Search

Amorphous Ge/SiO2 multilayers were deposited in a high vacuum by an e-gun assisted physical vapor deposition technique with continuous Ge layers either 2 or 4 nm thick, separated by 2 nm thick SiO2 layers. The aim was to explore whether annealing of these multilayers at a rather low temperature will produce Ge nanoparticles suitable for solar cell applications. All samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (ARM), transmission electron microscopy (TEM) in cross-section, grazing incidence X-ray diffraction, Raman spectroscopy and grazing incidence small-angle X-ray scattering (GISAXS). It is found that annealing of very thin continuous amorphous Ge layers will lead to mostly spherical crystalline nanoparticles (NPs) of the desired size. On the other hand, from thicker Ge layers, a bimodal distribution is obtained consisting of smaller sphere-like and larger oblate spheroids, as confirmed by a calculated simulation.

The silver (Ag) films were deposited on the monodispersed polystyrene spheres that were drop-coated on hydrophilic glass substrates in order to form a self-assembled 2D monolayer. Thus prepared Ag films over polystyrene nanospheres (AgFONs) were used to record the surface-enhanced Raman scattering (SERS) spectra of rhodamine 6G (R6G) and pyridine (λex = 514.5 nm). AgFONs were prepared by depositing 120, 180 and 240 nm thick Ag layer on the 1000 nm polystyrene spheres and 80, 120, 160 and 200 nm thick Ag layer on the 350 nm spheres as well as on their mixture (350 + 1000 nm). The silver was deposited by electron beam evaporation technique. The best enhancement of the Raman signal for both test molecules was obtained using 180 nm Ag film deposited on the 1000 nm spheres and using 80 nm Ag film deposited on the 350 nm polystyrene spheres. The lowest detectable concentrations of R6G and pyridine were 10−9 mol L−1 and 1.2 × 10−3 mol L−1, respectively. This study has shown that AgFONs could be regarded as good and reproducible SERS substrate for analytical detection of various organic molecules.

Photodynamic therapy (PDT) is a treatment that aims to kill cancer cells by reactive oxygen species, mainly singlet oxygen, produced through light activation of a photosensitiser (PS). Amongst photosensitisers that attracted the most attention in the last decade are cationic and amphiphilic molecules based on porphyrin, chlorin and phthalocyanine structures. Our aim was to join this search for more optimal balance of the lipophilic and hydrophilic moieties in a PS. A new amphiphilic porphyrin, 5-(4-octadecanamidophenyl)-10, 15, 20- tris(N-methylpyridinium-3-yl)porphyrin trichloride (5) was synthesised and characterised by 1H NMR, UV–vis and fluorescence spectroscopy, and by MALDI-TOF/TOF spectrometry. In vitro photodynamic activity of 5 was evaluated on HeLa cell lines and compared to the activity of the hydrophilic 5-(4- acetamidophenyl)-10, 15, 20-tris(N- methylpyridinium-3-yl)porphyrin trichloride (7). Low fluence rate (2 mW cm−2) of red light (643 nm) was used for the activation, and both porphyrins showed a drug dose-response as well as a light dose-response relationship, but the amphiphilic porphyrin was presented with significantly lower IC50 values. The obtained IC50 values for 5 were 1.4 μM at 15 min irradiation time and 0.7 μM when the time of irradiation was 30 min, while for 7 these values were 37 and 6 times higher, respectively. These results confirm the importance of the lipophilic component in a PS and show a potential for 5 to be used as a PS in PDT applications.

A simple and reliable e-gun assisted physical vapor deposition technique was used to deposit alternatively amorphous thin (2 nm) continuous layers of Ge and SiO2 in high vacuum. Our goal was to explore whether annealing of these multilayers in inert atmosphere at rather low temperature (525 °C) will produce isolated sphere-like Ge nanoparticles embedded in amorphous SiO2 matrix suitable for solar cell applications, and which analyzing technique will provide the most comprehensive information on this composite material. All samples were characterized by the following complementary techniques: grazing incidence X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM) and grazing incidence small-angle X-ray scattering (GISAXS). All techniques confirm Ge nanoparticles formation. It was demonstrated that GISAXS provides the most detailed description of the particle size and shape on a macroscopic scale.

