Synthesis of zinc and cadmium complexes of 1, 1, 5, 5-tetramethyl-2-4-dithiobiuret (M{N(SCNMe2)2}2) (M = Zn, Cd) is described together with X-ray single crystal of cadmium complex. These complexes have been used as a single molecular precursor for the deposition of ZnS, CdS and ZnxCd1-xS thin films by aerosol assisted chemical vapour deposition (AACVD) method. Adherent specular films of ZnS and CdS were obtained in the temperature range 300 – 500 °C. Hexagonal ZnxCd1-xS films were obtained at 400 °C by varying the precursor concentration. XRD of ZnS films showed cubic to hexagonal phase conversion above 350 °C. SEM showed that the morphology of the films varied depending on the deposition temperature. Films were also characterized by atomic force microscopy (AFM). To the best of our knowledge these complexes are the first in its class to be used as a single molecular precursor to deposit ZnS, CdS, and ZnxCd1-xS thin films.

We have demonstrated that Si single-electron or single-hole SOI-MOSFETs with the multi-dots channel have attractive new functions such as photon detection and single-electron transfer. Multi-dots formed by selective-oxidation-induced patterning of the thin SOI layer have been used in the experiments of photon detection, while, most recently, we have utilized smaller dots consisting of individual dopant potentials in single electron transfer devices. Furthermore, in order to directly observe spatial landscape of single charges in the channel region, we have developed Low Temperature-Kelvin Probe Force Microscopy and succeeded in detecting single-dopant potential in the channel region. In this paper, photon detection by these devices will be primarily described.

Three-dimensional SiGe nanostructures grown on Si using molecular beam epitaxy exhibit photoluminescence (PL) in the important spectral range of 1.3–1.6 μm. At a higher level of photo-excitation, thermal quenching of the PL intensity is suppressed and the previously accepted type II energy band alignment at Si/SiGe cluster hetero-interfaces no longer controls radiative carrier recombination. Instead, a dynamic type I energy band alignment governs the strong decrease in carrier radiative lifetime and further increase in the luminescence quantum efficiency. In contrast to the strongly temperature dependent and slow radiative carrier recombination found in bulk Si, Auger mediated PL emanating from the nanometer-thick Si layers is found to be nearly temperature independent with a radiative lifetime approaching 10−8 s, which is comparable to that found in direct band gap III-V semiconductors. Such nanostructures are thus potentially useful as CMOS compatible light emitters and in optical interconnects.

We have already reported that Au or B doped SiGe amorphous thin films have superior thermoelectric properties which are attribute to amorphous phase. For the practical use, the bulk materials are required. In this work, we have tried and succeeded to fabricate Si-Ge-B amorphous bulk samples. First, fine particles were prepared by three kinds of mechanical process, such as roller milling method, mechanical alloying method and planetary milling method. It was intended to introduce a large amount of defects and strain into samples and/or gamorphouslization'h. Then, the prepared fine particles were pressed and formed into 2 x 5 x 15 mm^3 samples. Thermoelectric power and electrical resistivity of samples were measured by steady state measurement and four terminal method with temperature range of room temperature to 873 K in N2 flow at atmosphere pressure, respectively. Thermal conductivity was measured by photo-pyroelectric method in room temperature. Some samples have maximum value of thermoelectric power over 10-3 V/K. therefore≤ we were succeeded to prepare bulk materials which have higher thermoelectric power than that of conventional crystal materials. X-ray diffraction measurement and scanning electron microscope observation were performed on fabricated samples. From XRD measurement and SEM observation, the samples were in mixed condition of disordered microcrystals and amorphous state.

Nanoporous carbon is a widely studied material due to its potential applications in hydrogen storage or for filtering undesirable products. Most of the developments have been experimental although some simulation work has been carried out based on the use of graphene sheets and/or carbon chains and classical molecular dynamics. Here we present an application of our recently developed ab initio method [1] for the generation of group IV porous materials. The method consists in constructing a crystalline diamond supercell with 216 atoms of carbon and a density of 3.546 g/cm3, then lengthening the supercell edge to obtain a density of 1.38 g/cm3, yielding a porosity of 61.1 % in order to be able to compare with experimental results reported in the literature [2]. We then subject the resulting supercell to an ab initio molecular dynamics process at 1000 K during 295 steps. The radial distribution functions obtained are compared to experiment to discern coincidences and discrepancies.

Cytotoxicity of human cervical carcinoma cell line (HeLa cells) labeled with the nanocrystalline silicon (nc-Si) particles before and after ultraviolet (UV) light exposure has studied on the viability and cellular membrane damages. The viability and cellular membrane damages of HeLa cells changed at high particle concentration of 1.12 mg/ml. The viability of HeLa cells labeled with the UV-exposed nc-Si particles was higher than that of unexposed nc-Si particles. However, the variation of cellular membrane damages was almost same for the nc-Si particles before and after UV exposure. These results substantiated the low toxicity of nc-Si particles. Moreover, the HeLa cells labeled with the nc-Si particles exhibited green fluorescence. On the other hand, in vivo test of nc-Si particles estimated by the visualization observation of the circulation from the lymphatic vessel to the lymph node of a mouse. The transfer pathway of nc-Si particles could be clearly monitored by the strong emission of red light.

