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1.
The transmission spectrum of linearly polarized visible light through double metal thin films perforated with nano-hole arrays is investigated and simulated by using the three dimensional finite-difference time-domain method. The results show that the transmission spectra can be controlled by changing the longitudinal interval G between films and, their lateral displacements Lx and Ly, which are parallel and perpendicular to the polarization direction of the incident light, respectively. We have two important peaks (due to guided mode and SP mode) in these spectrums. The variation in longitudinal distance results a wavelength shift in guided mode peak of transmission spectrum while the wavelength of SP mode peak remains fixed. The lateral displacement Lx leads to the higher transmission of the guided mode peak, while the lateral displacement Ly suppresses the transmission of this peak. Here we try to discuss the physical explanations of these spectral behaviours by surface plasmon waves on the metal films and by using the concepts of surface plasma (SP) and guided modes in our double metal structure.  相似文献   

2.
The properties of wave transmission in a strongly dispersive semiconductor-dielectric photonic crystal (SDPC) are theoretically investigated. We consider a one-dimensional finite SDPC, air/(SD) N S/air, where, N is the stack number, S is an extrinsic semiconductor, n-type InSb (n-InSb), and D is a dielectric layer of SiO2. Transmission peaks can be found in the frequency region where the real part of the complex permittivity of n-InSb is negative. The number of peaks is equal to the stack number N. The positions of peaks can be tuned by the thicknesses of S and D. The peaks are seen to be blue-shifted as the doping density increases, leading to a tunable filter. The locations of peaks are also strongly dependent on the incidence angle, but weakly dependent on the polarization of the incident wave. The results suggest that a tunable multichannel filter can be achieved by using such an SDPC. Filters with tunable and multichannel features are of technical use in photonic applications such as in the optical electronics and communications.  相似文献   

3.
The oxide potential barrier in metal-SiO2-Si junctions is examined experimentally for oxide thickness 4 ? 50 Å using tunnel currents. The importance is emphasized of finding the electron concentration, ns, at the Si surface before deducing the tunneling transmission coefficient of the oxide barrier. ns increases rapidly with increasing δ, and is larger with Al than with Au electrodes.The SiO2 layers give appreciably lower transmission coefficients (1) with Al than with Au electrodes, and (2) for SiO2 grown in wet O2 at 900°C than for SiO2 grown in dry O2 at 700°C.  相似文献   

4.
We systematically investigated the role of the top interface for TaCx and HfCx/HfO2 gate stacks on the effective work function (Φm,eff) shift by inserting a SiN layer at the gate/HfO2 top interface or HfO2/SiO2 bottom interface. We found that Φm,eff of the TaN gate electrode on HfO2 was larger than that on SiO2 because of the HfO2/SiO2-bottom-interface dipole. On the other hand, we found that Φm,eff values of the TaCx and HfCx gate electrodes on HfO2 agree with Φm,eff on SiO2. This is because the potential offset of the opposite direction with respect to the bottom interface dipole appears at the metal carbide/HfO2 interface. It is thus concluded that the top interface in the metal carbide/HfO2 gate stacks causes the negative Φm,eff shift.  相似文献   

5.
In this work, we theoretically investigate the properties of defect modes in a defective photonic crystal containing a semiconductor metamaterial defect. We consider the structure, (LH)N/DP/(LH)N, where N and P are respectively the stack numbers, L is SiO2, H is InP, and defect layer D is a semiconductor metamaterial composed of Al-doped ZnO (AZO) and ZnO. It is found that, within the photonic band gap, the number of defect modes (transmission peaks) will decrease as the defect thickness increases, in sharp contrast to the case of using usual dielectric defect. The peak height and position can be changed by the variation in the thickness of defect layer. In the angle-dependent defect mode, its position is shown to be blue-shifted as the angle of incidence increases for both TE and TM waves. The analysis of defect mode provides useful information for the design of tunable transmission filter in semiconductor optoelectronics.  相似文献   

6.
SiOx nanowire bunches were fabricated on a SiNx film with Au catalytic metal in the presence of an Ar flow of 50 sccm at 1150 °C. The resulting samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. A SiNx film serves as a barrier to the diffusion of Si atoms from the Si substrate to the catalytic Au metal, where a substrate is a Si source material for SiOx nanowire (NW) growth. Using this process, we could temporally control the initial growth step of SiOx NWs and easily grow the NW bunch.  相似文献   

