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Surface plasmon-assisted catalytic reaction of p–aminothiophenol (P-ATP) to p-nitrothiophenol (P-NTP) on ultrasensitive magnetic Au@Ag nanoparticles (Fe 3 O 4 /Au@Ag NPs) has been observed by surface-enhanced Raman scattering (SERS). The as-prepared magnetic nanoparticles integrate magnetic and desired plasmonic on the same nanostructure, show great potential for simultaneous magnetic separation and SERS-based catalytic analysis. In acid media, high concentration of nitrite ion triggered the P-ATP molecules quickly transform into P-NTP on Fe 3 O 4 /Au@Ag NPs. These unique attributes enable in-situ SERS monitoring nitrite-triggered oxidation reactions of P-ATP to P-NTP and the subsequent NaBH 4 -drived reduction reactions of P-NTP to P-ATP on Fe 3 O 4 /Au@Ag could achieve under optimized condition. Moreover, this circulated reversible redox process could provide a circular and efficient approach to detection of nitrite ion. Considering this method without sample pretreatment and can circulate many times, indicating that it is a promising method in-situ fast detection nitrite ion.

The homogeneous surface-enhanced Raman scattering (SERS) active hot spots on a SERS substrate is the most crucial factor in ensuring their application as reproducible and ultrasensitive sensing platforms. In this paper, we report on a simply shaking-assisted liquid–liquid (water-chloroform) interfacial assembly process for fabricating aligned Ag nanowire (AgNW) bilayer films on solid substrates. A scalable fabrication process can be easily realized by using a large size of container. These AgNW bilayer films can be used as ideal SERS active substrates for chemical and biomolecular detection with highly sensitivity and excellent reproducibility. Significantly, sensitive and quantitative detection of carbaryl with a detection limit of 0.1 ppm using these SERS substrates to demonstrate potential applications for environmental pollutant analysis.

Fe3O4@SiO2@Ag magnetic–plasmonic nanospindles with efficient SERS performance and magnetic responsiveness have been successfully fabricated. Uniform and monodispersed Fe3O4@SiO2 nanospindles were prepared by a robust strategy through annealing the obtained β-FeOOH@SiO2 nanospindles in hydrogen atmospheres at 350 °C; the SiO2 shell could be regarded as an interlayer to maintain the morphology and offer a solid support for the further growth of Ag nanoparticles. Ag nanoparticles were introduced via in situ reduction of AgNO3, and the coverage rate of Ag nanoparticles anchored on Fe3O4@SiO2 was adjusted through regulating the AgNO3 concentration. Fe3O4@SiO2@Ag magnetic–plasmonic nanospindles can serve as highly efficient SERS active substrates with controllable magnetic aggregation due to steady enrichment of mass molecules in close proximity to abundant hot spots. Moreover, these nanospindles are used for label-free detection of thiram, and the detection limit is as low as 1 × 10−7 M (about 0.024 ppm), which is lower than the maximal residue limit of 7 ppm in fruits prescribed by the U.S. Environmental Protection Agency. Therefore, such magnetic–plasmonic nanospindles in the magnetic aggregation state may be potentially applied in rapid trace detection of residual pesticides or other specific analytes.

As a novel SERS nanocomposities, cube-like Fe3O4@SiO2@Au@Ag magnetic nanoparticles have been synthesized for the first time. Cube-like α-Fe2O3 NPs with uniform size can be achieved by optimizing reaction temperature and time. Firstly, the cube-like Fe3O4@SiO2 with good dispersity were achieved by calcining α-Fe2O3@SiO2 NPs in hydrogen atmosphere at 360 °C for 2.5 h, followed by self-assembling PEI shell via sonication. Furthermore, the Au@Ag particles can be densely assembled on the Fe3O4@SiO2 NPs to form the Fe3O4@SiO2@Au@Ag composite structure via strong Ag-N interaction. The obtained nanocomposites exhibit an excellent surface-enhanced Raman (SERS) behavior, reflected from low detection of limit (p-ATP) at 5×10-14 M level. Moreover, these nanocubes are used for detection of thiram and the detection limit can reach up to 5×10-11 M, while the rule of U.S. Environmental Protection Agency specifies that the residue in fruit must be lower than 7 ppm. Hence, the resulting substrate with high SERS activity has great practical potential applications in rapid detection of chemical, biological and environment pollutants with a simple portable Raman instrument at trace level.

