摘要:

A study has been made to determine the resolution limitations of electron beams interacting with thin films, due to scattering in the film and substrate. For a typical film thickness of 3000 Å, and an incoming Gaussian electron distribution with half‐amplitude at 1500 Å radius, forward‐scattering becomes significant for solids with atomic numberZ≳20. Back‐scattering from a substrate produces negligible resolution loss, and in fact heavy substrates may be used to advantage to increase electron densities in the thin film. Computer programs have been written that are capable of determining scattering data for a large range of materials and incident electron conditions.

ISSN:0021-8979    

DOI:10.1063/1.1657860

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The fluorescence spectra of anthracene and naphthalene in the visible region, when excited by a giant‐pulse ruby laser, were recorded. The spectrum of anthracene consisted of four very broad bands extending from blue to violet. In the case of naphthalene, the spectrum consisted of comparably much sharper bands extending from blue to deep violet. Two‐photon excitation from vibrationally excited levels of the ground electronic state is believed to be the process involved in producing the fluorescence in naphthalene.

ISSN:0021-8979    

DOI:10.1063/1.1657861

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Studies of electron density are reported for a quiescent neon‐argon gas plasma generated by fission fragments in the core of a nuclear reactor. Reaction kinetic equations for the various ionic and excited species are solved self‐consistently with electron‐energy balance equations to yield values of electron density and temperature. It is shown that for containers of diffusion length of about 1.6 mm or greater, there exists a maximum value of electron density at a total gas pressurep≈90 Torr and [Ar]/[Ne]≈10−4; the dominant ion in this case is the atomic Ar+ion. At low values of neutron flux (∼1010cm−2sec−1) and electron density (∼1010cm−3), the electron temperature is computed to be at or near the gas temperature, but at high values of neutron flux (∼1013cm−2sec−1) and electron density (∼1012cm−3), the electron temperature is higher than the gas temperature by an important amount (∼600°K). Inpile measurements of electron density using microwave techniques are in very good agreement with the theoretical predictions.

ISSN:0021-8979    

DOI:10.1063/1.1657862

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The equivalent dielectric tensor for an unbounded, beam‐electron plasma system is derived in detail. The plasma model simulates that plasma found in the positive column of low pressure, weakly ionized discharges. Electron stream drift, electron‐electron thermal interactions, and velocity dependent electron‐neutral collision interactions are included in the model.

ISSN:0021-8979    

DOI:10.1063/1.1657863

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A perturbation theory is developed for a nonlinear longitudinal monochromatic wave in a weakly ionized plasma. The effect of collisions between electrons and neutrals is treated by means of a relaxation term in the Boltzmann‐Vlasov equation. With the distribution function developed to all orders in the amplitudeE0of the oscillating electric field (assumed exponentially damped sinusoidal in form), a constant damping decrement &lgr; is indicated for two cases: Either (i) &lgr; must be negligible or (ii) the collision frequencyvRof the resonance electrons must be negligible in the calculation of the distribution function of the resonance electrons in terms of the electric field. With the nonlinear correction developed to lowest order, the Landau damping decrement is reduced from its linear value &ggr;k0by the factor 1−⅛(&OHgr;4/vR4) for case (i), and by the factor1−116[&OHgr;4/(|&ggr;k0|+v¯)4]for case (ii). Herev¯is the collision frequency appropriately averaged for direct collisional damping, &OHgr;=(eE0k0/m)1/2is the frequency of oscillation of the resonance electrons,k0is the wavenumber, andeandmare the electronic charge and mass, respectively.

ISSN:0021-8979    

DOI:10.1063/1.1657864

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The nonlinear interaction of the dominant TE(10) waveguide mode of a fundamental frequency with a plasma slab in an infinitely long rectangular waveguide is analyzed utilizing an approximate technique. Explicit expressions for the first three harmonic components of the electron density and current density in the plasma are given. General expressions for the nonlinearly generated second‐harmonic electric fields are derived. Numerical results show that the second‐harmonic power generated in the TM(11) wave‐guide mode is more than ten times that generated in the TE(11) waveguide mode.

ISSN:0021-8979    

DOI:10.1063/1.1657865

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The relationship between lattice constanta0, alloy fractionx, and stoichiometry has been studied for the PbxSn1−xTe alloy system. Using the hole concentrationpas a measure of the deviation from stoichiometry, it is shown thata0for SnTe varies withpaccording toa0(SnTe)=−1.7×10−23p+6.327, wherea0is measured in Å, andpin cm−3. For small deviations from stoichiometry it is shown that the alloys obey Vegard's law. Evidence is presented that Vegard's law holds in general providing fixed deviations from stoichiometry are considered. The functional relationship betweena0,x, andpmay be expressed asa0(alloy)=0.133x+a0(SnTe), wherea0(SnTe) is given by the expression presented above. On the basis of this equation it is shown that previously reported deviations from Vegard's law arise in a natural way from the varying deviations from stoichiometry which characterize these alloys.

ISSN:0021-8979    

DOI:10.1063/1.1657866

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An investigation has been made of the two polarization processes that occur in phosphosilicate glass films formed on thermally oxidized silicon. The MOS capacitance‐voltage technique and ac measurements of capacitance and loss angle were used to investigate the component of the polarization that is operative at lower temperatures (i.e., ≲120° C). The magnitude of this component was found to increase quadratically with the P2O5concentration of the glass film. The concentration dependence and related data were used to formulate a model for the low‐temperature polarization. This model suggests that rearrangement of nonbridging oxygen ions is responsible for the glass polarization. The rate of glass polarization that occurs at higher temperatures (≳200° C) was found to increase very rapidly with increasing P2O5concentration. It is shown that the polarization can be markedly reduced for practical applications by lowering the P2O5concentration.

ISSN:0021-8979    

DOI:10.1063/1.1657867

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Using Ga¨rtner's equations, effect of sample thickness on the Cember potential (VD) for strong and weak absorption is discussed. It has been found that for strong absorption, as the thickness of the sample increases,VDtends to a saturation value which decreases as the front‐surface recombination velocity increases. For weak absorption, initially the behavior ofVDdepends upon front and back surface recombination velocities, but for large thickness it becomes independent of them and increases linearly with thickness. When front‐surface recombination velocity is large as compared to back surface recombination velocity, a sign reversal can take place. Expressions are obtained forVD(i) when surface recombination is dominant, or (ii) when bulk recombination is dominant, for weak and strong absorption in the case of thin and thick specimens. A physical explanation of anomalous Dember effect is given by considering the contribution of the concentration gradients set up by front, back, and bulk recombinations. It appears that simultaneous measurements of Hall angle and ratio of PME and Dember potential can be helpful in measuring electron‐hole mobility ratio.

ISSN:0021-8979    

DOI:10.1063/1.1657868

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Uniformly doped GaAs platelet lasers (77°K) are studied on a time basis and are shown to lase without significant delay. Data are presented showing that the turn‐on time and wavelength of longer wavelength laser modes are controlled by electron‐hole pair density and not the usual impurity effects.

ISSN:0021-8979    

DOI:10.1063/1.1657869

出版商:AIP    

年代:1969

数据来源: AIP