Edge Of Wire Research Articles

Small mesas and holes in split-gate quantum wires acting as ‘‘artificial impurities’’ fabricated with scanning tunneling microscope

This article discusses fabrication of ‘‘artificial impurities’’ such as small mesas and holes with a scanning tunneling microscope (STM) in split-gate quantum wires and their transport properties. In order to make and properly place these small structures on the wire surface, we employed a combined STM/scanning electron microscope system operated in vacuum. The fabrication method involves simple electrical evaporation with a Tungsten tip. In a wire having a small mesa (70 nm diameter and 15 nm height) at the center, clear Coulomb blockades and staircases corresponding to the size of the mesa were observed at 0.3 K. In a wire with a hole (200–300 nm upper diameter and 100–150 nm depth) near the gate electrode, both quantized plateaus and damage-induced telegraphic switching were observed in the two-terminal conductance also at 0.3 K. This means that a deep hole at the wire edge can behave, depending on the evaporation condition, either as a simple constriction or as a constriction with electron traps.

Fabrication of nanostructures in AlGaSb/InAs using electron-beam lithography and chemically assisted ion-beam etching

Electron-beam patterned wires in InAs/AlGaSb heterostructures were fabricated using chemically assisted ion-beam etching (CAIBE) with Cl2 and an Ar ion beam. The CAIBE process yielded very vertical sidewalls and smooth wire edges. CAIBE was also used to etch deep trenches through the AlGaSb barrier layer which provided isolation for the wires and suppressed the parallel conductance of the AlGaSb barrier. The interdevice leakage current was also decreased by a final CAIBE device isolation step. Wires 1 μm long and having varying widths between 70 and 210 nm have been fabricated.

Magnetophonon resonance in quantum wires

Magnetophonon resonance effects in quantum wires are discussed. In a narrow quantum wire with a parabolic confinement potential, energy spacing ℏΩ, the magnetoconductivity exhibits extrema at resonance Nℏ√ω 2 c + Ω 2 = ℏω 0 , where ω c = eB/m ∗ and N = 1, 2, 3, … The magnetoconductivity is found to consist of two dominant terms, the one ϱ e-ph, due to the scattering of electrons located near the center of the quantum wire by LO phonons resulting in maxima of the magnetoconductivity at resonance, and the other, ϱ po due to the disturbance of the skipping motion of electrons near the edge of the quantum wire giving rise to minima in the magnetoconductivity. Experiments have been carried out in quantum wires with different structures, and revealed maxima in the magnetoresistance ( ϱ xx = 1 ϱ xx ) in the temperature range 100–200 K, which indicates the term ϱ po dominates. Determination of the energy spacing and the effective mass is discussed.

The low-temperature conductivity of etched quantum wires

Low-temperature transport measurements made on nearly depleted n+ GaAs quantum wires fabricated by molecular beam epitaxy and reactive ion etching are described. In such wires, damage generated by the etching process introduces traps at the wire edges and increases the effective depletion regions there. Exposure of the wires to low-level visible light at low temperatures causes conductance increases whereas the application of a high electric field to the wires causes a subsequent reduction in low-field conductance. Both nonequilibrium states decay slowly and logarithmically with time and can be annealed away by raising the temperature to around 150 K. It is postulated that the traps resulting from damage induced in the wire surfaces during preparation are responsible for the nonequilibrium low-temperature effects and suggest microscopic models for the mechanisms concerned.

腰椎前方固定術におけるＡＯ螺子使用例の検討

Anterior spinal fusion is a useful method for lumbar spinal disorders even though the fusion rate is not particularly high. However it has been demonstrated that the fusion rate is greater than 98% when using the A-O screw and wiring method. We used this method for 12 cases. In our seres there were 4 cases with wire-loosening (28.6%), which can be dangerous for vessels as the wire edge is sharp. We Therefore investigated the possibility of using Tekimron thread as a substitute for the wire. In vitro, the inter-column pressure measured by pressure gauge showed that Tekmiron thread was as useful as the wire.

Light polarization effect in measurement of thin wire diameter by laser diffraction and its explanation with boundary diffraction wave

The polarization effect in the measurement of thin wire diameter by laser diffraction has been studied experimentally and theoretically in this paper. The experimental values of a diameter vary sinusoidally with the vibration direction of incident polarized light. The difference between measured diameter values with S and P component of incident light is nearly proportional to the imaginary part of the complex index which represents the optical property of metal wire. Taken into account the phase change of boundary diffraction wave originating from the edges of metal wire, the physical cause of this polarization effect, and its experimental results have been clearly explained.

Binding energies and density of impurity states of shallow hydrogenic impurities in cylindrical quantum-well wires.

