Generalized rotating-compensator ellipsometry

The extension of rotating-compensator ellipsometry (RCE) to measurements of the system Jones matrix J of optical systems is reported. The similarities and differences of generalized RCE as compared to other methods are noted. Measurements of several anisotropic materials, as well as of “standard” optical systems having one, two and three essential (complex) elements of J are described. Finally, a completely automated procedure for the measurement and analysis of a uniaxially anisotropic surface with the optic axis in the plane of the surface is presented.     

Electrooxidation of pyrrole-terminated self-assembled lipoic acid derivatives

New pyrrole derivatives, pyrrolyl lipoic acid (Py-LA 3) and dipyrrolyl lipoic acid (Py₂-LA 2) have been used for surface attachment and immobilisation on gold surfaces, by self-assembly. The electrooxidation of the surface-confined pyrroles was analysed by cyclic voltammetry and the modified electrodes morphological and thickness changes addressed by scanning probe microscopy and ellipsometry. The data support the formation of oligomers as a result of the pendant-pyrrolyl units ease oxidation but provide no evidence of an effective subsequent polymerisation.     

Quantitative 2D exchange spectroscopy using time-proportional phase incrementation

We have used a version of 2D exchange spectroscopy which employs amplitude modulation during evolution to obtain pure absorption-mode exchange maps of several multisite systems. Quadrature detection in ω₁ is provided by 90° phase incrementation of the excitation pulse in concert with incrementation of t_i. The matrix A of normalized peak amplitudes is determined by the dynamic processes which occur during the mixing interval τ_m according to the rate matrix R, which contains chemical exchange and longitudinal relaxation terms. The R matrix may be directly calculated from A using an eigenvalue-eigenvector method. In principle all of the dynamic parameters of a spin system of any size may be calculated from a pair of phase-sensitive exchange spectra acquired with and without mixing. This approach distinguishes between direct and indirect (relay) couplings irrespective of mixing time. The principles and practical aspects of exchange spectroscopy with time-proportional phase incrementation are briefly discussed and the method is illustrated with the measurement of chemical exchange rates in three-site and five-site spin systems.     

Sensitivity analysis of vibrating systems

In this paper a method for the analysis of the sensitivity dynamical characteristics of mechanical linear systems to variations in the parameters is presented. The method presented has a general character and applies to conservative as well as non-conservative systems. In the method use is made of the Taylor formula for a matrix function of many variables, proved in reference [1]. Use of the result enables the sensitivity analysis to be carried out with parallel changes in all the parameters (M, C and K).The method is illustrated by a numerical example of a seven-degree-of-freedom system.     

非镜面膜的椭偏研究

本文提出了SnO_2:F绒面膜的三层膜模型;从表示平面波传播性质的界面矩阵和膜层矩阵出发,导出了三层膜系统的散射矩阵和总反射系数,建立了反射式椭偏术的基本公式;利用反射式椭偏光谱法,测得SnO_2:F绒面膜的厚度和色散关系.     

A perspective on ellipsometry

Two distinct and general definitions of ellipsometry and polarimetry are stated ab initio that account for the existing duality in usage of both terms. Ellipsometers and polarimeters are next defined accordingly. The definitions contrast these commonly used similar terms against one another. Viewed within the framework established by these general definitions, optical ellipsometry of interfaces and films (the main topic of this conference) is recognized as a narrow particularization of a broad scheme. Examples of ellipsometry (polarimetry) in different regions of the electromagnetic spectrum provide important perspective on the considerable extent of the field. Another perspective (in a different dimension) is gained when the application of ellipsometry (polarimetry) to different samples is considered. This relates ellipsometry of interfaces and films to polarimetry of bulk anisotropic samples and light scattering by systems of particles. Three individual procedures (namely, polarization measurement, application of electromagnetic theory, and computation) are identified as essential to the complete utilization of ellipsometry (polarimetry).     

Effects of band structure and matrix element on RKKY interaction

The effects of band structure and matrix elements on the RKKY interaction J(R) are separately investigated. When the Fermi surface has planes perpendicular to R, effects appear on the period of oscillation, the phase shift and the amplitude of J(R). The applicable region of the asymptotic form for large R and the validity of the free electron approximation are also examined. If there are no tangential planes perpendicular to R, it is found that: 1) when two interacting localized spins are on lattice points in the crystal, exponential damping appears even for the constant matrix element model and the matrix element effects introduce competing terms causing a sign change; 2) when one of the spins is at an interstitial position, the constant matrix model gives a weaker J(R) ∝ R^-2 damping, but the character of this term changes into the exponential damping by taking into account matrix elements.     

