摘要:

We present an efficient method to compute the maximum transient drain current overshoot in silicon‐on‐insulator metal‐oxide‐silicon field effect transistors. The method is based on the physical idea that the number of majority carriers remains unchanged immediately after a change in the applied gate bias. The maximum overshoot is computed by solving the Poisson and the stationary minority carrier transport equations under the constraint that the number of majority carriers is conserved. Hence, the novel aspect of the method is that it allows one to compute the maximum drain current overshoot without resorting to a computationally costly transient simulation. The accuracy of the method is verified by comparing the value of the drain current computed by this method with the maximum value of the drain current computed by transient simulations. The comparisons show that, with this method, the maximum transient drain current overshoot can be computed quite accurately for fast changes in the gate bias.  

ISSN:0021-8979    

DOI:10.1063/1.353078

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The properties of physical systems whose observable properties depend upon random exceedances of critical parameters are quantitatively examined. Using extreme value theory, the dynamical behavior of this broad class of systems is derived. This class of systems can exhibit two characteristic signatures: generalized activation when far from equilibrium and noise with a characteristic power spectrum (including 1/f ) when in quasiequilibrium. Fractal structures can also arise from these systems. It is thus demonstrated that generalized activation, noise, and fractals, in some cases, are simply different manifestations of a single common dynamical principle, which is termed ‘‘extremal dynamics.’’ Examples of physical processes governed by extremal dynamics are discussed, including data loss of nonvolatile memories and dielectric breakdown.

ISSN:0021-8979    

DOI:10.1063/1.353079

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

It is suggested that an originally long x‐ray pulse may be shortened substantially, or, alternatively, a short sharp dip may be introduced into an originally long x‐ray pulse, by passing the x rays through a resonant absorbing medium that is illuminated by an intense ultrashort laser pulse at certain chosen times. The various conditions for this scheme are stated. Neon and xenon gas media are discussed as examples.  

ISSN:0021-8979    

DOI:10.1063/1.353080

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Interface dislocations present in a Si0.85Ge0.15/Si sample have been imaged using the channeling scanning transmission ion microscopy (CSTIM) method with a 2 MeV proton beam 200 nm across. Groups of parallel dislocations gave dark bands of contrast down to ∼1.5 &mgr;m across, the contrast arising from dechanneling of the beam by the bent lattice planes. Tilting of the sample caused the band contrast to change and gave quantitative data concerning the local bending of the lattice planes. A low‐angle boundary model was developed to describe the effect of the groups of dislocations on the channeling contrast. Channeling and topography contrast were obtained from mesa structures present on the sample. Improvements in the sensitivity of the CSTIM method are discussed. The dislocations in the sample were initially characterized by transmission electron microscopy.

ISSN:0021-8979    

DOI:10.1063/1.353081

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The resonance characteristics of stainless‐steel cantilevers vibrated photothermally in a liquid have been investigated using an optical detection system. Resonance frequencies of vibrating cantilevers in liquids are lower than those in air as a result of the action of reaction forces in the liquid. It is shown that experimental values of the resonance frequencies for several types of cantilevers in water agree well with those calculated. The half power width at resonance broadens with increasing viscosity of the liquid. The possibility for using this photothermal vibration method as an optical sensing system for the density or viscosity of liquids is described.

ISSN:0021-8979    

DOI:10.1063/1.353060

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Superconducting Nb/AlOx/Nb tunnel junctions have been fabricated on Si membrane windows of only 1.2 &mgr;m thickness acting as substrates. The membrane windows with areas between (600 &mgr;m)2and (1200 &mgr;m)2remained undamaged after the different fabrications steps. The tunnel junctions positioned on the membranes and the bulk silicon substrate have very similar current‐voltage characteristics. Using low‐temperature scanning electron microscopy the two‐dimensional heat diffusion process has been imaged in the detector geometry. This two‐dimensional heat diffusion leads to a new cryoelectronic radiation detector concept combining high energy and spatial resolution with a large effective detector area. Applications of this detector concept include soft‐x‐ray spectroscopy and the nuclear &bgr; decay.  

ISSN:0021-8979    

DOI:10.1063/1.353061

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A new high‐current density electron source is described. The source consists of a polarized ferroelectric ceramic disk with silver electrodes coated on both faces. The front electrode consists of a periodic silver grid alternating with exposed ceramic. A rapid change in the polarization state of the ceramic results in the emission of a high‐density electron cloud into a 1–10‐mm accelerating diode gap. The anode potential is maintained by a charged transmission line. Some of the emitted electrons traverse the gap and an electron current flows. The emitted electron current has been measured as a function of the gap spacing and the anode potential. Current densities in excess of 70 A/cm2have been measured. The current is found to vary linearly with the anode voltage for gaps ≤10 mm, and typically exceeds the Child–Langmuir current density by at least two orders of magnitude. The experimental data is compared with predictions from a model in which the electrons emitted from the ferroelectric reflex in the diode gap.

ISSN:0021-8979    

DOI:10.1063/1.353062

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We report the results of a study of amplified spontaneous emission (ASE) in the I2(B→X) system. For many (v’,v‘) bands, severalJ’→J‘transitions contribute to the ASE in a cooperative manner. We present spectroscopic and kinetic data that contrast this cooperative stimulated emission to the emission in previously reported optically pumped lasers. Transitions that involve several cooperatively emitting levels produce efficient conversion of the pump laser to near‐infrared output.

ISSN:0021-8979    

DOI:10.1063/1.353063

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Laser‐beam temporal pulse shaping is examined using a technique based on beam deflection. The deflection is induced by encoding the beam with phase‐modulated bandwidth and passing the beam through a diffraction grating. Pulse‐shaping examples are modeled numerically to determine the resolution of this technique. Other applications using this method of spectral beam deflection are discussed.

ISSN:0021-8979    

DOI:10.1063/1.353038

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The infrared atomic xenon laser (5d→6p) is an attractive candidate for fission fragment excitation, which provides low‐power deposition (1–100 W cm−3), long pulse lengths (1–10 ms), and high‐energy deposition (100s J l −1). Optical gain at 1.73 and 2.03 &mgr;m has recently been measured in a reactor‐excited xenon laser yielding values exceeding 0.03–0.05 cm−1at power depositions of less than 10s W cm−3. Gain was also found to rapidly terminate before the peak of the pump pulse for some experimental conditions. A computer model has been developed to predict gain in fission‐fragment‐excited xenon lasers and these experiments have been analyzed. It is found that the termination of gain is most likely attributable to gas heating which increases the electron density, leading to electron collision quenching. The specific dependence of gain on pump rate suggests that a reduced rate of recombination of molecular ions with increasing gas temperature is partly responsible for this behavior.

ISSN:0021-8979    

DOI:10.1063/1.353039

出版商:AIP    

年代:1993

数据来源: AIP