In this paper production process of Zn nanocrystals in SiO2 by using an implantation of high dose zinc ions with energy of 130 keV and annealing process in 700°C were described. Using electron microscopy was established that annealing causes extension of admixtures distribution on depth and zinc nanoparticles size increasing from approx. 1 - 6 nm to 12 - 18 nm.
For prepared material AC conductivity measurements were made in temperatures range from liquid nitride temperature (LNT) to 373 K and at frequencies range from 50 Hz to 5 MHz. Strong frequency dependence on conductivity proves that in this nanocomposite Zn-SiO2 conduction takes place by electron hopping exchange (tunneling) between metallic phase nanoparticles.
It was established that three activation energies of conductivity occurs in temperatures range of LNT – 373 K – in low temperatures ΔE1≈0.001 eV, in medium temperatures ΔE2≈0.025 eV and in higher temperatures area ΔE3≈0.096 eV. This is due to the presence of at least two types of nanoparticles. First there are zinc nanoparticles with zinc oxide coating, second there are nanoparticles without the coating. The highest activation energy occurs during electrons tunneling between nanoparticles with zinc oxide coating. Intermediate activation energy corresponds to tunneling from nanoparticle with coating to nanoparticle without coating or conversely. The lowest activation energy corresponds to electrons hopping between nanoparticles without coatings.
In this paper measurements results of electrical and optical properties of SiNx thin layers are presented. Layers were produced by chemical vapor deposition on n-type (100)-oriented silicon substrates. Measurements were performed for samples directly after deposition and for samples annealed in temperature of 1073 K.
Resistance Rp, capacity Cp, phase angle shift θ and dielectric loss factor tgδ were the measuring parameters on AC in the frequency range from 50 Hz to 5 MHz as a function of measurement temperature from the range 20 K – 373 K. Based on this, the conductivity σ and the activation energy of conductivity were determined. Photoluminescence spectra were recorded at room temperature in the spectral region of 350 – 800 nm using a He-Cd laser source with λ=325 nm.
The influence of annealing on the electrical and optical properties was explained. Current resonance phenomenon and reduction of photoluminescence spectra were observed.
The results of calculation of electron drift velocity in GaAs-in-Al2O3 and GaAs-in-AlAs quantum nanowires as well as
the electric current in the armchair single-wall carbon nanotubes versus time are presented at various electric fields
applied along the structures and different temperature.
KEYWORDS: Field effect transistors, Monte Carlo methods, Electron transport, Scattering, Oxides, Silica, Silicon, Interfaces, Quantization, Surface roughness
The Monte Carlo model of electron transport in SOI MOSFETs is proposed. Both 2D and 3D conditions are considered.
The Poisson equation and boundary conditions are presented for every case. Fully depleted SOI MOSFETs and partially
depleted SOI MOSFETs are contradistinguished. The values of electron current as well as drift velocity in different
parts of SOI MOSFETs channel are calculated by means of the Monte Carlo simulation. The SOI MOSFETs with the
channel length equal to 0.5, 0.25 and 0.1 μm as well as the channel depth equal to 10, 20, 100, 200, 1000 nm are
studied. Drift velocity as a function of the channel depth is obtained. It is shown that the function has a peak at the
channel depth equal to 20 nm.
Compound refractive X-ray lens, consisting of a lot number of placed in-line concave microlenses, is a unique device to control X-ray beams. It works like ordinary refractive lens for visual light and, in contrast to other X-ray optical devices, is useful for forming image of X-ray source. The size of the source image S1 depends on the distance a between the source and the lens and may be calculated as S1=S M, where S is source size, M- magnification. The magnification M depends on a and b as M=b/a, where b is distance from the lens to the source image. This distance b satisfies to a well-known lens formula 1/a+1/b=1/f, where f is lens focal length. This lens property may be used for forming small-sized X-ray spots at a large enough distances from the lens. Such beams are of great interest for experiments on SAXS and X-ray diffraction.
Here we report results of our first experiments in Istituto per lo Studio dei Materiali Nanostrutturati and Laboratori Nazionali di Frascati on using compound refractive X-ray lenses for forming X-ray beams.