The films consisting of gold nanoparticles, prepared by electron beam evaporation on glass substrates, exhibit interesting optical properties due to localized surface plasmon resonance. The tailoring of optical properties has been achieved by varying deposition mass thickness and substrate temperature. The relation between optical and structural properties has been studied. Optical characterization of samples has been carried out by variable angle spectroscopic ellipsometry and for structural characterization grazing incidence small angle X-ray scattering and atomic force microscopy have been used. Results show how the structural properties, obtained by using specific fabrication parameters, influence the resulting optical characteristics. The differences in concentration, shape and size of the produced gold nanoparticles result in a spectral shift of localized surface plasmon resonance, and a change of its width and intensity. The appearance of percolation is signed by Drude-like infrared absorption.

The annealing behavior of very thin SiO2/Ge multilayers deposited on Si substrate by e-gun deposition in high vacuum was explored. It is shown that, after annealing at moderate temperatures (800°C) in inert atmosphere, Ge is completely outdiffused from the SiO2 matrix leaving small (about 3 nm) spherical voids embedded in the SiO2 matrix. These voids are very well correlated and formed at distances governed by the preexisting multilayer structure (in vertical direction) and self-organization (in horizontal direction). The formed films produce intensive photoluminescence (PL) with a peak at 500 nm. The explored dynamics of the PL decay show the existence of a very rapid process similar to the one found at Ge/SiO2 defected interface layers.

Metal island films of noble metals are obtained by deposition on glass substrates during the first stage of evaporation process when supported metal nanoparticles are formed. These films show unique optical properties, owing to the localized surface plasmon resonance of free electrons in metal nanoparticles. In the present work we study the optical properties of gold metal island films deposited on glass substrates with different mass thicknesses at different substrate temperatures. The optical characterization is performed by spectroscopic ellipsometry at different angles of incidence and transmittance measurements at normal incidence in the same point of the sample. Fitting of the ellipsometric data allows determining the effective optical constants and thickness of the island film. A multiple oscillator approach was used to successfully represent the dispersion of the effective optical constants of the films.

Bimetallic islands films consisting of composite Au-Ag nanoparticles are deposited on glass substrates by electron beam evaporation. Broad tuning of the surface-plasmon resonance (SPR) characteristics can be achieved by controlling film composition, deposition temperature and post-deposition thermal annealing. Optical and structural characterization of the samples enable one to establish the link between the SPR and the morphological and compositional characteristics of nanoparticles.

The coatings having refractive index changing with the thickness present interesting optical performance, improved mechanical properties and smaller light scattering in comparison with classical multilayer stacks. Lot of theoretical work and experimental advances have been done for designing and production of mixture layers with such particular performances. The effective refractive index of the mixture coatings can be calculated by the use of effective medium theories. The refractive index profile characterization of inhomogeneous films that are mixtures of SiO 2 and Nb 2 O 5 is presented. The composition is linearly changed through the thickness of the layers. Ex-situ spectrophotometric measurements, i.e. reflectance and transmittance at different incidence angles, are used for the precise characterization of the refractive index profiles. Linear, Maxwell-Garnet, Bruggeman and Lorentz-Lorenz effective medium theories are applied and quality and differences of the results are studied and analyzed. It is shown that the Lorentz-Lorenz model is the most appropriate for the given mixture, suggesting components are well mixed and there are no separated phases.

