摘要:

The absolute density of the cyanogen fluoride (FCN) molecule has been measured in aCHF3/N2electron-cyclotron-resonance (ECR) plasma using infrared diode laser absorption spectroscopy. TheR(22)rotational-vibrational line at1060.340 cm−1in the&ngr;1fundamental of19F12C14Nwas used for the spectroscopy. The extinction process of FCN in the afterglow was discussed on the basis of the decay rate after discharge termination. Moreover, the absolute FCN density in aCHF3ECR plasma during etching of silicon nitride has been calculated on the basis of the data shown in our previous study [K. Miyata &etal;, J. Vac. Sci. Technol. A15, 568 (1997)]. It was found that approximately 10&percent; of nitrogen atoms coming from silicon nitride formed FCN. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366335

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A chemical kinetics model is developed to analyze the time evolution of the different main species involved in a flue gas initially stressed by a pulsed corona discharge at the atmospheric pressure and includingN2,O2,H2O,andCO2with a few ppm of NO. The present chemical kinetics model is coupled to a gas dynamics model used to analyze the radial expansion of the gas in the ionized channel created during the discharge phase. It is also meant to analyze the gas heating due to the Joule effect. This chemical kinetics model is also coupled to charged particle kinetics models based on a Boltzmann equation model to calculate the electron-molecule reaction coefficients in the flue gas and on a Monte Carlo code to estimate the energy and momentum transfer terms relative to ion-molecule collisions which are the input data for the gas dynamics model. It is shown, in particular, that the evolution of the radicals and the oxides is substantially affected by the gas temperature rise (from the initial value of 300 K up to 750 K near the anode) thus emphasizing the present coupling between gas dynamics, charged particle, and chemical kinetics models. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366336

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Computer simulations on the display characteristics of chiral-homeotropic liquid crystal cells are performed. This normally black display mode exhibits an excellent contrast ratio, nearly achromatic light transmission, and low operation voltage. The optimal twist angle for suppressing the wavelength and voltage dependencies ranges from 90° to 150°. Promising applications of this operation mode for both transmissive and reflective displays are discussed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366337

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electronic properties of silicon rich amorphous silicon alloys were investigated using diode structures and thin films on Corning 7059 glass following the implantation of 1 MeVGe+ions with doses up to2.4×1015 ions/cm2.Optical absorption measurements on hydrogenated amorphous silicon (a-Si:H) and amorphous silicon nitride(a-SiNx:H)showed that the optical band gap decreases with the implanted ion dose. The hydrogen concentration was not affected by the implantation and therefore the change in optical band gap was consistent with a broadening of the band tails as confirmed by dual beam photoconductivity measurements. Annealing studies showed that recovery of the band gap could be achieved at temperatures of≈250 °C.This recovery was almost complete following low dose ion implantation, but a residual amount of damage remained which increased with the dose before saturating. Results of electrical measurements on metal-semiconductor barriers showed a correlation between optical and electrical behavior with ion dose. We propose a model in which the barrier height and the optical band gap vary in the same way with the ion dose. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366338

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In crystalline silicon, irradiated with 60 and 80 MeV energy silicon ions, regions of high defect densities were located by repeatedly etching the sample and measuring the lifetime of minority carriers, &tgr;. The values of &tgr;  before etching were 10 and 8 &mgr;s in the 60 and 80 MeV ion irradiated sides, respectively, and 19 &mgr;s in the unirradiated side. On etching the samples, these values of the irradiated side initially increased slowly but later on, as the total thickness of the etched silicon approached the ion ranges, they increased steeply. However, the value of &tgr; in the unirradiated side remained unchanged even after etching. These results show that the regions of high defect densities are situated below the surface at depths of 20 and 27 &mgr;m, respectively, in 60 and 80 MeV ion irradiated samples. These coincide, respectively, with the projected depth in silicon at which the 60 and 80 MeV silicon ions deposit a maximum amount of energy through nuclear collisions. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366339

