摘要:

The changes in the absolute values of the elastic constantsC′,CLandC44by the ultrasonic technique over the temperature range 144–320 K with varying amounts of hydrogen in Vanadium up to 1.5 at.% have been determined. In the &agr; phase, the changes in the absolute values ofC′ andCLwere found to be linear with negative slopes of 2.0% and 0.5%/at.% H, respectively. The changes inC44in the &agr; phase varied between 0 and 0.5 or 0.9% H. The bulk modulus and Voight‐Reuss average Young’s modulus in that phase were found to decrease 0.70% and 0.65%/at.% H, respectively. The elastic constants in the temperature range of the &agr; phase exhibited no change in their temperature dependences by the addition of hydrogen. The present results are compared to the results of other published investigations. The anharmonic effects are discussed in the light of the volume expansion due to H in V upon the elastic constants, the possible electronic effect by suggesting the addition of H to V is analogously similar electronically to adding Cr to V and finally the Snoek relaxation effect. It is concluded that the Snoek relaxation best describes the &Dgr;C′ effect observed when hydrogen is present in the &agr; phase. This effect yields an asymmetric distortion energy parameter [3(A−B)/(A+2B)] of the order of 0.47.

ISSN:0021-8979    

DOI:10.1063/1.327729

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A generalized form of the Herrmannp‐&agr; model equation of state is analyzed with respect to the question of predicted sound velocity. It is shown that only for a porosity factor of &agr;−n, withn≳1, does the predicated sound velocity decrease with increasing porosity as observed ultrasonically. The Mazzellaetal. relationship between the Gru¨neisen parameter and the sound velocity is shown to be satisfied with any exponentnin the porosity factor.

ISSN:0021-8979    

DOI:10.1063/1.327656

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Ultrasonic measurements show that the shear modulus 1/2 (C11−C12) softens dramatically as single crystals of Nb3Sn approach the martensitic transition near 50 K. It is expected that Young’s modulus of polycrystals will also soften, but previous ultrasonic measurements, which suffer from severe damping, fail to show the expected effect. We have measured Young’s Modulus of polycrystalline Nb3Sn between 4.2 and 300 K by static beam‐deflection methods and observe marked softening. A value of 1.32×1012dyn cm−2was obtained at 300 K by the deflection of thin Nb3Sn‐Nb‐Nb3Sn composite strips by external stress. The variation of the modulus withTwas obtained from the change in the radius of curvature of internally stressed Nb3Sn‐Nb composite strips. (This method is made possible by the near‐perfect match between the thermal expansion coefficients of Nb and Nb3Sn.) The modulus is found to be proportional to lnTbetween 50 and 300 K and is temperature independent below the superconductingTc, resulting in a decrease by a factor of ∼2 between 300 and 18 K. The observed softening is somewhat less than that predicted by a polycrystalline average of the experimental single‐crystal elastic constants,but is much larger than that observed with ultrasonic measurements.

ISSN:0021-8979    

DOI:10.1063/1.327730

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Thick, machinable, and amorphous 1Sm‐5Co plasma‐sprayed deposits show a high resistance to magnetization and demagnetization at room temperature. This behavior is believed to be related to large internal stresses and variations in chemical composition present in the as‐sprayed material. Thermal treatments of these deposits, in argon, at temperatures substantially lower than those required for crystallization, produce little change in their magnetic behavior. Similar treatments in hydrogen, however, result in an easy approach to saturation and very low coercivity values. This different response of the material to hydrogen has been attributed to an increased mobility of the atoms in hydrogen, which permits sufficient rearrangement of the atoms so that high magnetization and low coercivity are achieved in the amorphous state. Use of a hydrogen atmosphere also results in a considerable increase in the temperature required for crystallization. Whereas crystallization occurs at about 500 °C in argon, temperatures of about 700 °C are needed to produce similar effects in hydrogen. The suppression of the crystallization processes in hydrogen has been attributed to a deposit‐hydrogen chemical interaction at the low temperatures. The results of this study indicate that amorphous 1Sm‐5Co is probably more suited for use as a means for storing hydrogen than is crystalline SmCo5material.

ISSN:0021-8979    

DOI:10.1063/1.327731

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Deep‐level transient spectroscopy (DLTS) and neutron‐activation analysis have been applied to measure the gold distribution after a phosphorus gettering step. It is found that the gettering mechanism is able to operate without induced dislocations but depends mainly on the surface phosphorus concentration. For example, whenCs=1021/cm3, the gold concentration is reduced by a factor 103over the whole thickness of a wafer. This Au trapping phenomenon is attributed to the presence of a phosphorus‐induced point defect and related to the emitter push effect mechanism.

