摘要:

Recent experiments have reported difficulties in nucleating the transformation of domains during the hcp to fcc phase transition in cobalt at 400 °C. By writing the energy associated with these domain patterns explicitly in terms of anisotropy, magnetostatic pole, and domain‐wall energies, in addition to the energies associated with an applied external field and domain‐wall pinning, a condition of instability, i.e., a free transformation of the domain structure, is obtained. It was found that the field needed to nucleate this domain transformation is increased by the effects of magnetostatic energies and wall pinning, but decreased by the effects of anisotropy. Furthermore, it was found that for an internal planar defect, such as a stacking fault, the transformation between the domain structures indigenous to each crystal phase occurs spontaneously in agreement with experimental observations.

ISSN:0021-8979    

DOI:10.1063/1.325094

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The hydrogen content of glow‐discharge‐deposited silicon nitride (SiN) films made at 330–350 °C has been determined. Preparation conditions were varied to produce a range of compositions of Si/N=0.7–1.4. Quantitative hydrogen profiling of the samples was carried out using the resonant nuclear reaction15N+H→12C+4He+&ggr; ray. Calibration factors for Si‐H (2160 cm−1) and N‐H (3350 cm−1) absorption‐band areas or absorbances have also been determined, enabling infrared transmission spectra to be used for hydrogen analyses of these films. All samples were homogeneous in hydrogen content and were in the range (1.6–2.1) ×1022H atoms/cm3, or about 20–25 at.&percent; H. Roughly three‐quarters of the H is bonded to Si, the remainder to N. One plasma SiO2sample made at 300 °C from SiH4and N2O was measured also, and contained 5.7 at.&percent; H, all as OH. Although there was little variation in the H content of SiN, there is a correlation between the total H concentration and the buffered HF etch rate. Some observations on the effects of the15N ion beam (6–8 MeV) on the SiN are reported. Many Si‐H and N‐H bonds are broken, but the liberated H atoms or ions are unable to diffuse out of the film.

ISSN:0021-8979    

DOI:10.1063/1.325095

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A novel technique is described which was used to study the intrinsic breakdown mechanism in films of thermal SiO2in the thickness range 30–300 A˚. It was determined that high‐field and high electron injection current conditions existing in the films just prior to breakdown result in the generation of a very high density of defects which behave electrically as stable electron traps. These traps are most likely generated close to the injecting electrode. The internal field in the oxide due to trapped electrons can approach 3×107V/cm which appears to be the maximum field strength which Si‐O bonding can withstand. At all temperatures between 77 and 393 °K, the breakdown mechanism is intimately related to the rate of generation of the electron traps. No evidence was found to support the impact ionization breakdown model. The technique is also described as a tool for yield measurements, with important implications for long‐term reliability of MOS IC’s.

ISSN:0021-8979    

DOI:10.1063/1.325096

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Thermal depolarization current (TDC) of a cross‐linked polystyrene composite whose conductive phase is mica has been measured in order to study in detail interfacial polarization (Maxwell‐Wagner effect) in polymer composites with stratified structure. The volume fraction of mica flakes in the composite was varied from 0.16 to 0.37. A peak characteristic of the composites is observed at a temperature above theTgof the composites. The maximum current of the peak increases with the fraction of mica flakes. The behavior of the peak is different from that of TDC due to dipole polarization and the space‐charge polarization of injected electrons. The beginning of a dielectric dispersion corresponding to the peak is observed below 1 Hz at 164 °C. The TDC peak can be explained by Maxwell‐type interfacial polarization. It is proposed that the TDC peak is attributed to interfacial polarization due to trapping or localizing of conductive ions in mica flakes at boundaries between the polymer matrix and mica flakes.

ISSN:0021-8979    

DOI:10.1063/1.325097

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Ferroelectric ceramic specimens 2–10 mm thick were impact loaded in uniaxial strain to a stress of 1.6 GPa. Material velocity‐time wave profiles were measured using a laser interferometer system. Specimen states studied were unpoled, poled and shorted, and poled with a high resistive load (E?2 kV/mm). The results show clearly the effect of the specimen electrical state on the mechanical response. Evolution of the mechanical wave was studied by measuring profiles for several different thicknesses with the same electrical state. For poled specimens, simultaneous measurements were made of the depolarization current during the impact loading. Measured wave speed of the first detectable disturbance was sonic in some but not all cases. Measurements of Hugoniot states for unpoled material were also obtained.

