Dielectrics, thick-film properties

The breakdown field strength is a thickness dependent property, a probable reflection of pinhole density variation with thickness. For a typical value of Interlevel dielectric film thickness (1 - 2 p), the breakdown field strength is 1 - 2.5 x 10 V/cm which is adequate for most applications. 

A complete review of the reported properties of ferroelectric thin films prepared by CSD is beyond the scope of this chapter. Suffice it to say that fabrication approaches from each of the three CSD categories noted above have been used to prepare high-quality films in a range of thicknesses. The dielectric response and ferroelectric hysteresis behavior have been widely reported and the reader is referred to References 12 and 13 for representative results. Despite space limitations, three aspects of CSD processing and film properties warrant consideration here. These are (i) the ability to prepare oriented films by CSD (ii) typical stress levels within the films and (iii) the general dielectric properties of the thin film materials compared to the corresponding bulk materials. 

It has been widely demonstrated that the preparation of oriented, and in some cases epitaxial films by CSD is possible, despite the relatively large thickness of the films that is deposited in a single step. Lange ° reviewed the various mechanisms that lead to oriented growth, and a variety of factors including reactions at the electrode interface, - organic content within the film," " and the use of seed layers" to promote homoepitaxy have been discussed. The ability to control film properties (remanent polarization, dielectric constant, etc.) through manipulation of film orientation has also been shown. 

M. Nagai, K. Yamashita, T. Umegaki and Y. Takuma, Electrophoretic Deposition of Ferroelectric Barium TiTanate Thick Films and Their Dielectric Properties J. Am. Ceram. Soc. 76 (1993) 253-255. 

Concerning the two-layer model, the thickness and properties of each layer depend on the nature of the electrolyte and the anodisation conditions. For the application, a permanent control of thickness and electrical properties is necessary. In the present chapter, electrochemical impedance spectroscopy (EIS) was used to study the film properties. The EIS measurements can provide accurate information on the dielectric properties and the thickness of the barrier layer [13-14]. The porous layer cannot be studied by impedance measurements because of the high conductivity of the electrolyte in the pores [15]. The total thickness of the aluminium oxide films was determined by scanning electron microscopy. The thickness of the single layers was then calculated. The information on the film properties was confirmed by electrical characterisation performed on metal/insulator/metal (MIM) structures. 

We note that the dielectric properties of relaxor ferroelectric films have been investigated numerically in Ref. [81] by Monte-Carlo method. The authors obtained the increase of the temperature of dielectric susceptibility maximum and the decrease of the maximum height under the film thickness decrease. Below we investigate the relaxor films properties theoretically on the base of approach suggested in Ref. [82]. 

It is claimed to be able to measure thicknesses with an accuracy of about 0.3 A, approximately the thickness of an atomic layer. Because the method relies on polarized fight, ellipsometry is a nondestructive technique, which makes it suitable for in situ measurements in some cases. One disadvantage is that the substrate must be reflective, so gold or sUicon wafer is often used. However, a major disadvantage with the technique is interpretinging the data, which is not trivial models of the air—thin film-substrate must be used. The dielectric and optical properties of the thin film must be known accurately to calculate the thickness of the film, and even then the modelling usually assumes a homogeneous layer which may not always be justified. 

Properties of Thick-Film Dielectric Materials Multilayer Dielectric Materials... 

Rumeau, A., Lebey, T., and Dutarde, E. (2008) CaCu3Ti40i2 ceramics from co-precipitation method dielectric properties of pellets and thick films. 

Nakai N., Kozuka H. PVP-assisted sol-gel preparation of BaBi4Ti40is thin films and dielectric properties. Trans. Mater. Res. Soc. Jpn 2004, in press Ohya Y., Itoda S., Ban T, Takahashi Y. Lead zirconate titanate thick films fabricated from sols with and without its powder. Jpn J. Appl. Phys. Pt. 1 2002 41 270-274 Parrill T.M. Heat-treatment of spun-on acid-catalyzed sol-gel silica films. J. Mater. Res. 1994 9 723-730... 

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