Backscattering Raman Spectroscopy Research Articles

FTIR study of silicon carbide amorphization by heavy ion irradiations

We have measured at room temperature (RT) the Fourier-transform infra-red (FTIR) absorption spectra of ion-irradiated thin epitaxial films of cubic silicon carbide (3C–SiC) with 1.1 µm thickness on a 500 µm thick (1 0 0) silicon wafer substrate. Irradiations were carried out at RT with 2.3 MeV 28Si+ ions and 3.0 MeV 84Kr+ ions for various fluences in order to induce amorphization of the SiC film. Ion projected ranges were adjusted to be slightly larger than the film thickness so that the whole SiC layers were homogeneously damaged. FTIR spectra of virgin and irradiated samples were recorded for various incidence angles from normal incidence to Brewster’s angle. We show that the amorphization process in ion-irradiated 3C–SiC films can be monitored non-destructively by FTIR absorption spectroscopy without any major interference of the substrate. The compared evolutions of TO and LO peaks upon ion irradiation yield valuable information on the damage process.Complementary test experiments were also performed on virgin silicon nitride (Si3N4) self-standing films for similar conditions. Asymmetrical shapes were found for TO peaks of SiC, whereas Gaussian profiles are found for LO peaks. Skewed Gaussian profiles, with a standard deviation depending on wave number, were used to fit asymmetrical peaks for both materials. A new methodology for following the amorphization process is proposed on the basis of the evolution of fitted IR absorption peak parameters with ion fluence. Results are discussed with respect to Rutherford backscattering spectrometry channeling and Raman spectroscopy analysis.

A biomineralization study of the Indo-Pacific giant clam Tridacna gigas

The giant clam, Tridacna gigas, is an important faunal component of reef ecosystems of the Indo-Pacific region. In addition to its ecological role, shells of this bivalve species are useful bioarchives for past climate and environmental reconstructions. However, the biomineralization processes involved in shell aragonite deposition are insufficiently understood. Here, we present a study of the shell microstructure of modern specimens from Palm Island, Great Barrier Reef (GBR), Australia, and Huon Peninsula, Papua New Guinea (PNG), using a combination of petrography, scanning electron microscopy, electron backscatter diffraction, Raman spectroscopy and stable carbon isotope ratios. Daily growth increments were recognizable in all specimens through ontogeny, and counting these growth lines provides a robust specimen age estimate. For the internal layers, paired increments of organized aragonitic needles and compact, oblong crystals were recognized in a specimen from PNG, whereas specimens from GBR were composed of shield-like crystals that were not definable at the microscale. The combination of nutrient availability, rainfall and solar irradiance are likely to be the most significant factors controlling shell growth and may explain the observed differences in microstructure. The external layer, identical in all specimens, was composed of dendritic microstructure that is significantly enriched in 13C compared to the internal layer, suggesting different metabolic controls on layer deposition. We propose that the mineralization of the internal and external layers is independent from each other and associated with the activity of specific mantles. Future studies using T. gigas shells as bioarchives should consider the microstructure as it reflects the environment in which the individual lived and the differences in mineralization pathways of internal and external layers.

Enhanced light absorption and quenched photoluminescence resulting in photoactive poly(3-hexyl-thiophene)-covered ZnO/TiO2 nanotubes for high light harvesting efficiency