Ellipsometry study of interband transitions in TlGaS2xSe2(1−x) mixed crystals (0≤x≤1)

In this paper, the spectroscopic ellipsometry measurements on TlGaS_2xSe_2(1?x) mixed crystals (0≤x≤1) were carried out on the layer-plane (001) surfaces with light polarization E⊥c^? in the 1.2–6.2 eV spectral range at room temperature. The real and imaginary parts of the dielectric function, refractive index and extinction coefficient were calculated from ellipsometric data using the ambient-substrate optical model. The critical point energies in the above-band gap energy range have been obtained from the second derivative spectra of the dielectric function. Particularly for TlGaSe₂ crystals, the determined critical point energies were assigned tentatively to interband transitions using the available electronic energy band structure. The effect of the isomorphic anion substitution (sulfur for selenium) on critical point energies in TlGaS_2xSe_2(1?x) mixed crystals was established.     

Spectroscopic ellipsometry and polarimetry for materials and systems analysis at the nanometer scale: state-of-the-art, potential, and perspectives

This paper discusses the fundamentals, applications, potential, limitations, and future perspectives of polarized light reflection techniques for the characterization of materials and related systems and devices at the nanoscale. These techniques include spectroscopic ellipsometry, polarimetry, and reflectance anisotropy. We give an overview of the various ellipsometry strategies for the measurement and analysis of nanometric films, metal nanoparticles and nanowires, semiconductor nanocrystals, and submicron periodic structures. We show that ellipsometry is capable of more than the determination of thickness and optical properties, and it can be exploited to gain information about process control, geometry factors, anisotropy, defects, and quantum confinement effects of nanostructures.     

Application of spectroscopic ellipsometry to the investigation of the optical properties of cobalt-nanostructured silica thin layers

Spectroscopic ellipsometry is used to investigate optical properties of cobalt-implanted silica thin films. The films under investigation are 250 nm thick thermal SiO₂ layers on Si substrates implanted with Co⁺ ions at energy of 160 keV and at fluences of 10¹⁷ ions/cm² for different temperatures of substrate during implantation (77 and 295 K). Changes due to Co⁺ implantation are clearly observed in the optical response of the films. Optical behaviours are furthermore different for the three implantation temperatures. To understand the optical responses of these layers, the ellipsometric experimental data are compared to different models including interference effects and metal inclusions effects into the dielectric layer. The simulated ellipsometric data are obtained by calculating the interferences of an inhomogeneous layer on a Si substrate. The material within this layer is considered as an effective medium which dielectric function is calculated using the Maxwell-Garnett effective medium approximation. We show that although the structures of these layers are very complicated because of ion-implantation mechanisms, quite simple models can provide relatively good agreement. The possibilities of ellipsometry for the study of the optical properties of such clusters-embedded films are discussed. We especially provide the evidence that ellipsometry can give interesting information about the optical properties of nanostructured layers. This is of special interest in the field of nanostructured layered systems where ellipsometry appears to be a suitable optical characterization technique.     

On the problems of multiple overlayers in ellipsometry and a new look at multiple angle of incidence ellipsometry

In this paper we consider the effect of multiple overlayers on the ellipsometric parameters. We emphasize the substantial reduction in the computational problem provided by the transfer matrix formalism of Abelès. We are able to show that multiple angle of incidence ellipsometry may provide useful information even for thin overlayers, and we show how this information may be best extracted from measured data.     

Observation of a Kondo effect for a dilute alloy containing Sm impurities

Measurements of the depressions of the superconducting transition temperature T_c with Sm impurity concentration and the specific heat jump at T_c as a function of T_c, and the temperature dependences of the normal state specific heat and magnetic susceptibility are reported for the matrix impurity system (LaSm)Sn₃. The results constitute the first definitive evidence of a Kondo effect for a dilute alloy containing Sm impurities.     

Calculation of high-order rotational centrifugal-distortion matrix elements for a Hund's case (a) basis set

The derivation of explicit expressions for the Hund's case (a) matrix elements of R^2k is discussed, where R is the mechanical rotational angular momentum operator of the molecule. A recursion relation is developed that permits matrix elements of R^2k to be expressed in terms of those of R^2(k?1), thus affording a straightforward means of calculating the case (a) matrix elements of rotational centrifugal-distortion constants D_v, H_v, L_v, M_v, etc., to an arbitrarily high order. The explicit matrix elements of L_v are listed.     

Can multiband coupling effects due to remote bands cause significant normal-incidence absorption inn-type direct-gap semiconductor quantum wells?

Surprisingly, several experiments have reported that normal-incidence light absorption due to inter-conduction-subband transitions in direct-gap semiconductor quantum wells is as strong as in-plane-incidence absorption. In contrast to other models, a recent theoretical study claimed that a 14-bandk  pmodel including multiband coupling terms due toremote-conduction bandsis able to explain the experimental results. In this work, a concise formulation extends the model beyond 14 bands. Nevertheless, after rederiving the optical transition matrix elements, this analysis clearly shows that the oscillator strength for the in-plane polarized optical intersubband transition due to the multiband coupling effects is much smaller than the oscillator strength for the normal-to-plane polarized optical intersubband transition. These results indicate that the multiband coupling effects due to remote-conduction bands cannot cause a sufficient in-plane polarized optical intersubband transition to produce the observed normal-incidence absorption in the desirablen-type III–V compound semiconductor quantum wells.     

