摘要:

Diffusion from a metallic gold source into SiO2films on (100) silicon substrates at 1000 °C for 15 min leads to large negative shifts in theC‐Vcurves and distortion of theC‐Vcharacteristics. Annealing in hydrogen in the temperature range 300–450 °C, in argon at 1100 °C, or short exposure to steam at 950 °C is only partially effective in reversing these changes. Gold from a metallic source appears to diffuse in SiO2mostly or exclusively as metallic gold and to cause the generation of a very large density of interface states. Most of the negativeC‐Vshift is due to these interface states and not due to a laterally uniform fixed oxide charge, as claimed by other researchers. The magnitude of the effect depends in thethickness of the gold film, and hence directly or indirectly on the amount of gold diffused into the SiO2film because thicker gold films result in larger amounts of gold diffusion in uniform fashion into the SiO2. The total amount of gold in the SiO2film after diffusion, however, is insufficient by several orders of magnitude to account, on a one‐to‐one basis, for either the supposed oxide charge or the interface‐state density. It must be concluded that gold diffusion in SiO2films leads to the formation of interface states by an entirely new and unexplained mechanism.

ISSN:0021-8979    

DOI:10.1063/1.1663498

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The spontaneous‐emission spectra of liquid‐phase‐epitaxial grown double‐heterostructure light‐emitting diodes with a Si‐doped GaAs active region and Ga1−xAlxAs barrier regions have been measured as a function of the Si concentration in the growth solution and the thickness of the active region. The results indicate that a graded band‐gap region is probably formed at the GaAs&sngbnd;Ga1−xAlxAs interface. The double‐heterostructure light‐emitting diodes are compared with homojunction diodes as potential excitation sources for upconverting phosphors.

ISSN:0021-8979    

DOI:10.1063/1.1663499

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A generalized model is developed for the electronic behavior of deep traps in ap‐n‐junction depletion region. The depletion region is shown to consist of two parts: (i) a space‐charge region which is totally depleted of free carriers and (ii) a transition region which is only partially depleted. The influence of this junction structure on free‐carrier profiling measurements is considered in detail for donor and acceptor traps with both homogeneous and inhomogeneous spatial distributions. Experimental observations of deep‐trap distributions produced by proton bombardment ofn‐type silicon are analyzed within the framework of the model. Implications of the model in the measurement of junction capacitance transients and photocapacitance are considered in Appendices A‐C.

ISSN:0021-8979    

DOI:10.1063/1.1663500

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The band‐gap energyEgof silicon has been reevaluated with high precision between 2 and 300 K by the following method: the derivative of the absorption coefficient, resulting from free‐exciton absorption, has a well‐defined singularity, which can be detected unambiguously by wavelength‐modulation spectroscopy. The energy of this singularity yields the band gap. Our data deviated by more than 5 meV from the earlier results of MacFarlaneet al.and Hayneset al.and fell between theirEg(T) curves. The approximation ofEg(T) =A + BT + CT2givesA= 1.170 eV,B= 1.059×10−5eV/K, andC= −6.05×10−7eV/K2, for 0<T≤190 K, andA= 1.1785 eV,B= −9.025×10−5eV/K, andC= −3.05×10−7eV/K2, for 150≤T≤300 K, which fits our data within 0.2 meV. The major uncertainty of about 1 meV lies in the energies of exciton and TO phonon.

ISSN:0021-8979    

DOI:10.1063/1.1663501

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The present work reports a detailed experimental investigation of Schopper's formula for investigating the case of a uniaxial nonabsorbing film of barium stearate on a transparent substrate. The required theoretical conditions for the experimental study of Schopper's formulas are well fulfilled for the film studied. The experimentally measured values of the reflectances and transmittances for Ba stearate films are found to be in agreement with the corresponding values calculated from the corrected Schopper's formulas. The experimental values, in general, are found to be in considerable disagreement with the corresponding values calculated by assuming the films to be isotropic. The studies have thus tested the validity of Schopper's formulas and have, indeed, confirmed the films to be anisotropic. Thus, assuming the validity of Schopper's formulas, the refractive indices of several other Blodgett‐Langmuir films have been determined.

