We report, for the first time, ballistic magnetoresistance effects in a two-dimensional electron gas (2DEG) subjected to spatially modulated periodic magnetic field. The field is formed by presence of superconducting stripes on surface heterostructure with 2DEG. observe oscillatory due commensurability effect between classical cyclotron diameter and period modulation. behavior agreement existing theory no adjustable parameters.

We have observed a series of sharp peaks in the low-temperature I(V) characteristics gated 1 \ensuremath{\mu}m\ifmmode\times\else\texttimes\fi{}1 \ensuremath{\mu}m GaAs/(AlGa)As resonant tunneling diode, which gate is used to reduce effective cross-sectional area from 0.7 0.1 \ensuremath{\mu}${\mathrm{m}}^{2}$. These peaks, occur at voltages well below calculated threshold, show weak dependence on temperature, magnetic field, and area. argue that this subthreshold structure due an...

We have investigated the magnetoresistance of a two-dimensional electron gas subjected to periodic potential variable amplitude. The potential, period 300 nm, is generated with use gate deposited over layer patterned resist, and its amplitude controlled by voltage. At low voltages, two series oscillations in inverse magnetic field are observed. One series, at field, due other usual Shubnikov--de Haas oscillations. application small voltage generates an increase low-field oscillations,...

A novel microelectronic "pill" has been developed for in situ studies of the gastro-intestinal tract, combining microsensors and integrated circuits with system-level integration technology. The measurement parameters include real-time remote recording temperature, pH, conductivity, dissolved oxygen. unit comprises an outer biocompatible capsule encasing four microsensors, a control chip, discrete component radio transmitter, two silver oxide cells (the latter providing operating time 40 h...

Raman scattering from arrays of GaAs quantum cylinders with radii down to 30 nm has been observed. The spectra show an enhanced TO phonon intensity due a change in the first-order selection rules. In addition, smallest exhibit extra spectral feature between and LO phonons. behaviour this additional peak as function geometry, cylinder size variation medium surrounding is consistent theoretical model surface phonons cylinder.

The fabrication and operation of a 1μm × gated GaAs/(AlGa)As resonant tunnelling diode is described. By biasing the gate I/V characteristic can be varied hence negative differential resistance controlled. Using wafer with an appropriate doping profile ensures that maximum depletion due to will occur close (AlGa)As tunnel barriers. When large bias applied extra structure develops in which may related modification sub-band well lateral quantum confinement electrons by gate. potential this...

Platinum/palladium lines (17 nm wide) have been defined by the electron-beam exposure of a film poly(methyl methacrylate) 60 thick supported on 30-nm-thick carbon-film substrate followed liftoff overcoated metal. Line pitch may be reduced to 50 before fails. An 8-nm-diam 50-kV electron beam is used for exposure. A combination finite source diameter, molecular size effects, and secondary are believed responsible observed resolution limit. It shown that pattern-size accuracies few nanometers...

The electrochemical regeneration of real spent activated carbons (AC) used in drinking water treatment plants was studied at different reactor scales. carried out a 6 g filter-press cell and 3.5 kg batch reactor, allowing the scaling-up process between two electrolytic reactors. effect electrolyte, divided/undivided compartment configuration current density were cell. influence time scaled-up reactor. A 0.025 cm−2 electrodes Pt/Ti as anode stainless-steel cathode. ACs characterized by N2...

We have investigated the magnetoresistance of a heterostructure containing near surface two-dimensional electron gas subject to periodic magnetic field that alternates in sign. The is produced by an array submicrometer ferromagnets fabricated on heterostructure. observe giant low-field due electrons propagating open orbits along lines zero field. are able account for observed form and magnitude this semiclassical model.

This paper presents our work toward the integration of a multisensor microsystem with wireless communication, using system-on-chip (SoC) methodology. Four different forms microelectronic sensors have been fabricated on two separate 5/spl times/5 mm/sup 2/ silicon chips measuring pH, conductivity, dissolved oxygen concentration, and temperature. The are integrated sensor fusion chip comprising analog circuitry for operation signal amplification prior to digital decoding transmission....

A new type of nonlocal oscillatory magnetoresistance effect is observed in heavily doped ${\mathit{n}}^{+}$-GaAs wires over a limited range temperature (10\ensuremath{\le}T\ensuremath{\le}50 K) and at magnetic fields sufficiently large to give rise Landau quantization. The when quantum ballistic transport along the edges coexists with diffusive dissipative conduction bulk.