Inspired by the hierarchical seta arrays on the legs of a water strider, ribbed hair arrays have been fabricated on a polymethylmethacrylate (PMMA) substrate using polystyrene (PS) sphere colloidal lithography, followed by oxygen plasma reactive ion etching. Microscopic analyses of the as-synthesized samples demonstrate that each microhair is sculptured with elaborate nanogrooves, leading to a unique hierarchical micro/nanoscale feature and all the hairs are vertically aligned in a large area. Inspired by the novel hierarchical hair arrays, their static and dynamic wettability has been investigated. It is revealed that after fluorination, the hierarchical hair arrays can present robust superhydrophobicity, and the wettability can be tuned by altering the morphologies of the hair arrays. Based on these remarkable wetting properties, a simple aquatic device has been fabricated by covering both sides of a PMMA plate with the superhydrophobic hair arrays; the device shows both an excellent self-cleaning performance and a large loading capacity. It can carry a load that is 4.6 times heavier than its own weight. Experimental results and theoretical analysis demonstrate that the superhydrophobic properties of the upper and lower surfaces are responsible for the large loading capacity.

Highly ordered silver nanodishes which consist of nanorings and a film were fabricated as surface-enhanced Raman scattering (SERS) substrates. Numerical simulation reveals the bottom film can dramatically enhance the local electromagnetic (EM) field in the ring cavity, due to the plasmonic interaction between the nanorings and the film. Raman results show that the nanodishes can produce about sevenfold stronger signal than the nanorings alone, in accordance with the theoretical simulation. The detection limit for Rhodamine 6G (R6G) in the order of 10−12 M and the average relative standard deviation (RSD) of less than 12% indicate the excellent sensitivity and reproducibility of silver nanodishes. The SERS enhancement factor (EF) of R6G on the nanodishes was calculated to be 6.17 × 107. For practical application, the silver nanodishes were also used to detect thiram, one dithiocarbamate fungicide that has been extensively used as a pesticide in agriculture. The detection limit of thiram molecules is as low as 1 × 10−7 M, which can meet the requirements for ultra trace detection of pesticide residues. The resulting substrate with high SERS activity, stability and reproducibility makes it a perfect choice for practical SERS detection applications.

This paper reports the generalized green synthesis of a series of LnF3–Ag (Ln = Nd, Sm, Eu, Tb) hybrid architectures with tunable shape, surface features, and composition. These intriguing hybrid structures are formed through the uniform magnetron sputtering of silver (Ag) nanoparticles on LnF3 micro-supporters. The LnF3–Ag surfaces are corrugated with high-density and numerous Ag nanogaps (which can serve as Raman active ‘hot spots’, to amplify the Raman signal), providing the sound reliability and reproducibility of Raman detection. We find that the special spindle structure of TbF3–Ag particles display the highest Raman enhancement efficiency compared to disk-, pancake-, peanut-, and rice-like structures. These experimental observations are in good agreement with the theoretical calculation by using the three-dimensional finite difference time domain (3D-FDTD) method. It is found that the produced LnF3–Ag composites are robust and efficient SERS substrates for high sensitivity detection of molecular adsorbates. Raman results show that the limit of detection (LOD) for crystal violet (CV), p-aminothiophenol (PATP) and Rhodamine 6G (R6G) of the optimized TbF3–Ag spindles substrate are as low as 10−11 M, 10−10 M and 10−14 M, respectively, which meets the requirements for ultratrace detection of analytes. In addition, the LnF3–Ag substrates are stable and can be produced with high reproducibility, which shows great potential applications for universal SERS substrates in practical SERS detection.

