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The prototype of an infrared spectroscopic ellipsometer using a Fourier transform PC-based infrared spectrometer is described. Several applications in thin-film characterization are given, particularly in the case of bulk substrate, thick-layered materials, and determination of the dielectric function of layered materials such as silicon oxide and silicon nitride. The sensitivity and possible improvements of this technique are discussed.

Sil-x-yGeXCy pseudomorphic heterostructures have been grown on Si(100) substrates using a rapid thermal chemical vapor deposition reactor, Due to the lattice parameters of Si, Ge, and C(diamond), the strained Si] _xGe x layers can be strain compensated by thc addition of substitutional C. The epitaxial layers were fabricated at reduced pressure and the reactive gases (silane, dichlorosilane, gennane, and organometallic C-Si compound) were diluted in purified hydrogen. The growth temperatures were 650 and 550 (lC, in order to have a reasonable growth rate and not form the stable SiC phase. The epitaxial layers, up to 4000 A in thickness and x=20%, were compensated by up to 1 % of substitutional C as measured by infrared spectroscopy at 605 em -I. The lattice parameters were measured by x-ray diffraction using the [004] and [2241 substrate difraction peaks to directly obtain the strain parameters. Partial strain compensation was observed in layers thicker than the critical thickness for Si j -xGcx' These results arc also compared to those of photoluminescence spectroscopy, where the observed misfit dislocation related bands (DJ and D 2 ) are minimized in compensated samples.

The spin dynamics in a nearlywne&imensional Heisenberg systemthe solid free radical Tanol (2,2,6,6-tetramethyl+piperidinol-1&xyl)is studied through dynamical-nuclear-polarization {DNP) experiments (Overhauser efFect) and proton spin-lattice relaxation-time (T,) measurements. As the couplings between the electronic spins and the protons have been determined in Tanol, absolute deteraunations of the values of the electronic-spin-frequency correlation functions at the electronic Larmor frequency (co,) and at the nuclear I.armor frequency {eo")can be achieved by performing both DNP and T, measurements. The value obtained at eo, is in agreement with theoretical calculations in one-dimensional Heisenberg systems using the method of Tahir-Kheli and McFadden. The value obtained at co" together with the frequency dependence of T, are explained by introducing a cutofF efFect in the spin-difFusion process in one dimension. A derivation is given which expresses the magnitude of the cutofF efFect in terms of the interchain couplings. An evaluation of the interchain couplings, using T& measurements, is presented. The values of the interchain couplings, which are consistent with both the T, measurements and the'Neel temperature are J~J2 10 'J, where J is the intrachain exchange (J/k =4.1 K), and Ji and J2 are the interchain couplings along two axis perpendicular to the chain. Ho~ever, it cannot be excluded that, in Tanol, the disturbance of the spin-difFusion process is due to finite-length efFects.