We present a study on amorphous SiO/SiO 2 superlattice performed by grazing-incidence small-angle X-ray scattering (GISAXS). Amorphous SiO/SiO 2 superlattices were prepared by high-vacuum evaporation of 3 nm thin films of SiO and SiO 2 (10 layers each) onto Si(1 0 0) substrate. After the deposition, samples were annealed at 1100 °C for 1 h in vacuum, yielding to Si nanocrystals formation. Using a Guinier approximation, the shape and the size of the crystals were obtained. The size of the growing nanoparticles in the direction perpendicular to the film surface is well controlled by the bilayer thickness. However, their size varies more significantly in the direction parallel to the film surface.

Dark plasmon modes in metal nanoparticle systems are usually excited by non-optical means. We show that strongly focused illumination can lead to excitation of dark modes. We first use rigorous vectorial diffraction theory to compute the distribution of light at the focus and then numerically calculate the response of single particles and particle dimers. Controlling the distribution of light arriving at the focusing lens by pupil filters enables enhancing the excitation of dark modes. Overall, these results present guidelines for the excitation of dark plasmon modes using standard optical instrumentation.

We present a preliminary study of Ge island formation on Si(1 0 0) substrates using grazing-incidence small-angle X-ray scattering (GISAXS). Samples were prepared by high-vacuum evaporation of a 5 nm thick Ge layer on Si(1 0 0) substrate held at 200 °C. The samples were subsequently annealed at different temperatures for 1 h in vacuum, yielding to island formation. The Fortran program IsGISAXS was used for the simulation and analysis of Ge islands. The vertical cut (perpendicular to the surface) of the experimental 2D GISAXS pattern has been fitted using a Guinier approximation. The obtained parameters were used for the simulations. The simulated 2D GISAXS pattern well reproduce experimental data for cylindrically shaped islands with morphological parameters R = 4 nm , H / R = 0.25 and the average inter-island distance D = 5 nm .

In this work is studied the influence of annealing on metal island and compact Au films formed on the substrates with and without Ge seed layer. Samples with different thicknesses of Au were annealed at different temperatures. Optical characterization of the samples was performed based on ellipsometric measurements. The obtained results demonstrate that, even in the conditions of moderately elevated temperature, Ge seed layer promotes the percolation of metal islands.

Metal island films (MIF) are good candidates for sensors due to the strong sensitivity of the localised surface plasmon resonance to the environment refractive index. The strong near field enhancement in the vicinity of the island surface can be even higher if a metal layer (ML) is placed close to a MIF. Structures containing MIF with and without ML are prepared and sensitivities of spectrophotometric and ellipsometric features of the measurements are compared. It is shown that simple MIF is preferable for ellipsometry-based sensing and the one including ML in the case of spectrophotometric measurements.

A mathematical model for the heat deposition in tissue during the exposition to the red light, essential for the phototherapy, is presented. The comparison of model predictions with in vivo experimental data for the normal CBA/HZgr mice hind leg tissue is done in order to illustrate the domain of confidence of the theoretical model. The highest usable power of the light source, and consequently the lowest phototherapy treatment time with no influence upon normal tissue is determined.

Optical properties of metal island films (MIFs) can be combined with interference of dielectric coatings. A set of multilayer designs containing metal clusters reflecting different colours from front and back side of the coating was obtained by numerical optimization. The chosen designs presenting the range of feasible colours were deposited by electron beam evaporation. Spectrophotometric and ellipsometric measurements verified that the produced coatings present an excellent agreement with the optical performance calculated from the designs. Numerical optimization was verified as a useful method in designing of coatings containing MIFs. This approach can ease the implementation of metal clusters into multilayer designs and broaden the applications of MIFs.

Synthesis of buckminsterfullerene (C60) is highly simple and the mechanism of the molecule formation is quite well understood. It makes easier the search for the optimum conditions necessary for formation of massive fullerenes (more than 100 carbon atoms). The most popular graphite arc method has been used for fullerene synthesis in our laboratories. Other available methods, like laser ablation and E-gun evaporation, were not suitable for achieving of the convenient conditions. Results of the synthesis have been analyzed by laser desorption Fourier transform ion cyclotron resonance mass spectrometry (LD FT/ICR-MS). The conditions for massive fullerenes synthesis are discussed in the paper. The special care has been given to the LD FT/ICR-MS analysis. The importance of cooling gas during fullerene nucleation and growth in the very specific vacuum conditions is analyzed. The necessity for a thorough dynamic plasma diagnostic during the giant fullerenes growth is suggested.