A new turning-mechanism for Amoeba-like Robot was proposed in this paper, which based on the amoeba-like robot kinematics characteristics of tail contracting and skin flipping. First, one kind of variable-speed node composed of the spring and damp was designed. Because of the existing of the variable-speed nodes, the velocities of the two strip-skins depended not only on the velocities of threads that gone through the variable-speed nodes, but also on the spring and damp it contained. So, although the velocities of threads that induced the velocities of the strip-skins were the same, the velocities of the strip-skins still can be different since the variable-speed nodes existed. That difference in velocities made the turning movement possible. Second, the dynamic model for the turning movement of the Amoeba-like Robot was established and analyzed. The analysis results included the angular velocity and angle curve related to time, which were computed with the dynamic model when shortening speed of thread's length was constant. The results achieved in this paper provided an important basic for the research on the behaviors and control strategy of amoeba-like robot. The new turning-mechanism can be popularized to the tracked mobile robot, for it provided a new and available turning method.

The cube-like Fe3O4@SiO2@Ag (FSA) nanocomposites with great SERS activity have been successfully synthesized by a layer-by-layer procedure in this paper. The cube-like Fe3O4@SiO2 core–shell structures were prepared via a new route and Ag nanoparticles were introduced onto their surface through a one-pot hydrothermal reaction. By controlling the reaction time, the coverage rate of Ag on the FSA surface could be tuned, and then a series of FSA composites were obtained. The SERS properties of these FSA composites were investigated using p-aminothiophenol (p-ATP) as the probe molecule. It was found that the FSA composites synthesized with a reaction time of 6 h showed the best SERS performance, and the detection limit for p-ATP could reach 1 × 10−7 M. For practical application, the FSA composites were also used to detect thiram, one of the dithiocarbamate fungicides that has been widely used as a pesticide in agriculture. The detection limit is as low as 1 × 10−6 M (0.24 ppm), lower than the maximal residue limit of 7 ppm in fruit prescribed by the US Environmental Protection Agency. The resulting substrate with high SERS activity, stability and strong magnetic responsivity makes the FSA composite a perfect choice for practical SERS detection applications.

As a novel SERS nanocomposities, cube-like Fe3O4@SiO2@Au@Ag magnetic nanoparticles have been synthesized for the first time. Cube-like α-Fe2O3 NPs with uniform size can be achieved by optimizing reaction temperature and time. Firstly, the cube-like Fe3O4@SiO2 with good dispersity were achieved by calcining α-Fe2O3@SiO2 NPs in hydrogen atmosphere at 360 °C for 2.5 h, followed by self-assembling PEI shell via sonication. Furthermore, the Au@Ag particles can be densely assembled on the Fe3O4@SiO2 NPs to form the Fe3O4@SiO2@Au@Ag composite structure via strong Ag-N interaction. The obtained nanocomposites exhibit an excellent surface-enhanced Raman (SERS) behavior, reflected from low detection of limit (p-ATP) at 5×10-14 M level. Moreover, these nanocubes are used for detection of thiram and the detection limit can reach up to 5×10-11 M, while the rule of U.S. Environmental Protection Agency specifies that the residue in fruit must be lower than 7 ppm. Hence, the resulting substrate with high SERS activity has great practical potential applications in rapid detection of chemical, biological and environment pollutants with a simple portable Raman instrument at trace level.

This paper reports the generalized green synthesis of a series of Fe3O4/Ag composites by magnetron sputtering method. The amounts of silver nanoparticles located on the hollow Fe3O4 magnetic nanoparticles can be tuned by controlling the sputtering time. The surfaces of Fe3O4/Ag composites are rough with high density and numerous Ag nanogaps (which can serve as Raman active hot spots to amplify the Raman signal), providing the sound reliability and reproducibility of Raman detection. With p-aminothiophenol and Rhodamine 6G (R6G) for probe molecules, the surface-enhanced Raman scattering (SERS) properties of these Fe3O4/Ag composites were studied. It was found that the SERS signal reached the maximum with the sputtering time of 130 s, indicating that this compound had most hot spots. In this paper, we used the composite with the strongest SERS signal for thiram detection, and the detection limit can reach 5 × 10−7 mol/L (about 0.012 ppm), which is lower than the maximal residue limit of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency. The Fe3O4/Ag composites are readily available, easy to carry, and show great potential for applications in universal SERS substrates in practical SERS detection.