The adsorption and dissociation behavior of water molecule below and above the critical dissociation temperatures were studied by first principles calculations. We found that water-molecule adsorption (surface coverage, θ=0.25) on the down Si atom of a Si dimer in two dimers surface model was 0.26 eV more favorable than that on the up Si atom. The activation energies of water molecule on the down Si atom for interdimer and intradimer dissociations were 0.17 eV and 0.20 eV, respectively. Due to the lower activation energy, the water molecule splits into H and OH immediately once it adsorbs on down Si atom of the Si (001) surface at room temperature. There were three different adsorption sites among four sites of the two dimers for the second water molecule (θ=0.5): one was preoccupied by OH of the first water molecule; up Si atom of the same-dimer with 76.3 % probability, up Si atom of the adjacent-dimer with 23.6 % probability, and down Si atom of the adjacent-dimer with 0.1 % probability. Thus, ½ monolayer of OH sites on the Si (001) surface are irregularly distributed when water molecules are adsorbed and dissociated at room temperature.

We present a method to form semiconductor nanodots on Si substrates by using ultrathin Si oxide technology and the results on their opto-electronic properties. We can form ultra-small semiconductor nanodots with the size of ˜5nm and ultra-high density of ˜1012 cm−2 on Si surfaces covered with ultrathin SiO2 films of ˜0.3nm thickness. We focus on the Ge and GeSn nanodots on Si substrates and those embedded in Si films. These structures exhibit quantum confinement effects and intense luminescence in the energy region of about 0.8 eV.

Germanium nanocrystals (NCs) were formed by in-situ thermal annealing of an amorphous Ge layer deposited by molecular beam epitaxy on a thin SiO2 layer on Si(001). The Ge NCs were then capped in situ with a thin layer of amorphous Si to prevent oxidation. For the present range of particle sizes (2.5 to 60 nm), the NC photoluminescence (PL) appeared primarily as a wide near-infrared band peaked near 800 meV. The peak energy of the PL band reflects the average NC size and its shape depends on the NC size distribution. Using both the k·p and tight binding theoretical models, we have analyzed the PL spectrum in terms of the NC size distribution required to reproduce the observed asymmetric band shape, which includes, for the smaller diameter NCs, a band gap enlargement due to quantum confinement. The observed size distribution determined from transmission electron microscopy analysis allowed the determination of the nonlinear increase in the PL quantum efficiency with decreasing NC diameter. This implies that, given a good theoretical description of the system, it is possible to evaluate the size distribution of semiconductor NCs from their PL energy dependence.

The photoluminescence (PL) of silicon nanocrystals (Si-nc) obtained by ion implantation in the oxide layer of a MOS structure was measured during the application of a slowly varying electric field generated by biasing the gate electrode. As a result, both PL intensity enhancement and quenching have been observed. These reproducible intensity modulations exhibit a hysteresis effect when the applied electric field is varied and persist even after it is removed. The behavior of the current density and the absence of wavelength shift in the PL spectra during gate voltage sweeps suggest that these modulations are related to the motion of charge carriers rather than to field-induced mechanisms such as quantum-confined Stark effect (QCSE).

Photoluminescence (PL) spectra from Si nanocrystals embedded in silicon oxide matrix (Si-SiO2) thin films, Ge embedded in silicon oxide matrix (Ge-SiO2) thin films and both Ge and Si embedded in silicon oxide matrix (Ge/Si-SiO2) thin films prepared by RF magnetron sputtering were investigated. All as-deposited thin films were annealed for 1h in the temperature range from 500°C to 1100°C in Ar or H2 atmosphere. The PL spectra of Si-SiO2 thin films exhibited red luminescence at an annealing temperature of 1100°C and the PL intensity of the sample annealed in H2 gas increased by a factor of approximately 6.3 in comparison with sample annealed in Ar gas. Subsequently, The PL intensity of main peak centered at about 400 nm (V-band) of Ge-SiO2 thin films annealed in H2 gas exhibited strong comparison with the sample annealed in Ar gas. Finally, the PL spectra of Ge/Si-SiO2 thin films exhibited strong peak centered at approximately 500-530 nm (G-band) besides V-band and others in the temperature range from 700°C to 1000°C. The PL intensity of G-band of the samples annealed in H2 gas exhibited weak comparison with Ar gas.

Nanofocusing, high-resolution X-ray optics demand good surface quality, the absence of tapered sidewalls, and a depth reaching into tens, sometimes hundreds of microns, all requirements that must be satisfied over large areas. In this report, we discuss our motivation for choosing group IV materials (predominantly Si, and C in its diamond form) for nanofocusing and high resolution in the hard X-ray portion of the spectrum. We elaborate on the design and nanofabrication procedures, and detail the etching parameters that offer a path for overcoming obstacles in making better optics. We briefly review tests for the assessing the quality of the optics.

