Spectroscopic Ellipsometry (spectroscopic + ellipsometry)

Distribution by Scientific Domains
Distribution within Physics and Astronomy

Kinds of Spectroscopic Ellipsometry

  • angle spectroscopic ellipsometry
  • variable angle spectroscopic ellipsometry


  • Selected Abstracts


    Optical properties of TiO2 thin films prepared by chemical spray pyrolysis from aqueous solutions

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
    R. Ayouchi
    Abstract Titanium dioxide (TiO2) is known to have three different kinds of polymorphous crystalline forms: rutile, anatase, and brookite. The rutile phase is always formed at higher temperatures, while the anatase phase is formed at lower temperatures and transformed into rutile phase above 800 C. Various deposition techniques have been developed for depositing TiO2 thin films, including evaporation, sputtering, chemical vapour deposition and thermal oxidation of titanium. Among them, the Chemical Spray Pyrolysis (CSP) technique has many advantages, such as good conformal coverage, the possibility of epitaxial growth and the application to large area deposition. Also, this method is low cost and it is easy to control the deposition growth parameters. In the present work, TiO2 thin films have been deposited on p-Si (001) and fused silica substrates by Chemical Spray Pyrolysis (CSP) method from aqueous solution containing titanium (IV) isopropoxide (Ti[OCH(CH3)2]4. As-deposited thin films show anatase polycrystalline structure, and rutile phase formed for films annealed at 750C. SEM images have confirmed a smooth and crack-free surface with low surface roughness. X-ray photoelectron spectroscopy (XPS) combined with 4 keV Ar+ depth profiling has shown that crystallized films correspond to TiO2. Residual carbon coming from the organic precursor solution is only detected at the surface of the film. Thin films deposited on fused silica were highly transparent (more than 85%), with an indirect optical band gap of 3,43 and 3,33 eV for as-deposited and annealed films, respectively, and refractive indexes in the range between 2.01,2.29. Spectroscopic Ellipsometry (SE) also has been used to extract optical parameters. SE data fitted to triple-layer physical model revealed the same tendency to increase refractive index in annealed films. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Ellipsometric studies of diamond like carbon films prepared by PECVD using pulsed DC power supply

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008
    D. K. Rai
    Abstract Diamonds like carbon (DLC) films were deposited by DC and pulsed DC glow discharge plasma enhanced chemical vapor deposition technique (PECVD). High deposition rates and uniform thin film were obtained using pulsed DC PECVD glow discharge deposition technique. The optical and surface properties of these films were investigated using transmission spectroscopy, spectroscopic Ellipsometry and atomic force microscopy. Fourier transform infrared spectroscopy was employed to examine the compositional properties and sp3/sp2 ratio in our films. Phase modulated Spectroscopic Ellipsometry (SE) in wide range of 300-1650 nm was used to determine the complex refractive index ( (,) = n (,) +ik (,)) using Forouhi-Bloomer amorphous model in the analyses of SE data. The extracted parameters are reported. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Cu underpotential deposition on Au controlled by in situ Spectroscopic Ellipsometry

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008
    Mirko Prato
    Abstract We have studied Cu electrodeposition on well defined Au films using real time Spectroscopic Ellipsometry (SE). SE allows to discriminate the under-potential (UP) and over-potential (OP) regimes. In the UP regime, tiny yet reproducible variations of , and , parameters indicate the formation of two phases with slightly different optical behavior. The phase at the largest coverage is assigned to a Cu monolayer. The SE response in the OP regime shows a marked dependence on the potential scan rate. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Ultra-thin silicon solar cell: Modelling and characterisation

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008
    L. Danos
    Abstract An ultra-thin crystalline silicon solar cell with an active silicon layer of 200 nm has been fabricated and fully characterised electrically (I-V characteristic, spectral response) and optically (Variable Angle Spectroscopic Ellipsometry). Interference effects were observed in the spectral response of the cell due to multiple reflections from the layers within the cell. A mathematical model was developed to account for the different reflections and transmission within the cell which reproduced excellently the essential features of the experimental spectral response. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Sulphur passivation of GaSb, InGaAsSb and AlGaAsSb surfaces