The hierarchically nanosheet-assembled NiCo@SiO2@Ag (NSA) core-shell microspheres have been synthesized by a layer-by-layer procedure at ambient temperature. The mean particle size of NSA microspheres is about 1.7 μm, which is made up of some nanosheets with an average thickness of ∼20 nm. The outer silver shell surface structures can be controlled well by adjusting the concentration of Ag(+) ions and the reaction times. The obtained NSA 3D micro/nanostructures show a structure enhanced SERS performance, which can be attributed to the special nanoscale configuration with wedge-shaped surface architecture. We find that NSA microspheres with nanosheet-assembled shell structure exhibit the highest enhancement efficiency and high SERS sensitivity to p-ATP and MBA molecules. We show that the detection limits for both p-ATP and MBA of the optimized NSA microsphere substrates can approach 10(-7) M. And the relative standard deviation of the Raman peak maximum is ∼13%, which indicates good uniformity of the substrate. In addition, the magnetic NSA microspheres with high saturation magnetization show a quick magnetic response, good recoverability and recyclability. Therefore, such NSA microspheres may have great practical potential applications in rapid and reproducible trace detection of chemical, biological and environment pollutants with a simple portable Raman instrument.

The defects induced by boron-ion implantation with a relatively low dosage of 1 x 10 12 cm -2 in Si 1-x Ge x /Si single quantum wells are studied by deep level transient spectroscopy (DLTS). For low Ge content x, a defect level H 2 at an energy of 0.52 eV above the silicon valence band edge was found in the well region and its boundaries. For samples with higher Ge content, such that the strain is released, an electron trap E 2 rather than H 2 is formed by the ion implantation. Rapid thermal annealing at 600°C removes most of the H 2 defects induced by the ion implantation without changing the properties of the quantum well.

The theoretical expressions of the capacitance-voltage (C-V) characteristics of a single quantum well are derived in different bias voltage regions based on solving analytically Poisson's equation. A method to determine the parameters, including the doping concentrations in the well and the barrier, the location of the well, and the thickness of the cap layer, as well as the band offset at the heterointerface from an experimental C-V curve is presented. By carefully constructing a testing sample with the structure of the Al/(thin nitride layer)/Si/${\mathrm{Si}}_{0.67}$${\mathrm{Ge}}_{0.33}$/Si single quantum well, the measurement of a complete C-V curve in a wide voltage range is achieved. The structural parameters of the quantum well derived from the measured C-V curve agree well with the nominal values set by the experimental growth conditions. \textcopyright{} 1996 The American Physical Society.

The admittance spectroscopy technique has been used to study the hole confinement in boron δ-doped Si quantum wells. A carrier thermal emission model is proposed to derive the activation energies of holes confined in the quantum wells from the measured conductance spectra. For the same peak doping concentration, the conductance peak shifts towards higher temperatures as the thickness of the δ-doped layer increases. The activation energies obtained from the measurements coincide well with the results of a self-consistent calculation of the subbands in the quantum wells. It verifies that the conductance peaks correspond to the hole emissions from the hole ground states in the δ-quantum wells to the Si valence band.

The lattice parameters of heavily boron doped silicon homoepitaxial layers before and after rapid thermal annealing at different temperatures (800–1100 °C) are characterized by x‐ray double crystal diffraction. The results illustrate that although the strain relaxation occurs after the rapid thermal annealing (RTA) treatment, the improvement of the crystalline quality of epitaxial layers are observed at RTA temperatures higher than 1000 °C. The proportional relationship between the lattice mismatch and the substitutional boron concentration with the lattice contract coefficient β=5.3 (in units 10−24 cm3) is valid up to the concentration of 3×1020 cm−3.

The interfacial defects at the p‐Si epitaxial layer/p‐Si substrate interface have been studied by deep‐level transient spectroscopy (DLTS). By solving Poisson equation, the electron concentration at the defect level varied with external voltage is derived. The emission and capture of electrons at the defect level, which are not observable in conventional DLTS, can be detected simultaneously in a single temperature scan by properly choosing the experimental parameters. The experimental results show that the energy level of the interfacial defects is located at Ec−0.30 eV.