Organic/inorganic nanocomposites composed of a ploy(3-hexylthiophene) (P3HT) film and TiO2 nanotubes or ZnO-coated TiO2 (ZnO/TiO2) nanotubes were fabricated and the influence of the inorganic nanostructures on the optical properties correlated with their photoactivity was studied. The structures of the organic/inorganic nanocomposites were characterized by X-ray diffraction and Raman backscattering spectroscopy. The optical properties were evaluated by measuring the optical absorption and photoluminescence. The TiO2 nanotubes exhibit anatase structure and the ZnO coating is structured with hexagonal wurtzite. The inorganic nanostructures are fully covered by the P3HT films with some P3HT infiltrating into the lacunas of the one-dimensional nanostructures. The P3HT-covered TiO2 NTs show strong optical absorption and present evident photoluminescence quenching. Nano-heterostructured ZnO/TiO2 NTs are superior to nanostructured TiO2 NTs in composing organic/inorganic nanocomposites with P3HT. The presence of a thin ZnO coating between the P3HT film and the TiO2 nanotubes further increases light absorption and quenches photoluminescence, revealing efficient generation of excitons by optical excitation and suppression of radiative recombination of photo-generated excitons, and suggesting that the organic/inorganic nanocomposite P3HT-covered ZnO/TiO2 nanotubes exhibits high photoactivity and an enhanced light harvesting efficiency can be anticipated. The temperature-dependent photoluminescence was also measured for an examination of π-stacking aggregation and a discussion of exciton coupling in P3HT at different temperatures.

Annealing effects on the structural and optical properties of vanadium oxide film obtained by the hot-filament metal oxide deposition technique (HFMOD)

Vanadium oxide films amorphous, nonstoichiometric and highly absorbing in the optical region were deposited on ITO-coated glass and on silicon substrates, by the hot-filament metal oxide deposition technique (HFMOD) and oxidized by ex-situ annealing in a furnace at 200, 300, 400 and 500 oC, under an atmosphere of argon and rarefied oxygen. X-ray diffraction, Raman and Rutherford backscattering spectroscopy as well as optical transmission were employed to characterize the amorphous and annealed films. When annealed at 200 and 300 oC the as-deposited opaque films become transparent but still amorphous. Under treatments at 400 and 500 oC a crystalline nonstoichiometric V2O5 structure is formed. All the annealed films became semiconducting, with their optical absorption coefficients changing with the annealing temperature. An optical gap of 2.25 eV was measured for the films annealed at 400 and 500 oC. The annealing in rarefied oxygen atmosphere proved to be a useful and simple ex-situ method to modulate the structural and optical properties of vanadium oxide films deposited by HFMOD technique. This technique could be applied to other amorphous and non-absorbing oxide films, replacing the conventional and sometimes expensive method of modulate desirable film properties by controlling the film deposition parameters. Even more, the HFMOD technique can be an inexpensive alternative to deposit metal oxide films.

Carrier transport mechanism of highly-sensitive niobium doped titanium dioxide/p-Si heterojunction photodiode under illuminations by solar simulated light

Nano-crystalline Nb doped anatase TiO2 (NTO) thin film was deposited on p-type Si substrate for fabrication of n-NTO/p-Si heterojunction photodiode using RF magnetron sputtering technique. Rutherford backscattering spectrometry and Raman spectroscopy results suggest the substitutional incorporation of Nb5+ ions in anatase TiO2 lattice, which is evidenced from large stiffening of Eg(1) and softening of B1g Raman modes. The current density-voltage (J-V) characteristics are measured and important diode parameters of n-NTO/p-Si heterojunction diode are determined, such as ideality factor, barrier height, and series resistance. Diode exhibits excellent behavior under dark condition as rectification ratio is found to be ∼7 × 102 with high forward current density ∼1.54 A/cm2 at 5 V. The n-NTO/p-Si heterojunction works as an efficient photodiode in reverse bias under simulated solar light illumination with high contrast ratio ∼225 at −2 V and very high photo responsivity ∼2.7 A/W at −5 V. The high photo responsivity of photodiode is mainly due to the generation of high density electron-hole plasma in NTO depletion region by the absorption of incident UV range photons. Thus n-NTO/p-Si heterojunction diode is suitable device for highly sensitive Ultra-Violet photodiode applications.

Effects of postpolymerization microwave irradiation on provisional dental acrylics: physical and mechanical properties.