7.
The impact of HfO:N post nitridation anneal (PNA) and gate fabrication on the physico-chemical properties of the TiN/HfO:N/SiO2/Si stack are investigated using Soft X-ray Photoelectron Spectroscopy (S-XPS) and Vacuum UltraViolet Spectroscopic Ellipsometry (VUV-SE). Defects created in the high-k during plasma nitridation are passivated by PNA under O2. Both oxygen and nitrogen diffusion is observed towards the bottom SiO2/Si interface together with a regrowth of the SiO2. These defects play a major role regarding nitrogen diffusion during gate fabrication. Without PNA, no diffusion is observed because O and N atoms are trapped inside the high-k. With PNA and simultaneous defects passivation, nitrogen from both metal gate and high-k diffuses towards the bottom SiO2/Si interface.  相似文献   

8.
The early stages of iron silicide formation in the Fe/SiO x /Si(100) ternary system during solid-phase epitaxy are studied by high-resolution (~100 meV) photoelectron spectroscopy using synchrotron radiation. The spectra of core and valence electrons taken after a number of isochronous heat treatments of the samples at 750°C are analyzed. It is found that the solid-phase reaction between Fe and Si atoms proceeds in the vicinity of the SiO x /Si interface, which metal atoms reach when deposited on the sample surface at room temperature. Iron silicide starts forming at 60°C. Solid-phase synthesis is shown to proceed in two stages: the formation of the metastable FeSi interfacial phase with a CsCl-like structure and the formation of the stable β-FeSi2 phase. During annealing, structural modification of the silicon oxide occurs, which shows up in the growth of the Si+4 peaks and attenuation of the Si+2 peaks.  相似文献   

9.
Sapphire is a desired material for infrared-transmitting windows and domes because of its excellent optical and mechanical properties. However, its thermal shock resistance is limited by loss of compressive strength along the c-axis of the crystal with increasing temperature. In this paper, double layer films of SiO2/Si3N4 were prepared on sapphire (α-Al2O3) by radio frequency magnetron reactive sputtering in order to increase both transmission and high temperature mechanical performance of infrared windows of sapphire. Composition and structure of each layer of the films were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. Surface morphology and roughness of coated and uncoated sapphire have been measured using a talysurf. Flexural strengths of sapphire sample uncoated and coated with SiO2/Si3N4 have been studied by 3-point bending tests at different temperatures. The results show that SiO2/Si3N4 films can improve the surface morphology and reduce the surface roughness of sapphire substrate. In addition, the designed SiO2/Si3N4 films can increase the transmission of sapphire in mid-wave infrared and strengthen sapphire at high temperatures. Results for 3-point bending tests indicated that the SiO2/Si3N4 films increased the flexural strength of c-axis sapphire by a factor of about 1.4 at 800 °C.  相似文献   

10.
Very thin films of TiO2 and Ti2O3 were deposited by evaporation on Ag, on silver oxidized by an oxygen plasma and on Pt. Depending on the coverage, there were changes in the values of the binding energy (BE) and the Auger parameter (α′) of O and Ti. These shifts occur in the opposite direction with respect to that previously found for TiO2 supported on insulators. Among others, reasons for these shifts are the different relaxation energy of photoholes and the occurrence of charge transfer processes at the metal oxide/metal interface. UV-visible absorption spectra of thin films of TiO2Ag composites have shown a narrowing in the gap energy (Eg) of the oxide in respect to bulk titania. This observation shows the existence of a correlation between Eg and α′ when TiO2 is supported on a metal surface. The Auger parameter of O and Ti is also sensitive to the intercalation of TiO2 within a “sandwich” structure of SiO2 and Ag, and the values found for the spectroscopic parameters are intermediate between those of TiO2 supported on Ag and SiO2. This result opens up the possibility of modulating the electronic properties of thin layers of TiO2 by interaction with other materials.  相似文献   

11.
We report an investigation at the endpoint region of the spin density wave state in (TMTSF)2PF6 where metal and superconductivity emerge. Thanks to resistivity measurements along the three main crystallographic directions, we are able to follow the texture in this phase coexistence regime. In this respect, superconductivity is used as a decoration technique of the metallic pattern. We show that metal (superconductivity) emerges first along the c? direction in a counterintuitive manner. Then metal (superconductivity) domains evolves from filaments along the c? axis towards slabs perpendicular to the a-axis which melt together in the homogeneous phase at high pressure. This evolution is compatible with the proposition of the formation of a soliton phase in the vicinity of the critical pressure of the (TMTSF)2PF6 phase diagram.  相似文献   