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2007
    E. Papis
    Abstract The effects of electrochemical treatment in either 21%(NH4)2S-H2O or 16%Na2S-C3H7OH solutions on the surface properties of GaSb, In0.23Ga77As0.18Sb0.82 and Al0.34Ga0.66As0.025Sb0.975 have been investigated by complementary use of Variable Angle Spectroscopic Ellipsometry (VASE) and X-ray Photoelectron Spectroscopy (XPS). We have shown that electrochemical sulphuration enables to produce 94,350 nm thick insulating overcoats with good surface morphology. The main components of the passivating layers are Ga2S3 and Sb2S5when formed on GaSb, while additional components of In2S3, admixture of Al2O3 and appearance of Al-As bond were observed on InGaAsSb and AlGaAsSb, respectively. The main feature distinguishing the effect of electrochemical treatment in Na2S,C3H7OH when comparing to those in (NH4)2S-H2O is that passivating layers contain additional components of Na2SO3 and/or Na2SO4. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Spectroscopic Ellipsometry as a Tool for Damage Profiling in Very Shallow Implanted Silicon

    PLASMA PROCESSES AND POLYMERS, Issue 2 2006
    Iordan Karmakov
    Abstract Summary: Ion implantation is still one of the key steps in Si integrated circuit technology. Spectroscopic Ellipsometry (SE) detects the defects created in the implanted Si. The successful application of SE for damage profiling depends on the quality of the algorithm used for evaluating the damage profile from SE data. In this work, we present retrieved SE damage depth profiles by our previously published algorithm in the as-implanted Si with very low energies Ge+ ions- from 2 keV to 20 keV and 1 keV B+ ions (1,,1015 cm,2). The comparisons of the SE retrieved damage depth profiles with experimental atomic concentration depth profiles, or simulated by the state-of-the-art computer ATHENA code of Silvaco TCAD suits were made. The functional relation was obtained by proper fitting of measured by SE a/c depths, and the depths named "ends of damage" with the experimental or simulated ions concentration depth profiles. For reasons not understood, the damage profile of 5 keV Ge+ in c-Si is smoother in shape beyond the a/c depth, with a longer tail. The damage profiles measured by SE for 5 keV Ge+ in c-Si with two different doses: curve 1 - for 6,,1013 cm,2 and curve 2 - for 1,,1015 cm,2. Curve 3 - presents the damage profile simulated by ATHENA for Ge+ ions with 5 keV; 1,,1015 cm,2. [source]


    Growth and optical characterization of Cd1- xBexSe and Cd1- xMgxSe crystals

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 4-5 2005
    F. Firszt
    Abstract Cd1- xBexSe and Cd1- xMgxSe solid solutions were grown from the melt by the high pressure Bridgman method. Optical, luminescence and photothermal properties of these materials were investigated. Spectroscopic ellipsometry was applied for determination of the spectral dependence of the complex dielectric function (E) and refractive index n(E) at room temperature in the photon energy range 0.75-6.5 eV for samples with optic axis (c-axis) perpendicular to the air-sample interface. The critical point (CP) parameters for E0 and E1 transitions were determined using a standard excitonic CP function to fit the numerically calculated differential spectra ,2,2/,E2. The dispersion of the refractive index of the alloys was modelled using a Sellmeier-type relation. The values of fundamental and exciton band-gap energies were estimated from the ellipsometric and photoluminescence measurements. The origin of luminescence in Cd1- xBexSe and Cd1- xMgxSe was discussed. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Optical anisotropy of A - and M -plane InN grown on free-standing GaN substrates