The binding energies of hydrogenic impurities in both infinite and finite GaAs-(Ga,Al)As cylindrical quantum-well wires are calculated as functions of the wire radius and of the impurity location in the well for different radii of the wires using a variational procedure within the effective-mass approximation. Assuming there is no intentional doping, we treat the impurity position as a random variable and define a density of impurity states that we have calculated as a function of the impurity binding energy. As a general feature, the density of impurity states presents two structures associated with impurities at the center and at the edge of the quantum-well wire that may be important in the understanding of absorption and photoluminescence experiments of doped GaAs-(Ga,Al)As quantum-well wires.

Reconsideration of the Transient Line Source Technique. 4th Report. Analytical Discussion on the Influence of the Edge Effect.

In measuring thermal conductivities of liquids by a transient line source technique, one of the main error factors involved is the owing to the heat flow from the hot wire to the electrode through the wire edge. In this report, analytical investigation is performed concerning the edge effect on the measured thermal conductivity considering two basic cases; in the first case, a hot wire is directly connected to the electrode; and in the second case, a ringwise projection having a square cross section is attached at the connection of the hot wire to the electrode. Then the effectiveness, using a Wheatstone bridge circuit where two hot wires of different lengths are set to cancel and minimize the edge effects, is discussed analytically. As a result, the edge effect cannot be negligible even when using the bridge circuit, depending on the size of projection.

Conductance fluctuations and noise in barely conducting N+ wires

Conduction in narrow n +-GaAs wires prepared by reactive ion etching of epitaxial layers has been studied at low temperatures. Applications of high electric fields for short periods or exposure to low intensity visible light enables the number of carriers in the samples to be decreased or increased. Photocurrent noise is found to be anomalously large for samples with closely spaced voltage probes. When samples are allowed to relax after the introduction of a non-equilibrium carrier concentration, steps are observed in the conductance which we ascribe to single electrons interacting with traps. From the magnitude of these steps, we estimate the coherence length in these samples to be of the order of the wire width, and postulate that the electron coherence is limited by trapping events occurring at the wire edges.

Power-law shot noise

The behavior of power-law shot noise, for which the associated impulse response functions assume a decaying power-law form, is explored. Expressions are obtained for the moments, moment generating functions, amplitude probability density functions, autocorrelation functions, and power spectral densities for a variety of parameters of the process. For certain parameters the power spectral density exhibits 1/f-type behavior over a substantial range of frequencies, so that the process serves as a source of 1/f/sup alpha / shot noise for alpha in the range 0< alpha <2. For other parameters the amplitude probability density function is a Levy-stable random variable with dimension less than unity. This process then behaves as a fractal shot noise that does not converge to a Gaussian amplitude distribution as the driving rate increases without limit. Fractal shot noise is a stationary continuous-time process that is fundamentally different from fractional Brownian motion. Several physical processes that are well described by power-law noise in certain domains are considered: 1/f shot noise, Cherenkov radiation from a random stream of charged particles, diffusion of randomly injected concentration packets the electric field at the growing edge of a quantum wire, and the mass distribution of solid-particle aggregates.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Scaler sharpening. Effect of the cutting edge of scaler and the epoxy resin surface with several types of sharpening stones and strokes

The purposes of this study were to determine the characteristics of a sharpened scaler and planed epoxy resin surface under different sharpening conditions. Each scaler was sharpened with the following kinds of sharpening stones and sharpening strokes by using an originally designed sharpening machine: Stones: 1) Fine India stone (ISF) 2) Arkansas stone (AS) 3) Carborundum stone (CS) 4) ISF followed by AS (ISF + AS) 5) CS followed by AS (CS + AS). Strokes: 1) up strokes (PUSH) 2) down strokes (PULL) 3) up and down strokes (RE) Epoxy resin surfaces were planed (10, 20 and 40 strokes) by sharpened scalers. Before and after these sharpening procedures for each scaler, the cutting edge of each scaler was photographed with a scanning electron microscope (SEM) to determine its roughness and the number of wire edges. The epoxy resin surface was examined with the SEM and the surface roughness was analyzed with a profilometer. The following results were obtained: 1) ISF with three types of sharpening strokes produced the roughest cutting edge. 2) ISF and CS with three types of sharpening strokes produced the largest number of wire edges. 3) PUSH with the five types of sharpening stones showed the roughest cutting edge and the largest number of wire edges. 4) ISF and CS produced more surface roughness, and AS made a smoother surface. Epoxy resin surfaces were planed effectively after 10 strokes. However, no significant differences were found in the surface roughness after 10 to 40 strokes.

Scanning electron microscope evaluation of wear of dental curettes during standardized root planing.