The effect of rapid thermal annealing (RTA) on the electrical properties of heavily boron‐doped silicon epilayer grown at 680 °C by molecular‐beam epitaxy and coevaporation of B2O3 is studied. Through the RTA process, the boron clusters in the epilayer break into boron atoms and the interstitial boron enters the substitutional site. These two effects cause the improvement of the electrical properties of the silicon epilayer. After RTA at 1100 °C for 10 s, the hole concentration can reach 3.1×1020 cm−3 with the mobility of 39 cm2/V s, which is about the same as that of the bulk silicon, while the oxygen concentration is less than 1018 cm−3. It is also shown that the full width at half‐maximum of the x‐ray‐diffraction rocking curve decreases as the RTA temperature increases. The RTA process does not affect the steep distribution of carrier concentration at the epilayer/substrate interface which differs by about 6 orders of magnitude across the interface with the leading edge slope of 25–30 nm/decade.

A single‐frequency admittance spectroscopy technique is presented to determine the band discontinuity of the Si/Si1−xGex/Si single quantum well. The accuracy of determining the activation energy for thermionic emission of holes over the Si barrier is improved as compared with the multiple‐frequency admittance spectroscopy measurement. To derive the band offset from the activation energy, the Fermi energy with respect to the band edge is calculated more exactly by solving the Poisson equation which accounts for the carrier transfer at the heterointerface. The accuracy of this technique is verified by the reconstruction of the temperature dependence of capacitance and conductance by the computer simulation.

A low temperature substrate surface cleaning procedure for silicon MBE has been studied. By using HF dipping followed by a two-step annealing, we achieved great suppression of the interfacial boron spike down to the concentration below 1015 cm-3 and reduction of the density of deep level defects down to below 1012 cm-3. The preheating temperature to obtain a clear (2 × 1) RHEED pattern can also be lowered to 300–400°C.

Deep level defects are introduced into n-type floating zone silicon by rapid thermal annealing (RTA). The types of defects and their concentrations vary with RTA temperature. The minority carrier lifetime is degraded drastically due to these defects. Some of these defects might be attributed to the metal impurities frozen at the sites of lattice defects and can be removed by subsequent annealing near 650 degrees C, the other defects which remain after this annealing may be caused by thermal stress due to the temperature non-uniformity across the samples during RTA. The results suggest that the latter might be associated with dislocations.

Photovoltaic effect measurements have been carried out for the strained Si1−xGex/Si multiple quantum well samples. The absorption structures of the transitions from heavy‐hole ground state (HH0) to the unconfined conduction (EC) states, light‐hole ground state to EC states as well as the transitions of phonon (transverse acoustic and transverse optical)‐assisted HH0‐EC excitons of the sample with x=0.25 are identified by the photovoltaic measurement at the temperature of 18 K. The agreement between the experimental results and the calculations based on simple theoretical models is fairly good. Due to the rapid increase of the background absorption, the structures of the transitions from excited hole subbands to the conduction states are very difficult to identify. For the sample with x=0.5, the absorption related to the defects originated from the partial relaxation of the large misfit strain between Si0.5Ge0.5 and Si gives a great influence upon the identification of the interband absorption structures o...

Observation of the hole-confinement effect in boron \ensuremath{\delta}-doped Si quantum wells has been demonstrated using the deep-level transient spectroscopy (DLTS) technique, based on the concept of treating the quantum well as a big ``trap.'' For the same doping thickness but different doping densities, i.e., different boron sheet doping concentrations, the well depths and the subband positions are different and the peak shift of DLTS spectra is thus expected and is observed experimently for two samples with sheet doping concentrations of about 2.4\ifmmode\times\else\texttimes\fi{}${10}^{13}$ and 6.0\ifmmode\times\else\texttimes\fi{}${10}^{13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$, respectively. A self-consistent calculation of the subbands in the quantum wells verifies that the detected activation processes in DLTS correspond to the hole emissions from the hole ground states in the \ensuremath{\delta}-doped quantum wells to the top of the wells. \textcopyright{} 1996 The American Physical Society.

