摘要:

Diffraction topographs of oxidized silicon wafers made by the extinction contrast technique show extremely high intensity being diffracted from the silicon surface directly under steps etched in the oxide. Edges of metal or dielectric films evaporated on silicon similarly show enhanced intensity. In some cases, a decreased diffracted intensity (less than that diffracted by pure Si) is seen in these regions. These two effects are attributed to elastic strain transmitted to the Si by the step or edge, due to the adherence of the film to the substrate. Enhanced intensity is due to extinction contrast, while decreased intensity is due to a Borrmann anomalous transmission effect. The orientation of the step with respect to the diffraction vector ghkl, the height of the step, and the compositions of substrate and film are shown to be important parameters affecting the diffracted intensity.

ISSN:0021-8979    

DOI:10.1063/1.1702943

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Magnetization data have been obtained for Nb−33%Zr 0.010‐in.‐diam wires carrying a transport currentIin a constant external longitudinal magnetic fieldHextand with a liquid‐helium bath temperature of 4.2°K. The variation of magnetization withIfor a constantHextdepends on the relative directions ofIandHext. WhenIis antiparallel toHext, the specimens were observed to become paramagnetic at a threshold current less than the experimental critical current and remain paramagnetic up to the critical current. A linear relationship between the threshold current and the external field forHext<500 G is observed.

ISSN:0021-8979    

DOI:10.1063/1.1702944

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Measurements were made of the pyroelectric coefficient in three salicylideneanilines (``anils''). The nonpolar salicylidene‐3‐toluidine was found to be nonpyroelectric as expected. Pyroelectric coefficients of 3 to 6×10−10and 2 to 3×10−10C·cm−2·°C−1were found for salicylidene‐4‐bromoaniline and 5‐chlorosalicy‐lideneaniline, respectively, over the temperature range of 25° to 60°C. Anomalous pyroelectric behavior, possibly due to a structure change, was found in the 5‐chloro‐anil between 50° and 95°C.

ISSN:0021-8979    

DOI:10.1063/1.1702945

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The structure of Ge films deposited over a wide range of deposition rates and substrate temperatures onto hand‐polished (111) CaF2substrates in a vacuum of 10−9to 4×10−7Torr has been characterized. The epitaxial temperature and the amorphous to crystalline transition temperature were found to be rate dependent. The linear relation observed between the logarithm of the deposition rate and the reciprocal of the epitaxial temperature agrees generally with nucleation theory of small clusters and yields an activation energy of 1.43 eV. The observed linear relation between the logarithm of the deposition rate and the reciprocal of the amorphous to crystalline transition temperature has been interpreted in terms of simple surface diffusion theory and leads to an activation energy for surface diffusion of Ge on CaF2of 1.53 eV.

ISSN:0021-8979    

DOI:10.1063/1.1702946

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Ivory does not deform in a completely elastic manner prior to fracture, but instead plastic microyielding commences at a very small applied stress. The nature of the plastic deformation is determined by the orientation of the test specimen relative to the growth ring structure. Specimens oriented with the tension axis parallel to the tusk length (designated longitudinal) exhibit both a larger microscopic yield stress (the stress to produce a plastic strain of 2×10−6in./in.) and a higher rate of strain hardening than specimens oriented perpendicular to the tusk length (designated transverse). Prestraining has no effect on the rate of strain hardening of longitudinal specimens, but progressively reduces the measured rate of strain hardening of transverse specimens. A feature common to the deformation of both longitudinal and transverse specimens is the considerable anelastic contraction which occurs after unloading. The fracture characteristics, which are also a function of specimen orientation, are correlated with the relative planes of weakness provided by the interfaces between growth rings.

ISSN:0021-8979    

DOI:10.1063/1.1702947

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The results of resonance absorption measurements in cesium vapor are reported. It is shown that the half‐height width of the absorption (&ggr;) is directly proportional to the neutral cesium density. Over the reduced pressure range of 0.2 to 10 Torr, &ggr;k=10−22cm3, wherekis the photon‐atom absorption cross section. Ionization measurements are reported describing the effect of the absorption of resonance radiation in cesium vapor. On the basis of the results presented, an ionization mechanism has been hypothesized for the production of the cesium molecular ion (Cs2+) as the dominant ionic species in high‐pressure, low‐energy cesium vapor thermionic plasmas. The mechanism is based on the collision of two cesium atoms excited to the resonance level (1.45 or 1.38 eV). The excitation mechanism shifts from nearly complete photon‐induced excitation at a cathode temperature of 2000°K to equal contributions of photon induced and electron induced excitation at a cathode temperature of 1550°K. At lower cathode temperatures, the excitation is accomplished primarily by electron impact processes. Single impact electron ionization processes are shown to be inadequate for neutralization in the plasma of low‐energy discharges such as those found in cesium vapor thermionic converters. It is shown that for a condition of space charge neutralization in the plasma of low‐energy cesium vapor discharges the ratio of excited state population density to ion population should be between 2.5 and 5 to 1.