This study aimed to evaluate the effects of microwave irradiation on the physical and mechanical properties of poly(methyl methacrylate) (PMMA) provisional resins. Twenty bars and 20 disc-shaped specimens were fabricated for each selected provisional restorative material (Dencor and Duralay). Test groups were subjected to microwave irradiation (3 minutes at 600 W) after polymerization. Bar specimens were subjected to a flexural strength test. Disc-shaped specimens were used to evaluate microhardness. Backscattered Raman spectroscopy was employed for each group to define the degree of conversion of the monomer/polymer. The frequency bands corresponding to C = C and C = O groups were used to determine the conversion of methyl methacrylate (MMA) monomers into polymers. Glass transition temperature was determined using a differential scanning calorimeter. Microwave irradiation of both tested autopolymerizing PMMA provisional materials resulted in a statistically significant increase in microhardness, degree of conversion and glass transition temperature values. Also, the results demonstrated a significant increase in flexural strength after postpolymerization microwave irradiation for the Dencor specimens. It is concluded that mechanical and physical properties are positively influenced by microwave irradiation.

Retraction Note to: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

We review the discovery of new phases of carbon (Q-carbon) and BN (Q-BN) and address critical issues related to direct conversion of carbon into diamond and hBN into cBN at ambient temperatures and pressures in air without any need for catalyst and the presence of hydrogen. The Q-carbon and Q-BN are formed as a result of quenching from super undercooled state by using high-power nanosecond laser pulses. We discuss the equilibrium phase diagram (P vs T) of carbon, and show that by rapid quenching, kinetics can shift thermodynamic graphite/diamond/liquid carbon triple point from 5000 K/12 GPa to super undercooled carbon at atmospheric pressure in air. Similarly, the hBN-cBN-Liquid triple point is shifted from 3500 K/9.5 GPa to as low as 2800 K and atmospheric pressure. It is shown that nanosecond laser heating of amorphous carbon and nanocrystalline BN on sapphire, glass, and polymer substrates can be confined to melt in a super undercooled state. By quenching this super undercooled state, we have created a new state of carbon (Q-carbon) and BN (Q-BN) from which nanocrystals, microcrystals, nanoneedles, microneedles, and thin films are formed depending upon the nucleation and growth times allowed and the presence of growth template. The large-area epitaxial diamond and cBN films are formed, when appropriate planar matching or lattice matching template is provided for growth from super undercooled liquid. The Q-phases have unique atomic structure and bonding characteristics as determined by high-resolution SEM and backscatter diffraction, HRTEM, STEM-Z, EELS, and Raman spectroscopy, and exhibit new and improved mechanical hardness, electrical conductivity, and chemical and physical properties, including room-temperature ferromagnetism and enhanced field emission. The Q-carbon exhibits robust bulk ferromagnetism with estimated Curie temperature of about 500 K and saturation magnetization value of 20 emu g−1. We have also deposited diamond on cBN by using a novel pulsed laser evaporation of carbon and obtained cBN/diamond composites, where cBN acts as template for diamond growth. Both diamond and cBN grown from super undercooled liquid can be alloyed with both p- and n-type dopants. This process allows carbon to diamond and hBN to cBN conversions and formation of useful nanostructures and microstructures at ambient temperatures in air at atmospheric pressure on practical and heat-sensitive substrates in a controlled way without need for any catalysts and hydrogen to stabilize sp3 bonding for diamond and cBN phases.

Assessment and prediction of tablet properties using transmission and backscattering Raman spectroscopy and transmission NIR spectroscopy

This study investigated whether Raman and Near Infrared (NIR) spectroscopy could predict tablet properties. Granules were produced on a continuous line by varying granulation parameters. Tableting process parameters were adjusted to obtain uniform tablet weight and thickness. Spectra were collected offline and tablet properties determined with traditional analyzing methods. Partial Least Squares (PLS) regression was used to correlate spectral information to tablet properties, but predictive models couldn't be established. Principal component analysis (PCA) was effectively used to distinguish theophylline concentrations and hydration levels and multiple linear regression (MLR) analysis allowed insight on how granulation parameters affect granule and tablet properties.

Nanostructured SnO2-Ge Multi-layer thin Films with Quantum Confinement Effects for Solar Cell.