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010
    P. Schley
    Abstract Wurtzite A - and M -plane InN films were grown by molecular beam epitaxy (MBE) on free-standing GaN substrates. Spectroscopic ellipsometry (SE) in the photon energy range from 0.56 up to 15,eV was applied in order to determine the ordinary and extraordinary complex dielectric function (DF) of InN. A distinct optical anisotropy was found over the whole energy range. The extraordinary absorption edge in comparison to the ordinary one is shifted to higher energies confirming previous studies. The investigations in the upper vacuum-ultraviolet (VUV) spectral range (9.5,15,eV) yielded transition energies for four critical points (CPs) of the band structure (BS) which have not been observed so far. [source]


    Spectroscopic ellipsometry of SrTiO3 crystals applied to antiferrodistortive surface phase transition

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2010
    Alexandr Dejneka
    Abstract This work is devoted to the ellipsometric study of antiferrodistortive (AFD) ,,, cubic-to-tetragonal phase transition (PT) of SrTiO3 surface. Strong influence of surface defect structure on magnitude and temperature evolutions of surface refractive index related to PT was found and investigated. It is shown that even small surface imperfections result in enhancement and strong changes of the surface refractive index when approaching the temperature of PT. This effect is caused by emergence and evolutions in the surface of the structural changes corresponding to order parameter at the temperatures sufficiently higher than transition temperature in the bulk. In the case of structurally perfect crystal surface, the features of the temperature dependence of surface refractive index appeared to be very small and visible at the temperatures a little smaller than transition temperature for bulk that agrees well with predictions of Kaganov,Omel'yanchuk theory. [source]


    Optical investigation of CuPc thin films on vicinal Si(111)

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010
    Li Ding
    Abstract CuPc thin films were grown on the hydrogenated vicinal Si(111) surfaces by organic molecular beam deposition (OMBD). Spectroscopic ellipsometry was employed to determine the refractive index (n) and extinction coefficient (k). Furthermore, the ratio of the out-of-plane to the in-plane absorption intensity provides the average tilting angle of molecules in the film. Reflectance anisotropy spectroscopy (RAS) shows the optical anisotropy of CuPc thin films induced by the vicinal Si(111) surfaces, which indicates the in-plane orientation of molecules. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Determination of critical points on silicon nanofilms: surface and quantum confinement effects

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2008
    Emmanouil Lioudakis
    Abstract In this work, we present a comprehensive study of the optical properties of nanocrystalline silicon films with thickness varied from 5 to 30 nm. Spectroscopic ellipsometry is employed to determine the dielectric functions of these films using a structural two-layer model based on the rigorous Airy formula. Our investigation gives an important insight of the origin of critical points for direct and indirect gaps of nanocrystalline silicon films as well as the evolution of them with decreasing the film thickness. The influence of the quantum confinement effect due to the nanoscale grain size and the surface vibrations at the interface on the optical properties are examined in detail. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Spectroscopic ellipsometry and vector network analysis for determination of the electromagnetic response in two wavelength regions

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008
    C. kerlind
    Abstract In this work, spectroscopic ellipsometry and vector network analysis are used to determine the electromagnetic response of three samples, an epoxy polymer, a sample with ferrit-based nanoparticles in a polymer matrix and silicon, in the wavelength ranges 0.4-30 ,m and 0.75-7.59 cm. Both methods measure amplitude and phase changes due to interaction with a sample and can be used to measure the full complex-valued dielectric response to electromagnetic radiation. The data from the two methods show similar levels of the response at the two ends of the spectral gap between the ranges of the two methods. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Spectroscopic ellipsometry and ellipsometric porosimetry studies of CVD low-k dielectric films