The potential of random metal-dielectric nanocomposites as constituent elements of metamaterial structures is explored. Classical effective medium theories indicate that these composites can provide a tunable negative dielectric function with small absorption losses. However, the tuning potential of real random composites is significantly lower than the one predicted by classical theories, due to the underestimation of the spectral range where topological resonances take place. This result suggests that a random mixture consisting of a metal matrix with embedded isolated dielectric inclusions is a promising design guideline for the fabrication of tunable composites for metamaterial purposes.

Thin metal island films exhibit unique optical properties and possess a high potential in design and fabrication of multilayer coatings with sophisticated spectral performances over wide wavelength and angular ranges. Optical properties of these films are dependent on film thickness. In the present study we consider and solve a problem of designing multilayers which reflect different colors from their front and back sides and have specified average transmittance values. Additionally, in many cases the reflected colors are stable to variations of the incidence angle. In the design process we use optical constants of Ag metal island films, that were carefully determined based on recently proposed characterization approach.

The influence of the substrate temperature on the effective optical behavior ofAg-SiO 2 composites obtained by electron beam evaporation was studied. Optical characteriza-tion of the composites was performed by means of spectroscopic ellipsometry measurements.Theeffectivedielectricfunctionofthecomposites,modeledusingamultipleoscillatorapproach,could be widely tuned by controlling the deposition temperature. The spectral dependence ofthe composite absorption appeared to be better described with a Gaussian line shape than withthe classical Lorentz oscillator model. The description of the effective dielectric function usingstandard effective medium theories failed and the experimental results could be explained onlyin the general framework of the Bergman spectral density theory. C 2011 Society of Photo-OpticalInstrumentation Engineers (SPIE) . [DOI: 10.1117/1.3590238] Keywords: metal-dielectric composites; metal island films; surface plasmon resonance; opticalconstants; effective medium theory; spectroscopic ellipsometry.Paper 11015SSR received Jan. 28, 2011; revised manuscript received Apr. 15, 2011; acceptedfor publication Apr. 15, 2011; published online May 13, 2011.

A three-dimensional (3D) photonic microstructure consisting of metal clusters embedded in dielectric matrix is coated with a dielectric mirror. The produced photonic structure shows optical behaviour that combines the interferential effects of the multilayer stack and the surface plasmon resonance of metal clusters. Due to its feasibility and the possibility to widely modify the optical properties of the resulting interferential-plasmonic structure, this approach represents a promising method for the production of novel optical components.

We describe the optical properties of gold island films embedded between SiO2 and/or TiO2 layers. Plasmonic properties of gold films have been characterized using spectrometry and variable angle spectroscopic ellipsometry for various combinations of the embedding media. The obtained refractive indices of embedded gold island films have been used in the design of several types of multilayer reflectors.

Optical constants of thin metal films are strongly dependent on deposition conditions, growth mode, and thickness. We propose a universal characterization approach that allows reliable determination of thin metal film optical constants as functions of wavelength and thickness. We apply this approach to determination of refractive index dispersion of silver island films embedded between silica layers.

Metal island films show a characteristic absorption peak related to the surface plasmon resonance of free electrons. This kind of film can be used in absorbing coatings, together with dielectric layers. Such absorbing multilayer coatings, with and without the gradient of the silver mass thickness in metal island films throughout the coating, have been deposited by electron beam evaporation. It is shown experimentally that coatings with a gradient in the mass thickness of silver nanoparticles have higher absorption than equivalent nongradient coatings with the same total mass thickness of silver nanoparticles.

We describe the optical properties of gold island films embedded between SiO2and TiO2layers. Plasmonic properties of gold films have been characterized for various combinations of embedded media and used in design of reflectors.