ISSN:0021-8979    

DOI:10.1063/1.1702948

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Stoichiometric thin films of AlSb have been prepared by coevaporation of the elements onto glass substrates held at 550°C. Conductance activation energies of 0.17 and 0.29 eV were observed. Oxygen adsorption causes a level at 0.24 eV that dominates the conductance in air at room temperature. Space‐charge‐limited current flow was observed at room‐ and liquid‐nitrogen temperatures. The hole concentration and mobility in the layers are estimated at 1015cm−3and 1.5 cm2/V‐sec, respectively.

ISSN:0021-8979    

DOI:10.1063/1.1702949

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Reaction‐rate theory is applied to dislocation motion and it is shown that when the activated complex is allowed two degrees of freedom, the activation energy is inversely proportional to the applied stress, so the dislocation velocity,vdis related to the applied shear stress, &tgr; by a relation of the form:v=v0e−D/&tgr;, wherev0is the terminal velocity andDis called the characteristic drag stress. This relation is obeyed by LiF, Ge, NaCl, W, and possibly Fe−3% Si.The observed dependences of dislocation velocities on point defect concentrations and temperature are also predicted.Two classes of crystals are considered. Those in which drag is caused mainly by point defects; and those in which the intrinsic structure (chemical bonds) causes the drag.

ISSN:0021-8979    

DOI:10.1063/1.1702950

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The zero‐bias capacitanceCof a thin intrinsic semiconductor film sandwiched between identical electron‐injecting contacts is computed exactly and compared with the valueC0for noninjecting contacts. The effect of traps and recombination centers is omitted. The curve of normalized capacitance versus film thickness exhibits a bump for an intermediate value of thickness.C/C0is unity for very thin or very thick films and may reach a maximum value of 1.934 (nominally 2). Contact‐dominated conditions disappear for films thicker than four Debye lengths based on the intrinsic carrier concentration.

ISSN:0021-8979    

DOI:10.1063/1.1702951

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The dependence of the barrier height of metal‐semiconductor systems upon the metal work function is derived based on the following assumptions: (1) the contact between the metal and the semiconductor has an interfacial layer of the order of atomic dimensions; it is further assumed that this layer is transparent to electrons with energy greater than the potential barrier but can withstand potential across it. (2) The surface state density (per unit area per electron volt) at the interface is a property only of the semiconductor surface and is independent of the metal. The barrier height &phgr;Bnis defined here as the energy needed by an electron at the Fermi level in the metal to enter the conduction band of the semiconductor.With the above assumptions, the barrier height forn‐type semiconductor‐metal contacts is found to be a linear combination of the metal work function &phgr;mand a quantity &phgr;0which is defined as the energy below which the surface states must be filled for charge neutrality at the semiconductor surface. The energy &phgr;0is measured from the edge of the valence band. For constant surface state density the theoretical expression obtained is&Jgr;Bn=&ggr;(&Jgr;m−&khgr;)+(1−&ggr;)(Eg−&Jgr;0)−&Dgr;&Jgr;n,where &khgr; andEgare electron affinity and the band gap of the semiconductor, respectively, &Dgr;&phgr;nis the image force barrier lowering, and &ggr; is a weighting factor which depends mainly on the surface state density and the thickness of the interfacial layer.The theoretical expression is compared to the presently available &phgr;BnVS &phgr;mdata for Si, GaP, GaAs, and CdS, by fitting the data to straight lines using the method of least squares. The best straight‐line fit was obtained for the GaP data, with probable error limits on the slope and intercept of ±0.03 and ±0.13 eV, respectively.The parameter &ggr; in the theoretical expression is found to range from 0.07 for GaAs to almost unity for the CdS data reported by Goodman indicating weak and strong dependence of the surface barrier height on the metal work function, respectively.The value of &phgr;0is roughly a third of the respective band gap energies for Si, GaP, and GaAs, and the surface state density for these semiconductors is found to be in the range 1013−1014states/cm2/eV, for the experiments cited.Excessive scatter in the data points for the CdS data of Mead and Spitzer casts doubt on the significance of a straight‐line fit for this case. The data of Goodman for CdS obey the Schottky theory for a metal‐semiconductor barrier, but this agreement requires a value of the electron affinity &khgr; which is different from the vacuum‐photothreshold value measured by other authors.

ISSN:0021-8979    

DOI:10.1063/1.1702952

出版商:AIP    

年代:1965

数据来源: AIP