Thickness Of SiO2 Layer Research Articles

Combination of surface- and interference-enhanced Raman scattering by CuS nanocrystals on nanopatterned Au structures.

We present the results of a Raman study of optical phonons in CuS nanocrystals (NCs) with a low areal density fabricated through the Langmuir–Blodgett technology on nanopatterned Au nanocluster arrays using a combination of surface- and interference-enhanced Raman scattering (SERS and IERS, respectively). Micro-Raman spectra of one monolayer of CuS NCs deposited on a bare Si substrate reveal only features corresponding to crystalline Si. However, a new relatively strong peak occurs in the Raman spectrum of CuS NCs on Au nanocluster arrays at 474 cm−1. This feature is related to the optical phonon mode in CuS NCs and manifests the SERS effect. For CuS NCs deposited on a SiO2 layer this phonon mode is also observed due to the IERS effect. Its intensity changes periodically with increasing SiO2 layer thickness for different laser excitation lines and is enhanced by a factor of about 30. CuS NCs formed on Au nanocluster arrays fabricated on IERS substrates combine the advantages of SERS and IERS and demonstrate stronger SERS enhancement allowing for the observation of Raman signals from CuS NCs with an ultra-low areal density.

The effect of surface oxidized modification on the mechanical properties of SiC3D/Al

In this study, the effect of surface oxidized modification on the mechanical properties of silicon carbide 3D/aluminum composites (SiC3D/Al) is explained. The basis of this study may be outlined as follows: the shear force of extrusion testing proves the effect of SiO2 layer thickness from the perspective of interface failure mechanism; and the critical pore radius explains the effect of SiO2 layer distribution from the perspective of a biconnected structure. The compression and flexural tests prove that compressive strength is mainly affected by the average SiO2 layer thickness. Bending strength is affected by the critical pore radius, which is the primary contributor to SiO2 layer thickness of the special structural space and stress concentration. Thus, the structural characteristics of SiC3D/Al affect the SiO2 growth mechanism, as indicated by the aforementioned results.

Fabrication of graphene oxide decorated with Fe3O4@SiO2 for immobilization of cellulase

Fe3O4@SiO2–graphene oxide (GO) composites were successfully fabricated by chemical binding of functional Fe3O4@SiO2 and GO and applied to immobilization of cellulase via covalent attachment. The prepared composites were further characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Fe3O4 nanoparticles (NPs) were monodisperse spheres with a mean diameter of 17 ± 0.2 nm. The thickness of SiO2 layer was calculated as being 6.5 ± 0.2 nm. The size of Fe3O4@SiO2 NPs was 24 ± 0.3 nm, similar to that of Fe3O4@SiO2–NH2. Fe3O4@SiO2–GO composites were synthesized by linking of Fe3O4@SiO2–NH2 NPs to GO with the catalysis of EDC and NHS. The prepared composites were used for immobilization of cellulase. A high immobilization yield and efficiency of above 90 % were obtained after the optimization. The half-life of immobilized cellulase (722 min) was 3.34-fold higher than that of free enzyme (216 min) at 50 °C. Compared with the free cellulase, the optimal temperature of the immobilized enzyme was not changed; but the optimal pH was shifted from 5.0 to 4.0, and the thermal stability was enhanced. The immobilized cellulase could be easily separated and reused under magnetic field. These results strongly indicate that the cellulase immobilized onto the Fe3O4@SiO2–GO composite has potential applications in the production of bioethanol.

Investigation of the Copper Gettering Mechanism of Oxide Precipitates in Silicon

One of the reasons why the principal gettering mechanism of copper at oxide precipitates is not yet clarified is that it was not possible to identify the presence and measure the copper concentration in the vicinity of oxide precipitates. To overcome the problem we used a 14.5 nm thick thermal oxide layer as a model system for an oxide precipitate to localize the place where the copper is collected. We also analyzed a plate-like oxide precipitate by EDX and EELS and compared the results with the analysis carried out on the oxide layer. It is demonstrated that both the interface between the oxide precipitate being SiO2 and the silicon matrix and the interface between the thermal oxide and silicon consist of a 2–3 nm thick SiO layer. As the results of these experiments also show that copper segregates at the SiO interface layer of the thermal oxide it is concluded that gettering of copper by oxide precipitates is based on segregation of copper to the SiO interface layer.

