Optical film system design

Computer-aided optical film system design is to a large extent computer work and will therefore not be treated here in more detail. For practical application, a medium-sized or even small table model computer in which the system design refinement program - which may be commercially available - is recorded, is fed with the optical data of the substrate, the film and the adjoining medium as well as with the desired values of the spectral characteristics of, say, a reflection curve. 

This type of instrument is widely applied to measurements other than chemical composition, such as film thickness, turbidity, color, and optical rotation. The DuPont Company manufactures a versatile instrument, in modular form, that is used for all of these measurements. The same company also produces automated systems designed specifically for SOa, NO, and H2S/SO2 ratio, all of which are useful in stack-gas pollution control. Other manufacturers are Beckman Instruments, ITT Barton Co., and GEC-Elliot Ltd. (Hallikainen Instruments). 

Fig. 1.4. (a) Characteristic (H and D) curve of a mam-mographic screen-film system. Optical density (OD) of the processed film is plotted versus the log of the relative X-ray exposure to the fluorescent intensifying screen, (b) Characteristic response of a detector designed for digital mammography (from Pisano et al. 2004. With permission)... 

Thin films are integral parts of many micro-electro-mechanical systems designed to serve as sensors or actuators. For example, a piezoelectric or piezoresistive thin film deposited on a silicon membrane can be used to detect electronically a deflection of the membrane in response to a pressure applied on its surface or by an acceleration of its supports. Devices based on thin film technology are used as microphones in hearing aids, monitors of blood pressure during exercise, electronically positioned thin film mirrors on flexible supports in optical display systems, and probes for detecting the degree of ripeness of fruits. 

Currently, scaiming probe microscopy (e.g., atomic force microscopy) is often used for testing instead of optical and electron microscopes. A few advanced destructive techniques have been reported for the evaluation of nanostructured material. " However, they are still not good enough for the evaluation of a nanoscaled thin film system (such as electrochemically/electrolessly deposited metal films) owing to critical defects such as voids, delaminations, and debonding sites of the system which often exist in the interior. Therefore, microscopy designed for surface analysis may not be suitable for application to the system directly. 

An unusually extensive battery of experimental techniques was brought to bear on these comparisons of enantiomers with their racemic mixtures and of diastereomers with each other. A very sensitive Langmuir trough was constructed for the project, with temperature control from 15 to 40°C. In addition to the familiar force/area isotherms, which were used to compare all systems, measurements of surface potentials, surface shear viscosities, and dynamic suface tensions (for hysteresis only) were made on several systems with specially designed apparatus. Several microscopic techniques, epi-fluorescence optical microscopy, scanning tunneling microscopy, and electron microscopy, were applied to films of stearoylserine methyl ester, the most extensively investigated surfactant. 

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