Photodynamic therapy (PDT) is a noninvasive therapy for non-melanoma skin cancer. The aim of this study was comparison of efficacy between fractioned versus single dose illumination in photodynamic therapy (PDT) of actinic keratosis (AK) and Bowen's disease (BD). Fifty-one patients (36 AK and 15 BD) were treated with PDT They were randomly arranged in two treatment groups. Group one included 26 patients (20 AK and 6 BD) that, after five hours of incubation with 20% 5-ALA, were treated with a single illumination of 100 Jcm(-2) at fluence rate of 30 mWcm(-2). Group two included 25 patients (16 AK and 9 BD) that, after 16 hours of incubation with 20% 5-ALA, were treated with two light fractions (50 plus 50 Jcm(-2)) at same fluence rate with dark interval of two hours between fractions. Twenty-four weeks later, a treated area was incubated for four hours again with 5-ALA in order to detect occult areas of abnormal skin with possible remaining tumor tissue. In case of fluorescence, histological examination was performed. In the group one, fluorescence at the end of the session was absent in 19 (73%) or very weak in 7 (27%). Residual tumor was found in 15 (75%) AK and in 4 (66.6%) BD. In the group two, fluorescence at the end of second session was more intense; in one patient (4%) was absent, very weak in 5 (20%) and weak in 19 (76%) of patients. In this group histology revealed remaining tumor tissue in only 2 (12.5%) AK and 2 (22.2%) BD. Among the patients in the first group, the remaining tumor tissue was significantly bigger (p=0.005). The treatment response with clearing of tumor tissue was significantly higher in fractionated illumination than in a single dose illumination group. Fractionated illumination scheme with 16 hours of incubation separated by two hours dark interval significantly improves the therapeutic outcome in tumor eradication.

We present a study on amorphous SiO/SiO2 superlattice formation on Si substrate held at room temperature and annealed in the temperature range 600-1100 degrees C. Grazing-incidence small-angle X-ray scattering (GISAXS) and X-ray reflectivity were used to study such samples. Amorphous SiO/SiO2 superlattices were prepared by high vacuum physical vapor deposition of 4 nm thin films of SiO and SiO2 (10 layers each) from corresponding targets on silicon substrate. Rotation of the Si substrate during evaporation ensured homogeneity of the films over the whole substrate. We observed that the inhomogeneities introduced into the SiO and SiO2 layers during the deposition (evaporation) give rise to small angle scattering at lower annealing temperatures. After an initial SiO layer thickness reduction for 600 degrees C annealing, these thicknesses remain virtually unchanged up to 1000 degrees C, where they start to decrease again which leads to particle formation. Nevertheless, this compacting at low temperatures may lead to the seed formation in SiO layers that will facilitate later Si nanoparticles growth.

Metal island films (MIFs) of Ag on glass substrates were fabricated by the e-beam evaporation technique. The dependence of the surface plasmon (SP) absorption properties on the deposition mass thickness and substrate temperature was quantified. The structural and optical characterization of the MIFs, obtained using spectrometry, grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM) evidences the evolution of SP characteristics depending on the fabrication parameters: the red shift of the absorption peaks with the increase of deposition thickness accompanied by peak widening and the blue-shift of peaks with the increase of deposition temperature followed by the peak narrowing. These findings were explained by the differences in the concentration, shape and size of the obtained silver islands.

Metal island films show unique optical properties owing to the local surface plasmon resonance of islands free electrons. In the present study, the electric field assisted dissolution of clusters in metal island films is reported. Island films of Au, Ag, and Cu are deposited under different conditions by thermal evaporation and coated with thin dielectric layers. The samples are treated with the simultaneous application of an intense electric field and temperature, leading to the sample partial or total bleaching due to the dissolution of metal clusters in the films. Owing the facility of production of metal island films and the inexpensive technical requirements of the dissolution process, this approach suggests a novel path for the production of low-cost photonic structures.

