Characterization of interface states at Au/SnO2/n-Si (MOS) structures

The purpose of this paper is to characterize the interface states in Au/SnO₂/n-Si (MOS) structures. The characteristic parameters of the interface states are derived from capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements as a function of frequency. The C-V and G/ω-V measurements have been carried out in the frequency range of 1 kHz to 1 MHz at room temperature. At each frequency, the measured capacitance and conductance decrease with increasing frequency due to a continuous distribution of the interface states. The frequency dispersion in capacitance and conductance can be interpreted in terms of the interface state density (N_ss) and series resistance (R_s). Especially at low frequencies, the interface states can follow the ac signal and yield an excess capacitance. Due to a continuous density distribution of interface states, the C and G/ω values decrease in depletion region with increasing frequencies. At high frequencies, the effect of series resistance on the capacitance is found appreciable due to the interface state capacitance decreasing with increasing frequency. Experimental results show that the locations of interface states between SnO₂/Si and series resistance have a significant effect on electrical characteristics of MOS structures.     

Positron annihilation study of vacancy-type defects in high-speed deformed Ni, Cu and Fe

Vacancies and vacancy clusters in Ni, Cu, and Fe induced by high- and low-speed deformations are studied systematically by positron annihilation techniques and are compared with those induced by the conventional-rolling. To clarify the nature of the defects, the experimental results are compared with our superimposed-atomic-charge calculations of the positron lifetimes in the vacancy clusters as a function of their size. It is found that the deformation-induced defects in the fcc and bcc metals are significantly distinct. In the fcc metals of Ni and Cu, monovacancies with high number densities are induced by the high- and low-speed deformations and by heavy conventional-rolling (>10% in Ni and >40% in Cu). Vacancy clusters are observed after the high- and low-speed deformation for Ni and after the conventional-rolling for Cu. On the contrary, dislocations and vacancy clusters are introduced in bcc Fe regardless of the type or degree of deformation.     

Characterization of implantation induced defects in Si-implanted SiO2 film

Si-implanted thermal SiO2 layers and their annealing behaviour were investigated. In the results of variable-energy positron annihilation spectroscopy, the defects caused by ion implantation are manifested as a particularly low S parameter in the Si ion implantation region of the SiO2 layer. Compared with Fourier transform infrared measurements, it suggests that the decrease of the line shape S parameter after implantation is related to the compaction of implanted layers induced by the breaking of the SiO2 network structure. The presence of blue band emission (430-470 nm) in the implanted SiO2 layer is associated with neutral oxygen vacancy. An increase of the S parameter in the implanted layers is observed after annealing at different temperatures, but it is impossible completely recover the pre-implantation condition after a thermal treatment.     

Positron annihilation study of defects in titanium

Positron annihilation linewidth measurements have been used to study defect behaviour in titanium samples which were first cold-worked and then annealed at temperatures ranging up to 850°C. The line width for a highly deformed high purity (0.9998) sample showed a gradual increase with increasing annealing temperature up to the recrystallization temperature, above which there was a rapid increase. In contrast, a commercially pure (0.9984) sample deformed by 20% displayed a smooth increase in linewidth over the entire annealing range. Hardness measurements correlate reasonably well with the overall trend of the positron lineshape parameter, but the positron annihilation measurements reveal defect changes that occur at temperatures too low to give any observed changes in hardness.     

Electrochemical deposition of Ni and Cu onto monocrystalline n-Si(100) wafers and into nanopores in Si/SiO2 template

Nickel and copper were potentiostatically deposited onto monocrystalline n-Si (100) wafers and in nanoporous SiO₂/Si template from 0.5 M NiSO₄ + 0.5 M H₃BO₃ and 0.005 M CuSO₄ + 0.5 M H₃BO₃ solutions. Nanoporous SiO₂/Si template was formed by etching in dilute HF solution of ion tracks. The latter were produced by high-energy (380 MeV) Au⁺ ions bombardment of silicon oxide thermally grown on silicon (100) substrate. The deposition of metals was studied using cyclic voltammetry (CV), chronoamperometry; the structure and morphology of products were ex-situ investigated by SEM and XRD. The level of pores filling was controlled by deposition time. Electrodeposition occurred selectively into nanopores and the deposition on SiO₂ layer was excluded. It was found out that Ni and Cu electrodeposited into nanopores of SiO₂/Si system formed the same structures as at electrodeposition on the surface of monocrystalline n-Si—granules for Ni and scale-shaped particles for Cu deposits.     