ISSN:0021-8979    

DOI:10.1063/1.1663502

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

It is shown theoretically and experimentally that the current density is not uniform in the neighborhood of a 180 ° domain wall, in a pure ferromagnet traversed by an electric current at low temperature. The effect is caused by the abrupt reversal of the internal fieldB=Msacross the wall, and by the corresponding gradual reversal of the Hall electric field. In a noncompensated ferromagnetic metal (Co, Ni) in the high field limit&ohgr;c&tgr;≫1, domain walls would act as if they were electrically insulating; the current could cross the wall only through a small ``hole'' located at one end of the wall, creating an infinite current density there. A cobalt single crystal of limited purity (R300/R4.2= 65) was cut in the shape of a thin slab normal to thecaxis. One‐half of the slab is magnetized to saturation in thecdirection and the other half is magnetized in the opposite direction, thus simulating one domain wall. When a dc current crosses the wall, the current density is found to be larger at one end of the wall than at the other end in a ratio of 1.7, in agreement with predictions. Current density is monitored locally with pairs of voltage probes. The magnitude and sign of the effect is consistent with &ohgr;c&tgr; = 0.18 and electronlike carriers.

ISSN:0021-8979    

DOI:10.1063/1.1663503

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The propagation characteristics of exchange‐free magnetoelastic (ME) Rayleigh waves are treated for the case of propagation on a YIG substrate that is magnetized perpendicular to its surface. As a result of the wave anisotropy of the constituent ME plane waves, these waves differ substantially from the ME Rayleigh waves propagating on a YIG substrate along or obliquely to a tangential bias field. Computed dispersion and polarization properties are presented for a low saturation magnetization Ga‐YIG substrate whose surface is eitherunmetallizedormetallizedwith a thin perfectly conducting metallic film. In either case, the dispersion diagram consists of two branches, one of which represents bound surface waves for frequencies below a spectrum of frequencies given approximately by the magnetostatic bulk‐wave spectrum, and the other branch represents bound surface waves for frequencies above this spectrum. Within the spectrum the surface waves are of the leaky variety, and can be used to obtain beam steering over an angle of 90 ° in the forward direction.

ISSN:0021-8979    

DOI:10.1063/1.1663504

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A closely spaced pair of nonsymmetrically opposing rectangular poles is reduced to a combination of opposing corners; the mutual forces between the poles can then be written in terms of the simple direct formulas obtained for the two‐corner problem. The results obtained involve only elementary functions and do not require implicit solution of nonalgebraic equations.

ISSN:0021-8979    

DOI:10.1063/1.1663505

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A sample of sputtered Sm2(Co0.7Fe0.3)17was found to havemHc=5600 Oe and (B H)max=12 MG Oe after heat treatment. These are both record values for 2:17 alloys, and the energy product is a record value for an isotropic magnet. This material is the first 2:17 alloy to exhibit useful permanent‐magnet properties.

ISSN:0021-8979    

DOI:10.1063/1.1663506

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The possibility of using very‐high‐Qsuperconducting microwave cavities to obtain a strong coupling between the electromagnetic field and a Josephson junction has prompted a study of such systems. Expressions have been obtained describing the dcI‐Vcharacteristic of a junction biased so that the Josephson radiation frequency is near a resonance of the cavity in which it is located. The rf power coupled into anX‐band (10 GHz) TE011mode cavity from a weakly coupled junction is approximately3×10−13 I02 Q W, whereI0is the critical current of the junction andQis the cavityQ. When the coupling between the junction and cavity is large enough, theI‐Vcharacteristic becomes multiple valued and the power coupled to the cavity depends on the state of the system. The maximum power which can be coupled to the cavity is approximately 0.58I0Vdc, whereVdcis the voltage required to bias the junction to the resonant frequency of the cavity.

ISSN:0021-8979    

DOI:10.1063/1.1663507

出版商:AIP    

年代:1974

数据来源: AIP