It is well-known that multi-layer films with nanostructure can give novel properties by interfacial phenomenon and quantum confinement effects. Nanostructured multi-layer thin films are presently being analyzed for their vast applications in the area of optoelectronics technology particularly photovoltaics. Hereof, two dimensional thin films with nanostructure are of prime importance due to their structure dependent optical, electrical, and opto-electronic properties. It has been revealed that these films exhibit quantum confinement effects with band gap engineering. The main focus of the research is to evaluate the effect on structural and optical properties with number of layers. Nanostructured SnO2-Ge multi-layer thin films were fabricated using electron beam evaporation and resistive heating techniques. Alternate layers of SnO2 and Ge were deposited on glass substrate at a substrate temperature of 300 °C in order to obtain uniform and homogeneous deposition. The substrate temperature of 300 °C has been determined to be effective for the deposition of these multi-layer films from our previous studies. The films were characterized by investigating their structural and optical properties. The structural properties of the as-deposited films were characterized by Rutherford Backscattering Spectroscopy (RBS) and Raman spectroscopy and optical properties by Ultra-Violet-Near infrared (UV-VIS-NIR) spectroscopy. RBS studies confirmed that the layer structure has been effectively formed. Raman spectroscopy results show that the peaks of both Ge and SnO2 shifts towards lower wavenumbers (in comparison with bulk Ge and SnO2, suggesting that the films consist of nanostructures and demonstrate quantum confinement effects. UV-VIS-NIR spectroscopy showed an increase in the band gap energy of Ge and SnO2 and shifting of transmittance curves toward higher wavelength by increasing the number of layers. The band gap lies in the range of 0.9 to 1.2 eV for Ge, while for SnO2, it lies between 1.7 to 2.1 eV. Analysis of results suggests that the nanostructured SnO2-Ge multi-layer thin film can work as heterojunction materials with quantum confinement effects. Accordingly, the present SnO2-Ge multi-layer films may be employed for photovoltaic applications. Few relevant patents to the topic have been reviewed and cited.

RETRACTED ARTICLE: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

We review the discovery of new phases of carbon (Q-carbon) and BN (Q-BN) and address critical issues related to direct conversion of carbon into diamond and hBN into cBN at ambient temperatures and pressures in air without any need for catalyst and the presence of hydrogen. The Q-carbon and Q-BN are formed as a result of quenching from super undercooled state by using high-power nanosecond laser pulses. We discuss the equilibrium phase diagram (P vs T) of carbon, and show that by rapid quenching, kinetics can shift thermodynamic graphite/diamond/liquid carbon triple point from 5000 K/12 GPa to super undercooled carbon at atmospheric pressure in air. Similarly, the hBN-cBN-Liquid triple point is shifted from 3500 K/9.5 GPa to as low as 2800 K and atmospheric pressure. It is shown that nanosecond laser heating of amorphous carbon and nanocrystalline BN on sapphire, glass, and polymer substrates can be confined to melt in a super undercooled state. By quenching this super undercooled state, we have created a new state of carbon (Q-carbon) and BN (Q-BN) from which nanocrystals, microcrystals, nanoneedles, microneedles, and thin films are formed depending upon the nucleation and growth times allowed and the presence of growth template. The large-area epitaxial diamond and cBN films are formed, when appropriate planar matching or lattice matching template is provided for growth from super undercooled liquid. The Q-phases have unique atomic structure and bonding characteristics as determined by high-resolution SEM and backscatter diffraction, HRTEM, STEM-Z, EELS, and Raman spectroscopy, and exhibit new and improved mechanical hardness, electrical conductivity, and chemical and physical properties, including room-temperature ferromagnetism and enhanced field emission. The Q-carbon exhibits robust bulk ferromagnetism with estimated Curie temperature of about 500 K and saturation magnetization value of 20 emu g−1. We have also deposited diamond on cBN by using a novel pulsed laser evaporation of carbon and obtained cBN/diamond composites, where cBN acts as template for diamond growth. Both diamond and cBN grown from super undercooled liquid can be alloyed with both p- and n-type dopants. This process allows carbon to diamond and hBN to cBN conversions and formation of useful nanostructures and microstructures at ambient temperatures in air at atmospheric pressure on practical and heat-sensitive substrates in a controlled way without need for any catalysts and hydrogen to stabilize sp3 bonding for diamond and cBN phases.