A class of problem dealing with narrow-band reflectors under oblique light incidence has been selected, and a group of design procedures leading to satisfactory results is analyzed. Initially performance criteria and design restrictions are set. Various designs are then created and analyzed. Conclusions can then be drawn on the relative merits of the designs. Two different types of target function have been chosen. A global search for 50 or more layers with varied optical thicknesses between 0 and lambda/2 and a needle design method have been applied to the synthesis. Gradient and variable metrics have been used for further refinement. Results are compared, and it is shown that all the design methods used yield similar results for this problem. The issue of how to determine the best method is addressed.

The dissolution of metal clusters in metal island films by the simultaneous application of electric field and temperature is reported. The consequent fading of surface plasmon resonance greatly modifies the optical properties of the samples. The dissolution process is verified in island films of different metals, obtained under different conditions and covered by different dielectric materials, as well as on multilayer dielectric stacks showing interferential properties. The tailoring possibilities of the optical behavior of metal island films combined with the inexpensive technical requirements of this approach open up the possibility to produce low-cost photonic heterostructures.

The absorption coefficient of composite films consisting of niobia (Nb2O5) and silica (SiO2) mixtures is studied for photon energies around the band gap. The films were deposited by co-evaporation and their composition was varied by changing the ratio of deposition rates of the two materials. Both, as-deposited and thermally annealed films were characterized by different techniques: the absorption coefficient was determined by spectrophotometric measurements and the structural properties were investigated using infrared spectroscopy, transmission electron microscopy and X-ray diffraction. The correlation between the variations of absorption properties and film composition and structure is established. The absorption coefficients determined experimentally are compared with the results derived from effective medium theories in order to evaluate the suitability of these theories for the studied composites.

Summary Photodynamic detection (PDD) of skin tumours is based on the visualization of a fluorophores, with the ability to accumulate in tumour tissue, by the use of fluorescence imaging. Of particular importance is the application of δ-5-aminolaevulinic acid (ALA) that, through the process of biosynthesis causes formation of the protoporphyrin IX (PpIX). The PpIX has the ability of selective fluorescence after basal cell carcinoma (BCC) has been treated with ALA. Higher concentration of PpIX in tumour tissue compared to surrounding normal skin is the basis for PDD. Our contribution in this preliminary study is application of the independent component analysis (ICA) to extract the BCC spatial map, by processing fluorescent RGB image acquired under excitation with 405 nm light. Comparative performance analysis with other two widely used image processing methods: ratio imaging and optimal threshold based imaging, reveals that ICA produces BCC spatial map that is most consistent in term of diagnostic quality by both visual assessment and calculation of the BCC demarcation line. We believe this represents a solid basis for the design of a compact and low-cost multi-spectral fluorescence imaging system, capable for real time calculation of the skin tumour demarcation.

We have deposited a 12 nm thick Ge layer on Si(1 0 0) held at 200 °C by thermal evaporation under high vacuum conditions. Upon subsequent thermal annealing in vacuum, self-assembled growth of nanostructural Ge islands on the Ge layer occurred. Atomic force microscopy (AFM) and grazing incidence small-angle X-ray scattering (GISAXS) were used to characterize such layers. GISAXS measurements evidenced the formation of cylinder shaped structures upon annealing at 700 °C, which was confirmed by AFM measurements with a very sharp tip. A Ge mass transport from the layer to the islands was inferred by X-ray reflectivity and an activation energy of 0.40 ± 0.10 eV for such a process was calculated. © 2006 Elsevier B.V. All rights reserved.

We present a study on amorphous SiO/SiO 2 superlattice prepared by high vacuum physical vapor deposition of 4 nm thin films of SiO and SiO 2 (10 layers each) from corresponding targets on silicon substrate. After evaporation the samples were annealed at different temperatures in the 600 °C to 1100 °C range. The analysis of the 2D grazing-incidence small-angle X-ray scattering pattern has shown the existence of a clear Bragg peak due to the bilayer correlation in vertical direction. It is shown that annealing linearly reduces the thickness of the bilayer up to 1100 °C when the conversion to the SiO 2 phase is completed. The particles formed at that temperature are not completely spherical and their vertical correlation is maintained only partly. We attribute this bahavior to a not optimal control of the silicon diffusion within the ex SiO layer.

