摘要:

The redistribution of implanted As and Sb following metal‐silicide formation of Pt, Pd, and Ni has been studied. The phases of the silicides used were PtSi, Pd2Si, and NiSi. Investigations with Rutherford backscattering analysis showed that after the formation of the silicides, the Sb was always found in the silicide layer near the surface of the samples, whereas PtSi and Pd2Si caused a partial rejection of As for implanted doses of 2×1015cm−2and higher. No rejection of As was found after the formation of NiSi. The results are discussed in terms of solid solubilities and impurity‐metal compound formation. The data presented has implications in the fabrication of Ohmic contacts and the adjustments of the heights of Schottky barriers on silicon.

ISSN:0021-8979    

DOI:10.1063/1.324599

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Leslie’s differential equations describing the orientation of the optic axis through a twisted nematic layer are solved for the case where there is a nonzero tilt bias angle. Three classes of solutions are investigated: the simple solution of constant tilt angle through the layer with uniform twist, symmetric solutions where the tilt angle in the middle of the layer has an extreme value, and antisymmetric solutions where the tilt angle in the middle of the layer is identically zero. These solutions and their corresponding elastic deformation energies are compared for typical values of the splay, twist, and bend elastic constants of nematic liquid crystals. For 90° twisted nematic layers the antisymmetric solution always has a higher elastic energy than the symmetric solution. This result explains why regions of reverse twist are suppressed in twisted nematic display devices which have finite tilt bias angles at both boundaries. Reverse‐twisted domains can also be avoided by adding chiral dopants to the nematic mixture and by making layers having total twist angles of less than 90°. The effectiveness of these three techniques is discussed in terms of a comparison of the elastic energy difference between the oppositely twisted configurations.

ISSN:0021-8979    

DOI:10.1063/1.324600

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Patterns have been observed on the surfaces of silicon epitaxial layers grown on annealed‐silicon substrates which had been implanted with arsenic at high doses and high dose rates. The patterns take the form of bands which lie parallel to the scanning direction of the ion beam and which contain a large density of pits. X‐ray topography reveals that the bands are present immediately after the slice had been annealed and the band contrast is sensitive to the diffraction conditions employed. Transmission electron microscopy shows that the bands contain a high density of dislocation loops, as well as the pits which always contain a small precipitate at their center. These results are discussed in terms of temperature variations in the slice during the implantation process which lead to inhomogeneities in the damage and impurity distribution.

ISSN:0021-8979    

DOI:10.1063/1.324601

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Gas‐gun impact techniques have been used to pulse charge nanofarad capacitors from the shock depoling of PZT 56/44 and PZT 95/5 ferroelectric ceramics. The PZT materials were depoled in the normal mode. Pulse powers of hundreds of kilowatts were produced in a few microseconds. The PZT 56/44 material was impacted in the stress range from 4.4 to 11.8 GPa. A maximum load voltage of 55 kV was produced at 7.9 GPa, resulting in a charge release of about 78&percent;. Shock‐induced electrical breakdown in the PZT material occurred at 11.8 GPa. The PZT 95/5 material was impacted at 1.4 and 2.9 GPa stress levels. A maximum load voltage of 81 kV was produced at the higher stress, resulting in a charge release of about 74&percent; before electrical breakdown occurred in the PZT material.

ISSN:0021-8979    

DOI:10.1063/1.324602

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Certain properties of vacuum‐deposited thin films ofa‐Se were measured and compared with those of melt‐quenched Se glass. After annealing in the temperature range 25–50 °C, the creep, heat capacities, and far‐infrared behaviors of the vapor‐deposited films were indistinguishable from those of melt‐quenched specimens. The shear‐viscosity &eegr; measurements on the films were extended into a temperature range well below that where such data on melt‐quenched samples are available. Over this temperature range, 25–35 °C, theTdependence of &eegr; of the equilibrated films was well fit by an Arrhenius relation with an activation energy of 130 kcal/mole. The stress and thermal‐relaxation rates for annealed films were also measured as functions ofT. They are controlled by different sets of relaxation processes and are not directly proportional to the equilibrium &eegr;. However, they are in good agreement with each other, except that the thermal‐relaxation times are more widely dispersed over a span of about two orders of magnitude. The isothermal relaxation of the films to their equilibrium creep rates, though not a simple exponential decay with a single time constant, can be simply described by a relaxation time &tgr; (t), which is proportional to the instantaneous viscosity &eegr; (t). As deposited, the films exhibited glass‐transition temperatures as much as 10 °C below those of annealed films. Also they showed a broad exothermic peak at about 50 °C. These results, on annealed and as‐deposited films, are consistent with the hypothesis that the various molecular constituents, presumably eight‐membered rings and polymeric chains ofa‐Se, readily interconvert to an equilibrium distribution at temperatures as low as 30 °C. This distribution is temperature dependent and the same in vapor‐deposited and melt‐quencheda‐Se.