Performance of carbide tools coated with DLC in the drilling of SAE 323 aluminum alloy

Abstract The development of new coatings in the last years contributed to the improvements of machining industry. In general, it is known that the performance of drilling tools increases with the application of a proper coating, and it is worth remembering that the adhesion is an important condition for the success of any coating. This work presents a performance of cemented carbide cutting tool coated with diamond-like carbon (DLC). The deposition of the coating used in this study has been done using plasma enhanced chemical vapor deposition system. Suitable adhesion between film and the substrate did not occur in the initial deposition parameters tested. To enhance adhesion of the film, an intermediate silicon layer has been added. To evaluate this adhesion, VDI 3198 standard adhesion test was used. Spectra analyses collected using Raman backscattering spectroscopy have been used to characterize the composition and structural information of the film. The silicon layer was evaluated using atomic force microscopy. Drilling tests were performed using workpieces casting in aluminum alloy (SA-323) and roundness, radial deviation, deviation of diameter and roughness of geometries changes were measured as a function of the number of holes produced. The results showed that the DLC coating improves the tool performance, which subsequently improves the drilling quality.

Microbiological and compositional features of green stains in the glaze of the Portuguese “Great View of Lisbon” tile panel

The “Great View of Lisbon” is one of the most remarkable blue-and-white Portuguese tile panels, which depicts the city before the tragic earthquake of 1755. This panel presents visible colored alteration in the glaze of tiles both from the exhibition and the depository of the Museu Nacional do Azulejo (Portugal). This work is a contribution to identify the origin of green stains in the glaze by using microbiological techniques, scanning electron microscopy with back-scattered electron imaging (SEM-BSE), Raman spectroscopy, and proton-induced X-ray emission (PIXE). The microbiological assays showed that the filamentous fungi were detected only at a frequency <10 % of the microbiota of tiles surface, and the microbial entities from the green stains cultures were identified as Aspergillus fumigatus by molecular biology techniques. However, no microorganisms or other biological elements were found by SEM-BSE in the green stains. Raman spectroscopy and PIXE results showed that the green stains appear to be related with the presence of chromium atoms in the outer part of the glaze. Eskolaite, a “green pigment” used before 1850 AD was clearly identified by Raman spectroscopy in the darker green stains. Nevertheless, no chromium oxide signatures were identified in the lighter green stains by Raman spectroscopy.

Extended photoresponse of ZnO/CdS core/shell nanorods to solar radiation and related mechanisms

We report the study on the influences of shell thickness and core–shell structure on the optical properties of ZnO/CdS core/shell nanorods (NRs) for an elucidation of the mechanisms responsible for the extended photoresponse of ZnO/CdS core/shell NRs to solar radiation. Well aligned ZnO/CdS core/shell NRs were fabricated on indium tin oxide substrates using hydrothermally grown ZnO NRs as the cores and pulsed laser deposited CdS coatings as the shells. The sample structure was characterized by X-ray diffraction and Raman backscattering spectroscopy, revealing the wurtzite structure of both the ZnO cores and CdS shells, and the improvement in the structure after annealing. The optical properties were studied through optical transmittance, absorbance and photoluminescence measurements, showing the optical properties featured with type-II heterogeneous nanostructures constructed from ZnO and CdS. The results provide a support that the optical properties of the CdS covered ZnO NRs are attributed to the suppressed radiative recombination of photogenerated carriers due to the efficient spatial separation of electrons and holes in the nanosized ZnO–CdS heterostructures.

