摘要:

The transient behavior of the flux from a valved effusion cell containing red phosphorus is shown to result from a low elemental sublimation coefficient (&agr;=1.3×10−7) and not from the presence of white phosphorus in the sublimator region. The criteria for generating white phosphorus in the sublimator are given. The conversion from tetramers to dimers is modeled as a function of temperature and pressure. At higher pressures, higher temperatures are needed to convert P4to P2. Experimental results are shown to be in qualitative agreement with results from thermodynamic equilibrium arguments. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360261

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have studied morphological changes of an interface in a strong electric field which is normal to the initially planar interface. Electromigration along the interface in a two phase metallic systemA‐Bof the immiscible components has been considered. The stresses arising during electromigration of the components were taken into account. A nonlinear equation has been derived for the interface evolution in the electric field, allowing for curvature of the interface. It was shown that the interface diffusion in an electric field leads to the formation of a periodic corrugation on the interface if the components are distinguished by their electric charges. The corrugation increases with time and is transformed into a channel‐hillock‐like structure. The nonlinear equation was analyzed numerically for the steady‐state case. The shape and the growth rate of hillocks on the interface have been calculated. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360262

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Silicon oxynitride films were deposited by plasma‐enhanced chemical‐vapor deposition. The elemental composition was varied between silicon nitride and silicon dioxide: SiO0.3N1.0, SiO0.7N1.6, SiO0.7N1.1, and SiO1.7N0.5. These films were annealed in air, at temperatures of 40–240 °C above the deposition temperature (260 °C), to determine the stability and behavior of each composition. The biaxial modulus, biaxial intrinsic stress, and elemental composition were measured at discrete intervals within the annealing cycle. Films deposited from primarily ammonia possessed considerable hydrogen (up to 38 at. %) and lost nitrogen and hydrogen at anneal temperatures (260–300 °C) only marginally higher than the deposition temperature. As the initial oxygen content increased a different mechanism controlled the behavior of the film: The temperature threshold for change rose to &bartil;350 °C and the loss of nitrogen was compensated by an equivalent rise in the oxygen content. The transformation from silicon oxynitride to silica was completed after 50 h at 400 °C. The initial biaxial modulus of all compositions was 21–30 GPa and the intrinsic stress was −30 to 85 MPa. Increasing the oxygen content raised the temperature threshold where cracking first occurred; the two film compositions with the highest initial oxygen content did not crack, even at the highest temperature (450 °C) investigated. At 450 °C the biaxial modulus increased to &bartil;100 GPa and the intrinsic stress was &bartil;200 MPa. These increases could be correlated with the observed change in the film’s composition. When nitrogen was replaced by oxygen, the induced stress remained lower than the biaxial strength of the material, but, when nitrogen and hydrogen were lost, stress‐relieving microcracking occurred. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360263

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

X‐ray reflectivity is applied to investigate the effect of a surfactant on the growth of Ge1−xSix/Si superlattices. It is demonstrated that the antimony layer deposited on the surface can effectively prevent the intermixing of silicon and germanium. The specular reflectivity curves show that the width of the interface is sufficiently reduced by the surfactant. The transverse scans show that the interface roughening exponenthfor the sample with surfactant is larger than for the sample without surfactant, and the in‐plane correlation length for the former is much larger than for the latter. This indicates that the surfactant makes less jagged and smoother interfaces and induces a different surface growth mode. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360264

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Highly strained InxGa1−xAs/GaAs quantum well structures on GaAs substrates were grown by molecular‐beam epitaxy. Even with high In composition (0.4 or higher), sharp spectra were obtained from samples grown at 400 °C due to the reduction of In surface segregation. The full width at half maximum of the photoluminescence spectrum from a 6.4‐nm‐thick (21 monolayers) In0.42Ga0.58As/GaAs single quantum well at 77 K and at room temperature was only 9.78 and 18.4 meV, respectively. The peak wavelength of this sample at room temperature was 1.223 &mgr;m. The theoretically calculated peak wavelengths, using a finite square‐well model are in good agreement with the experimental ones over a wide In composition range (between 0.14 and 0.44), and with well widths between 6 and 53 monolayers. This study suggests that the performance of pseudomorphic devices can be improved by using high‐quality InxGa1−xAs layers with high In composition pseudomorphically grown on GaAs substrates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360265