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Local structures of dilute isovalent and heterovalent impurity atoms in Si crystal (Si:X, X=Ga, Ge, As) have been studied by fluorescence x-ray absorption fine structure. The distortion of local lattice around the impurity atoms was evaluated from the Si–X bond length determined by extended x-ray absorption fine structure. The results demonstrate that the local lattice deformation is strongly dependent on the electronic configuration of impurity atoms, i.e., we find an anomalous expansion(0.09±0.01 Å)along the [111] direction for donor (As) atoms but much smaller magnitude(0.03±0.01 Å)for isovalent (Ge) atoms and acceptor (Ga) atoms. The results suggest that the local lattice distortions are strongly affected by the Coulomb interactions between the localized charge, which piles up to screen the ion core and the bond charge, and the ion-core repulsion. Absence of anomaly in case of negatively charged Ga atoms suggests that the former mechanism is a dominant factor for anomalous lattice expansion. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366340

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A dislocation model of a subsurface crack parallel to the surface is presented. For tensile loading, the results agree with those of previous workers except that we studied the crack very close to the surface and found thatKII(mode II stress intensity factor) approachesKI(mode I stress intensity factor) to within about 22&percent;(KII=0.78KI).(Note thatKIIis zero when the crack is far away from the surface). Using bending theory for such situations, it is found that both stress intensity factors are inversely proportional to the3/2power of the distance between the subsurface crack and the free surface. For shear loading, the crack faces overlap each other for the free traction condition. This indicates the failure of the model. However, there was no overlap for tensile loading even though the stresses in front of the crack oscillate somewhat when the crack is very close to the surface. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366341

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Atomic-scale material responses of dynamic metal-like substrates due to single and repeated indentation by metal-like or covalent rigid tips are interpreted in light of three-dimensional molecular dynamics simulation results. Single-indentation results for a face-centered-cubic metal substrate indented by a relatively blunt tip of the same material and a sharper pyramidal tip of a covalent material are compared to elucidate the effects of interfacial atomic potential and tip shape on the deformation behavior. Force hysteresis occurs due to inelastic deformation and heating of the substrate. The abrupt decrease of the repulsive force during penetration is attributed to permanent deformation. The formation of a connective neck during unloading observed only in the indentations involving the metal tip is associated with the stronger interatomic forces and larger tip surface area in these simulations. The rapid decrease of the attractive force during retraction of the tip is associated with the reconstruction of the elongated neck. Results for different metallic substrates repeatedly indented by a rigid covalent tip up to a fixed maximum depth or maximum normal force are presented in order to reveal the evolution of deformation and heating in the substrate with indentation cycles. Repeated indentation gives rise to behaviors resembling cyclic hardening and softening observed at the macroscale. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366342

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The third-order, nonhomogenized, dynamic method of cells is used to calculate the particle velocity for a shock wave experiment involving an epoxy–graphite laminate. Constitutive relations suitable for the various materials are used. This includes linear and nonlinear elasticity and, when appropriate, viscoelasticity. It is found to be beneficial to incorporate artificial viscosity into the analysis. Artificial viscosity successfully removes the unphysical high-frequency ringing in the numerical solutions of the theory, while leaving the physical oscillations, characteristic of wave propagation in a periodic laminate, largely undiminished. It also allows the viscoelastic relaxed moduli to be closer to their unrelaxed counterparts than in a previous calculation, thus making them more acceptable. The results agree well with the corresponding plate-impact experiment, and are compared to the second-order theory of Clements, Johnson, and Hixson [Phys. Rev. E,54, 6876 (1996)]. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366343

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The steady state growth equation for a paraboloid of revolution and a parabolic cylinder, taking the interfacial energy into account, is revisited. Although the consideration of the interfacial energy was necessary, the growth equation was much more complicated than the original equation with a zero interfacial energy, since both the thermodynamics and kinetics of the growth are considered in one equation. In the present work, we take advantage of the development in computational thermodynamics and consider the thermodynamics and kinetics of the process in separate equations, but solve them simultaneously. A consistent framework to describe the phenomena and compare it with previous treatment of the interfacial energy will be presented. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366344

出版商:AIP    

年代:1997

数据来源: AIP