Thin-Film Properties

The technological importance of thin films in snch areas as semicondnctor devices and sensors has led to a demand for mechanical property infonnation for these systems. Measuring the elastic modnlns for thin films is mnch harder than the corresponding measurement for bnlk samples, since the results obtained by traditional indentation methods are strongly perturbed by the properties of the substrate material. Additionally, the behaviour of the film under conditions of low load, which is necessary for the measnrement of thin-film properties, is strongly inflnenced by surface forces [75]. Since the force microscope is both sensitive to surface forces and has extremely high depth resolntion, it shows considerable promise as a teclnhqne for the mechanical characterization of thin films. 

E. Pugh and T. O. Mohr, Thin Films Properties of Ferromagnetic Films, ASM, Metals Park, Ohio, 1963, Chapt. 7. 

PZN-PT, and YBa2Cug02 g. For the preparation of PZT thin films, the most frequently used precursors have been lead acetate and 2irconium and titanium alkoxides, especially the propoxides. Short-chain alcohols, such as methanol and propanol, have been used most often as solvents, although there have been several successful investigations of the preparation of PZT films from the methoxyethanol solvent system. The use of acetic acid as a solvent and chemical modifier has also been reported. Whereas PZT thin films with exceUent ferroelectric properties have been prepared by sol-gel deposition, there has been relatively Httle effort directed toward understanding solution chemistry effects on thin-film properties. 

As we have seen, the orientation of crystallites in a thin film can vary from epitaxial (or single crystalline), to complete fiber texture, to preferred orientation (incomplete fiber texture), to randomly distributed (or powder). The degree of orientation not only influences the thin-film properties but also has important consequences on the method of measurement and on the difficulty of identifying the phases present in films having multiple phases. 

Several aspects of polymer thin films have thus been investigated while many others are still unexplored. These include structural and conformational aspects where polymer thin film properties are theoretically well-treated but experimental data are generally missing. However, with further development of experimental techniques this area might become accessible in the near future. 

Table IV. Examples of Thin Film Property Modification By Ion Bombardment During Deposition...

Peng, R. Xia, C. Peng, D. Meng, G. 2004. Effect of powder preparation on (Ce02)o.8(Sm203)o.i thin film properties by screen-printing. Mater. Lett. 58 604-608. 

Table 14. Unoriented thin film properties of poly(arylene ether benzimidazole)s...

CHANGES IN THIN FILM PROPERTIES AS A FUNCTION OF INCORPORATION OF LOW MOLECULAR WEIGHT SURFACTANT IN THE ADSORBED PROTEIN LAYER... 

Yoon, M.-H., Facchetfi, A., Stem, C.E. and Marks, T.J. (2006) Fluorocarbon-modified organic semiconductors Molecular architecture, electronic, and crystal tuning of arene- versus fluoroarene-thiophene oligomer thin-film properties. Journal of the American Chemical Society, 128, 5792-801. 

Acoustic wave (AW) devices are ideally suited to thin film characterization due to their extreme sensitivity to thin film properties [10]. The sensitivity of AW devices to a variety of film properties (see Chapter 3), such as mass density, viscoelasticity and conductivity, makes them versatile characterization tools. The ability to rapidly monitor changes in device responses resulting from changes in thin film properties permits their use for monitoring dynamic processes such as film deposition, chemical modification (e.g., photo-polymerization, corrosion), and diffusion of species into and out of films. 

In this chapter, we explore the current and potential future applications of AW devices for materials characterization and process monitoring. Because of the limited mass of material that can be applied to the AW device surface, the majority of these applications deal with the chemical and physical characterization of thin-film properties. This thin film focus should not be thought of as a limitation of AW devices, but rather as a useful capability — the direct measurement of properties of materials in thin-film form. Since material properties can depend on the physical form (e.g., film, bulk) of the material (see Section 4.3.1.3), AW devices are uniquely suited to directly characterize thin-film materials. These considerations also indicate that even though it is possible to use AW thin-film data to predict bulk material properties, such extrapolations should be performed with care. 

In conclusion, the results presented in this chapter demonstrate the extreme versatility of AW devices for the characterization of materials. The inherent sensitivity of AW properties to the mechanical and electrical properties of thin films can be used to advantage to directly monitor a wide variety of film properties. Since the properties and behavior of thin-film materials can be very different from those of similar bulk materials, this ability to directly measure thin film properties can be a significant advantage in materials research and development. The ability to use thin films instead of bulk samples has the added advantage that the time required to perform an evaluation of dynamic processes such as diffusion and corrosion can be greatly decreased. The number of applications of AW devices to thin-film characterization continues to increase, and is limited only by the ingenuity of AW device researchers and developers. 

Radiation damage Superconductivity of bombarded metals Variations of thin film properties Simulation of radiation damage e.g. in nuclear power plants Radiation Chemistry Ion sputtering Ion reflection Radiation decomposition of gases... 

Insertion of impurities Superconductivity of bombarded metals Variations of thin film properties Wear, friction and lubrication of materials Wear, friction and lubrication of materials Chemical state of implanted atoms Reactivity of ion-bombarded surfaces Reactivity of ion-bombarded surfaces Ionization phenomena Charge exchange studies... 

Surface acoustic waves (SAW), which are sensitive to surface changes, are especially sensitive to mass loading and theoretically orders of magnitude more sensitive than bulk acoustic waves [43]. Adsorption of gas onto the device surface causes a perturbation in the propagation velocity of the surface acoustic wave, this effect can be used to observe very small changes in mass density of 10 g/cm (the film has to be deposited on a piezoelectric substrate). SAW device can be useful as sensors for vapour or solution species and as monitors for thin film properties such as diffusivity. They can be used for example as a mass sensor or microbalance to determine the adsorption isotherms of small thin film samples (only 0.2 cm of sample are required in the cell) [42]. 

C. G. Granquist, Electrochromic Tungsten-Oxide-Based Thin Films Properties, Chemistry, and Technology, in Physics of Thin Films (M. Francombe and C. Vossen, eds.), Vol. 17, pp. 301-370, Academic Press, San Diego (1993). 

G. Chen and C. L. Tien, Partial Coherence Theory of Thin Film Properties, ASME Journal of Heat Transfer, 114, pp. 636-643,1992. 

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