Simulation and modeling of off-leakage current in InGaZnO thin-film transistors

We investigate the mechanism of off-leakage current in InGaZnO (IGZO) thin-film transistors with the help of a two-dimensional device simulator. The deep donorlike states probably originating from the oxygen vacancies are introduced in the IGZO channel, and it is shown that these trap states significantly affect Id–Vg characteristics in the off-state region through the pinning of the channel potential. A simple analytical model to explain the simulation results is proposed, which suggests that the off-leak characteristics is controlled by the amount and the depth of the deep donorlike states as well as the thicknesses of IGZO and SiO2 layers in TFT.

Instability of Ferromagnetic Nanoclusters in Fe Implanted Amorphous SiO2

A 460nm thick amorphous SiO2 layer, formed on a Si (100) surface by air-annealing the Si substrate at 1100oC for 24h, was implanted with 57Fe to a fluence of 1 x 1016/cm2 at room temperature and annealed at temperatures up to 1000oC. The implanted and annealed samples were studied by conversion electron Mössbauer spectroscopy (CEMS) and magnetization measurements.The CEMS spectra up to an annealing temperature of 600oC showed the presence of a singlet due to dispersed Fe ions and paramagnetic doublets with hyperfine parameters characteristic of Fe2+ and Fe3+. The spectrum after the 1000oC annealing was dominated (> 80%) by ferromagnetic sextets, the main components of which were sextets with a hyperfine field of 320(20) kOe and 264(20) kOe, showing the formation of Fe0 clusters, in agreement with previous observations. Magnetization measurements (m(H)) on the sample after the 1000oC annealing showed a small hysteresis at 4K and saturation magnetization with zero hysteresis at room temperature, reached with application of small external field.The CEMS measurement on this sample was repeated after storing the sample under ambient conditions for a period of 6 months. The spectrum showed complete disappearance of the ferromagnetic sextets and the presence only of paramagnetic doublets due to Fe2+. Evidently progressive oxidation of the Fe clusters had occurred. Magnetization results confirm the paramagnetic transformation of the Fe clusters.

Characterization of thin-film thickness

Analysis methods and instrumentation for obtaining optical parameters and thickness profiles of thin-film samples from spectrophotometric and ellipsometric measurements are presented. Measured samples include thermally grown and evaporated SiO2 on a silicon substrate and a polymer photoresist layer on silicon. Experimental results at multiple sample positions give the thickness uniformity and optical constants of thin films. The thickness results obtained with spectrophotometry and ellipsometry agree within 1 nm for the 300 nm thick layer of SiO2 on silicon. For the 1600 nm thick resist sample the agreement of the measurement methods is within 8 nm. For the sample with a nominally 6000 nm thick layer of SiO2 on silicon, there is a deviation of ∼100 nm between the spectrophotometry and ellipsometry results. As an application, the optical parameters of a SiO2 layer on an induced junction silicon photodiode are determined by spectrophotometry and are used to confirm earlier values and uncertainties of the SiO2 refractive index and layer thickness non-uniformity.