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008
    P. Marsik
    Abstract Aurora ELK, a porous low-k SiCOH film deposited by CVD, was used to study the effect of UV curing. Samples were cured for various curing times and the purpose of this work is to observe the effects of UV curing on optical, mechanical and structural properties of the low-k film. We have used 1) ellipsometric porosimetry to determine the porosity and the pore-size distribution and 2) nitrogen purged UV ellipsometry in a range from 2 to 9 eV to observe the changes of the dielectric function of the cured material. Additional FTIR and laser-induced surface acoustic wave measurements were performed. The porogen removal and the increase of porosity were observed, and a k-value of 2.3 was reached for the optimum curing time. However for longer curing times, densification and reduction of the porosity occurs. The growth of the hydrogen incorporation has been observed. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Characterisation of Cd1,x,yZnxBeySe crystals by spectroscopic ellipsometry and luminescence

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006
    A. A. Wronkowska
    Abstract Optical and luminescence properties of Cd1,x,yZnxBeySe solid solutions grown in the composition range 0 < x < 0.15 and 0 < y < 0.30 by the high pressure Bridgman method are reported. Spectroscopic ellipsometry was employed for determination of spectral dependence of the complex dielectric function ,(E), refractive index n(E) and absorption coefficient ,(E) in the photon energy range 0.75,6.0 eV. The dispersion of the refractive index of the alloys was modelled using a Sellmeier-type relation. The excitonic band-gap energies were estimated from the ellipsometric and photoluminescence measurements. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Polytype control and properties of AlN on silicon

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
    V. Cimalla
    Abstract In this paper we report on the optical and structural characterisation of cubic polytype AlN thin films on 3C-SiC/Si(111) pseudo-substrates prepared by carbonisation. We have found that 3C-AlN phase can be stabilised on the "waved" 3C-SiC(111) surface by polytype replication. On the other hand, 2H-AlN was grown on atomically smooth surfaces. X-ray diffraction and transmission electron microscopy imply that the cubic AlN was grown along with hexagonal inclusions up to 20%. Spectroscopic ellipsometry in the infrared region show the typical phonon lines for the two polytypes. The appearance of the TO phonon at 646 cm,1 confirms the existence of 3C-AlN. In the ultraviolet region the critical points in the band structure were identified. For 3C- and 2H-AlN the first direct transition at the ,-point was determined to be at 5.74 eV and 6.16 eV, respectively. No indirect transition at lower energies was detected. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Ellipsometric studies of diamond like carbon films prepared by PECVD using pulsed DC power supply

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008
    D. K. Rai
    Abstract Diamonds like carbon (DLC) films were deposited by DC and pulsed DC glow discharge plasma enhanced chemical vapor deposition technique (PECVD). High deposition rates and uniform thin film were obtained using pulsed DC PECVD glow discharge deposition technique. The optical and surface properties of these films were investigated using transmission spectroscopy, spectroscopic Ellipsometry and atomic force microscopy. Fourier transform infrared spectroscopy was employed to examine the compositional properties and sp3/sp2 ratio in our films. Phase modulated Spectroscopic Ellipsometry (SE) in wide range of 300-1650 nm was used to determine the complex refractive index ( (,) = n (,) +ik (,)) using Forouhi-Bloomer amorphous model in the analyses of SE data. The extracted parameters are reported. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Development of InN metalorganic vapor phase epitaxy using in-situ spectroscopic ellipsometry

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005
    M. Drago
    Abstract Metalorganic vapor phase epitaxy of InN layers on sapphire was studied in-situ by spectroscopic ellipsometry (SE), ex-situ atomic force microscopy and optical microscopy. Surface morphology has been largely improved by using nitrogen instead of hydrogen as carrier gas during sapphire nitridation. Using the sensitivity of in-situ SE with respect to roughness we established a new growth procedure with low V/III ratio (104) at high temperature (580 C) and growth rates as high as 350 nm/h, leading to improved electronic layer properties and allowing for growth of comparably thick layers. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Spectroelectrochemical Sensing Based on Multimode Selectivity Simultaneously Achievable in a Single Device.