The capacitance-voltage (C-V) characteristics of SiGe/Si quantum wells located near or in the space-charge region of a Schottky barrier have been numerically simulated by solving the Poisson equation. A physical picture of the variations of energy band and charge density in the quantum-well structure under the bias voltage is presented. The predominant feature of the C-V curves of quantum-well structures is the appearance of a capacitance plateau for single quantum wells or a series of plateaus for multiple-quantum-well samples. From the coincidence between the measured C-V curve and the simulated one, the band offset at the heterointerface could be derived. Moreover, the structural parameters of the quantum-well sample could be obtained from the measured C-V curves. It is found that the carrier-concentration profile derived from the C-V curve by the ordinary differential method does not coincide with the real carrier distribution in the quantum well; only the peak height of the C-V carrier concentration profile is related to the average carrier concentration in the well. \textcopyright{} 1996 The American Physical Society.

This paper reports the synthesis of a new class of NaLnF(4)-Ag (Ln = Nd, Sm, Eu, Tb, Ho) hybrid nanorice and its application as a surface-enhanced Raman scattering (SERS) substrate in chemical analyses. Rice-shaped NaLnF(4) nanoparticles as templates are prepared by a modified hydrothermal method. Then, the NaLnF(4) nanorice particles are decorated with Ag nanoparticles by magnetron sputtering method to form NaLnF(4)-Ag hybrid nanostructures. The high-density Ag nanogaps on NaLnF(4) can be obtained by the prolonging sputtering times or increasing the sputtering powers. These nanogaps can serve as Raman 'hot spots', leading to dramatic enhancement of the Raman signal. The NaLnF(4)-Ag hybrid nanorice is found to be robust and is an efficient SERS substrate for the vibrational spectroscopic characterization of molecular adsorbates; the Raman enhancement factor of Rhodamine 6G (R6G) absorbed on NaLnF(4)-Ag nanorice is estimated to be about 10(13). Since the produced NaLnF(4)-Ag hybrid nanorice particles are firmly fastened on a silicon wafer, they can serve as universal SERS substrates to detect target analytes. We also evaluate their SERS performances using 4-mercaptopyridine (Mpy), and 4-mercaptobenzoic acid (MBA) molecules, and the detection limit for Mpy and MBA is as low as 10(-12) M and 10(-10) M, respectively, which meets the requirements of the ultratrace detection of analytes. This simple and highly efficient approach to the large-scale synthesis of NaLnF(4)-Ag nanorice with high SERS activity and sensitivity makes it a perfect choice for practical SERS detection applications.

A template-free solvothermal combined with precursor thermal transformation method has been developed for the preparation of flower-like Fe3O4 nanostructured hollow microspheres. The reaction mechanism and the self-assembly evolution process were studied, and it was found that the synthetic conditions for the precursor such as reaction time, urea concentration and non-aqueous media are all crucial for the formation of the flower-like hierarchical precursors. The flower-like Fe3O4 microspheres obtained by calcining the precursor in Ar gas exhibit superparamagnetic behavior and show relative high saturation magnetization at room temperature. To endow them with SERS activity, silver coating was conducted by magnetron sputtering. The obtained Fe3O4/Ag hybrid microflowers make a positive influence on the high sensitivity of SERS to 4-pyridinethiol (4-Mpy) and Rhodamine 6G (R6G) molecules when compared with the silver film substrates. More importantly, the detection limit of Fe3O4/Ag hybrid microflowers for R6G dye can reach up to 10−15 M, which meets the requirements of ultratrace detection of analytes using SERS. Thus, the SERS-active magnetic hybrids prepared in this work may possibly be used as an optical probe with magnetic function for application in high-sensitivity bioassays.