Investigations on crack generation mechanism and crack reduction by buffer layer insertion in thermal-plasma-jet crystallization of amorphous silicon films on glass substrate

The crack generation mechanism and the effect of crack reduction by buffer SiO2 layer insertion in thermal-plasma-jet (TPJ) crystallization of an amorphous silicon film on a glass substrate have been investigated. The crack generation was clearly observed 13.7 s after TPJ irradiation using a high-speed camera, which indicates that cracks are generated not during heating, but during cooling. From the measurement and simulation of substrate deformations, it was clarified that the substrate deformed convexly during heating and it consequently deformed concavely after cooling owing to the substrate surface densification. This result indicated that the tensile stress generated by the concave deformation is the origin of cracks. The deposition of the buffer SiO2 layer generated compressive stress, which minimizes accumulation of tensile stress after TPJ annealing. The number of cracks in unit length significantly decreased owing to the decrease in tensile stress with the increase in the thickness of the buffer SiO2 layer.

Investigation of the effectiveness of SiNWs used as an antireflective layer in solar cells

Morphological, optical and electrical properties of SiNWs are studied under different preparation conditions. Despite an ultra-low reflectivity revealing a high light-trapping effect, we obtained a degradation of the resistivity and the minority carrier lifetime in SiNWs which are ascribed to a high electron-trapping. For solar cells application, we determine a trade-off between optical and electrical properties of SiNWs. However, even with this optimization, we obtained a degradation of the electrical parameters of the solar cell when SiNWs are used as compared to the cell without SiNWs. From the obtained results in this work, we put in evidence for the first time that despite the very low reflectivity that a SiNWs film has, its use in PV is faced to four major challenges; (1): an unbalancing between the length of SiNWs and the electron diffusion length, (2): a thick SiO2 layer covering silicon wires formed during the solar cell processing (observed using dark field transmission electron microscopy), (3) a high density of dangling bonds of porous-SiNWs when the SiO2 film is etched, and, (4) a poor metal/SiNWs front contact.

Inelastic electron tunneling spectroscopy for molecular detection

Inelastic electron tunneling spectroscopy (IETS) [R. C. Jaklevic and J. Lambe, Phys. Rev. Lett. 17, 1139 (1966); R. G. Keil et al., Appl. Spectrosc. 30, 1 (1976); K. W. Hipps and U. Mazur, J. Phys. Chem. 97, 7803 (1993); U. Mazur et al., Anal. Chem. 64, 1845 (1992); P. K. Hansma, Tunneling Spectroscopy (Plenum, New York, 1982)] measurements are performed on Si nanowire (NW)/SiO2/Al NW tunnel junctions. The tunnel junction area is ∼50 × 120 nm and tunneling occurs across a 10 nm thick SiO2 layer. IETS measurements are performed at 300 K for ammonium hydroxide (NH4OH), acetic acid (CH3COOH), and propionic acid (C3H6O2) molecules. The I–V, dI/dV–V, and d2I/dV2–V characteristics of the tunnel junction are measured before and after the adsorption of molecules on the junction using vapor treatment or immersion. Peaks can be observed in the d2I/dV2–V characteristics in all the cases following molecules adsorption. These peaks may be attributed to vibrational modes of N–H and C–H bonds.

Maximum SiO2 layer thickness by utilizing polyethylene glycol as the surfactant in synthesis of core/shell structured TiO2–SiO2 nano-composites

TiO2-SiO2 nano-composites with the core/shell structure have been prepared by means of a technique based on an extension of well-known Stober process. In this way, the silica coating of TiO2 nano-particles in the presence of various commercially available surfactants of cationic, anionic and nonionic has been conducted with the aim to increase barrier properties against UV (UV block- ing) radiation, in order to optimize photo-killing ability of the TiO2 nano-particles and decline of the high photo- catalytic property of titania. The influences of varying coating parameters such as time and temperature on the silica content of nano-composites have been studied and optimum conditions for attaining a thick layer of SiO2 have been determined. Electro-phoretic mobility measurements indicated that the silica coating shifted the iso-electric point of titania toward that of a typical pure colloidal silica. Surface elemental composition of core/shell structured TiO2-SiO2 nano-composites was verified by using energy dispersive X-ray analysis. It was found that maximum silica shell thickness can be obtained in the presence of polyethylene glycol as a nonionic surfactant at 80 � C for 360 min. The photo-catalytic activities were evaluated by the degradation of an aqueous solution of methylene blue under UV light irradiation. In addition, the resultant opti- mum nano-composites have been characterized by FE- SEM, TEM, BET, FTIR and UV-Vis spectroscopy.

