Spectral ellipsometry

Band gaps in semiconductors can be investigated by other optical methods, such as photoluminescence, cathodoluminescence, photoluminescence excitation spectroscopy, absorption, spectral ellipsometry, photocurrent spectroscopy, and resonant Raman spectroscopy. Photoluminescence and cathodoluminescence involve an emission process and hence can be used to evaluate only features near the fundamental band gap. The other methods are related to the absorption process or its derivative (resonant Raman scattering). Most of these methods require cryogenic temperatures. 

In this work the studies of optical characteristics, including photoluminescence and optical conductivity a(E) of the C6o and Cd-C6o films with different radiation doses by argon ions with the energy of 0,3 keV are carry ouied. The films of fullerenes C6o and Cd-C6o with the admixture of the C70 molecules ( 10 mass %) are precipitated out to the substrates from the stainless steel (temperature of the substrate was equal to 473 K) during the vacuum sublimation [7]. Photoluminescence was studied with the laser excitation with a wavelength of 514,5 nm [8], Optical conductivity was measured with the use of a method of spectral ellipsometry [9-10],... 

Spectral Ellipsometry Surface Plasmon Resonance Spectroscopy Ultramicroporous Polymer... 

In this study, for an accurate understanding of the interaction behaviour of the ultramicroporous polymer Makrolon, as a receptor, under the influence of three alcohols is investigated by three transduction methods Spectral ellipsometry (SE), RIfS and SPR. 

In Spectral Ellipsometry, changes in the state of polarisation of white light upon reflection at surfaces are monitored. This enables separation of the refractive index and physical thickness by modelling of a layer system. To handle correlations between layer thickness and refractive index, adequate layer thicknesses have to be guaranteed to avoid physically unreasonable solutions of the fitting due to local minima. 

All sensitive layers were prepared from solutions of Makrolon in mixtures of chloroform and dichlorobenzene by a spin-coating process. By adjustment of the rotation speed and time the thickness of the layers were varied between 35 nm and 455 nm. Layer thicknesses and refractive indices were determined by spectral ellipsometry. Furthermore the polymer thicknesses were verified by a surface profilometer (Alpha Step 500, Tencor Instruments, Mountain View, USA). 

The interaction behaviour of the homologous alcohols methanol, ethanol and 1-propanol and the ultramicroporous polymer Makrolon was investigated by three different optical methods spectral ellipsometry, surface plasmon resonance and reflectometric interference spectroscopy. 

Fig. 2 Relative change in the refractive index (gray squares) and relative change in the physical thickness (open cycles) of a Makrolon layer of 170 nm during exposition to different concentrations of 1-propanol, measured by spectral ellipsometry...

Fig. 12. Refractive indices (n) and absorption (/c) of film of PIC 2-18 in the monomeric (a) and J-aggregated (b) form as functions of dispersion measured by spectral ellipsometry...

If measuring equipment for ORD and CD (Section 16.3.7.2) is combined with a reflection system, either ellipsometry at one wavelength or spectral ellipsometry can be carried out at defined angles (Fig, 23). In this apparatus, a rotating polarizer is used to produce rotating plane-polarized light. After reflection, an analyzer is used to meas-... 

Ch. Striebcl. A. Brecht. G. Gauglitz "Characterization of Biomembranes by Spectral Ellipsometry. Surface Plasmon Resonance and Interferometry with regard to Biosensor Application. in Biosen. Bio-eiectr.. 9(1994) 139. 

The STG was cast from alx 10 3 M solution into which the mirror had been immersed for from 10 to 20 min (see Appendix 1). The presence of a monolayer was confirmed by ellipsometry (18 A). The spectral data agreed with data gathered on a similar system in a powder form. In this case, CuzO powder was immersed in a 0.01 M solution of isooctyl thioglycolate (OTG) in isopropanol for from 1 to 10 min, washed with pure isopropanol, dried in air, and analyzed via infrared transmission in a KBr dispersion pellet (see Appendix 2). A similar spectral shift of approximately 15 cm 1 (1739— 1724 cm-1) was observed and the lack of two distinct carbonyl absorbances suggested the formation of a monolayer. In both cases, the formation of a copper-mercaptoester salt may be responsible... 