ISSN:0021-8979    

DOI:10.1063/1.327732

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Annealing behavior of molybdenum films 320–4900 A˚ thick deposited by the e‐gun evaporation method on a silicon dioxide layer has been investigated directly by means of a high‐resolution scanning electron microscope (SEM). The grain growth of Mo films occurs drastically at 900 °C annealing or higher. The structures of Mo films annealed higher than 900 °C exhibit film thickness dependency. At 1000 °C annealing, 1200 A˚ or thinner samples show columnarlike monolayer structure. In the case of the 4900‐A˚‐thick sample, it reveals a faceted multilayer structure, and its grain size is about 1700 A˚. Grain size annealing temperature dependency is well correlated to electrical resistivity dependency. In addition, it is also found that, at 900 °C annealing or lower, no interfacial reaction occurs.

ISSN:0021-8979    

DOI:10.1063/1.327708

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The electronic density of states in the forbidden gap of polycrystalline silicon has been determined from an analysis of capacitance and conductance of a Metal/SiO2(∼60 A˚)/polycrystalline silicon(∼250 A˚)/Si(111) (MOSS) structure. In this structure the thickness of the polycrystalline silicon is comparable to its grain size. Net density of trapped charges in the polycrystalline silicon is enough to terminate the electric field penetrating from the oxide layer. Then, two‐terminal admittance of the MOSS structure is dominated by charging or discharging of the trapping states in a wide range of applied gate bias. TheU‐shaped distribution of trapping state density has been found for thin polycrystalline silicon films.

ISSN:0021-8979    

DOI:10.1063/1.327709

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The glass‐forming region was determined for the system Ge‐Bi‐Se; 13 at.% Bi was found to be incorporated at its maximum content into glasses, the Ge content of which was 20 at.%. Electrical resistivity, thermoelectric power, and optical absorption coefficient were measured mainly on a series of Ge20BixSe80−xglasses (x=0 –13). The resistivity decreased by about four orders of magnitude betweenx=9 and 10, and remained almost constant forx?10. The thermoelectric measurement showed the change of conduction type frompton, accompanied by the above‐mentioned abrupt decrease of resistivity. Inn‐type glasses, hopping conduction in the tail of localized states was proposed in parallel with conduction in extended states. The optical band gap was very slightly changed with the incorporation of more than 2.5 at.% Bi, in contrast to the remarkable decrease in the activation energy for conduction betweenx=9 and 10. The discussion based on the concentration of covalent bonds formed in the glasses led to the conclusion that the formation of a fairly large number of Bi‐Se bonds and the disappearance of Se‐Se bonds nearx=10 were closely related to the composition dependence of the electrical and optical properties of the glasses in the present system.

ISSN:0021-8979    

DOI:10.1063/1.327710

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Conditions are discussed for which the concentration, binding energy, and compensation of a set of impurities can be deduced from the temperature dependence of the thermal free‐carrier population. Improved methods for verifying the quality of a numerical fit to the mass‐action equations are illustrated with data for germanium doped with indium or mercury acceptors. The graphical methods illustrated permit a critical assessment of whether the data really conforms to the generally used equations, and how various forms of error or inapplicability can be observed. It is pointed out that these same techniques can be useful in analysis of thermal emission data under nonequilibrium conditions.

ISSN:0021-8979    

DOI:10.1063/1.327711

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Electrical properties and the acceptor energy level in Zn‐dopedp‐Ga1−xAlxAs (0<x<0.85) prepared by liquid‐phase epitaxy have been investigated. During the LPE growth of Zn‐dopedp‐Ga1−xAlxAs layer, Zn diffuses from Zn‐doped Ga‐Al‐As melt into the undopedn‐GaAs substrate to form thep‐GaAs region. The modified van der Pauw method proposed by Petritz was used to measure the electrical properties ofp‐ (GaAl)As andp‐GaAs. The resistivity and the hole concentration of Zn‐dopedp‐Ga1−xAlxAs were found to be strongly affected by the acceptor energy level for Zn. The acceptor energy level in Zn‐dopedp‐Ga1−xAlxAs was found to increase from 15 meV forx=0 to 90 meV forx=0.85. The increase of the acceptor energy level with increasingxhas been theoretically explained by the modified hydrogenic model proposed by Baldereschi and Lipari.

ISSN:0021-8979    

DOI:10.1063/1.327712

出版商:AIP    

年代:1980

数据来源: AIP