During the last few years, refractive index profiles are being studied more intensively. Several papers have been written about the use of optical methods, spectrophotometry, ellipsometry, together with reverse engineering, these have yielded interesting results. Here we study the differences of a ZrO 2 film grown on an amorphous substrate and that of a pre-evaporated layer of another material, Y 2 O 3 . In the first run, two glass substrates have been coated with an Y 2 O 3 layer. In the second run a bare glass substrate and the pre-coated Y 2 O 3 have been coated with a ZrO 2 layer. Each of the materials used had exactly the same growth conditions for all layers. The only difference was the nature of the substrates. The spectra of R and T of both samples have been used for the optical characterisation. Multisample analysis with gradual introduction of new parameters has been carried out. It was found that for the appropriate modelling of the layer, grown on the pre-coated substrate, introduction of an interface layer between the two materials was necessary. The refractive index profiles of both ZrO 2 layers have been determined and discussed.

We have studied the direct synthesis of nanoparticles formed by dual implantation of large and equal doses of Cd + S, Zn + Te, Cd + Te or Pb + Te ions into SiO2 substrate. Grazing incidence small angle X-ray scattering (GISAXS), transmittance measurements and Raman spectroscopy were used to investigate implanted composites. The 2D GISAXS patterns suggest the synthesis of nanoparticles already during ion implantation, performed either at 300 or at 77 K, while annealing at higher T causes an increase of the fraction and the average size of synthesized nanoparticles. After high-T annealing both optical methods detected nanocrystals of compound semiconductors CdS, ZnTe or CdTe through the appearance of the respective first optical gaps, Eg, in transmittance measurements and characteristic LO peaks in Raman spectra. It is proposed that at high ion doses a fraction of implanted atoms synthesize already during implantation into amorphous aggregates of compound semiconductor, which transform into crystalline nanoparticles after annealing. � 2003 Elsevier B.V. All rights reserved.

In some recent papers it was shown that ZrO2 single films can be modeled using inhomogeneous models. A similar modeling approach to analyze CeO2 layers has been used. Films have been produced using a standard reactive evaporation technique. Following the measurement results, obtained by normal incidence transmission and variable angle spectroscopic ellipsometry, reverse engineering of the monolayer with its sub-layers has been performed. Novel in this method is that no assumption of refractive index profile is needed. A very good fit of the experimental data with the reverse engineered multi-layers has been obtained, showing that it is possible to find a fine substructure of analyzed films.

Single crystal CZ Si samples were implanted with hydrogen ions to the dose of 2E16 He ions/cm 2 at room temperature and subsequently annealed in vacuum in the temperature interval from 100 to 900 °C. The aim of the experiment was to determine the conditions for bubble formation within the solid film, which may have important technological application. Defects produced in such samples were studied by deep-level transient spectroscopy (DLTS) and electron paramagnetic resonance (EPR) spectroscopy. It is shown that high dose hydrogen implantation produces vacancy-related and silicon selfinterstitial clusters. The latter are thought to be responsible for the formation of the weak displacement field. The annealing at higher temperatures creates multivacancy-related clusters responsible for the strong displacement field formation.

There is a considerable current interest in polycrystalline silicon material grown in ribbon form because of the significant potential for reduced solar cells application. However, if this potential is to be realized, it is essential to understand much more about the impurities and other defects present in the source material. Of the particular importance are impurities and other defects present in the source material. Of the particular importance are intrinsic point defects population in such samples due to their influence on the electronic properties of material. However, a study intrinsic point defects behavior is additionally complicated due to their interaction with the present impurities and different structural defects. Experiments were performed on EFG polycrystalline silicon material rich with carbon and different structural defects such as dislocations and various grain boundaries. Samples were irradiated with gamma-rays from Co60 source and 2 MeV electrons to the doses of 300 Mrad and 10^16 el/cm^2, respectively, to introduce simple point defects into the bulk material. The result obtained with DLTS spectroscopy showed a significant difference between electron ang gamma-rays irradiation. The results are discussed in the light of intrinsic-extrinsic point defects irradiation.