Antireflective hydrophobic si subwavelength structures using thermally dewetted Ni/SiO2 nanomask patterns

We report the disordered silicon (Si) subwavelength structures (SWSs), which are fabricated with the use of inductively coupled plasma (ICP) etching in SiCl4 gas using nickel/silicon dioxide (Ni/SiO2) nanopattens as the etch mask, on Si substrates by varying the etching parameters for broadband antireflective and self-cleaning surfaces. For the fabricated Si SWSs, the antireflection characteristics are experimentally investigated and a theoretical analysis is made based on the rigorous coupled-wave analysis method. The desirable dot-like Ni nanoparticles on SiO2/Si substrates are formed by the thermal dewetting process of Ni films at 900 degrees C. The truncated cone shaped Si SWS with a high average height of 790 +/- 23 nm, which is fabricated by ICP etching with 5 sccm SiCl4 at 50 W RF power with additional 200 W ICP power under 10 mTorr process pressure, exhibits a low average reflectance of approximately 5% over a wide wavelength range of 450-1050 nm. The water contact angle of 110 degrees is obtained, indicating a hydrophobic surface. The calculated reflectance results are also reasonably consistent with the experimental data.     

Trap-assisted tunneling in p-Si/SiO2 structures

Conduction in p-Si/SiO₂ structures in which a 65.3-nm SiO₂ layer has been subjected to hydrogen-plasma treatment at 20 °C does not depend on temperature in the range 77–300 K, in the accumulation regime under an electric field of 0.7–4.5×10⁶ V cm^?1 in the SiO₂ layer. A trap-assisted tunneling mechanism in the SiO₂ layer has been proposed as an explanation for this tunneling-type conduction in the p-Si/SiO₂ structures.     

DLTS study of the influence of annealing on deep level defects induced in xenon ions implanted n-type 4H-SiC

In this study, nitrogen-doped 4H-SiC samples were bombarded with 167 MeV xenon ions to a fluence of 1?×?10⁸ cm^?2 at 300 K prior to the fabrication of Schottky barrier diodes. The implanted samples were annealed at approximately 900 °C for 1 h before the resistive evaporation of nickel Schottky barrier diodes. In comparing the current–voltage results of the implanted devices with as-deposited ones, generation-recombination took place in the implanted Schottky barrier diodes. Four defects (100, 120, 170, and 650 meV) were present in as-deposited Schottky barrier diodes when characterized by deep level transient spectroscopy (DLTS). In addition to the defects observed in the as-deposited samples, two additional defects with activation energies of 400 and 700 meV below the conduction band minimum were induced by Xe ions implantation. The two deep level defects present have signatures similar to defects present after irradiated by MeV electron. The two defects present after irradiation disappeared after annealing at 400 °C which indicate instability of the defects after annealing implanted samples.

     

Positron annihilation study of boron-doped Ni3Al

Positron-lifetime and Doppler-broadening measurements were performed at room temperature on well-annealed polycrystalline Ni_75?xAl_25+x alloys (x = ?1, 0, and + 1) containing 0, 100, and 500 wt. ppm boron. The large grain size ( ≈ 300–500μm) in these alloys rendered the grain-boundary contribution negligible in the positron annihilation process. Systematic dependences of the positron lifetimes and the Doppler-broadening lineshape parameter were observed as a function of both the aluminum and boron contents of the alloys. Positron trapping by defects was found in both the x = 0 and x = + 1 alloys, but was most pronounced in the nominally-stoichiometric alloys containing boron. No positron trapping was evident in the x = ?1 alloys with or without boron. A model is suggested for the relationship between these results and the problem of ductilizing poly-crystalline Ni₃Al by boron doping.     

