Anomalous Switching Research Articles

Investigation of Switching Kinetics of Interface Traps in Metal-Oxide-Semiconductor-Field-Effect-Transistors with Ultra-narrow Channels

In this paper, we report on the switching kinetics characteristics of interface traps in n-metal-oxide-semiconductor-field-effect-transistors (n-MOSFETs) with ultra-narrow channels. By analyzing the gate bias voltage and temperature dependence of the transition time and amplitude of the random telegraph signals (RTSs), it has been demonstrated experimentally that a thermally activated process may be dominant for Coulomb-repulsive centers and quantum mechanical tunneling is a favored process to Coulomb-attractive centers. The anomalous switching behaviors of RTSs having very large amplitude are well explained by the quantum mechanical tunneling model.

Fabrication of Optically Designed Multidomain Layer Structure using Azo-Dye-Doped Ferroelectric Liquid Crystal Having N*‒C* Phase Sequence

We proposed an optical fabrication method of designed multidomain structure in an azo-dye-doped ferroelectric liquid crystal with chiral nematic (N*) – chiral smectic C (SmC*) phase sequence (NC-FLC). This layer alignment control is based on the N*−SmC* phase transition induced by the photoisomerization of doped azo-dye. This photo-assisted layer switching can be applied to the fabrication of the designed multidomain structure in the electrooptic elements such as display, optical memory and optical grating. Anomalous layer switching upon the electric field has also been observed.

A systematic study of MOCVD grown InP/InGaAIAs heterojunction bipolar transistors with anomalous switching behavior

A new S-shaped switch based on the InP/InGaAlAs material system has been successfully fabricated and demonstrated. Due to the avalanche multiplication and potential redistribution process, the interesting multiple-negative-differential-resistance (MNDR) is found under the inverted operation mode at room temperature. The three-terminal NDR characteristics are investigated under the applied base current I B . Moreover, the anomalous multiple-route and multiple-step current-voltage (I-V) characteristics at 77K are also observed. The switching behaviors demonstrate that the proposed structure is a good candidate for multiple-valued logic applications.

Geometry dependence of magnetization vortices in patterned submicron NiFe elements

When the magnetization is switched in patterned submicron Ni80Fe20 thin-film elements, magnetization vortices, local micromagnetic structures with a core size of 10 nm, are often trapped. This lowers the magnetostatic self-energy of the elements. Trapped vortices can cause anomalous switching during spin reversal between stable magnetization states. To expel trapped vortices, a large external magnetic field, the vortex exit field, is required. The dependence of the vortex exit field on lateral dimensions of the patterned elements is measured. In the limit where the lateral dimensions of the patterned elements are much larger than the vortex core size, smaller structures are more prone to the formation of trapped vortices.

Magnetization vortices and anomalous switching in patterned NiFeCo submicron arrays

Switching characteristics of 20-nm-thick NiFeCo submicron arrays are systematically studied by means of magnetometry, magnetic force microscopy, and micromagnetic simulation based on solution of the Landau–Lifshitz–Gilbert equation. A switching anomaly found in these structures could not be described by the magnetization coherent rotation model. Both experimental data and simulation results indicate that trapped magnetization vortices are responsible for the switching anomaly.

On the seemingly antiferroelectric behaviour of cfrtain ferroelectric liquid crystals

Abstract Double current peak, double hysteresis loop and even in some sense three electro-optic states, the main characteristics of the antiferroelectric liquid crystal phase, are found also in the ferroelectric smectic C* phase, observed so far on several liquid crystal materials possessing a C*—N* phase sequence. In the observed cases, the confining surfaces bring about a pronounced monostable surface anchoring of the liquid crystal molecules forcing the layers to be broken in two alternating directions, corresponding to the equivalent surface directions of positive and negative molecular tilt relative to the layer normal. The resulting striped texture is very reminiscent of certain domain patterns in solid ferroelectrics. The seemingly anomalous electric switching behaviour of this C* texture mimics an antiferroelectric and may thus easily lead to an incorrect designation of the phase if not supplemented by other identification methods. Hysteresis shape and switching current peaks are thus by themselve...