Annealing temperature and barrier thickness effect on the structural and optical properties of silicon nanocrystals/SiO2 superlattices

The effect of the annealing temperature and the SiO2 barrier thickness of silicon nanocrystal (NC)/SiO2 superlattices (SLs) on their structural and optical properties is investigated. Energy-filtered transmission electron microscopy (TEM) revealed that the SL structure is maintained for annealing temperatures up to 1150 °C, with no variation on the nanostructure morphology for different SiO2 barrier thicknesses. Nevertheless, annealing temperatures as high as 1250 °C promote diffusion of Si atoms into the SiO2 barrier layers, which produces larger Si NCs and the loss of the NC size control expected from the SL approach. Complementary Raman scattering measurements corroborated these results for all the SiO2 and Si-rich oxynitride layer thicknesses. In addition, we observed an increasing crystalline fraction up to 1250 °C, which is related to a decreasing contribution of the suboxide transition layer between Si NCs and the SiO2 matrix due to the formation of larger NCs. Finally, photoluminescence measurements revealed that the emission of the superlattices exhibits a Gaussian-like lineshape with a maximum intensity after annealing at 1150 °C, indicating a high crystalline degree in good agreement with Raman results. Samples submitted to higher annealing temperatures display a progressive emission broadening, together with an increase in the central emission wavelength. Both effects are related to a progressive broadening of the size distribution with a larger mean size, in agreement with TEM observations. On the other hand, whereas the morphology of the Si NCs is unaffected by the SiO2 barrier thickness, the emission properties are slightly modified. These observed modifications in the emission lineshape allow monitoring the precipitation process of Si NCs in a direct non-destructive way. All these experimental results evidence that an annealing temperature of 1150 °C and 1-nm SiO2 barrier can be reached whilst preserving the SL structure, being thus the optimal structural SL parameters for their use in optoelectronics.

Characterization of Fe3O4/SiO2/Gd2O(CO3)2 core/shell/shell nanoparticles as T1 and T2 dual mode MRI contrast agent

Core/shell/shell structured Fe3O4/SiO2/Gd2O(CO3)2 nanoparticles were successfully synthesized. Their properties as a new type of T1–T2 dual model contrast agent for magnetic resonance imaging were investigated. Due to the introduce of a separating SiO2 layer, the magnetic coupling between Gd2O(CO3)2 and Fe3O4 could be modulated by the thickness of SiO2 layer and produce appropriate T1 and T2 signal. Additionally, the existence of Gd3+ enhances the transverse relaxivity of Fe3O4 possibly because of the magnetic coupling between Gd3+ and Fe3O4. The Fe3O4/SiO2/Gd2O(CO3)2 nanoparticles exhibit good biocompatibility, showing great potential for biomedical applications.

Effect of Thickness and Temperature of SiO2 Layer on Leakage Currents in MOS Capacitor Materials with High Dielectric Constant by Involving the Charge Trap

Modeling of the leakage current in a field-effect transistor metal-oxide-semiconductor (MOSFET) with high dielectric material has been developed by taking into account the effect of charge traps formed at the interface of high-k material/SiO2. Transmittance calculated using Airy wave function approach and involving the anisotropic electron mass and the effect of coupling between transverse and longitudinal energy represented by the speed of the electrons in the metal gate. Transmittance obtained is then used to calculate the leakage current in the structure of n+Poly-Si/HfSiOxN/trap/SiO2/p-Si for oxide voltage variations, temperature, and thickness of the SiO2. From the calculation that the leakage current decreases with decreasing of oxide voltage and increasing of the thickness of the oxide layer of SiO2. Also obtained that the temperature of the device does not give a great influence on the change of leakage current. Keywords: Leakage current, electron speed, charge traps