Diamond synthesis in aluminum matrix in molten alkali-halide at ambient pressure

The interaction of the molten aluminum with the carbon-containing admixture in a molten halide-alkali medium at atmospheric pressure with temperatures of 700–800°С under strong non-equilibrium conditions is studied. Cubic diamond crystals of 2–100μm and nanorods of 20–100nm diameter and 5μm lengths are first found forming inside the aluminum matrix under certain cooling regimes. The X-ray diffraction analysis, electron backscatter diffraction spectroscopy, electronic microscopy, Raman spectroscopy and microhardness detection register the perfect cubic diamond formation inside aluminum without applying of high temperature and high-pressure. Diamond formation mechanism is growing by carbon atom diffusion through an aluminum droplet. Diamond and nanodiamond synthesis conducted directly at the carbon ion interaction with the molten metal volume and subsequent cooling regimes. Prime novelty statementDiamond synthesis has been performed in molten aluminium via the interaction between molten aluminium and carbide-containing halide melt at 700–750°C with ambient pressure.The X-ray diffraction analysis, electron backscatter diffraction spectroscopy, electronic microscopy, Raman spectroscopy and microhardness detection register the perfect cubic diamond formation inside aluminium without high temperatures and high-pressure regimes.

Effects of Lattice Relaxation on Composition and Morphology in Strained In x Ga1−x As y Sb1−y Epitaxial Layers

InxGa1−xAsySb1−y is an important semiconductor material for a variety of mid-infrared devices. Its tunable bandgap, adjustable lattice constant, and other material properties make it appealing for developing optoelectronic devices in the 2 μm to 4 μm region. In this work, we report on the mechanisms of strain relaxation in InxGa1−xAsySb1−y epitaxial layers with low arsenic and high indium concentrations grown on GaSb (100) substrates. Samples were grown via solid-source molecular beam epitaxy with indium mole fractions between x = 0.1 (0.7% lattice mismatch) and x = 0.4 (2.5% lattice mismatch), and arsenic mole fractions between y = 0 and y = 0.02. Sample thicknesses between 10 nm and 100 nm were produced in order to observe the progression of structure formation. Samples were monitored in situ via reflection high-energy electron diffraction and ex situ using scanning electron microscopy, energy-dispersive spectroscopy, Rutherford backscattering spectroscopy, backscattering Raman spectroscopy, and atomic force microscopy. Results suggest that strain relaxation occurs preferentially along the [011] direction, although some crosshatching is observed. A compositional gradient in the growth direction is also observed, suggesting preferential incorporation of gallium at strained interfaces in order to minimize strain energy.

Low Temperature Geometrically Confined Growth of Pseudo Single Crystalline GeSn on Amorphous Layers for Advanced Optoelectronics

The geometrically confined growth of highly crystalline semiconductor materials like Ge on amorphous layers (without epitaxial template) has been a challenge in materials science. The success of this technology, especially at low fabrication temperature can enable 3D Si photonics by building photonic devices on metal/interconnect layers, and enable inexpensive, high-throughput fabrication of devices such as tandem solar cell and thin-film transistor.Here we report that, by incorporating Sn into Ge, we are able to obtain highly crystalline GeSn thin film on amorphous substrates at low crystallization temperatures ranging from 340 to 464 ºC through enhanced crystallization from the Ge-Sn euetectic system, and are able to transform the material toward a direct band-gap material through band structure modification. A highly textured Ge0.91Sn0.09 is obtained from the sample with 9.5 at. % as-deposited Sn composition, which shows grain sizes up to tens of microns, as revealed by electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and Raman spectroscopy. EBSD confirms that most grain boundaries are either twin or low angle boundaries, which are benign to optoelectronic properties. Strikingly, the nucleation center distances range from 0.1 to 1 mm, orders of magnitude larger than common solid state crystallization, which indicates an exceedingly high grain growth rate vs. a low nucleation rate. As a result of this feature, we are able to fabricate geometrically confined pseudo single crystalline GeSn grain using patterning techniques. Another remarkable result is that 9 at.% Sn is incorporated substitutionally into Ge, far exceeding the equilibrium solubility limit of ~1%. The high Sn composition, with the addition of ~0.24% tensile strain in the film, shifts the direct band gap to 0.5 eV (2500nm), right on the verge of indirect-to-direct band gap transition. This transition will greatly enhance the material’s optoelectronic performance as a photonic device, and will also broaden the absorption spectrum for a tandem solar cell.