Finally, n was determined by spectroscopic ellipsometry. The main drawback with this technique when applied to anisotropic samples is that the measured ellipsometric functions tanlF and cos A are related both to the incidence angle and the anisotropic reflectance coefficient for polarizations parallel and perpendicular to the incidence plane. The parameters thus have to be deconvolved from a set of measurements performed with different orientations of the sample [see (2.15) and (2.16)]. The complex refractive index determined by ellipsometry is reliable only in the spectral region where the sample can be considered as a bulk material. In fact, below the absorption... 

A chemical sensor is a device that transforms chemical information into an analytically useful signal. Chemical sensors contain two basic functional units a receptor part and a transducer part. The receptor part is usually a sensitive layer, therefore a well founded knowledge about the mechanism of interaction of the analytes of interest and the selected sensitive layer has to be achieved. Various optical methods have been exploited in chemical sensors to transform the spectral information into useful signals which can be interpreted as chemical information about the analytes [1]. These are either reflectometric or refractometric methods. Optical sensors based on reflectometry are reflectometric interference spectroscopy (RIfS) [2] and ellipsometry [3,4], Evanescent field techniques, which are sensitive to changes in the refractive index, open a wide variety of optical detection principles [5] such as surface plasmon resonance spectroscopy (SPR) [6—8], Mach-Zehnder interferometer [9], Young interferometer [10], grating coupler [11] or resonant mirror [12] devices. All these optical... 

With ellipsometry the polarization state of reflected radiation rather than just its intensity, is experimentally determined. Ellipsometry is not so much another experimental technique but a more thorough variety of the traditional ones, whether external or internal reflection. Two results per resolution element, namely the ellipsometric parameters (cf. Eq. 6.4-17) and A, are derived independently from the measurements. These can further be evaluated for the two optical functions of the medium behind the reflecting surface or other two data of a more complex sample. In any case there is no information necessary from other spectral ranges as it is for Kramers-Kronig relations. In comparison to the conventional reflection experiment, ellipsometry grants more information with a more reliable basis, e.g. since no standards are needed. 

The main point to be made here is that the phase shift data obtained from spectral interferometry has two contributions surface motion and optical effects. These two contributions to the phase versus time data can be separated by performing these experiments at two angles of incidence and two polarizations, at technique we term ultrafast d3mamic ellipsometry. The optical effects during shock breakout in nickel films were hidden because they produce phase shifts of the same sign as that caused by surface motion. Ultrafast dynamic ellipsometry allowed that contribution to be measured [71]. In our experiments on bare metals, the observed optical effects are due to changes in the material s complex conductivity under shock loading. We will see below that this is only one of several kinds of optical effects that can be observed in these and other materials. 

Growth of multilayer periodic Z nS/ZnSe h eterostructures b y m etallorganic c hemical vapor deposition, their optical properties examined by ellipsometry and traditional spectroscopy are described. The results obtained evidence that the structures proposed are promising as efficient Bragg reflectors for blue semiconductor lasers. Reflection coefficient higher than 90% in the blue-green spectral range have been obtained. 

In situ FTIR " also had to overcome serious difficulties in its application to electrochemical problems. Unlike ellipsometry, where the wavelengths used are in a region of low solvent absorbance, IR is strongly absorbed by most familiar organic solvents and most particularly by water. This leads inevitably either to thin-layer cells or the development of internal reflection techniques. The former has the advantage of simplicity in interpreting spectral data, but it severely limits the type of electrochemistry that can be carried out. The latter requires not only a suitable high-refractive index substrate, such as Ge or Si, but also an adherent very thin layer of metal as the electrode. Technically this is difficult to fabricate so that the metal layer is continuous, and a substantial lateral resistance is inevitable. 

The capabilities and value for money of instrumentation and desktop computing power continue to improve apace, which combine to make ellipsometry more accessible and powerful. Recent significant improvements include the use of CCD spectral detectors at a reasonable cost, making spectroscopic ellipsometry a more viable technique. 

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