    ELECTROANALYSIS, Issue 5 2007

    Abstract Quaternized poly(4-vinylpyridine) (QPVP) has been incorporated as an anion exchanger into sol-gel derived silica films for use in a spectroelectrochemical sensor. The preparation, characteristics and performance of these films are described. The films, which are spin-coated onto the surface of a planar optically transparent electrode, are optically transparent and uniform. Scanning electron microscopy and spectroscopic ellipsometry have been used to examine film structure, thickness and optical properties. These films have been shown both spectroscopically and electrochemically to preconcentrate ferrocyanide, a model analyte for the sensor. The films can be regenerated for multiple measurements by exposure to 1,M KNO3. The effects of polymer molecular weight and storage conditions on film performance are described. The overall response of this film is comparable to the poly(dimethyldiallylammonium chloride)-silica films previously used for this sensor. [source]


    Optical properties of InN grown on Si(111) substrate

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010
    E. Sakalauskas
    Abstract A comprehensive characterization of the optical properties of wurtzite InN films grown by molecular beam epitaxy on Si(111) substrates is presented. Two types of films are investigated in this work: InN on AlN/Si(111) and InN on GaN/AlN/Si(111). Their properties are compared to a layer deposited on GaN/sapphire substrate. The dielectric function (DF) is obtained from spectroscopic ellipsometry (SE). The infrared studies yield the plasma frequency and thus the electron density, while the interband absorption is probed between 0.56 and 9.8,eV. For InN grown on Si(111) substrate, the absorption onset is slightly shifted to higher energies with respect to the InN film grown on GaN/sapphire which can be attributed to higher electron concentrations. Despite this, strongly pronounced optical transitions due to critical points of the band structure are found in the high-energy part of the DF. It emphasizes the already promising quality of the InN films on silicon. Band-gap renormalization (BGR), band filling, and strain are taken into account in order to estimate the intrinsic band gap of wurtzite InN. For the InN layers on silicon, we get a band gap between 0.66 and 0.685,eV. [source]


    Spectroscopic ellipsometry studies of Mg-doped ZnO thin films prepared by the sol,gel method

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009
    Shenghong Yang
    Abstract Zn1,xMgx O (ZMO) thin films with x = 0, 0.1, 0.2, and 0.3 were prepared on Si(100) substrates by the sol,gel method. The influence of Mg content on the structural and the optical properties was studied by X-ray diffraction and spectroscopic ellipsometry (SE) in the UV,visible region. The measured SE spectra were analyzed with an appropriate procedure to accurately determine the thickness and the optical constants of the thin films. It was found that the optical constants of the ZMO films are functions of the film composition. The refractive indices of the ZMO films decrease with increasing Mg content, and the optical bandgap energy exhibits nonlinear behavior or a bowing effect with the change of Mg mole fraction. A maximum band gap of ,3.91 eV was achieved at x = 0.3. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Monitoring critical dimensions of bidimensional gratings by spectroscopic ellipsometry and Mueller polarimetry

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008
    M. Foldyna
    Abstract In this work we characterized two bidimensional gratings consisting each of a square array of square holes etched in a photoresist layer deposited on silicon. Data were taken on both samples with a spectroscopic UV,VIS ellipsometer (SE) operated at 70 incidence and zero azimuth (with the incidence plane parallel to the lines of holes) and a VIS Mueller matrix polarimeter (MMP) at various incidence and azimuthal angles. The robustness of the parameters derived from the MMP data was evaluated from the stability of the values provided by regression the spectra taken at different angles. The optimal measurement geometries, featuring high sensitivity and low correlation of the fitting parameters, were determined theoretically, and validated experimentally with the sample featuring wider holes (500 500 nm), for which 45 incidence provided better results than the usual 70 value. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Observation of interfacial electrostatic field-induced changes in the silicon dielectric function using spectroscopic ellipsometry