Optical Constants Determination of Pseudomorphic Si1-XGex Layers on Si(001), with 0

Spectroscopic ellipsometry (SE) is the technique of choice for the fast, non-destructive characterization of pseudomorphic Si1-xGex/silicon heterostructures in a manufacturing environment. Because of its small spot, SE can indeed be used on blanket wafers for epitaxial process monitoring and on patterned wafers for measurement in dedicated structures as small as 50 x 50 μm². Still, SE analysis is sometimes plagued by correlation effects, i.e. difficulties in determining the thickness and optical properties in a de-convoluted manner. A reliable alloy model that would accurately describe the optical constants of fully strained Si1-xGex material in a large range of germanium content is thus required to minimize correlation in the SE analysis of Si1-xGex/Si heterostructures. Such an alloy model must be based on a set of high-quality epitaxial films characterized with i/ an accurate spectroscopic ellipsometer in order to access to the Ψ and Δ angles over a wide spectral range and ii/ analytical techniques such as X-ray reflectometry (XRR) or high-resolution X-ray diffraction (XRD), in order to accurately gain access to the thickness of the epitaxial film and its germanium content and confirm that films are indeed fully pseudomorphic.The pseudodielectric function <ε>=<ε1>+i<ε2> deduced from the Ψ and Δ angles (figure) contains contributions from surface over-layers (native oxide, surface roughness, airborne molecular contamination) and from the substrate, since the penetration depth is most of the time higher that the critical thickness for plastic relaxation of Si1-xGex, above which such layers are not fully pseudomorphic anymore. Pickering et al. described the impact of surface over-layers and provided ways to access the true dielectric function of the Si1-xGex alloy. The most effective approach is a SE measurement immediately after removing the sample from the growth reactor together with a modelling of the SE data with a {overlayer/Si1-xGex /substrate} system. Some micro-roughness and potentially some excess Ge segregating on the growing surface can indeed contribute to this over-layer. Supposing that it is in fact a 0.5-0.7nm thick SiO2layer will however introduce negligible errors. Other authors did not include time constraints between process and measurement and determined the thickness of the overlayer from the non-vanishing pseudoabsorption below the bandgap, resulting in oxide thickness up to 2 nm, depending on the aging of the layer.Optical constants of strained Si1-xGex are usually available in the x = 0 - 0.35 range. This abstract describes variable-angle spectroscopic ellipsometry (VASE) measurements from 0.73 to 6.48 eV on a Woollam M2000 rotating compensator ellipsometer on a series of high-quality pseudomorphic Si1-xGex films (0<x<0.54) grown by Reduced Pressure Chemical Vapor Deposition (RP-CVD) on Si(001) substrates. XRD and XRR were used to determine the germanium content and the thickness of the Si1-xGex films, respectively. The management of the surface over-layer combined a “HF-last” wet cleaning step immediately followed by SE and XRR measurements, so as to get rid of the contributions of airborne molecular contamination and aging of the epitaxial layer. The dielectric function of each Si1-xGex film of this reference wafer set was calculated using XRR-deduced thickness as a reference and describing the over-layer as SiO2 with fixed thickness equal to 0.7nm. The Si1-xGex optical constants determined at ten compositions were interpolated for arbitrary Ge composition up to 54%. This alloy model was then tested on a large number of Si1-xGex films (evaluation wafer set) in order to demonstrate its ability to accurately characterize inline pseudomorphic Si1-xGex films over a wide range of germanium contents (0.5-1 at.% accuracy concerning the determination of the Ge content).