Thermal annealing behaviour of Si/SiO2 structures

The interaction of vacuum-deposited silicon films with the underlying oxide at annealing temperatures of 1050–1250°C was studied by means of low energy electron diffraction, Auger spectroscopy, IR spectroscopy, and optical and electron microscopy. The deposition of silicon onto SiO₂-covered silicon substrates and the annealing of the samples was carried out in ultrahigh vacuum. The results obtained revealed that the silicon and oxide layers are etched away by heat treatment. The dependence of the etching on the thickness of the silicon film, the thickness of the SiO₂ layer and the annealing temperature was determined. A qualitative model of the etching process is proposed.     

Enhancement of magneto-conductance in n-Si/n-PS/NPB structures at room temperature

Hybrid organic–inorganic semiconductor heterojunction with a sandwich structure have been prepared and studied. The inorganic semiconductor is n-type Porous Silicon (n-PS) elaborated on n-type crystalline silicon, the used conjugated polymer is the N,N′-diphenyl-N,N′-bis(1-naphthyl-pheny1)-(1,1′-biphenyl)-4,4′-diamine (NPB). Current–voltage (I–V) at transverse static magnetic field effect was used to study the electrical properties of the devices at room temperature. The electrical parameters such as the ideality factor ‘n’, the barrier height and the series resistance are determined from the I–V curve. We report the observed magneto-conductance (MC) in a weak magnetic field. The observed positive MC was enhanced when we partially filled pores with the NPB. This effect reaches up to 4.7% at a magnetic field of 0.8 T.     

Properties of sensors based on shear-horizontal surface acoustic waves in LiTaO3/SiO2 and quartz/SiO2 structures

Acoustic wave devices based on waveguide modes with shear-horizontal polarization, i.e., Love modes, are very promising for sensor application, especially in liquid environments. They can be used for the determination of liquid density and viscosity as well as for chemical sensors. Up to now, several systems have been reported based on standard ST quartz. Those devices lack temperature stability, which is essential for field application. Thus, temperature-compensated systems based on different Y-rotated quartz and lithium tantalate (LiTaO3) plates with SiO2 guiding layers have been investigated. Temperature behavior as well as relevant acoustic properties were considered. Furthermore, experimentally determined data for device sensitivity are compared with theoretical predictions from numerical calculations.     

Numerical study on optical properties of Ag/SiO2SiO2/Ag sandwich nanocrescents substrate

A novel structure of a metal/dielectric/metal (Ag/SiO₂SiO₂/Ag) sandwich nanocrescent has been proposed and studied. We make a detailed numerical analysis on the extinction efficiency and LSPR property of the sandwich nanocrescent by using the finite difference time domain (FDTD) method. It clearly demonstrates that a comparable field enhancement can be achieved by varying the thickness of the SiO₂SiO₂ layer at different incident polarizations. Excited in the Y-polarization, the maximum electric field enhancement factor reaches 600 at the peak wavelength 1108.9?nm, which is six times higher than previous reported single layer nanocrescent. The refractive index sensitivity of this new sandwich nanocrescent is 375.5?nm/RIU (refractive index unit). The structure is shown to produce a high local field enhancement as well as wide plasmon resonance tunabilities. Besides, compared with adjusting the shape and size of the single layer nanocrescent structure, it is much more convenient and easier to change the thickness of the sandwich nanocrescent. Due to its excellent properties, this structure is very suitable for LSPR and SERS nanosensing substrate.     

Effect of illumination on electrical characteristics of Au/Mn-complex/n-Si photodiode structures

Journal of Materials Science: Materials in Electronics - We were produced a various Mn-doped complex and presented it in Au/Mn-complex/n-Si structure as an interfacial layer. For this aim, a...     