We have measured the thermopower of small ${\mathit{n}}^{+}$-GaAs wires using a novel electron heating technique. The results show very large fluctuations which are in good agreement with existing theories. believe this to be first observation universal fluctuations.

We investigate a new type of magnetoresistance (MR) in which the resistivity near-surface two-dimensional electron gas is controlled by magnetization submicron ferromagnetic grating defined on surface device. observe an increase resistance up to ∼1500% at temperature 4 K and ∼1% 300 K. The magnitude dependence MR are well accounted for semiclassical theory. Optimization device parameters expected considerably room MR.

A comprehensive RF analysis technique based on ensemble Monte Carlo (EMC) simulation of compound FET's with realistic device geometry is presented. Y-parameters are obtained through Fourier transformation the EMC transients in response to small changes terminal voltages. The currents statistically enhanced and filtered allow for reliable y-parameters extraction. Improved analytic procedure extracting intrinsic small-signal circuit components described. As a result, stable can he extracted...

Dry etching using ions can cause damage to the underlying semiconductor. This paper discusses in III–V semiconductors and presents examples of conditions under which it be effectively eliminated. A distinction between surface sidewall is made methods measuring both parameters are reviewed. It noted that noble gases relatively deep damage, while correct circumstances, etchants have a marked chemical effect much less damage. The present state understanding mechanisms for discussed.

We report the results of capacitance measurements on quantum wires in which only lowest one-dimensional subband is occupied. The are generated metal-insulator-semiconductor-field-effect-transistor-type AlAs/GaAs heterojunctions with an interdigitated gate. In such devices strong lateral confinement and a well-defined threshold voltage achieved. limit at very low electron density signal recorded as function gate exhibits substructure that we discuss view drastic change effective channel width...

The high-frequency polarizability of quantum wires in a novel metal-insulator-semiconductor field-effect transistor heterojunction is studied the far-infrared regime. Whereas on conventional narrow only fundamental mode dimensional resonance observed, investigated here exhibit higher harmonics. Additionally, at high electron densities and intermediate magnetic fields we observe completely unexpected splitting mode. behavior discussed view nonparabolic confinement as well interwire interaction.

We have studied universal conductance fluctuations in the nonlocal magnetoresistance of ${\mathit{n}}^{+}$-GaAs wires. The Lee-Stone correlation field \ensuremath{\Delta}${\mathit{B}}_{\mathit{c}}$ increases by a factor 5 as magnetic from 0 to 12 T but amplitude does not change. It is possible explain increase quantitatively terms variation size phase coherence length. However, this should also give rise large change fluctuation amplitude, which observed. This implies that scaling valid high fields.

We have measured the magnetoresistance at various temperatures of a two-dimensional electron gas subjected to one-dimensional periodic potential. A series oscillations in inverse magnetic field is observed low fields due resonant drift electrons potential, while higher Shubnikov--de Haas (SdH) are observed. The low-field persist much temperature than SdH oscillations. argue that quenched when thermal smearing cyclotron orbit diameter equal period Using this simple model, we show which larger...

Abstract A non-conventional, bioinspired device based on polypyrrole coated electrospun fibrous microstructures, which simultaneously works as artificial muscle and mechanical sensor is reported. Fibrous morphology preferred due to its high active surface can improve the actuation/sensing properties, preparation still being challenging. Thus, a simple fabrication algorithm electrospinning, sputtering deposition electrochemical polymerization produced electroactive aligned ribbon meshes with...

We have measured the magnetoresistance of a two-dimensional electron gas subjected to one-dimensional periodic potential using structures with periods 150, 300, and 500 nm. In all we observe low-field positive magnetotresistance, which extends up critical field at new form magnetic breakdown occurs. This is found be inversely proportional period potential, in agreement model based on semiclassical dynamics electrons. addition, developed quantum-mechanical formulation this problem streaming,...

Conducting wires of widths down to 0.1 μm have been fabricated in modulation-doped GaAs/AlGaAs material using SiCl4 reactive ion etching with a negative resist mask. The used was high-resolution (HNR) and its applicability microstructure fabrication is discussed. A novel dry etch for GaAs, CH4/H2 etching, produces low damage shows much promise wire fabrication.