12.
Silica (SiO2)-coated ceria (CeO2) nanoparticles were prepared using water-in-oil microemulsion. Polyoxyethylene (15) cetylether and cyclohexane were used as a surfactant and organic solvent. SiO2-coated CeO2 nanoparticles were obtained by hydrolysis of metal alkoxide (tetraethylorthosilicate, TEOS) in the solution containing CeO2 precursor nanoparticles. The effects of CeO2 sources (Ce metal salt) and CeO2 particle-forming agents on the morphology of SiO2–CeO2 particles were investigated. Observation via transmission electron microscopy revealed that the type of particle-forming agent affected the nanoparticles' morphology and that CeO2 nanoparticles were spherically coated with SiO2 when using oxalic acid ((COOH)2) as a particle-forming agent of CeO2. Furthermore, the transmittance of the particles was high in the visible region (above 400 nm) and decreased in the ultraviolet region.  相似文献   

13.
Strontium ferrite (SrM) thin films deposited on thermally oxidized silicon wafer (SiO2/Si) and single crystal sapphire with (0 0 l) orientation (Al2O3(0 0 l)) substrate using Pt underlayer were prepared by DC magnetron sputtering system. It was found that the intensity of (1 1 1) line for Pt and that of (0 0 l) diffraction line for SrM increases with increasing substrate temperature, Tu. The c-axis dispersion angle, Δθ50, of SrM(0 0 8) depends on that of Pt underlayer. Both dispersion angle of Pt(1 1 1) and SrM(0 0 8) decrease with increasing temperature. It was observed that the saturation magnetization of SrM/Pt deposited on SiO2/Si is higher than that of Al2O3 substrate. The coercivity and remanent squareness ratio in perpendicular direction are higher than that in in-plane direction. The maximum of coercivity in perpendicular direction of SrM/Pt films deposited on single crystal Al2O3 is about 4.2 kOe.  相似文献   

14.
Regenerable antimicrobial N-halamine/silica hybrid nanoparticles (NPs) containing chlorinated 5,5-dimethylhydantoinyl (Cl-DMH) groups, Cl-DMH/SiO2 hybrid NPs, have been prepared by a co-condensation reaction between N-(3-triethoxysilylpropyl)-5,5-dimethylhydantoin (TS-DMH) and tetraethoxysilane (TEOS) and then a chlorination reaction in NaClO solution. The as-synthesized Cl-DMH/SiO2 NPs were characterized by transmission electron microscopy, Scanning electron microscopy, X-ray photoelectron spectra, Specific surface area, Differential scanning calorimetry, and Fourier transform infrared. Experimental results showed that the size of the as-synthesized Cl-DMH/SiO2 NPs could be well adjusted by changing the mass ratio of TS-DMH/TEOS and the volume ratio of 28 % NH4OH/H2O. Antimicrobial tests showed that the as-prepared Cl-DMH/SiO2 hybrid NPs had excellent antimicrobial activities against both Escherichia coli and Staphylococcus aureus. The minimum inhibitory concentration and minimum bactericidal concentration values of the as-prepared Cl-DMH/SiO2 hybrid NPs are 15 and 20 μg/mL for S. aureus, 25 and 30 μg/mL for E. coli, respectively. Paper disk diffusion assay showed that smaller-sized Cl-DMH/SiO2 hybrid NPs have bigger inhibition zone diameters, indicating stronger antimicrobial efficacies. Also, the storage stability and regenerability of Cl-DMH/SiO2 hybrid NPs were investigated.  相似文献   

15.
The morphology and electronic properties of Au nanoclusters on the surface of SiO2 thin films on n +-Si substrates are studied using the combined scanning tunneling microscopy (STM) and atomic-force microscopy (AFM) technique. The peaks associated with the resonant tunneling of electrons from the states of the valence band of the probe material to the states of the conduction band of the substrate material through Au nanoclusters are observed on the current-voltage characteristics for the contact of a p +-Si AFM probe with Au nanoclusters. Experimental results are interpreted by calculating the tunnel transparency of the SiO2/Au/SiO2 double barrier structure in a strong electric field.  相似文献   

