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Self-Assembly Monolayer (SAM) technique, as a novel and developing technique for fabricating layer-by-layer nanofilm on substrates of various sizes, shapes and materials, has received more and more attention in the areas of light-emitting devices, nonlinear optical materials, conductive films, permselective gas membranes, sensors, modification of electrodes, resistance and printing technique. In comparison with other traditional methods, SAM technique has many significant advantages, including simple process, universality, formation with densely packed, well defined, highly ordered surfaces. This paper will give a review on the recent development in SAM technique.

Our present work deals with the formation and thermal behavior of a nonbulk alloy phase confined within about 8 nm across the interfaces of Au/Cu multilayer systems. These multilayers deposited on silicon and float glass by DC magnetron sputtering have been studied by secondary ion mass spectrometry (SIMS), X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). Along with the highly oriented growth of the Cu and Au layers along [111], Cu₃Au alloy was found to be present only at the Cu/Au interfaces in the nonbulk tetragonal D0₂₃ phase. Co-sputtering of Au and Cu under similar conditions produces only conventional fccCu₃Au alloy phases, suggesting that interfacial confinement plays a significant role in producing the novel Cu₃Au alloy phase in gold/copper multilayers. This novel phase is found to form only when the interfacial width is less than 10 nm. The D0₂₃ alloy phase tends to stabilize, rather than transforming to the bulk L1₂ phase, when the multilayer is vacuum-annealed at 150°C. As alloy formation spreads out of the interfaces (on vacuum annealing at 200°C), the dominant alloy is CuAu, consistent with the Cu:Au atomic ratio averaged over the multilayer.

Two sets of multilayer structures consisting of 44 alternating layers of a-SiN_x:H (~ 4 nm and 6 nm) and SiO₂ (5 nm) have been fabricated using the plasma-enhanced chemical vapor deposition (PECVD) technique. The a-SiN_x:H that has a lower bandgap forms the well layer, while the large bandgap SiO₂ forms the barrier layer. A single bulk layer of a-SiN_x:H has also been grown to serve as a reference for comparison with the multilayer structures. The samples were studied using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), spectroscopic ellipsometry (SE), and photoluminescence (PL) techniques. The SE data have been successfully fitted, and the complex refractive indices of the a-SiN_x:H in the bulk and multilayers have been determined. The effects of quantum confinement on the optical bandgap and refractive indices of a-SiN_x:H have been investigated. The results are correlated to the PL spectra of the samples.