Invited: Critical Role of Si Nanoparticles Surface on Lithium Cell Electrochemical Performance

The surface of Si particles is strongly involved in different phenomena of crucial importance for the electrochemical performance of lithium batteries with Si-based composite electrodes. Indeed, Si electrodes suffer from poor cyclability due to the large volumetric expansion of Si particles upon cycling. The successive swelling and shrinkage upon alloying/dealloying of the stack of Si particles within the confined space of the electrochemical cell leads to major geometrical change of granular texture with a vast redistribution of inter-particle contacts, the formation of cracks within the composite electrode and loss of electrical contacts at the current collector interface. The repetition of all these processes with frictional sliding of the particles leads to a damaging of the SEI layer that exposes again the Si particles surface to the liquid electrolyte. It results in an irreversible capacity loss at each cycle by the reduction at low potential of some liquid electrolyte on the exposed surface [1]. Silicon is always recovered by a native silicon oxide layer. An electrochemical reduction of the SiO2 surface layer occurs at the first cycle with the formation of lithium silicate, Li4SiO4, and Li2O as degradation products as proven by XPS [2]. Moreover, the silicon oxide layer is composed of hydroxylated silanol (SiOH) groups which likely dramatically increases the reactivity compared to the dehydroxylated siloxane phase (Si-O-Si) [3]. As a consequence various efforts have been made to reduce the thickness of SiO2 layer on silicon nanoparticles to decrease the first irreversible capacity and to enhance electrochemical performance. Although the surface of Si particles is playing a major role in the electrochemical performance, it has rarely been characterized in depth. A combination of techniques is here used to finely describe the surface of Si nanoparticles: Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy combined with TGA, Raman spectroscopy, solid-state high-resolution Nuclear Magnetic Resonance (MAS NMR), TEM coupled with Electron Energy Loss Spectroscopy (EELS), X-Rays Photoelectron Spectroscopy (XPS), and finally Broad Band Dielectric Spectroscopy (BDS). With respect to previous works and common belief, we demonstrate, on the electrochemical performance, a favorable effect of a particular thin layer silicon oxide with a well-defined SiO2 composition at its extreme surface.

Photoacoustic Drive of Microfluid Using Au/SiO2 Heterostructured Nanorods Array

There is a growing interest in photoacoustic emission from noble metal nanoparticles (NPs) because of their potential applications in the field of manipulation of fluid or particles by convection flow and thermophoresis. Especially, two-dimensional noble metal NPs arrays are suitable for microfluid manipulation because they can establish a spatial temperature gradient at nanometer scale. However, their optical absorption is only a few tens of percent of the incident light even at the wavelength of the local plasma resonance, so that they are inefficient from the viewpoints of photothermal conversion efficiency.Recently, we demonstrated the self-assembly of Au NPs/ SiO2 nanocolumns/ SiO2/ Ag mirror structures, i.e., local plasmon resonators, by taking advantage of dynamic oblique angle deposition technique. Since they form an optical cavity, the optical absorption of Au NPs array can be modulated from 3% to 97% by varying the thickness of the SiO2 layer due to the interference. In our previous study [1], we reported the photothermal conversion efficiency of the local plasmon resonators is proportional to their optical absorption. This result suggests that their heat generation can be spatially controlled through the patterning of the SiO2 layer thickness. If the local plasmon resonator with a high optical absorption can produce strong photoacoustic emission, they are expected to realize flexible fluid manipulation by a spatio-temporally controlled temperature gradient at nanometer scale. In this study, we investigate their potential for the fluid manipulation through photoacoustic measurements and simple fluid manipulation experiments.The photoacoustic spectra are obtained by irradiating the samples with a laser (wavelength 785 nm) whose intensity was modulated sinusoidally (1–100 kHz) and recorded the amplitude of the acoustic signal as a function of the frequency. In order to demonstrate the fluid manipulation with local plasmon resonators, we created a PDMS cell, which was filled with water in which polystyrene microspheres were dispersed, on a sample. Then, we observed the motion of the polystyrene microspheres under laser illumination.The photoacoustic amplitude of a local plasmon resonator with a high optical absorption (A = 97%) is much larger than the amplitude not only of a high reflective Ag film (A ≤ 5%) but also of a graphite (A = 85%). In addition, the photoacoustic amplitude of the local plasmon resonators remains at high value even in the high frequency region from 20 kHz and 100 kHz, while those of the graphite and Ag thin film attenuated significantly. These results suggest that the heat generation in the local plasmon resonators is well localized in the thin Au NPs layer (∼ 10 nm) and contributes to the efficient photoacoustic emission. In addition, the sample with a high optical absorption rapidly drive the polystyrene microspheres dispersed in water under laser illumination, whereas that with a low optical absorption dose not drive the microspheres at all. Consequently, the local plasmon resonators are suitable for flexible microfluid manipulation.[1] K. Namura, et al., Opt. Lett. 36, 3533 (2011).