ISSN:0021-8979    

DOI:10.1063/1.324603

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The stress‐strain curves for 3% cobalt cemented tungsten carbide and sintered diamond compact are determined up to a plastic strain of 8 and 0.2%, respectively, by measuring the permanent deflection at the center of the circular flat face of anvils used in ultrahigh‐pressure experiments. The yield strength based on 0.2% offset for 3% cobalt cemented tungsten carbide is 50±5 kbar, and that for sintered diamond compact ranges from 200 to more than 500 kbar, depending on the sintering quality.

ISSN:0021-8979    

DOI:10.1063/1.324604

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We report, for the first time, observations of the acoustic harmonics generated by steady‐state vibration at amplitudes so large that long‐range dislocation motion occurs. Most of the measurements have been made on the second and third harmonicsA2andA3. At low amplitudes the experimental results of Hikata and Elbaumetal. are confirmed, but there is some discrepancy with theory forA3. At amplitudes such that dislocation sources operate, the harmonic spectrum departs strongly from the Hikata‐Elbaum predictions. The harmonic amplitudes do not always increase monotonically with strain;A2occasionally shows a maximum,A3sometimes, andA5even more frequently, in a pattern sensitive to mechanical history. The spectrum depends on grain size and prestress, varying jointly with the modulus defect and internal friction as these indicators of dislocation motion vary. The results on strain dependence are in accord with a simplified model of dislocation breakaway and Frank‐Read source operation proposed previously to account for the internal friction and modulus defect.

ISSN:0021-8979    

DOI:10.1063/1.324605

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The phase transition in amorphous selenium under high pressure was studied. The high pressures were generated using a diamond‐indentor technique. From the behavior of electrical resistance of amorphous selenium under high pressure, it was found that amorphous selenium at room temperature starts transforming to a crystalline phase when the pressure is near 97 kbar. The effect of temperature on the electronic transition in amorphous selenium under high pressure was also studied. Amorphous selenium was heated to approximately 80 °C; when under a pressure of 26 kbar, it transformed to a conducting phase. The conducting phase was retained for hours at 26 kbar after the temperature was lowered to room temperature.

ISSN:0021-8979    

DOI:10.1063/1.324552

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Viscosity and thermal expansion have been measured for 12 series of lithium aluminosilicate glasses. The compositional dependency of the viscosity, glass‐transformation temperature, dilatometric‐softening temperature, and refractive index all exhibit an abrupt change in slope at an aluminum‐to‐lithium ratio between 1.05 and 1.10. The thermal‐expansion coefficients of these glasses were found to depend only on the lithium oxide content, i.e., to be independent of the aluminum‐to‐silicon ratio. These results suggest that the traditional structural model for these glasses must be modified slightly. A new model is proposed which allows some aluminum to act as a modifier in all alkali aluminosilicate glasses.

ISSN:0021-8979    

DOI:10.1063/1.324553

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Using a dynamic electrical‐heating technique, we have measured the thermal conductivity and specific heat of NdP5O14, a high‐Nd‐concentration laser material. The measured values of the thermal‐conductivity tensor elements (in W/cm K) are &Lgr;a=2.10×10−2, &Lgr;b=9.66×10−3, and &Lgr;c=1.40×10−2. The specific heat is 0.141 cal/g K, in excellent agreement with the value of 0.139 cal/g K that we measured by differential scanning calorimetry.

ISSN:0021-8979    

DOI:10.1063/1.324554

出版商:AIP    

年代:1978

数据来源: AIP