We have fabricated and tested short focal-length compound refractive lenses for X-rays (CRLs) and considered its
application for focusing coherent beams. The lens is designed in the form of glass capillary filled by micro-air-bubbles
embedded into epoxy. The interface between the bubbles formed 90 to 196 spherical bi-concave microlenses with curvature
radius equals to the capillary one. When compared with CRLs manufactured using other methods, the micro-bubble lenses
have shorter focal lengths with higher transmission for moderate energy X-rays (e.g. 7 - 12 keV). The lenses are inexpensive
and are ideally suited for focusing X-rays generated by high power single pulsed operation coherent X-ray sources with
Source size 50-100 microns. We used beamline 2-3 at the Stanford Synchrotron Radiation Laboratory (SSRL) to measure
focal lengths between 100-150 mm and absorption apertures between 90 to 120 pm. Transmission profiles were measured
giving, for example, a peak transmission of 27 % for a 130-mm focal length CRL at 8 keV. The focal-spot sizes were also
measured yielding, for example, an elliptical spot of 5 × 14-μm2 resulting from an approximate 80-fold demagnification of
the 0.44 × 1.7 mm2 source.
Current methods for synthesizing and studying carbon nanotubes (CNTs) as well as nanochannel structures based on
CNT arrays, Al2O3 and Si02 are discussed in this paper. A few processes of material self-organization provide for
preparing the ordered patterns of such nanocapillaries. Potential applications of these nanochannel structures in the field
of quanta and particle transportation are treated.
In this article the rates of electron scattering via phonons in the single-wall armchair carbon nanotubes were calculated within the approximation of tight-binding atoms and graphene zone folding.
KEYWORDS: Ionization, Field effect transistors, Monte Carlo methods, Quantization, Scattering, Electron transport, Transistors, Silicon, Neodymium, Nanoelectronics
The Monte Carlo model of the impact ionization in deep submicron MOSFETs is worked out. This model allows the influence of the secondary charge carrier current on the drain current to be evaluated. The developed model is built on the basis of the reduction scheme. Moreover, the model takes into account all the major features of electron transport in deep submicron MOSFETs, the dominant scattering mechanisms, the quantization of electron spectrum as well as the modeling of constructive parameters and basic drain breakdown mechanisms.
In this article the results of calculation of electron scattering rates and the drift velocity of these particles in free standing in vacuum GaAs quantum wire, electron scattering rates via polar optical and acoustic phonons in transistor device structure based on GaAs-in-AlAs quantum wire versus gate voltage, the electric current in armchair single-wall carbon nanotube versus strength of electric field applied along the channel and temperature are presented.
The model of transient enhanced diffusion of ion-implanted As is formulated and the finite-difference method for numerical solution of the system of equations obtained is developed. The nonuniform distribution of point defects near the interface and a new description of arsenic clustering are simultaneously taking into account. Simulation of As diffusion during rapid thermal annealing gives a reasonable agreement with the experimental data.
KEYWORDS: Scattering, Gallium arsenide, Surface roughness, Phonons, Monte Carlo methods, Acoustics, Solids, Electron transport, Particles, Electromagnetic scattering theory
In present investigation the function of average value of drift velocity versus electric field strength in GaAs quantum wires with various dimensions at temperature T=77 K at electric quantum limit is studied. In the framework of the eveloped model the nonparabolicity is taken into account. The scattering rates in the considered structures are calculated with account both noncollisional and collisional broadening of energy levels.
We have applied spectroscopic ellipsometry with binary polarization modulation to study the refractive index n(λ) and extinction coefficient k(λ) spectra of as-deposited and irradiated with nitrogen ions polymethylmethacrylate (PMMA) and polystyrene (PS) films in 300-1030 nm range. The results of performed investigation confirmed the possibility and estimate restrictions of the ion implantation for local change the refractive index of polymeric materials.
KEYWORDS: Monte Carlo methods, Field effect transistors, Algorithm development, Ionization, Scattering, Electron transport, Computer simulations, Instrument modeling, Software development, Doping
The ensemble Monte Carlo algorithm for simulation of charge carrier transport in short channel MOSFET was developed. The mobile charge carrier concentration and electrostatic potential calculation procedures were worked out. The drain current increasing mechanisms caused by secondary holes transport in short channel MOSFET were considered. It was found out that at channel length about 0.1 μm the influence of secondary holes transport is quite significant.
We have fabricated and tested short focal-length compound refractive lenses (CRLs) composed of micro-bubbles embedded in epoxy. The bubbles were formed in epoxy inside glass capillaries. The interface between the bubbles formed 90 to 196 spherical bi-concave microlenses reducing the overall focal length inversely by the number of lenses.
