Oxide film, optical constant

The oxide layers on polycrystalline Pt in acid media have been studied most thoroughly by Plieth et The film optical constants have been... 

Early work in ellipsometry focused on improving the technique, whereas attention now emphasizes applications to materials analysis. New uses continue to be found however, ellipsometry traditionally has been used to determine film thicknesses (in the rang 1-1000 nm), as well as optical constants. " Common systems are oxide and nitride films on silicon v ers, dielectric films deposited on optical sur ces, and multilayer semiconductor strucmres. 

The admittance response at 1 kHz has also been interpreted in terms of the behavior at residual defects in anodic films. This interpretation is based on electron optical characterization, which shows that anodic films contain a distribution of preexisting defects associated with substrate inclusions and mechanical flaws (96,102). In aggressive environments, pits nucleate from these defects and propagate into the metal substrate. In this model, pits are distinct from anodic film flaws, and both can contribute to the measured admittance. Measurements of anodic films exposed to chloride solutions showed that the dissipation factor increased with time, but the capacitance remained nearly constant. Under these conditions, pit propagation at a flaw led to a pit area increase, which increased the resistive component of the admittance, resulting in an increased dissipation factor, but no increase in the capacitance. Measurements at 100 kHz were reflective of the electric double layer and not the components of the oxide film. 

Washington P.L., Ong H.C., Dai J.Y., Chang R.P.H. (1998) Determination of the optical constants of zinc oxide thin films by spectroscopic ellipsometry Appl. Phys. Lett. 72 3261-3263. 

Structure and optical parameters of the porous oxide films are listed in Table 1 for different Ti content. The size of the porous oxide cells is seen to change considerably in comparison with pure alumina films. Dielectric constant and refractive index can be changed gradually with varying of the Ti content in the alloy films. 

Ellipsometry at noble metal electrode/solution interfaces has been used to test theoretically predicted microscopic parameters of the interface [937]. Investigated systems include numerous oxide layer systems [934-943], metal deposition processes [934], adsorption processes [934, 944] and polymer films on electrodes [945-947]. Submonolayer sensitivity has been claimed. Expansion and contraction of polyaniline films was monitored with ellipsometry by Kim et al. [948]. Film thickness as a function of the state of oxidation of redox active polyelectrolyte layers has been measured with ellipsometry [949]. The deposition and electroreduction of Mn02 films has been studied [950] below a thickness of 150 nm, the anodically formed film behaved like an isotropic single layer with optical constants independent of thickness. Beyond this limit, anisotropic film properties had to be assumed. Reduction was accompanied by an increase in thickness, which started at the ox-ide/solution interface. 

Figure 10. The grid shows ij/ and A calculated for bare metal with optical constants shown on the axes. The extra line shows the dependence of ij/ and A on thickness of oxide for M2 — 3 5 and k2 2.4. If these films were neglected the value of M2 would be wrongly estimated, for example as 2.4 for 80 A of oxide [from Kumagai and Young, J. Electrochem. Soc. Ill (1964) 1411].

When reflectance spectroscopy was first used for the in situ study of electrode surfaces, the main emphasis was placed on monitoring the formation of adsorbates and thin films, e.g., the underpotential deposition of metals or the formation of oxides, because a rather strict correlation between coverage and adsorbate- or film-induced reflectance change was generally observed/ In the beginning of the seventies, the evaluation of adsorbate optical constants from measurements of with the help of stratified multilayer models... 

PPQs possess a stepladder stmcture that combines good thermal stabiUty, electrical insulation, and chemical resistance with good processing characteristics (81). These properties allow unique appHcations in the aerospace and electronics industries (82,83). PPQ can be made conductive by the use of an electrochemical oxidation method (84). The conductivities of these films vary from 10 to 10 S/cm depending on the dopant anions, thus finding appHcations in electronics industry. Similarly, some thermally stable PQs with low dielectric constants have been produced for microelectronic appHcations (85). Thin films of PQs have been used in nonlinear optical appHcations (86,87). 

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