16.
We experimentally evaluate the electrical properties of carbon nanotube (CNT)-network transistors before and after 60Co gamma-ray irradiation up to 50 kGy in an air environment. When the total dose is increased, the degree of the threshold voltage (Vth) shift towards positive gate voltages in the drain current–gate voltage (IDVGS) characteristics decreases for total irradiation doses above 30 kGy, although it is constant below 30 kGy. From our analysis of the IDVGS characteristics along with micro-Raman spectroscopy, the gamma-ray irradiation does not change the structure of the CNT network channel for total doses up to 50 kGy; it instead generates charge traps near the CNT/SiO2 gate insulator interfaces. These traps are located within the SiO2 layer and/or the adsorbate on the device surface. The positively charged traps near the CNT/SiO2 interface contribute less to the Vth shift than the interface dipoles at the CNT/metal electrode interfaces and the segment of the CNT network channel below doses of 30 kGy, while the contribution of the charge traps increases for total doses above 30 kGy. Our findings indicate the possibility of the application of CNT-network transistors as radiation detectors suitable for use in air for radiation doses above 30 kGy.  相似文献   

17.
The impact of hydrogen desorption on the electrical properties of TiOx on crystalline silicon (c-Si) with SiOy interlayers is studied for the development of high-performance TiOx carrier-selective contacts. Compared with the TiOx/c-Si heterocontacts, a lower surface recombination velocity of 9.6 cm/s and lower contact resistivity of 7.1 mΩ cm2 are obtained by using SiOy interlayers formed by mixture (often called SC2). The hydrogen desorption peaks arising from silicon dihydride (α1) and silicon monohydride (α2) on the c-Si surface of the as-deposited samples are observed. The α1 peak pressure of as-deposited heterocontacts with SiOx interlayers is lower than that of heterocontacts without a SiOy interlayer. Furthermore, the hydrogen desorption energies are found to be 1.76 and 2.13 eV for the TiOx/c-Si and TiOx/SC2-SiOy/c-Si heterocontacts, respectively. Therefore, the excellent passivation of the TiOx/SC2-SiOy/c-Si heterocontacts is ascribed to the relatively high rupture energy of bonding between Si and H atoms.  相似文献   

18.
The optically detected magnetic resonance (ODMR) observation of dangling bonds at the Si/SiO2 interface (Pb centers) is reported in this Communication. A luminescence quenching signal is identified as arising from the Pb center through its axially symmetry g tensor along the <1 1 1#62; direction. The negative sign observed for both the Pb center and the neutral phosphorus donor resonances allows us to interpret the recombination mechanism as a spin dependent electron transfer from the phosphorus donor to the Pb center.  相似文献   

19.
Diamond-like carbon (DLC) films were deposited on Si (1 0 0) substrate using a low energy (219 J) repetitive (1 Hz) miniature plasma focus device. DLC thin film samples were deposited using 10, 20, 50, 100 and 200 focus shots with hydrogen as filling gas at 0.25 mbar. The deposited samples were analyzed by XRD, Raman Spectroscopy, SEM and XPS. XRD results exhibited the diffraction peaks related to SiO2, carbon and SiC. Raman studies verified the formation amorphous carbon with D and G peaks. Corresponding variation in the line width (FWHM) of the D and G positions along with change in intensity ratio (ID/IG) in DLC films was investigated as a function of number of deposition shots. XPS confirmed the formation sp2 (graphite like) and sp3 (diamond like) carbon. The cross-sectional SEM images establish the 220 W repetitive miniature plasma focus device as the high deposition rate facility for DLC with average deposition rate of about 250 nm/min.  相似文献   

20.
《Current Applied Physics》2009,9(5):1046-1053
Multilayer bandpass and bandstop filters have been produced using electron beam evaporation. Initially bandstop filter is modeled with non absorbing zinc sulphide (ZnS) and zinc selenide (ZnSe). When the absorption data was incorporated for the said materials significant absorption was observed at shorter wavelengths of the spectral band restricting the practical usage of the filter. ZnS and ZnSe were then replaced by dispersive silicon dioxide (SiO2), tantalum penta oxide (Ta2O5) and titanium dioxide (TiO2) along with their absorption and the filters are optimized to get desired bandpass and bandstop data. Bandpass and bandstop filters with desired performance were experimentally characterized with two combinations SiO2/Ta2O5/glass and SiO2/TiO2/glass. The measured average transmission for both combination (bandpass) in the pass band was about 92% with T < 1% in the stop band. Slightly narrow bandwidth was observed for SiO2/TiO2/glass as compared to SiO2/Ta2O5/glass which is attributed to layers densification. Similarly Tavg  80% was achieved for two combinations of bandstop filters with T < 0.1% in the stop band. The structure and surface morphology of the prepared filters were characterized by X-ray diffraction and scanning electron microscopy. XRD analysis reveals amorphous structure. SEM analysis also reveals that the layers are compact and have good surface quality.  相似文献   

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