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Hexagonal cadmium selenide (CdSe) nanowires, with diameter around 20 nm, were synthesized using a simple vapor-phase growth. Silicon (Si) powder acts as a source material assisting the synthesis, which is very important to the formation of the CdSe nanowires. We also suggest that self-catalysis at the Cd-terminated (0001) surface, together with the assistance action of Si, leads to the formation of wire-like structures to be formed. Meanwhile, the assistance of Si is responsible for the fineness and uniformity of the CdSe nanowires. The possible growth mechanism of the CdSe nanowires is proposed, and the optical property of the as-grown CdSe nanowires is characterized.

Composition-dependent electronic structure and optical properties of Hf1-xSixOy (0.1≤x≤0.6) gate dielectrics on Si at 450 °C grown by UV-photo-induced chemical vapor deposition (UV-CVD) have been investigated via x-ray photoemission spectroscopy and spectroscopy ellipsometry (SE). By means of the chemical shifts in the Hf 4f, Si 2p, and O 1s spectra, the Hf–O–Si bondings in the as-deposited films have been confirmed. Analyses of composition-dependent band alignment of Hf1-xSixOy/Si gate stacks have shown that the valence band (VB) offset (ΔEv) demonstrates little change; however, the values of conduction band offset (ΔEc) increase with the increase in the silicon atomic composition, resulting from the increase in the separation between oxygen 2p orbital VB state and antibonding d states intermixed of Hf and Si. Analysis by SE, based on the Tauc–Lorentz model, has indicated that decreases in the optical dielectric constant and increase in band gap have been observed as a function of silicon contents. Changes in the complex dielectric functions and band gap Eg related to the silicon concentration in the films are discussed systematically. From the band offset and band gap viewpoint, these results suggest that Hf1-xSixOy films provide sufficient tunneling barriers for electrons and holes, making them promising candidates as alternative gate dielectrics. [ABSTRACT FROM AUTHOR]

Temperature-dependent interfacial chemical bonding states and band alignment of HfOxNy/SiO2/Si gate stacks have been investigated by X-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry (SE). By means of the chemical shifts of Hf 4f, Si 2p, O 1s, and N 1s core-level spectra, it has been found that the chemical stability of the HfOxNy/SiO2/Si stacks strongly depends on the annealing temperature. Analysis of temperature-dependent band alignment of HfOxNy/SiO2/Si stacks suggests that the valence band offset ΔEv increases slowly from 1.82 eV for as-grown film to 2.55 eV for annealed film at 700 °C; however, the values of conduction band offset ΔEc only demonstrates a slight change in the vicinity of 1.50 eV. From the band offset viewpoint, HfOxNy/SiO2/Si gate stack could be a promising candidate for high-k gate dielectrics. [ABSTRACT FROM AUTHOR]

A ZrO2/TiO2/Si gate stack has been prepared by using solid phase reaction between sputtered ZrO2/Ti stack and underlying SiO2/Si substrate through in situ vacuum annealing. X-ray photoelectron spectroscopy was used to analyze interfacial properties of the ZrO2/TiO2/Si stack after annealing at high temperatures. The interfacial silicate is composed of Ti silicate and ZrO2 layer does not take part in the interfacial reaction to form Zr silicate. Such a stack has the advantage of combining high dielectric constant of ZrO2 and excellent interfacial property of Ti silicate/Si interface, and will have potential applications in the advanced metal-oxide-semiconductor devices. [ABSTRACT FROM AUTHOR]

Nanoscale silicon powders of 10 nm scale have been prepared by laser-induced chemical vapor deposition. Diffuse reflectance spectra (DRS) of the silicon powder at different annealing temperatures have been measured. Both the maximum and the drop-edge in reflectivity have been found to shift toward a shorter wavelength with increasing annealing temperature below 700 °C. The observed shifts in the spectra are ascribed to the reduction of the silicon crystallite size by oxidation of the surface in an annealing process. [ABSTRACT FROM AUTHOR]