Anomalous switching phenomenon in critical-current measurements when using conductive mandrels

NIST and other laboratories have observed an anomalous switching phenomenon that can occur in critical-current measurements of coiled Nb-Ti and Nb/sub 3/Sn superconductors when mounted on an electrically-conductive measurement mandrel. During acquisition of the voltage-current (V-I) characteristic, large voltage discontinuities are observed, This switching phenomenon results in a multivalued V-I curve, and apparently multiple "critical current" values, An explanation of this phenomenon, some necessary conditions for the switching to occur, as well as methods of detecting the phenomenon are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Anomalous hysteresis loops in KNbO3 single crystals

Abstract It is found that KNbO3 single crystals containing cooperatively ordered impurity dipoles exhibit anomalous hysteresis loop behaviour. At freauencies of 50 Hz and lower, large sudden changes in polarization and electric field are observed. The orientation, shape and size of the loop change strongly with freauency, and the loop traces are broad, particularly at Iow freauencies of the order of 1 Hz. There is no well defined coercive field or remnant polarization. Earlier work on switching in these crystals has shown that domains in the crystal have a characteristic response time and can participate in the switching process only if the tracing freauency is of the order of this time. Against this background, it is shown that the sudden changes in polarization are due to nucleation or evaporation of a domain in the crystal. The origin of the anomalous nature Iies in the fact that the polarization is not only a function of field E but also of time t. Experiments conducted with a d.c. bias confirm the role of impurity dipoles in the nucleation process, and hence in switching. The loops observed at various temperatures showed that the domains have stability on account of impurity dipoles associated with them. The importance of this work lies in the fact that cooperative ordering of the dipoles has to be avoided to prevent anomalous switching effects coming into play.

Nonlinear soliton transport in charge transfer compounds

Nonlinear conductivities and anomalous current switching effect have been widely observed in single crystals of semiconducting organic charge transfer compounds. These features are found to be strongly dependent on the molecular ionicity and the stack structures, indicating that the switching effect is attributed to the breakdown of bond-ordered-wave (BOW) state induced by soliton current.

Individual, attractive defect centers in the SiO2-Si interface of ?m-sized MOSFETs

In a micron-sized p-channel MOSFET, the alternate capture and emission of holes into a Coulomb-attractive defect center is analyzed by the random telegraph signal in the source-drain current. Anomalous switching is observed with a high channel conductance when the defect center is occupied, and a low channel conductance after re-emission. The rate constants show an inverse symmetry for capture and emission. The measured results are interpreted by a tunneling transfer of a hole bound in the channel at the attractive center to the defect center 2.4 nm deep in the oxide and vice versa. The energy offset of the two stable configurations can be linearly varied by the gate voltage. An excited state 40 meV above the ground state is observed for the defect level. The anomalous switching is caused by a mobility change rather than by a change in mobile charge carrier density. The tunneling transfer for Coulomb-attractive centers differs from the transfer observed for Coulomb-repulsive centers where activated emission is reported.

Multistabilities and anomalous switching in the Lorenz-Haken model.

Multistabilities and anomalous switching in the Lorenz-Haken model.

Switching of reaction pathways due to methylene chain length effects

AbstractReaction products of bifunctional chain molecules with structure X(CH2)nY may critically depend on the chain length n. When the chain length is short (n ≤ 5), reaction products particular to an intramolecular reaction can be dominant, while a process corresponding to an intermolecular reaction between XCH3 and H3CY may take place for higher homologues having large n (≥10). The reaction switching dependent on n is explained in terms of the encounter probability for both end groups (X and Y) with conformations pertinent to product formation. The reaction switching of this sort is discussed on the basis of a reactivity profile recorded as a function of the chain length. Similar reactivity profiles have been observed for thermal Friedel–Crafts cyclization and photo‐Smiles rearrangement/photoredox reaction. It is anticipated that the magic methylene chain length of 7 may give rise to an appreciable decrease in reaction yields (e.g. ‘difficulty in medium‐sized ring closure’) or an anomalous switching of reaction pathways due to chain length effects.

Ferroelectric Liquid Crystal Display with High Contrast Ratio

To obtain zig-zag defect-free liquid crystal cells by means of a standard rubbing technique, the effect of a new polyimide film on pretilt angle at a surface has been investigated. This new polyimide imposes the high pretilt over wide rubbing density, and good orientation of liquid crystals without zig-zag defects can be obtained for rubbing densities higher than 0.5×103. A new driving scheme to realize display devices with a high contrast ratio is proposed. This scheme is devised by utilizing anomalous switching behavior and AC-stabilized effect. The prototype of the ferroelectric liquid crystal display device shows the maximum contrast ratio of 40:1.