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The structural and magnetic properties of Mn in Co/Mn (001) multilayers were investigated by x‐ray scattering, by magneto‐optical Kerr effect measurements, and with a Faraday balance. The multilayers were deposited by rf‐sputtering on MgO(001) substrates. Small angle x‐ray reflectivity scans and high angle Bragg scattering confirmed good layer quality and crystal coherence properties. In‐ and out‐of‐plane x‐ray scattering revealed a coherent growth of face‐centered‐cubic (fcc) (or fct) Mn on fcc Co(001). The stability limit of the metastable fct Mn structure is about 20 A˚ or 10 atomic layers. The magnetic exchange coupling appears to be partly antiferromagnetic with a first maximum located between 20 and 30 A˚. Saturation magnetization measurements indicate no ferromagnetic moment for the fct Mn layers. Furthermore, the saturation moment per unit volume is reduced as compared to the bulk Co value, suggesting the presence of ‘‘dead layers’’ at the Co/Mn interfaces. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360266

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Interfacial defect theory is applied to the epitaxial ferroelectric system consisting of a tetragonal ferroelectric such as BaTiO3or PbTiO3grown onto a cubic (001) substrate. The interfacial defects that result from the diffusionless paraelectric to ferroelectric (PE→FE) phase transition are treated under the constraint that no misfit dislocations are generated during or as a result of the transition. The domain pattern develops to provide strain relief in the film. The interfacial defects for the ...c/a1/c/a1... domain pattern include coherency edge dislocations and coherency wedge disclinations. Interfacial defects for the ...a1/a2/a1/a2... domain pattern include coherency edge and screw dislocations. Far‐field strain states for both domain patterns can be predicted from the interfacial defect content. From the twinning geometry, general expressions are derived for the far‐field rotations of the crystal axes of individual domains for the ...a1/c/a1/c... and the ...a1/a2/a1/a2... domain pattern. The geometrically predicted rotation angles for ...c/a1/c/a1... domain pattern are verified by x‐ray‐diffraction and transmission electron diffraction for epitaxial PbTiO3films grown on (001) SrTiO3substrates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360267

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

NiSi2(111) and NiSi2(100) layers with good crystalline quality have been formed by ion‐beam synthesis. An unusual Ni atom distribution showing two completely separated layers during a single implantation step has been observed by Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM). The orientation, strain, and stiffness of the NiSi2layers have been studied by RBS/channeling, x‐ray diffraction, and TEM. The results show that the continuous NiSi2layers have type‐A orientation with a parallel elastic strain larger than the theoretical value of 0.46% for pseudomorphic growth. The perpendicular strain of the NiSi2(111) layers is apparently smaller than that of NiSi2(100) layers, indicating a higher stiffness in the ⟨111⟩ direction. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360268

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The growth and properties of PbS thin films, chemically deposited on bulk lead titano‐zirconate ceramics, are investigated. Scanning electron microscopy photographs reveal that the medium size of crystallites is much larger for PbS films grown on poled ferroelectric substrates than for the films grown onto glass or onto unpoled ferroelectric substrates. In the first case the medium size of crystallites is about 1–1.5 &mgr;m while in the second case it is less than 0.3 &mgr;m. Spectral distribution of photoconductivity and thermally stimulated currents (TSC) measurements were performed on all samples. Experimental results indicate that the properties of the PbS films can vary, depending on the substrate nature and in the case of poled ferroelectric substrates, on the polarity. The photoconductive signal is usually larger, the dark resistivity is smaller, and the TSC current value is higher for PbS films deposited on the positive face of the ferroelectric substrate than for those deposited on the negative face. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360269

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new technique on the formation of TiN film with large grain size from TiNxis described. The TiNxlayer (defined in Sec. II A) was deposited by sputtering in argon and nitrogen. The nitrogen atoms in Ti matrix relaxed the mechanical stress of the deposited film and limited the surface mobility during the deposition process, resulting in a nanocrystalline structure with extremely uniform thickness. After rapid thermal annealing (RTA), the TiNxyielded a bilayer structure of TiN/TiSixOy, in which the TiN showed (111) preferred texture, extremely smooth surface, and large grain size without any columnar structure. In addition, the resistivity of the bilayered TiN was as low as 40 &mgr;&OHgr; cm. In the TiN multilayered aluminum structure (i.e., TiN/Al/TiN), epitaxial continuity and the intermetallic compound such as TiAl3were clearly observed at the aluminum/TiN interface. The multilayered structure showed better endurance against EM in comparison with the same structure using the conventional TiN (also defined in Sec. II A). ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360200

出版商:AIP    

年代:1995

数据来源: AIP