Group IV nanostructures have attracted a great deal of attention because of their potential applications in optoelectronics and nanodevices. Raman spectroscopy has been extensively used to characterize nanostructures since it provides non destructive information about their size, by the adequate modeling of the phonon confinement effect. However, the Raman spectrum is also sensitive to other factors, as stress and temperature, which can mix with the size effects borrowing the interpretation of the Raman spectrum. We present herein an analysis of the Raman spectra obtained for Si nanowires; the influence of the excitation conditions and the heat dissipation media are discussed in order to optimize the experimental conditions for reliable spectra acquisition and interpretation.

Heterogeneous catalysts that accelerate the photolytic destruction of organic contaminants in water are a potentially inexpensive and highly effective way to remove both trace-level and saturated harmful compounds from industrial waste streams and drinking water. Porous photocatalytic materials can have the combined qualities of high surface area and relatively large particle sizes, as compared with nanoparticulate catalyst powders like titanium dioxide . The larger particle sizes of the porous materials facilitate catalyst removal from a solution, after purification has taken place.

We have synthesized new kinds of photocatalytic porous oxide materials that can be used to purify contaminated water by accelerating the photodegradation of any kind of organic pollutant. The new materials have very large open pore structures that facilitate the diffusion, the surface contact of contaminants, and solvent flow through the catalyst. These qualities enhance surface reactions important to the process. The new catalysts have shown robust physical and chemical properties that make them candidates for real applications in polluted water decontamination.

In order to improve the efficiency of quantum emitters, in particular nitrogen-vacancy (NV) color centers in diamond nanocrystals (NCs), it is important to enhance their photon production rate as well as the collection efficiency of the emitted photons. This can be achieved by embedding the emitters within optical cavities. Here we describe the design and fabrication of 1-D photonic crystal nanocavities in an air-bridge silicon nitride (SiNx) structure. In spite of the low index of silicon nitride (n˜2), we were able to design optical nanocavities with Quality factors as high as Q˜1 × 106. These nanocavities were designed to operate near 637 nm in order to strongly enhance the zero-phonon line (ZPL) emission of an NV center in a diamond NC while suppressing the in-plane emission into the phonon side-band. Simulation results show that a NV center placed near the top of the cavity would experience a reduction of radiative lifetime from ˜15ns to ˜2ps (Purcell factor ˜7000), thus significantly improving the photon production rate. Experimental results show a cavity resonance at ˜630nm, with a linewidth corresponding to Q˜1250, limited by the spectrometer resolution. The presented work is an important step towards the realization of diamond-based single photon devices, including switches.

The memory effect of MOS diodes made on Si substrate with Si nanocrystals (NC-Si) and interfacial Si nano-pyramids deposited by PECVD at different ICP powers is characterized. TEM analysis on the NC-Si reveals that the NC-Si average size are around 3.9±1.1 nm and 4.7±0.7 nmwhen grown at ICP power of 20 W and 30 W, respectively. The interfacial Si nano-pyramids can only be observed by growing at 30 W or larger. The density of NC-Si of 4.4 × 1018 and 5.6 × 1018 cm−3 are relatively in good agreement with the corresponding PL intensities of 45 and 73 count/nm, respectively, for 20 and 30-W grown SiOx samples.. The C–V curves of the NC-Si embedded MOSLEDs show flat-band voltage shift of 0.74 and 18.46 Vfor 20 and 30-W samples, respectively. The C-V hysteresis width also increases by enlarging the range of sweeping voltage. A strong correlation between the size/density of Si nanocrystals and the flatband voltage difference has been concluded. In the case of the C–t measurement, the charging and discharging behaviors were found to depend on charging conditions. Finally, the relationship of the electron/hole charge density with the retention time is analyzed. Our data shows the charge loss rate of 1.3 % for electron is better at 20-Wsample, but the charge loss rate of 0.23 % for hole is better at 30-Wsample with Si NCs embedded in MOSLED after 102 s.

We used a surface-plasmon antenna to obtain small photodetectors for LSI on-chip optical interconnection by using near-field light generated by the antenna. Such near-field devices are not constrained by the diffraction limit and they offer an approach to integrated nanoscale photonic devices. A small semiconductor structure is located near the antenna to absorb the near-field light. This structure can be made as small as the Schottky depletion layer, so the separation between electrodes can be reduced to almost the size of the near-field region. We have demonstrated a “Si nano-photodiode” or plasmon photodiode that uses the near-field localized in a subwavelength region, which is usually relatively large in size because of the long absorption length for Si (˜10 μm at a wavelength of ˜800 nm). The Si nano-photodiode has a fast impulse response with a full-width at half-maximum of ˜20 ps even when the bias voltage is small (˜1 V or less). We demonstrated an on-chip optical interconnect chip to operate circuitry in an LSI chip by using waveguide-coupled Si nano-photodiodes.