Plasmonic properties of Au/SiO2 nanoparticles: effect of gold size and silica dielectric layer thickness

Metallic nanoparticles with plasmonic properties have extensive potential applications in biodiagnostics and sensing, bioimaging and solar cells, but a comprehensive theoretical and experimental investigation of the phenomenon is far from being complete. In this manuscript, about 30, 40 and 50 nm Au nanoparticles were synthesised by Frens method, and Au/SiO2 nanoparticles were obtained by a modified Stöber method; the thickness of SiO2 layer were adjusted from 15 to 45 nm. The effect of Au size and SiO2 dielectric layer thickness on the plasmonic properties of Au/SiO2 nanoparticles were numerically simulated by 3D comsol and were experimentally studied by UV-vis absorption spectra. UV-vis absorption spectra showed that the increase in Au particle size or SiO2 thickness resulted in a red shift of the surface plasmon resonance absorption peak of Au/SiO2 nanoparticles, which is consistent with the simulation results by 3D comsol. Thicker SiO2 layer and smaller Au nanoparticles led to the decrease of electric field.

Dielectric spectroscopy investigations of nanostructured silicon

Dielectric spectroscopy measurements were performed on planar silicon nanostructures buried within a crystalline Si that form a nanoscale Si-layered system. An insight into the specific behavior of the free-carrier population confined in the surface potential well was then made possible. It was found that the presence or the absence of the SiO2 passivation modifies considerably relaxation responses of the studied structures. A clear differentiation of two dielectric responses: from the same sample with and without electronic passivation allowed determination of the conduction behavior in the surface c-Si delimited by the nanoscale Si-layered system. The sample with a 100 nm thick SiO2 layer (and an excellent quality of the SiO2/c-Si interface) exhibits a fractional power-law dielectric response, corresponding clearly to the generalized Mittag–Leffler pattern. Simultaneously, the dielectric response of a bare sample (after the total RIE of the previously deposited SiO2 layer, about 10 nm native SiO2 layer and poor quality of the SiO2/c-Si interface) is dominated by the conductivity term.

Fabrication of multilayered superparamagnetic particles based on sequential thermal deposition method

A simple method for the fabrication of superparamagnetic particles was developed. Polystyrene spheres were used as templates, and their surfaces were coated with a magnetic element (Ni) by thermal deposition, controlling their thicknesses strictly. Magnetic properties of fabricated particles depended on the Ni layer thickness; the fabricated particles were typically superparamagnetic for a Ni layer thinner than 3 nm and ferromagnetic for a Ni layer thicker than 4 nm. For the improvement of the force generated on a particle in a magnetic field, the formation of multiple Ni layers on a particle was examined by sequential depositions of Ni and SiO2, isolating two Ni layers with a SiO2 layer. The SiO2 layer thickness should be larger than 10 nm for a sufficient isolation of two Ni layers to maintain the superparamagnetic properties of the particle, and the magnetic charge of the particle increased proportionally with the number of Ni layers on a particle. These results indicate that enhanced superparamagnetic particles with various diameters can easily be fabricated by the suggested method.