Raman and Photoluminescence Study of ZnO Films Grown by Chemical Method

In this paper phonon and emission properties of ZnO films grown by metalorganic chemical vapour deposition (MOCVD) at ambient pressure and by molecular beam epitaxy (MBE) are investigated using Raman and photoluminescence (PL) spectroscopy. It is shown that high-frequency shift of non-polar phonon modes corresponds to elastic compressive strain in the plane parallel to c-axis and is equal to 3.2×10−3 and 2.2×10−3 for ZnO film grown by MOCVD and MBE, respectively. The possibility of obtaining highquality ZnO films grown by MOCVD was demonstrated. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3501

Anisotropy of elastic deformations in multilayer (In,Ga)As/GaAs structures with quantum wires: X-ray diffractometry study

Using the method of high-resolution X-ray diffraction (HRXRD), we have studied 17-period In₀.₃Ga₀.₇As/GaAs multilayer structure with self-assembled quantum wires (QWRs) grown by the MBE and subjected to postgrowth rapid thermal annealing (RTA) at temperatures (Tann) from 550 to 850 °C for 30 s. It has been shown that the spatial arrangement of QWRs (lateral and vertical) causes the quasi-periodical strain distribution, the strains being essentially anisotropic relatively to crystallographic directions of 〈011〉 type. At Tann ≤ 750 °С, the driving mechanism of structural transformations is relaxation of residual strains due to thermally-activated and strain-enhanced processes of In/Ga atom interdiffusion at the interface QWRs-2D layer, which does not result in considerable changes of the In concentration in (In,Ga)As QWRs. The presence of two superlattice vertical periods in the samples under study and their changes during RTA we explained by an anisotropic character of elastic strain distribution and lowered structure symmetry. The revealed increase in the (In,Ga)As QWRs lateral period caused by RTA is a direct evidence of running lateral mass-transfer processes and can be explained using the model “nucleation plus strain-enhanced In/Ga atom lateral interdiffusion”. At low annealing temperatures, there takes place dissolution of intermediate QWRs as a result of interdiffusion enhanced by residual anisotropic strains. At high RTA temperatures, the interdiffusion process is mainly determined by the composition gradient existing between QWRs and 2D layer

Comparison of properties inherent to thin titanium oxide films formed by rapid thermal annealing on SiC and porous SiC substrates

The comparative analysis of optical characteristics inherent to TiO2/SiC and TiO2/por-SiC/SiC structures has been performed. It has been shown that, in these structures regardless of the substrate structure, formation of TiO2 layers with approximately the same width 60 nm takes place. In this case the TiO2 film composition is close to the stoichiometric one. At the same time, the presence of an additional porous layer in the TiO2/por-SiC/SiC structure leads to blurring the oxide film – substrate interface but promotes an increase in the intensity of the Raman scattering signal from the oxide film

Probing plasmonic system by the simultaneous measurement of Raman and fluorescence signals of dye molecules

The simultaneous measurement of Raman and fluorescence signals was proposed to find out the molecule-metal distance. The ratio between Raman and fluorescence intensities was used to estimate molecule-metal distance in nanometer scale. A low-value intensity of the fluorescence of the dye molecules was found using the photobleaching effect. Made was a comparison of experimental results with a theoretical model, which showed well agreement

Effect of low-temperature annealing on light-emitting properties of na-Si/SiOx porous nanocomposite films

The effect of low-temperature annealing on light emitting properties of naSi/SiOx porous column-like nanocomposite films has been studied. Influence of type of chemically active gas or inert ambient on PL characteristics is shown. Existence of metastable defects in such structures is shown. A temperature interval for healing the metastable defects is defined. Mechanisms to reduce a non-radiative recombination channel depending on the gas ambient are proposed

Plasma treatment of titanium dioxide film for black TiO₂

The results of the treatment of TiO₂ film in volume discharge with an Ar/H₂ mixture are presented. The treated film demonstrates the changes in transparency and conductivity. Raman spectra show no changes in the phase state of the film after plasma treatment.Представлено результати обробки плівки ТіО₂ в об’ємі розряду на суміші Ar/H₂. Оброблена плівка демонструє зміни в прозорості та провідності. Раманівські спектри показують відсутність змін у поліморфному стані плівки після плазмової обробки

Self-heating effects in AlGaN/GaN HEMT heterostructures: Electrical and optical characterization

The effect of self-heating on the transport characteristics and electronic properties of transistor AlGaN/GaN heterostructures was investigated. The electrical, micro-Raman and photoluminescence techniques were used for temperature estimations for transistor structures under electrical load. The thermal resistance of these structures has been calculated to obtain the temperature of conducting channel heating from the current-voltage characteristics. The differences in the obtained temperature data from applied techniques have been analyzed

Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition

Nanocomposite porous films with silver nanoparticle (Ag NP) arrays were prepared by the pulsed laser deposition from the back flux of erosion torch particles in argon atmosphere on the substrate placed at the target plane. Preparation conditions of the films were set by argon pressure, energy density of laser pulses, their amount and substrate position relatively to the torch axis. The films were prepared with gradient thickness, variable Ag NP sizes and distance between them along the length of substrate as well as corresponding maxima in the spectra of local surface plasmon absorption. Plasmon effects of the Raman scattering enhance in the matter of the Ag NP shell gave the opportunity to register the spectral bands caused by an extremely small quantity of silver compounds with oxygen and carbon. The possible nature of individual bands in the Raman spectrum was analyzed. The obtained results are important for interpretation of the Raman spectra of analytes based on the prepared SERS substrates

Eco-friendly Synthesis of Gold Nanoparticles Using Camellia sinensis Phytoextracts

Biosynthesis of metal nanoparticles using plant materials involves a fairly rapid reduction of metallic materials. The reduction potential of phytochemicals in a tea extract to reduce gold salt (NaAuCl4) to the highly homogenous gold nanoparticles is presented. Phytoextracts were derived from the mixture of Camellia sinensis var. sinensis and Camellia sinensis var. assamica (green tea) leaves. The appearance of the phytoextract's sloping absorption peak with Au salt at the wavelength range 530-550 nm corresponded to the absorption of gold nanoparticles. Obtained nanoparticles were purified from phytoextract excess by centrifugation. Then they were studied by Raman and FTIR spectroscopy and AFM. It was found that the size of produced gold nanoparticles was in the range from 3 nm to 10 n

Raman study of L-Asparagine and L-Glutamine molecules adsorbed on aluminum films in a wide frequency range

Using micro-Raman spectroscopy, a detailed study of vibrational spectra of L-Asparagine and L-Glutamine amino acids adsorbed on aluminum foils were carried out within the frequency range 80…3500 cm–1 under different excitation wavelengths. On the basis of detailed analysis of Raman spectra of the mentioned above amino acids and data of DFT-calculations of normal modes and isotopic substitution for these analytes available in literature, interpretation of amino acids vibrational bands were performed. The polarized Raman spectra of studied amino acids indicate different ordering of polycrystalline structure in distinct spots on the sample. The most significant variations of ratios between polarized bands are principally observed for deformation vibrations of NH2, COO– and CH2 groups within entire “fingerprint” range and valence vibrations of CC and CN bonds within the range 1000…1100 cm–1