Root planing relies upon the quality of instrument cutting edges. This study evaluated the sharpness and wear of some dental curettes available in the market following standardized root planing procedures. Nine working edges of nine Gracey No. 1/2 DE curettes, three each from three different manufacturers, were used as controls. These unused factory-sharpened edges were examined by scanning electron microscope (SEM). Eighteen edges of nine curettes of the same brands were likewise examined after root planing procedures. Root planing was carried out on extracted one-rooted teeth mounted in natural positions in manikin jaws. Working areas measuring 3 X 5 mm were marked on root surfaces previously exposed by periodontitis. Root planing procedures included 15 vertical strokes done by either Side 1 or Side 2 of each instrument in relation to a single working area of a tooth, and the same procedure repeated 3 times using the opposite side of the curette. All working edges were examined at points 1 and 2 mm from the tip under 500 times magnification. Edge deformation increased significantly from the control group to the "15-stroke" group and from the "15-stroke" group to the "45-stroke" group. Factory-sharpened curettes (control) were sharp, with functional wire edges present on 55% of the specimens. After 15 strokes, nonfunctional wire edges and narrow edge deformations with bevels measuring less than 15 mu were present. After 45 strokes eight cutting edges (88.9%) showed bevels wider than 15 mu. The difference between the three brands was not significant in any group (i.e., controls, 15 strokes, 45 strokes). Further study is indicated to evaluate the relationships between bevel dimensions and root planing effectiveness.

Modification in Waveform of Traveling Pulse Voltages Due to Corona Production Along Transmission Line

A very short pulse voltage traveling on a corona transmission line producing streamer coronas is subjected to a time-dependent distortion of its waveform owing to energy consumption by coronas. In the case of a wire-to-duct corona transmission line, only negative streamers appear from the edges of a corona wire. On the other hand, in the case of a wire-to-wire corona transmission line, where the positive wire is located parallel to the negative wire with a considerably small gap, positive streamers also appear when the applied pulse voltage is sufficiently high. The first (negative) streamer is launched from the negative wire at the leading part of the pulse crest voltage, while the second (positive) streamer is emitted from the positive wire at its rear part. The negative streamers in both cases produce a small distortion in the leading part of the crest, whereas the positive streamers cause a large dip in the succeeding region of the voltage waveform. Corona loss is estimated from these modifications in the waveforms for both negative and positive streamers. The other factors to cause waveform modifications are also studied. These are the skin effect enhanced resistance loss to lower the rising rate of pulses and the electromagnetic coupling between the wires.

The Preparation of Fine Recrystallized Tungsten Wire for Transmission Electron Microscopy

In a study of the structure and properties of tungsten wire used for lamp filaments, it became desirable to perform transmission electron microscopy on the wire in the annealed as well as in the drawn condition.Wire used for lamp filaments is generally drawn to diameters less than 0.010" which is too fine for the preparation of transmission samples from single wires. Thus, it is clear that some assembly of wires must be used to form a “wire sheet” similar to that used by Glenn and Duff.Commercially-doped (218) tungsten filament wire in diameters of 0.001", 0.004", and 0.010" was wound on 1" square tungsten plates, 0.060" thick, using standard coil-winding techniques. After winding, the plates were annealed at temperatures of 1800°C to 2200°C, in vacuo. Following the anneal, the samples were treated in one of two ways. The 0.010" and 0.004" diameter wire sheets were encapsulated in epoxy and ground from both faces to a thickness of about 1/2 the wire diameter. The exposed wires were then electropolished with 107. NaOH electrolyte. The epoxy protected the edges of the flat wires so that the central area of the wire could be thinned.

DEFECTIVE HYPODERMIC NEEDLES

To the Editor:— I have examined 226 hypodermic needles and found that 152, or 67%, are definitely defective, so much so that they would not meet the federal specification requirements for hypodermic needles and, in my opinion, present a therapeutic hazard. The defects consist of deposits of metal powder in the lumen, metal slivers extending from the inner edge into the lumen, a very rough interior surface of the lumen, and rough surface of the point from grinding. As a rule, needles are defective in two or more of these respects. The rough interior seems to be a major cause of excess deposits of metal powder and wire edges. All brands showed a large percentage of failures, some more than others. Below is a breakdown of the failures of the brands we have examined under a 30 power stereo microscope for (1) powdered metal deposits, (2) wire edges, (3) metal

A QUICK METHOD FOR SHARPENING OCULAR TREPHINES

The necessity for a sharp trephine in performing the Elliot sclerocorneal trephining for glaucoma is undebatable. A mounted dental Arkansas stone can be obtained from a dental supply house or a dentist. A wet mounted stone, as shown in 1 of the accompanying illustration, is placed in the rotary chuck of a dental engine and sharpened in a circumferential manner on the outside beveled portion of the trephine, as shown in 2. The full amount of sharpening should be done on the outer beveled portion. The wire edge is removed by a light circumferential reaming on the inside of the trephine, as shown in 3. The revolving stone should not be forced down to occlude the trephine opening, as the stone will jam. Caution should also be observed not to produce an internal bevel or cornucopia effect. This condition might cause a serious complication should the sclerocorneal plug drop into