A Novel Approach for Subsurface Through-Skin Analysis of Salmon Using Spatially Offset Raman Spectroscopy (SORS)

In the present study, the possibility of employing spatially offset Raman spectroscopy (SORS) in the qualitative and quantitative characterization of quality parameters of salmon through the skin has been explored. A laboratory-based SORS setup comprising an 830 nm laser was employed, and intact samples and model samples made of salmon tissue constituents were used to investigate the penetration of Raman signals through the dark and light part of salmon skin. Intact salmon samples with both dark and light skin were measured at different spatial offsets. When using spatial offsets in the range of 5-6 mm, the results clearly show that information regarding fatty acid composition and carotenoid content could be obtained from both dark and light parts of the skin. Similar information could not be obtained using conventional backscattering Raman spectroscopy. Model samples of ground salmon spiked with either solutions of carotenoids or a range of vegetable oils were also measured, and at a spatial offset of 5 mm, a clear relationship between Raman carotenoid band intensities and carotenoid concentrations in the model samples was revealed. In addition, high correlations for the estimation of iodine values (i.e., fatty acid unsaturation) could be obtained for SORS measurements through light and dark parts of the salmon skin. A crude estimate suggested that information from around 5 mm beneath the surface area of the salmon skin could be obtained. The choice of a laser line in the near-infrared region is a major prerequisite for successful through-skin analysis of salmon. This feasibility study could pave the way for future Raman analysis of intact salmon.

Strain relaxation in graphene grown by chemical vapor deposition

The growth of single layer graphene by chemical vapor deposition on polycrystalline Cu substrates induces large internal biaxial compressive strain due to thermal expansion mismatch. Raman backscattering spectroscopy and atomic force microscopy were used to study the strain relaxation during and after the transfer process from Cu foil to SiO2. Interestingly, the growth of graphene results in a pronounced ripple structure on the Cu substrate that is indicative of strain relaxation of about 0.76% during the cooling from the growth temperature. Removing graphene from the Cu substrates and transferring it to SiO2 results in a shift of the 2D phonon line by 27 cm−1 to lower frequencies. This translates into additional strain relaxation. The influence of the processing steps, used etching solution and solvents on strain, is investigated.

Effect of thermal annealing on the physical properties of Zn1−x Cu x Se thin films deposited by close spaced sublimation technique

Thin films of Zn1−x Cu x Se (x= 0.00, 0.05, 0.10, 0.15, 0.20) were grown on glass substrates by closed space sublimation technique. The deposited films were annealed at 200 °C and 400 °C in air for 1 h. The annealed samples have been investigated through Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), spectroscopic ellipsometer, spectrophotometer and Raman spectroscopy. Through RBS, the composition of the films was calculated and compared with the initial concentration. Structural characterization including crystal structure, crystal orientation, lattice parameter, grain size, strain and dislocation density were carried out using XRD data. From XRD spectra it was revealed that the as-deposited and annealed films were polycrystalline in nature with zinc-blende structure. However, the crystallinity and the grain size were improved with the increase of annealing temperature. According to Raman spectroscopy, it was observed that as deposited and annealed samples have the same characteristic vibrational modes of ZnSe at low and high frequency optical phonon modes while another mode was observed for 400 °C annealed samples at 745 cm−1. Spectroscopic ellipsometer has been used to found annealing effect on the optical properties of ZnSe. The band gap energy has been determined using transmission spectra. It was found that the band gap energy of the film increased with the increase of annealing temperature.

Determination of the biaxial stress in strained silicon nano-stripes through polarized oblique incidence Raman spectroscopy

We report on the experimental determination of the biaxial stress characteristic of the strain state present in strained silicon nano-stripes on insulator structures. Conventional confocal backscattering Raman spectroscopy being insensitive to the tensorial nature of strain, a methodology based on the use of polarized oblique incidence backscattering Raman spectroscopy is employed. The stress component values thus obtained are compared with those provided by grazing incidence x-ray diffraction as a reference technique. By combining the oblique backscattering configuration with polarization control of the incident and scattered beams, an efficient method for the accurate measurement of biaxial stress in patterned silicon structures results.