具有核壳结构的Ni／SiO2催化剂的制备及加氢性能研究

采用水热法制备了Ni3Si2O5（OH）4,在823K下通过氢气还原制备出了具有核壳结构Ni／SiO2催化剂,探讨以Ni／SiO2为催化剂,反应时间、温度、压力等因素对硝基苯液相加氢性能的影响,确定了硝基苯液相加氢适宜的条件,在该条件下硝基苯的转化率为97％,苯胺的选择性为99％。     

Photoelectron spectroscopy study of Mn/n-Si interfacial structure

The Mn/n-Si interfacial structure is susceptible to intermixing even at room temperature. To investigate the chemistry as a result of the intermixing, valence band and core level photoelectron spectroscopy of Mn/Si has been carried out using synchrotron radiation of 134 eV energy and Al K_α X-ray (λ = 1,486.6 Å) source. The fabricated structures have also been irradiated from swift heavy ions (Fe⁷⁺ of ~100 MeV) to investigate the ion beam mixing in such structures. Valence band photoelectron spectroscopy with 134 eV photons shows the evolution of Mn3d, Mn3p and Si2p levels with a shifting towards lower binding energy side compared to their elemental values of the binding energy. This binding energy shift shows the formation of chemical compound of Si and Mn. Evolution of Si2p core level prior to and after the swift heavy ion irradiation shows strong chemical reactivity of manganese thin film with silicon. Deconvolution of Mn3d valence band has shown the formation of silicide phase due to the hybridization of Mn3d and Si3sp states. Mn2p core level study shows that the oxide and silicide formation takes place during the growth and for successive etching, oxide part is decreasing whereas silicide part is increasing.     

Nanosized Ni/SiO2 catalyst prepared by homogeneous precipitation in wet silica gel

A Ni/SiO2 catalyst was prepared by homogeneous precipitation of nickel hydroxide in a sol-gel-derived wet silica gel. The preparation process consists of two successive steps: gelation of silica in the presence of nickel nitrate and urea at 50 degrees C, followed by aging at higher temperature, typically at 80 degrees C, to decompose the urea. The decomposition of urea increases the pH of the solution in the wet gel, leading to the concurrence of structural rearrangement of silica gel and deposition of nickel species. As a result, the structure of the silica changes from a ramified polymeric network into particle aggregates that entrap the nickel cations in the particles. The resulting Ni/SiO2 contains large mesopores that have high thermal stability up to 1000 degrees C and highly dispersed Ni metal particles with typical crystallite size of 4 nm even at high Ni content at 20 wt%.     

Synthesis and characteristics of p-CuAlO2/n-Si heterostructure

In this paper the CuAlO₂/Si heterostructure was synthesized by the radio-frequency magnetron sputtering. The CuAlO₂ thin film tends to be oriented on the (001) surface. The positive Hall coefficient confirms p-type nature of the film and the value of hole concentration is found to be around 3.6 × 10¹⁵ cm⁻³. The contact between the n- and p-type semiconductors was found to be rectifying within the measured temperature range from 320 to 120 K, and the diffusion potential increases with decreasing temperature. The ratio of forward current over the reverse current exceeds 35 within the range of applied voltages of −1.5 to +1.5 V and the turn-on voltage is about 0.5 V.     

High temperature oxidation of Ni2AlTi

The isothermal oxidation process in bulk and powdered Ni₂AlTi (L2₁ structure) has been studied in the temperature range of 600 to 1200° C in air by means of X-ray diffraction and scanning electron microscopy. At 900 and 1200° C, the transient oxides, NiO and TiO₂ were formed in the initial stage on the outer surface. Subsequent oxidation was dominated by outward diffusion of aluminium, resulting in the formation of a Ni₃Ti layer beneath an internal precipitation layer containing Al₂O₃-NiAl₂O₄ aggregates, NiTiO₃ and Ni₃Ti. Formation of NiTiO₃ and NiAl₂O₄ at the expense of NiO, TiO₂ and Al₂O₃ indicated the reaction among constituent oxides also occurred in the late stage of oxidation at 900 and 1200° C. Only NiO and TiO₂ were identified in specimens oxidized at 600° C up to 24h. The oxidation rate of Ni₂AlTi is of the same order of magnitude as the dilute γ-NiAl alloy at 1200° C.