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008
    J. Price
    Abstract This work investigates the capability of spectroscopic ellipsometry to measure charge trapping centers in thin dielectric films. Specific interfacial electrostatic fields, induced by electrons injected into charge trapping states at the interface, have been identified that directly affect the underlying silicon substrate critical points. The effect of a field-induced change in the silicon fundamental absorption edge due to different processing conditions affecting the oxygen vacancy defects at the interface is presented. Measuring the field-induced change in the silicon dielectric function between a sample with a 2 nm HfO2 film as-deposited and the same sample after a 1000 C anneal in an N2 ambient reveals that a stronger interfacial field is present for the as-deposited HfO2 film. These results are consistent with the understanding that high temperature anneals work well to passivate oxygen vacancy defects at the silicon/HfO2 interface. Finally, we compare our results with Second Harmonic Generation where specific resonant features are identifiable with electric field enhancements at the same interface. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Spectroscopic ellipsometry study of thin diffusion barriers of TaN and Ta for Cu interconnects in integrated circuits

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008
    S. Rudra
    Abstract The objective of this work is to study the optical and electrical properties of tantalum nitride and tantalum barrier thin films used against copper diffusion in Si in integrated circuits using spectroscopic ellipsometry in the VUV and UV,visible range. Single layers of tantalum nitride and bilayer films of Ta/TaN were produced by reactive magnetron sputtering on Si(100) substrates covered with a native oxide layer. Ellipsometric measurements were performed in the energy range from 0.73,8.7 eV and the dielectric functions were simulated using Drude,Lorentz model and effective medium approximation (EMA) in order to obtain information regarding film thickness, film composition, free carrier plasma energy, mean relaxation time and electrical resistivity. The film thickness clearly affects the electrical resistivity and the electron mean free path. It was observed that for films of Ta on TaN even after maintaining the deposition condition suitable for the ,-phase of Ta, it turned out to be a mixture of ,- and ,-phases with higher contribution of the ,-phase. It is shown that even a very small intermixture of two different phases of Ta can be determined accurately using ellipsometry. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Influence of Sn doping upon the phase change characteristics of Ge2Sb2Te5

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 14 2004
    K. Wang
    Abstract The influence of Sn doping upon the phase change characteristics of Ge2Sb2Te5 alloys has been investigated using four-point-probe electrical resistance measurements, grazing incidence X-ray diffraction (XRD), X-ray reflectometry (XRR) and variable incident angle spectroscopic ellipsometry (VASE), a static tester and atomic force microscopy (AFM). For a Ge2Sb2Te5 alloy doped with 4% Sn, two transition temperatures are observed in the temperature dependent sheet resistance measurements at 125 C and 250 C, respectively. The evolution of structures upon annealing, investigated by XRD, reveals that the first transition is caused by the crystallization of the amorphous film to a NaCl-type structure, while the second transition is related to the transition to a hexagonal structure. The density values of 6.02 0.05 g cm,3, 6.38 0.05 gcm,3 and 6.42 0.05 gcm,3 are measured by XRR for the film in the amorphous, NaCl-type and hexagonal structure, respectively. Ultra-fast crystallization, which is correlated with a single NaCl-structure phase and the reduced activation barrier, is demonstrated. Sufficient optical contrast is exhibited and can be correlated with the density change upon crystallization. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Optical properties of monodispersive FePt nanoparticle films

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 13 2004
    S. J. Lee
    Abstract The optical properties of monodispersive FePt nanoparticle films were investigated using spectroscopic ellipsometry in the energy range of 1.5 to 5.5 eV. The monodispersive FePt nanoparticle film was stabilized on a Si substrate by means of an organosilane coupling film, resulting in the formation of a (Si/SiO2/APTS/FePt nanoparticles monolayer) structure. Multilayer optical models were employed to study the contribution of the FePt nanoparticles to the measured optical properties of the monodispersive FePt nanoparticle film, and to estimate the optical properties of the FePt nanoparticle layer. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Preparation and optical properties of amorphous and crystalline BLT thin films grown on SiO2/Si(100) substrates by a CSD process