Electro-optic pulse response of ferroelectric liquid crystals

Abstract The electro-optic response of ferroelectric smectic C* liquid crystals has been studied. Anomalous switching behaviour of such materials which possess a negative dielectric anisotropy has been reported. These materials show a minimum in response time at a sufficiently high field. We present results showing the dependency of this minimum upon spontaneous polarisation and the effect of AC bias. Calculations based upon the equation of motion of the director around the cone are presented which describe this effect and its dependence on the relative magnitudes of the spontaneous polarization and dielectric anisotropy of the material. Good agreement with the experimental results is found.

Anomalous switching behavior of a ferroelectric liquid crystal due to dielectric anisotropy

Abstract The switching characteristics of a ferroelectric liquid crystal with nagative dielectric anisotropy were studied. An anomalous behavior has been found in the applied voltage dependence of the switching time. A dynamic equation is presented to explain the experimental result.

Steady-state and pulse behavior of light transmitted through dispersive nonlinear media in a ring cavity

We study the propagation of electromagnetic radiation through a ring-cavity device containing a dispersive nonlinear medium. Under conditions appropriate for introducing the slowly varying envelope approximation and for adiabatically eliminating the atomic variables, we calculate analytical expressions between the steady-state-output intensity and the input-field amplitude for two models of the nonlinear susceptibility, the two-level atomic medium and the Kerr medium. The stability of these curves is determined, with special attention given to changes in the thresholds by varying the return-trip phase shift, the linear absorption, and the reflection coefficients of the mirrors. We investigate the positive-branch instabilities resulting in a pulsing output intensity and calculate the bifurcation rate for the period-doubling hierarchy and the fractal dimension of our two-dimensional maps for the Kerr medium. The convergence of the bifurcation rate to a constant is slow, and we find, as in the publications of Snapp et al. [ Opt. Commun.40, 68 ( 1981)] and Carmichael et al. [ Phys. Rev. A26, 3408 ( 1982)], that this constant is consistent with that found for the class of one-dimensional maps with a quadratic maximum. This universal constant is observed over a large range of fractal dimensions for the chaotic attractor. Discussions of pulse-output bistability, intermittency, and anomalous switching are given.

Regenerative switching in V-groove metal oxide semiconductor field-effect transistor structure

Anomalous regenerative switching has been observed in a power V-groove MOSFET with the drain terminal of the MOSFET at the top surface of the chip. This switching phenomenon is attributed to a rectifying junction formed at the drain terminal due to a thin oxide between the drain metal and the n-type drain diffusion. Because of the regenerative switching, the device characteristic changes from the MOSFET I( V) characteristic to a turned-on thyristor characteristic as the gate voltage is increased to a critical voltage. The ON-resistance of the device in the thyristor mode is found to be one-tenth of that in the MOSFET mode. Based on the explanation of the experimental results, an insulated gate controlled thyristor structure with substrate as the cathode is proposed.

Self-pulsing and transients of a Fabry–Perot interferometer with quadratic nonlinear medium

The dynamic properties of a Fabry–Perot interferometer filled with a material exhibiting second-order dispersive nonlinearity are studied both theoretically and experimentally. The response of the medium is described by an intensity dependent phase constant as derived from self-action effects. Considering two relaxation times, that of the material and that of the cavity, the basic relations for the stability analysis and for the numerical calculations are obtained. Bistability and self-pulsing effects are predicted. Moreover, the transient behavior is characterized by anomalous switching properties like overshoot and alternate switching. The corresponding experiments performed on a nonlinear transmission line resonator confirm the theoretical results. In a final discussion, the relations to the field of nonlinear optics are outlined.

Analytical description of anomalous switching in dispersive optical bistability

We give analytical description of anomalous switching in dispersive optical bistability, and determine approximately its threshold indicent field as a function of the parameters of the system.

Anomalous switching in dispersive optical bistability

The response of a dispersive bistable optical device to an instantaneous change in the driving field is studied theoretically. The device is shown to respond in ways that are significantly different from absorptive bistability. Threshold for switching between stable states do not occur at the same values as in the quasi-steady-state. Instead, anomalous thresholds are predicted. It is suggested that this anomalous switching behaviour may place limitations on the possible device applications. It also implies that dispersive bistable devices may be switched merely by an appropriate change of the phase of the driving field.