Application of longitudinal generalized magneto-optical ellipsometry in magnetic ultrathin films

The longitudinal generalized magneto-optical ellipsometry(GME) method is extended to the measurement of threelayer ultrathin magnetic films. In this work, the theory of the reflection matrix is introduced into the GME measurement to obtain the reflective matrix parameters of ultrathin multilayer magnetic films with different thicknesses. After that, a spectroscopic ellipsometry is used to determine the optical parameter and the thickness of every layer of these samples, then the magneto-optical coupling constant of the multilayer magnetic ultrathin film can be obtained. After measurements of a series of ultrathin Fe films, the results show that the magneto-optical coupling constant Q is independent of the thickness of the magnetic film. The magneto-optical Kerr rotations and ellipticity are measured to confirm the validity of this experiment. Combined with the optical constants and the Q constant, the Kerr rotations and ellipticity are calculated in theory. The results show that the theoretical curve fits very well with the experimental data.     

SPROM – an efficient program for NMR/MRI simulations of inter- and intra-molecular multiple quantum coherences

A software package has been designed to simulate nuclear magnetic resonance spectra and images. Combining the product operator matrix with the non-linear Bloch equations, the software can efficiently simulate classical and quantum effects including scalar coupling, dipolar coupling, translational diffusion, chemical shift, radiation damping, transverse relaxation, and longitudinal relaxation. One of the most unique features of the software is its ability to incorporate effects of inter- and intra-molecular multiple quantum coherences in complex multiple-spin coupled systems, which are difficult with other existing software packages. The software, written in Visual C++, has a friendly graphical user interface and is easy to use. To cite this article: C. Cai et al., C. R. Physique 9 (2008).     

X-ray photoelectron spectroscopy investigations of Si in non-stoichiometric SiNx LPCVD multilayered coatings

Si nanocrystals were formed in the non-stoichiometric Si-enriched SiN_x low-pressure chemical vapor deposited (LPCVD) coatings on Si wafers treated by various modes. The coating structure as a function of technological conditions was investigated by ellipsometry and X-ray photoelectron spectroscopy (XPS) depth profiling. It was found that nanocomposites on base of SiN_x films enriched by Si have a complex multilayered structure varying in dependence of deposition and annealing parameters. Analysis of the XPS spectra and Si 2s peaks shows the existence and quantity of four chemical structures corresponding to the Si–O, Si–N states, nanocrystalline and amorphous Si. The XPS results show evolution of the chemical structure of silicon nitride and formation of Si nanocrystals. It was found:

• The LPCVD technology of nanocrystals formation allows to get enough high concentration of Si nanocrystals on different depths from the sample surface.

• The volume fraction of nanocrystalline and amorphous Si is changed with depth; this relation depends from SiN_x composition and annealing parameters.

• XPS detects these two phase compositions of Si nanoparticles in SiN_x and SiO₂ layers. The ellipsometry, HR-TEM, and XPS results are in good agreement.

An investigation on the bonding in MgO,CaO, SrO and BaO from the MEM electron density distributions

The bonding in MgO, CaO, SrO and BaO has been studied using the electron density distribution maps obtained utilizing the reported X-ray data by the statistical approach maximum entropy method (MEM). The ionic/covalent nature of the bonding and the interaction between the atoms are clearly revealed by the maps. The bonding in these systems is shown two-dimensionally on the (100) and (110) planes and the one-dimensional electron density profiles along (100), (110) and (111) directions have also been plotted using MEM electron densities. The electron density at the saddle point between the ions has been estimated using these profiles and compared with the available reported results. The resolution of these maps is high and hence these maps can be regarded as the most precise electron density distributions seen inside the chosen materials. The electron content of the doubly ionic oxygen and the cations are estimated from the three-dimensional MEM electron densities by assuming spheres of various radii. The histograms drawn with [F_Mem(k)−F_Obs(k)]/σ(k) versus the number of reflections show the validity of the approach and the appropriateness of the Gaussian weighting scheme used in the analysis.     

Principal angle-of-incidence ellipsometry

In principal angle-of-incidence ellipsometry, or ?_P - K ellipsometry, one makes measurements of the principal angle of incidence, ?_P, and the imaginary part of the ellipsometric function ? for this angle of incidence, K, in place of Δ and tan ψ. The parameter K has often been referred to as the ellipticity at principal angle incidence. Following a discussion of the sensitivity of ?_P-K ellipsometry, the results obtained in recent years by ?_P-K ellipsometry are reviewed. A return-path type ellipsometer for use in ?_P-K ellipsometry is described, which requires no compensator and can be a powerful tool for spectroscopic ellipsometry.