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2004
    Ziping Cao
    Abstract Amorphous and crystalline Bi3.25La0.75Ti3O12 thin films deposited on SiO2/Si(100) substrates have been prepared by a chemical solution deposition (CSD) process. X-ray diffraction shows that the crystal structure is a bismuth-layered perovskite structure with some preferred (117) orientation. The refractive indices and extinction coefficients of the amorphous and crystalline films were obtained by spectroscopic ellipsometry as a function of photo energy in the range from 1.8 to 4.0 eV. The dispersion of refractive indices was fitted by the Wemple,Didomenico single electronic oscillator dispersion mode. An interesting exponential absorption was found in the amorphous and crystalline BLT films, which may be ascribed to the substitution of lanthanum for bismuth. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Valence-band splitting and optical anisotropy of AlN

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2010
    G. Rossbach
    Abstract The dielectric function (DF) of hexagonal AlN on Si(111) is determined in the range between 1 and 9.8,eV by spectroscopic ellipsometry (SE). Due to its large negative crytal-field splitting wurtzite AlN features large dichroism. Showing that SE is sensitive to both components of the DF around the absorption edge, a uniaxial model is applied which yields transition energies for the free excitonic state. The in-plane tensile stress leads to a red-shift of these transitions and to an enlarged splitting. The experimental data are compared to the results of band-structure calculations demonstrating excellent overall agreement. In addition, two high-energy critical points in the ordinary DF were determined at energies of about 7.75 and 8.85,eV. [source]


    Identification of van Hove singularities in the GaN dielectric function: a comparison of the cubic and hexagonal phase

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2009
    C. Cobet
    Abstract We present a detailed analysis of interband transition structures in the dielectric function of GaN. The dielectric function of the stable wurtzite and the metastable zinc blende phase were determined by means of synchrotron spectroscopic ellipsometry in the spectral range between 3 eV and 20 eV where the most significant structures of the dielectric function are located. In the hexagonal case, both the ordinary and extraordinary dielectric tensor component was measured on GaN films with M -plane/[1 00] orientation. In a comparative discussion of the two hexagonal tensor components and the zinc blende dielectric function, all prominent absorption structures were assigned to specific interband transitions at high symmetry points in the Brillouin zone. The assignment considers the individual dipole transition probabilities depending on the crystal symmetry and the geometry of the measurement. Furthermore, a detailed theoretical band-to-band analysis of dielectric function features, published by Lambrecht et al. [1], was considered. In conclusion, we suggest a new labeling of absorption structures as used in classical III,V materials like GaAs, which reflects the origin of transition structures from specific points in the respective Brillouin zones. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Assessment of phonon mode characteristics via infrared spectroscopic ellipsometry on a -plane GaN

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006
    V. Darakchieva
    Abstract Generalized infrared spectroscopic ellipsometry was applied to study the vibrational properties of anisotropically strained a -plane GaN films with different thicknesses. We have established a correlation between the phonon mode parameters and the strain, which allows the determination of the deformation potentials and strain-free frequency of the GaN A1(TO) mode. These results are compared with previous theoretical and experimental findings and discussed. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Optical properties of ZnS:Mn nanocrystals

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010
    F. Ahmed
    Abstract The optical properties of Mn-doped zinc sulfide (ZnS) nanocrystals embedded in SiO2 matrix are studied by spectroscopic ellipsometry (SE). The crystals are obtained by sequential multi-energy ion implantation of Zn, S, and Mn into a silica layer grown on Si(111) followed by a subsequent annealing for 30 min at 900 C. The formation of the nanocrystals is evidenced by transmission electron microscopy. The application of a critical-point based model for the analysis of the SE data yields die dielectric function (DF) between 0.6 and 6.5 eV. A pronounced shift of the absorption edge towards higher energies is detected for the nanocrystals In comparison to bulk ZnS ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]