The effects of rapid thermal annealing (RTA) on the electrical properties and the strain relaxation of the heavily boron doped silicon layers grown by molecular beam epitaxy have been studied by Hall effect measurements and double crystal x-ray diffraction. After the RTA treatment at temperatures above 1000°C, the increases of both carrier concentration and Hall mobility as well as the improvement of crystalline quality of epitaxial layers are acheived. It is verified that the lattice mismatch between the epitaxial layer and the Si substrate is proportional to the concentration of the substitutional boron rather than the total boron concentration. The lattice contraction coefficient ² is determined to be 5.3 (in units 10-24cm3) in the carrier concentration range of 0.75∼ 3×1020cnr-3.

3D rosettelike silver nanocrystals were synthesized in a large scale via a green synthetic method at room temperature without using any surfactants. The rosettelike silver nanocrystals exhibit a special textured surface morphology with a wedge-shaped architecture and higher specific surface area. The shape, size and surface morphology of the silver nanostructures can be well controlled by changing the reaction parameters. Further investigation shows different surface morphologies of silver lead to different surface plasmon resonance (SPR) and resulting surface-enhanced Raman scattering (SERS) properties. And the rosettelike silver with textured surface morphology displays much higher SERS enhancement ability than hollow sphere silver and stringlike silver, which demonstrates the crucial role of nanoscale surface texturing on the plasmonic response of silver particles. Importantly, the detection limit of rosettelike silver for Rhodamine 6G (R6G) dye can reach up to 10−14 M, which meets the requirements of ultratrace detection of analytes using SERS.

This paper reports a simple, sonochemical, surfactant-free synthesis of three-dimensional (3D) silver microflowers with high yield and good size distribution at ambient temperature. The shape, size and surface structure (controlled roughness of the surface topography) of the Ag microflowers could be tuned by controlling the experimental parameters. The special structural features with nanoscale corrugations of 3D silver microflowers make a significant contribution to the high sensitivity of SERS to Rhodamine 6G (R6G) and 4-mercaptobenzoic acid (MBA) molecules. The rougher Ag microflowers display a higher SERS activity compared to the smooth ones, which demonstrates the crucial role of nanoscale surface texturing in the plasmonic response of Ag microflowers. Raman results show that the detection limits for R6G and MBA of the optimized Ag microflower substrate are as low as 10−17 M and 10−12 M, respectively, which can meet the requirements for ultratrace detection of analytes. Furthermore, when the Ag microflower substrate is applied to detect biomolecules of bovine serum albumin (BSA), it also exhibits a high detection sensitivity and the detection concentration of BSA is as low as 10−12 M. This facile, large-scale, low-cost, and green chemistry synthesized Ag substrate with high SERS activity and sensitivity make it a perfect choice for practical SERS detection applications.

Interfacial defects related to the residual carbon on the hydrogenterminated Si(100) surface have been studied using the deep-level transient spectroscopy (DLTS) technique. The defect level is found to be donorlike which compensates the acceptor impurity at the interface. With a fast load-in and a two-step annealing, the defect density can be suppressed below the DLTS detection limit of 1012 cm-3.

2-MeV electron irradiation of Si at elevated temperature creates a dominant deep level at the energy E/sub c/-0.36 eV in addition to the oxygen vacancies. This level, which is less significant in room-temperature-irradiated Si, is found to be an efficient recombination center in the present situation. The optical cross section of this level measured by deep-level optical spectroscopy reveals a fine structure superimposed on the main transition. This fine structure is considered to be related to a new resonant phonon mode coupled with the above defect. The isochronal annealing behavior shows that this defect might be a kind of vacancy-oxygen complex. With the assumption of a V/sub 2/-O/sub 2/ complex structure, a calculation based on the Green's-function method of lattice dynamics indicates the existence of a defect-induced resonant phonon mode with energy of 10 meV, which is in good agreement with the experimental observation.

The effects of rf room temperature air plasma irradiation on Si surface have been studied by the C-V and DLTS measurements. It is found that a thin oxide film is formed on the Si surface by the air plasma anodization. The DLTS measurements show a continuously distributed interface state and a single energy level at EC−EB = 0.54eV which is a kind of localized defect existed in the oxide layer near the interface. In addition, there are two energy levels in the bulk Si induced by the plasma interaction. They behave as the divacancy usually observed in the electron beam irradiated Si. The cross section of these defect levels are measured and their isochronal annealing behaviours have been investigated.