Ellipsometry automatic

Returning to the basic equations for the surface tension 12.5.27 and 28 or 28a], we automatically ask how useful these are for predicting y for a given liquid. The answer is that for practical use these equations are not very suitable because the problem is translated into two esoteric sub-problems, viz. the measurement of the profile p (z) and the determination of van der Waals constant C. Determination of the profile is not simple. To that end optlcail methods such as ellipsometry and reflectivity measurements are needed, whose interpretation is not unambiguous because the profile cannot be obtained without making certain assumptions. We return to this in sec. 2.8. 

Ellipsometry is an old technique whose practical foundations were laid by Rayleigh in his experiments on reflection from liquids a hundred years ago. Its development as a routine tool in surface research received a boost in the mid-forties with the experiments of Rothen [17], but it was not until automatic recording instruments began to be available in the late sixties that its potential began to be realised. Single-wavelength instruments have been commercially available for some time, but spectroscopic instruments are only now moving out of the development laboratories on to the commercial scene. 

The thickness of the synthesized brashes was determined by means of ellipsometry performed on a COMPEL Automatic Ellipsometer (InOm Tech, Inc.) at a fixed 70o incidence angle. Refractive index for all polymers was asstrmed to be 1.5. Strrface characterization was performed by Scanning Probe Microscopy (SPM) in tapping mode on a Dimension 3100 microscope (Digital Irrstruments, Veeco ). Static contact angle measurements were made using a... 

A further type of fast automatic ellipsometer for electrochemical investigations has been described [933] and an experimental approach to observe fast transients with ellipsometry was reported [934]. In the photometric mode, the intensity of the reflected light is measured as a function of the position of polarizer and sometimes compensator in the incoming beam for further details and an overview, see [934]. A general overview of instrumental developments has been provided [935]. 

In 1960s, in order to reduce the time spending in angle calibration, H. Takasaki [11] used automation servomotor technology to drive polarizer and compensator and set the azimuth of polarizers automatically. However, in this configuration, it was still unavoidable to use human eye in the azimuth reading. Of course, the subsequent ellipsometry data processing was still involved in the human. So this type of ellipsometer was only a semi-automatic ellipsometer. 

Welin-Klinstroem et al used a null ellipsometer equipped with an automatic sample scanning device for studies of adsorption and desorption of fibrinogen and IgG at the liquid/solid interface on surface wettability gradients on silicon wafers. To follow the processes along the wettability gradient, off-null ellipsometry was used. The kinetics of adsorption and nonionic-surfactant-induced desorption varied considerably between fibrinogen and IgG. In the hydrophilic region, veiy little protein desorption was seen when a nonionic surfactant was used. 

This modified ellipsometry is the combined reflectance-ellipso-metry technique, also known as the three-parameter ellipsometry (TPE) in contrast to the conventional two-parameter ellipsometry. Since it was first introduced in 1971 by Paik and Bockris to study passivation film formed anodically on cobalt, TPE has proven to be a powerful technique for determining all three unknowns from purely optical measurements alone. The measurements for A, and R are made with the same experimental setup as for the conventional ellipsometer, with minor modifications of the measurement routine if necessary. Here, R is the reflectance at the same angle of incidence as for the A and if/ measurements. Therefore, no alignment change is necessary for additional measurement of R. With some automatic ellipsometers (see Section III.5), all three measurements can be recorded simultaneously. It should be emphasized once more that A, ij/, and R are mutually independent functions, despite the fact that both il/ and R are defined by combinations of and r. ... 

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