No abstract

A comparative analysis is made of the errors in deriving the optical parameters (n, refractive index; k, absorption coefficient; d, film thickness) of thin films from spectrophotometric measurements at normal light incidence. The errors in determining n, k, and d by the (TR(f)R(b)), (TR(f)R(m)), (TR(b)R(m)), (TR(f)), (TR(m)), and T(k = 0) methods are compared. It is shown that they are applicable to optical constants of thin films in the n > 1.5, k < 4.5, and d/lambda = (0.02-0.3) range, and their combinations make possible the determination of n and k to an accuracy of better than ?4%. To derive the optical constants in a wide spectral range with high accuracy and isolate the correct physical solutions reliably, one should apply all methods, using the relevant solutions with the lowest errors, as shown in this research, when determining the optical constants of As(2)S(3) and Sb(2)Se(3) films.

No abstract

We select the best combinations of spectrophotometric quantities for the most accurate determination of the optical constants, n (refractive index), k (absorption coefficient), and the thicknesses of thin absorbing films. The basic comparative criteria used are the maximum absolute errors in the determination of n, k, and d that result from experimental errors in photometric measurements and in the optical constants of the substrates. We studied all possible combinations of photometric quantities T, T(s)(theta), T(p)(theta), R, R(s)(theta), R(p)(theta), R(m), R(ms)(theta), and R(mp)(theta) at 0 degrees < theta < or = 70 degrees, where T denotes transmission; R, reflection; the subscripts s and p, s- and p-polarized light; m, reflection from a thin film coated upon an opaque substrate; and superscript theta, the angle of incidence of light. The absence of the subscripts s and p implies nonpolarized light; that of the subscript m, a nonabsorbing substrate; and that of superscript theta, normally incident light. The error analysis that is made admits the following conclusions: (1) The best double combinations are (TR), (TR(m)), (TR(p)(70)), and (TR(mp)(70)); (2) the best triple combinations are (TRR(m)), (TRR(p)(70)), (TRR(mp)(70)), (TR(m)R(p)(70)), and (TR(m)R(mp)(70)); (3) the methods indicated above, suitably combined, are quite sufficient to provide the maximum accuracy and reliability of n, k, and d for all practical situations; (4) TRR methods based on measurements with obliquely polarized light are more suitable for thin films with n < 1, such as some metal films; (5) the regions of n, k, and d/lambda with the highest and the lowest accuracies do not overlap in either the TR or the TRR methods. Hence more combinations, preferably all, should be applied for the most accurate determination of n, k (and d), and the errors should be evaluated as a criterion for the best combination.

No abstract

No abstract

The preparation and characterization of a reference mirror of protected aluminum (Al) is reported. The mirror is made of 50-60-nm-thick Al film, coated with several-nanometer-thick A12O5 and 30-nm-thick film of AIN. The mirror characterization is based on reliable and precise reflectance measurements relative to a silicon- (Si-) wafer reference mirror. The simple phenomenological Drude-Lorentz model is applied for modeling the dispersion relations n(lambda) and k(lambda) of the Al film. The reflection of the protected Al mirror is determined in the 400-800-nm spectral range with accuracy better than 0.01 for p- and s-polarized light at angles of incidence from 0 degrees to 70 degrees. The accuracy has been confirmed with an evaporated thin silver film with known n(lambda), k(lambda), and d derived by photometric measurements at normal light incidence.

Four benzothiazolium crown ether-containing styryl dyes were prepared through an optimized synthetic procedure. Two of the dyes (4b and 4d) having substituents in the 5-position of the benzothiazole ring are newly synthesized compounds. They demonstrated a higher degree of trans–cis photoisomerization and a longer life time of the higher energy forms in comparison with the known analogs. The chemical structures of all dyes in the series were characterized by NMR, UV–vis, IR spectroscopy and elemental analysis. The steady-state photophysical properties of the dyes were elucidated. The stability constants of metal complexes were determined and are in good agreement with the literature data for reference dyes. The temporal evolution of trans-to-cis isomerization was observed in a real-time regime. The dyes demonstrated a low intrinsic fluorescence of their Ba2+ complexes and high yield of E/Z photoisomerization with lifetimes of the higher energy form longer than 500 seconds. Density functional theory (DFT) calculations at the B3LYP/6-31+G(d,p) level were performed in order to predict the enthalpies (H) of the cis and trans isomers and the storage energies (ΔH) for the systems studied.