ISSN:0021-8979    

DOI:10.1063/1.325098

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Optical transmission of unbacked thin films of thermally grown SiO2films were measured in the vacuum uv. The absorption data indicate a band gap of 8.0±0.2 eV for SiO2, and this value is confirmed by measurements of electron and hole photoconductivity and positive charging thresholds in MOS samples. The observation of hole photoconductivity near 8 eV shows that the uppermost valence levels in SiO2are not nearly atomic, but form a band with sufficient orbital overlap that readily transport holes at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.325099

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Thermoluminescence measurements have been made as a function of pressure to 40 kbars on three ZnS phosphors, two doped with Cu+and Cl−, and one doped with Ag+and Cl−. The apparatus is briefly described. The major features of the thermoluminescent spectra were a low‐temperature peak which shifted to lower temperature with increasing pressure and a high‐temperature peak which shifted rapidly to higher temperature. The entire spectrum decreased in intensity, which is consistent with House’s measurements of the steady‐state intensity. Data from three different heating rates gave consistent values for the trap depth. The change in energy of the electron trap with pressure obtained from these thermoluminescence measurements was quantitatively consistent with House’s calculations based on steady‐state data.

ISSN:0021-8979    

DOI:10.1063/1.325100

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Red‐green up‐conversion and optical storage are measured in CdS crystals containing deep impurities such as P, N, Fe, and others. The presence of cadmium vacancies favors the formation of centers of self‐activated luminescence which reduce the up‐conversion efficiency considerably. Spatial fluctuations of the conduction‐ and valence‐band energies with respect to the Fermi level causes electrons and holes to separate after excitation and to populate distant islands in the crystal. The temperature limit of the up‐conversion and storage is determined by the energy barrier between the electron and hole islands.

ISSN:0021-8979    

DOI:10.1063/1.325101

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Oxygen partial‐pressure dependence of the length (L) of the oxidation‐induced stacking faults (OISF) in (100) silicon has been investigated in the temperature range 1150–1250 °C (so‐called retrogrowth range of temperatures). It has been observed that for a given time of oxidation the maximum temperature (TM), above which OISF start shrinking instead of growing decreases with decreasing partial pressure (pO2) of oxygen in the oxidizing ambient. On the other hand, for a givenpO2,TMdecreases with increasing time of oxidation. Based on the present results, the constantK′ in the equationL=K′pmO2tn exp(−Q/kT) has been calculated (wheremandnare number exponents,Qis the activation energy, andTis the temperature).K′ has been found to decrease rapidly at temperatures above 1150 °C. These results agree reasonably well with the quantitative model proposed by this author and the observation that the temperature at which OISF start vanishing could be lowered by reducing the oxidation rate constant of silicon (as done in present experiments by loweringpO2).

ISSN:0021-8979    

DOI:10.1063/1.325102

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An energy‐focused time‐of‐flight atom‐probe field‐ion microscope has been successfully employed to investigate the composition depth profile and the oxides species of metal oxide layers. Depth profiles ofp‐type semiconducting thin films formed byinsituoxidation of materials of three different crystal structures (bcc iron, hcp cobalt, and fcc nickel) showed, without exception, a metal‐rich near surface. After iron has been oxidized in pure research‐grade oxygen, iron oxide layers field evaporate mostly as FeO+, Fe2+, Fe+, O+, and O+2. A small number of FeO2+, FeO+2, and FeO+3have also been observed. However, iron oxide layers formed by oxidation in air field evaporate exclusively as FeH2+2and Fe(OH2)2+2. No Fe3O4or Fe2O3have been detected in both cases. No hydroxides and very few hydrides are found for nickel and cobalt when they are oxidized in air. Cobalt oxide layers field evaporate as CoO+, Co2+, O+2, and O+as well as a small number of Co+, CoO2+, and CoH+. Although we also expected Co3O4ions, none was found. Nickel oxide layers field evaporate mainly as NiO+, Ni2+, O+2, O+, and Ni+. In addition to these, some NiO+2and masses which can be assigned as Ni2O3+3and Ni2O4+3are detected. We have also discovered that the oxygen content in the thick oxide layer does not, in general, vary uniformly, possibly due to oxygen diffusion along grain boundaries. The oxide films are polycrystalline in nature, and the adhesive strength of the oxide to the metal is found to be weakest at the oxide/metal interface.

ISSN:0021-8979    

DOI:10.1063/1.325103

出版商:AIP    

年代:1978

数据来源: AIP