When compared with CRLs manufactured using other methods, the micro-bubble lenses have shorter focal lengths, better imaging, and focusing qualities with higher transmissions and gains for moderate energy x-rays (e.g. 7 - 12 keV). We used beamline 2-3 at the Stanford Synchrotron Radiation Laboratory (SSRL) to measure focal lengths between 100-150 mm and absorption apertures between 90 to 120 μm. Transmission profiles were measured giving, for example, a peak transmission of 27 % for a 130-mm focal length CRL at 8 keV. The focal-spot sizes were also measured yielding, for example, an elliptical spot of 5 x 14-μm2 resulting from an approximate 80-fold demagnification of the 0.44 x 1.7 mm2 source. The measured gains in intensity over that of unfocused beam were between 9 and 26. Theoretical gain calculations that include spherical aberrations show that these values are reasonable. The micro-bubble technique opens a new opportunity for designing lenses in the 8-9 keV range with focal lengths less than 30-40 mm.
KEYWORDS: Scattering, Phonons, Surface roughness, Monte Carlo methods, Signal attenuation, Gallium arsenide, Absorption, Electronics, Switching, Electron transport
The generation of electron drift velocity oscillations in GaAs-quantum wires with finite length at temperature T=77 K in uniform as well as nonuniform field is studied. The influence of wire length and dominant scattering processes on the amplitude, frequency and attenuation of the oscillations is investigated. The average time of electron drift in the various regions of the quantum wire is calculated.
We developed and studied refracting microcapillary lens for x-ray photons with energy 5.4 keV. This lens is a glass capillary wiht a central channel filled with a number of concave microlenses. The lenses are made by injection compressed air into a capillary channel, previously filled by liquid polymer. The images of 20-100μm width slits are obtained. A good agreement is seen betweenthe image and slits sizes. Ray tracing calculations of iamge formation are made. Experimental and calculated results are in a good agreement.
Refractive microcapillary lens for hard x-rays is presented. The lens is designed as glass capillary filled by a large number of biconcave microlenses. Fabrication technique for the lens is described. It is shown that the the microlenses have a spherical shape. The spherical aberrations of the lens are calculated. The possibility of production of micrometer sized x-ray beams by using the microcapillary x-ray lens is discussed.
A novel experimental method is presented for evaluating the crystal lattice imperfections using a reflection X-ray microscope (RXM). An X-ray microscope using an X-ray refractive lens is constructed on the reflected beam axis of the crystal. This method has a unique advantage that the image contrast due to the integral reflectivity variation and due to the phase-contrast of the crystal surface are easily discriminated by de-focusing technique. The sample crystals chosen were silicon circular Bragg Fresnel zone places (BFZPs). The BFZPs had circular zones on Si(111) plane with two different groove depths of 3.9 micrometers and 5.9 micrometers . The validity of the de-focusing method was proved and a clear difference of the X-ray microscope images was observed for the BFZPs with different groove depth.
Calculation procedures and experimental results form glancing angle x-ray fluorescence from thin films on a flat substrate are presented. A new x-ray tube unit with a super smooth-surface anode and a built-in waveguide collimator is described. The unit makes it possible to obtain narrowly- collimated beams of x-ray radiation with a microfocus line.
A new X-ray tube unit with a super smooth-surface anode and a built-in waveguide collimator is proposed. The unit makes it possible to obtain narrow-collimated beams of X-ray radiation with a line microfocus. Calculation procedure and experimental results for the glancing angle X—ray fluorescence are presented.
Keywords: X—ray tubes, X—ray waveguides, X—ray fluorescence
We have investigated the propagation of the characteristic radiation of the Mo and Re atoms through the planar X-ray waveguides. It is established that if the number of reflections in the waveguide channel is sufficiently large, it is necessary to take into account the scattering of the beam at the roughnesses of the channel walls for the description of the angle distribution of the radiation at the exist of the waveguide. One of the possible systems for scanning the objects by the X-ray beam on the base of the planar waveguides is proposed.
A study is made of transmission of straight and curved thin-film gamma-waveguides. It is shown that in curved waveguides maintaining the limited number of waveguide modes a radiation flux may be appreciably attenuated due to radiation of photons into the medium surrounding a waveguide. Measurement was made of the angular distribution of photons passed through the x-ray guide.
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