In a measurement of pulsed laser deposition of SrTiO 3 on SrTiO 3 ͑001͒, we demonstrate that the difference in relative reflectivity change ⌬R/R between s-and p-polarized light can be used in a real-time monitor of thin film growth at the level of a single atomic layer. This reflectance difference has the same sensitivity ͑0.01 monolayer͒, the real-time monitoring capability, and the spectral resolution as the conventional reflectancedifference spectroscopy developed by Aspnes and co-workers. The present reflectance-difference technique does not rely on the existence of optical anisotropy within the surface plane and therefore is applicable to investigation and control of thin film growth on all surfaces. Compared to the surface photoabsorption technique developed by Kobayashi and Horikoshi, our technique improves the signal-to-noise ratio by at least one order of magnitude through reducing the background to a level equivalent to ⌬R/Rϭ1ϫ10 Ϫ5 or below.

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adsorbed 0 or OH". Further SERS experiments using Tc04", an excellent passivating agent, should be a test of this proposal. ConclusionsIn this paper evidence is presented to support the following conclusions:1. (Ag,Cr)-0 and (Ag,Cr)-OH are formed on a Ag electrode after an ORC in a solution of KC1 containing micromolar quantities of Na2Cr207. The (Ag.Cr) adsorption site is similar to the (Ag,Mn) site discussed previously.4a,b 3. The (Ag,Cr)-0 is protonated to form adsorbed hydroxide, (Ag,Cr)-OH, as VSCe is swept cathodically. The addition of 02 gas to the electrolyte deprotonates the hydroxide to form the (Ag,Cr)-0 in a reversible process that involves increasing the interfacial pH.3. The (Ag,Cr)-OH is not further protonated at any obtainable VSCE, indicating that the surface potential for Ag metal with a ~1% Cr impurity level is strongly modified compared to the case when Cr is replace with Mn. This difference in the ability of the surface to form SERS-active H20 suggests that the passivation characteristics of Cr042"-treated metals are related to the H20metal interface.Acknowledgment. The partial support of this research by the Office of Naval Research is gratefully acknowledged.Dr. Bruce Laube and United Technology Corporation made the ISS and SIMS measurements, for which we are appreciative.

In this paper, we extend the conventional plane wave expansion method in 3D anisotropic photonic crystal to be able to calculate the complex k even if permittivity and permeability are complex numbers or the functions of ω. There are some tricks in the derivation process, so we show the process in detail. Besides, we also provide an example for testing and explaining, and we also compare the results with the band structure derived from conventional plane wave expansion method, then we finally find that there is a good consistency between them.