Using reflectometry

Avena and Koopal (1999) used reflectometry to study the kinetics of adsorption of Aldrich humic acid on hematite. Uptake was fast (diffusion-controlled) at low pH, but slow at pH > 5. The rate of uptake rose with ionic strength above the iep, but decreased with ionic strength below the iep. The adsorption of humic acid onto hematite rendered its surface hydrophobic and made it a suitable sorbent for hydrophobic organic compounds (Murphy et al., 1992). 

Fig. 4. Comparison of the raw data from 49-point diameter, 21-point contour, and 9-point contour measurement patterns to 49-point polar pattern data, showing (a) mean and (b) the nonuniformity (standard deviation divided by mean in percentage) using reflectometry.

Using reflectometry, Barten etal. [259] have investigated adsorption of quater-nized poly-2-vinyl pyridine, of a fixed charge per monomer, on a gold electrode. The total adsorbed amount of the compound decreased linearly with the double-layer potential of gold. Adsorption proceeded up to a relatively high doublelayer potential and was accompanied by a relatively high contribution of nonelectro-static interactions. 

A novel method for wire fault location using reflectometry and iterative deconvolution, in... 

The adsorption behavior of bovine serum albumin (BSA) has been examined on a number of different surfaces. Van Enckevort et al obtained a plateau value of 2.1 mg m" for the adsorption of BSA from 0.02 g solutions onto stainless steel surfaces, measured by radiochemical techniques (Fig. 14). They found that the adsorbed protein was essentially nonexchangeable. Using reflectometry measurements, El-gersma et al have investigated the effect of pH in the range 4-8 on the adsorption behavior of BSA on polystyrene-covered silicon wafers, since pH can affect the electrical charge on the protein, which in turn affects its structural stability. The maximum plateau value for adsorption over the... 

These samples were measured non-destructively by energy-dispersive XRF with synclirotron radiation excitation (SYXRS), by g-XRF, by wavelength-dispersive XRF (WDXRS), and by Rutherford back scattering (RBS), by X-ray reflectometry (XRR) and by destructive secondary ion mass spectrometry (SIMS) as well (both last methods were used for independant comparison). 

A commonly used form of internal modulation is differential reflectometry, in which the reflectance of the sample under investigation (or a portion of it) is compared to a standard material. This can be accomplished either by holding the sample stationary and scanning the probe beam between two regions or by holding the l t spot fixed and moving the sample. ... 

Reflectometry is a useful probe with which to investigate the structure of multilayers both in self-supporting films and adsorbed on surfaces [51]. Specular X-ray reflectivity probes the electron density contrast perpendicular to the film. The X-rays irradiate the substrate at a small angle (<5 °) to the plane of the sample, are reflected, and are detected at an equal angle. If a thin film is present on the surface... 

More sophisticated methods that actually measure volumetric water content can also be used, such as time domain reflectometry (TDR). In Figure 14, an example of TDR results is presented. Both the calculated and measured (i.e., TDR) volumetric water contents provide a similar picture of the profile water status by depth with time. Proper soil characterization data, such as those shown in Table 6, are necessary for these calculations and improve understanding of the test system. The determination of water-holding capacity (WHC) at 0.03 MPa field capacity (FC) and 1.5 MPa... 

Figure 2 demonstrates the principles of reflectometry and reffactometry by using a waveguide with a refractive index that is higher by n2 than that of the environment (ni). Radiation incident to an interface between media with different refractive indices is reflected in part most penetrates the medium. The radiation is reflected and refracted in dependence on the angle of incidence and the ratio of refractive indices in the two media according to Snellius law... 

Time-domain reflectometry (TDR) involves the use of two or more substantial metal rods inserted into soil. The rods are parallel and are attached to a signal generator that sends an electrical input down the rods. The time it takes the signal to travel down the rods is dependent on the soil s apparent dielectric constant, which, in turn, is proportional to the amount of water in the soil. Upon reaching the end of the rods, the signal is dissipated and the amount of... 

Other near-IR applications which use similar pulse and phase instrumentation as used in lifetime measurements include optical time-domain reflectometry(25) and photon migration in tissue. 26 ... 

Fig. 2. Empirical and theoretical response spectra of a TEOS-TiN-Al stack using the reflectometry. The TiN and TEOS thicknesses are 250 and 10,000 A, respectively. The empirical and theoretical curves are matched within a tolerance.

In reflectometry, the light passes through the films to be measured. Beneath the transparent films, there must be an opaque substrate through which light does not pass. The substrate characteristics must be modeled correctly to calculate the thicknesses of the films above. In silicon processing, theoretically, any of the commonly used metal materials, such as the titanium nitride (TiN), aluminum (Al), and tungsten (W), can be used as substrates. However, in reality, whereas a PMD oxide can be measured on the polysilicon material used in poly interconnections, an ILD oxide can not be measured directly on TiN, because the TiN layer used is too thin to be opaque. TiN is semitransparent if its thickness is less than 1000 A. A thin... 

Since reflectometry is a major metrology tool in CMP processes, another important issue is the number of measurement points on the wafer that are required to determine the film thickness and uniformity without sacrificing cycle time. Table II presents a comparison of number of data points vs the measurement efficiency and accuracy using the polar map pattern on the... 

Numerous tests using strips that change colour when dipped into a medium represent current applications of colorimetry. However, the result obtained by visual examination of the reflected light is related to reflectometry more than to transmission colorimetry (see Fig. 11.18). These selective tests, which are ready to use and do not require an instrument, are complementary to established methods. Because they yield immediate results, they are useful for all sorts of semiquantitative analyses. 

In contrast to swollen homopolymer films, only a limited number of studies on thin films of block copolymers have been reported in which the degree of the film swelling has been directly accessed. In situ SE has been used to evaluate the polymer-solvent interaction parameters [144], to construct phase diagrams of surface structures [49, 51], and to control the mechanism of lamella reorientation in thick swollen films [118, 163, 164], Spectroscopic reflectometry combined with real-time GISAXS has been used to follow structural instabilities in swollen lamella films [165], Recently, it was demonstrated that swelling of diblock copolymer films in organic selective and non-selective solvents follows the same physical behavior as in thin films of homopolymers [119]. 

Hart, G. L., Lowery, B., McSweeney, K., and Fermanich, K. J. (1994). In situ characterization of hydrologic properties of Sparta sand Relation to solute travel using time domain reflectometry. 

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... 

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