At the Laboratory for Precise Measurements of Length, currently the Croatian National Laboratory for Length, unique nano-roughness calibration standards were developed, which have been physically implemented in cooperation with the company MikroMasch Trading OU and the Rudee Boskovic Institute. In this paper, a new design for a calibration standard with two measuring surfaces is presented. One of the surfaces is for the reproduction of roughness parameters, while the other is for the traceability of length units below 50 nm. The nominal values of the groove depths on these measuring surfaces are the same. Thus, a link between the measuring surfaces has been ensured, which makes these standards unique. Furthermore, the calibration standards available on the market are generally designed specifically for individual groups of measuring instrumentation, such as interferometric microscopes, stylus instruments, scanning electron microscopes (SEM) or scanning probe microscopes. In this paper, a new design for nano-roughness standards has been proposed for use in the calibration of optical instruments, as well as for stylus instruments, SEM, atomic force microscopes and scanning tunneling microscopes. Therefore, the development of these new nano-roughness calibration standards greatly contributes to the reproducibility of the results of groove depth measurement as well as the 2D and 3D roughness parameters obtained by various measuring methods.

In the present study we determine the optical parameters of thin metal–dielectric films using two different characterization techniques based on nonparametric and multiple oscillator models. We consider four series of thin metal–dielectric films produced under various deposition conditions with different optical properties. We compare characterization results obtained by nonparametric and multiple oscillator techniques and demonstrate that the results are consistent. The consistency of the results proves their reliability.

Deep trap levels in the semi-insulating SI CdZnTe detector material were characterized by simultaneous multiple peak analysis based on thermally stimulated current TSC measurements. In our TSCs that have been published previously electron hole pairs were created through the use of proton beam irradiation. Charge carriers were captured in deep traps and afterward released by thermal emission, which was recorded in the 90– 300 K range. We showed that the obtained TSC spectra could be well fitted with a unique set of 14 different deep traps, which were all simultaneously and completely characterized. The obtained trap data are in good accordance with earlier deep trap characterizations of the other authors obtained on similar SI CdZnTe materials using different methods.

Aminopropylsilanetriol (APST) is one of the most frequently used organofunctional silane coupling agents. This molecule also emerges through the hydrolysis of other alkoxysilanes as a product of hydrolysis. Because of its two functional groups located at the opposite molecular sites, it can react with organic polymers as well as with inorganic substrates and fillers. Its functionality greatly depends on the conformation of the molecule through the number of the available OH and NH bonds. Amorphous pirogenic silica Aerosil 200 is frequently used as nanofiller for rubbers and different plastics. It reduces the sedimentation rate, strengthens the elastomers and disperses well in polymeric matrices. Silica nanoparticles have silanol groups at the surface and siloxane bonds inside the particles. The SiOH groups at the surface of the neighboring particles interact through hydrogen bonds creating three dimensional lattice like structure. In order to get hydrophobic silica and to prevent nanoparticles to interact among themselves their surface is frequently modified with organosilane compounds. In this work we investigate different structures that were formed in APST-SiO2 mixtures with different contents of silica nanoparticles. Two kinds of mixtures were prepared. In the first one the SiO2 nanoparticles were mixed in 25% water solution of APST. The second mixture was prepared from the APST that has already been solidified by slow evaporation of water, and then again dissolved in water. This procedure enabled us to get some oligomeric structures of APST with reduced number of available OH bonds. Thus obtained structures were then investigated by micro-raman spectroscopy and monitored by SEM.