, allowing the control of the spectral structure of transmitted electromagnetic radiation is reported. Two series of powder silicon, containing SiOx (type 1) and SiOx + SiNx (type 2) depending on conditions were obtained and investigated. The results of FTIR-spectroscopy of powder silicon claimed the formation of SiO2 and SiOx phases on the surface layer of sample type 1 and the formation of nitride phase on the surface layer of sample type 2. The Raman Spectroscopy investigation of two series samples allowed to appreciate the dimensions of nanoparticles and phase structure in powder silicon. The Raman Spectra of samples type 1 and type 2 at the region of 500-600 cm-1 demonstrated that our powder silicon is nanocristalline silicon with dimension of d=10±2 nm for type 1 and d=13±2 nm for type 2. We prepared emulsion composite samples with nanocristalline silicon; the test run of these materials was performed. The Spectra of optical density as well as the spectra of transmission and diffusive reflection into integrative sphere were measured for both types of samples. It was shown that the samples of type 2 are preferable as main protective ingredients of sunscreens.
In this paper we report on the results of the study of optical properties of CdxHg1-xTe epitaxial layers (EL) grown by the LPE method on Cd1-xZnyTe substrates. The values of the band gap of the solid solution forming EL have been obtained from the optical absorption spectra (FTIR) taken in the spectral region of the interband absorption at step-by-step decrease of EL thickness as a result of a chemical etching. In bridge with it the distribution and character of variations in the intensity of lattice vibrations over the layer depth of CdxHg1-xTe / CdZnTe epitaxial structures was investigated. Longitudinal and transverse lattice vibration frequencies of CdxHg1-x-yZnyTe have been evaluated from the experimental spectra and compared with the theoretically calculated ones within a unit cell version of the random element isodisplacement model. From the comparing ofthe experimental and theoretical results it is possible to draw a conclusion that in immediate neighborhood of the CdxHg1-xTe/Cd1-yZnyTe interface the CdxHg1-x-yZnyTe thin layer is formed under the certain conditions during the EL growth process i.e., zinc atoms in given EL area is necessary to consider not as an impurity atoms but as the components of the cationic sublattice.
The effect of arc plasma jet treatment (APJT) on the porous silicon (PS) structure, surface, and photoluminescence (PL) has been studied. The investigation of PS FTIR absorption spectra indicate that the Ar/air APJT induces the decreasing of the concentration of Si-Hn, C-Hn, (n equals 1, 2, 3) bonds and corresponding increasing of Si-Ox bonds more than an order of magnitude. This transformation of surface conditions resulted in not enough large decreasing (about 2 - 3 times maximum) of the PL intensity with red shifting of the peak from 665 nm to 700 nm. These results suggest that the change of PL occurs as a result of APJT induced replacement of the Si-Hn bonds with Si-Ox bonds. We have analyzed the effect of plasma conditions on the PL characteristics. The luminescence mechanism is also discussed.
InGaAs epitaxial layers (EL) have a number of physical properties which are very attracted for many practical applications. Special place in this system takes isoperiodical heterocomposition Inx Ga1-xAs/InP, in order to receive EL's with minimum of mismatch on heterojunction. However lattice parameters of binary compounds InAs and GaAs which formed this solid solution differ by 7 percent. This is a reason of existence in Inx Ga1-xAs considerable 'internal' strains, which are comparable with mixing enthalpy. Therefore phase transitions (ordering or clustering) take place in the solid solution. Such transitions decrease the system energy and may be occur during EL's growth. In this situation may be expected the fundamental properties dependence from thermal growth condition. In addition to the strains source inside EL's 'external' strains may be presented. They may be conditioned by EL's and substrate lattice mismatch, for example. Therefore it was interesting to retrace how physical properties of material change depending on layers lattice mismatch to substrate.
The role of silicon hydride species in the photoluminescence intensity behavior of porous silicon (PS) has been studied. The surface coverage was monitored using Fourier Transform Spectroscopy (FTIR). Porous silicon sample sets was prepared by the anodization of p-type (111) Si (10 Ohm X cm) and of n-type (111) Si (0.01 Ohm X cm) under a various current density for a different time of anodization with light illumination and in the dark. We have observed non- monotonous dependencies of PL intensity, IR absorption at Si-Hn stretching and wagging modes as well as of p-type Si and n-type Si versus anodization time and current density. In particular, the levels of IR absorption at the different Si-H modes have no correlation themselves and only wagging mode (628 cm-1) repeat the PL intensity behavior. To our opinion, the photoluminescence may originate from the specific combinations of the particle structure and sizes with the definite surface state conditions of the nanocrystalline porous silicon.
KEYWORDS: Semiconductors, Tellurium, Spectroscopy, Crystals, Fourier transforms, Fourier spectroscopy, Sensors, Temperature metrology, Plasma, Chemical species
Negative-beam (NB) FTIR measurements are made with no radiation source but with the sample and detector at different temperatures. They are a powerful tool in the study of thermo- stimulated effects in semiconductors without light excitation. They can be used to separate the influence of either photo-generated carriers or possible metastable transformations of impurities, lattice defects, etc. from thermo-induced processes in semiconductors. Moreover observations of stimulated emission from a semiconductor in the far-infrared (FIR) spectral range have only been reported so far at energies well above the multi-phonon energies. This is because the probability of FIR emission is strongly reduced due to non-radiative recombination channels like Auger processes which are strongly enhanced with decreasing band gap energy. Below the energy of the longitudinal optic (LO) phonons,optical emission becomes probable again since LO-phonon assisted scattering processes are energy forbidden.
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