摘要:

Electron paramagnetic resonance studies have been performed in oxygen‐doped germanium. Room‐temperature irradiation with 2‐MeV electrons produces a paramagnetic center ofS= ½ whosegtensor has (011), (01¯1), (100) principal axes. Thegshifts are consistent with this being the germaniumAcenter, i.e., an oxygen‐vacancy complex. Infrared absorption bands at 766, 807, and 847 cm−1may be associated with this defect.

ISSN:0021-8979    

DOI:10.1063/1.1714220

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Thin‐film sandwiches of Al&sngbnd;Al2O3&sngbnd;Al have been constructed with Al2O3layers in the range 80–120 Å thick. When illuminated with light in the wavelength range 2600–11 000 Å, the sandwiches exhibit photocurrents which are larger than the dark current. The photocurrent has been measured at room temperature as a function of bias voltage and photon energy, using light pulses of 0.1‐sec duration. The results are interpreted to give the shape of the potential barrier in the insulator. Within the accuracy of the data, the potential barrier is trapezoidal, with a relative work function of 1.0 eV at the oxidized electrode, and 2.9 eV at the electrode evaporated over the oxide. There is evidence that collisions of the photoelectrons in the insulator are important.

ISSN:0021-8979    

DOI:10.1063/1.1714221

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The hexagonal modification of ZnSe single crystals has been observed. The crystals were grown by the sublimation method. The lattice parameters are found to bea0= 4.003±0.001 Å andc0= 6.540±0.003 Å. The photoconductivity peaks observed in the spectral response curves at room temperature reflect the band symmetries of the wurtzite structure and obey the group theoretical selection rules. From the position of the photoconductivity maxima forE⊥C, the band gap energy at room temperature is estimated to be 2.795 eV.

ISSN:0021-8979    

DOI:10.1063/1.1714222

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A solid‐state diffusion theory is developed giving the distribution of impurities in epitaxial growth. It is shown that for most practical cases this theory takes on a particularly simple form. Extensive experiments were performed in the study of the distribution of the most common acceptor and donor type substrate impurities in silicon: boron and antimony. It is shown that the impurity distribution in most of the epitaxial film is uniform corresponding to the impurity doping of the SiCl4used in the epitaxial growth, and that the profile near the substrate—film interface is very close to the predictions of this simple theory. In addition, certain particular cases of interest were studied such as the spreading of a layer of impurities predeposited on the substrate surface prior to epitaxial growth, the effect of film growth rate on the impurity distribution, and the change in the impurity distribution during an additional high‐temperature step. In all cases, experiments and the solid‐state diffusion theory are in excellent agreement.

ISSN:0021-8979    

DOI:10.1063/1.1714223

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Measurements of flow stress andF‐band coloration have been made at room temperature on a number of ``pure'' and impurity‐doped KCl crystals as a function of gamma and electron irradiation. As has been observed, the flow stress increase, for late‐stage coloration, is proportional to the square root of theF‐band absorption. However, it is found that the early‐stage coloration does not contribute to the radiation hardening. These results suggest that the late‐stage production mechanism forFcenters involves interstitial formation and clustering, whereas no stable interstitials are formed during early‐stage coloration. Moreover, even though it is known that certain impurities enhance early‐stage coloration, it is found that the concentration of early‐stageFcenters is only a small percentage of the total impurity concentration. This suggests that only isolated positive‐ion vacancies are involved in theF‐center production mechanism for this stage.

ISSN:0021-8979    

DOI:10.1063/1.1714224

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Axial dislocations and other imperfections in single‐crystal whiskers of aluminum nitride (hexagonal, wurtzite structure) have been studied by transmission electron microscopy. Axial dislocations withcBurgers vectors and faults on the (101¯0) prismatic planes having fault vectors equal to ½chave been identified. In addition to simple axial dislocations, the variety of axial imperfections included zig‐zagged dislocations and wide periodic imperfections attributed to complicated faults, clearly related to the dislocation with acBurgers vector.One type of AlN whisker with growth direction ⟨c+2a⟩ always contained an axial dislocation or the related extended defect, and it is thus concluded that the growth of this type of whisker may have involved an axial dislocation.

ISSN:0021-8979    

DOI:10.1063/1.1714225

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Simultaneous and independent measurements have been made of the magnitude and direction of the lattice twist and of the direction of the Burgers vector of the axial dislocations in filamentary crystals of AlN, using electron microscopy and electron diffraction. The twist was revealed by extinction contours from reflecting planes with normals perpendicular to the filament axis, and measurements of the widths and separations of these contours were used to calculate the twist.Good agreement with theory was found in the case of crystals containing the simple axial dislocation, but crystals with a complicated extended axial imperfection were found not to be twisted. It is believed that the extended axial imperfection was a fault which met the surface of the crystal and which originated from an axial dislocation; the lack of twist was then due to one or more partial dislocations having left the crystal.

ISSN:0021-8979    

DOI:10.1063/1.1714226

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Resistive measurements of the critical current densityJcin transverse magnetic fields were made on single crystals of niobium, which had been subjected to systematic thermal, mechanical, and chemical treatments in order to produce a wide range of substructural densities, and variations in the oxygen content. The introduction of plastic deformation into niobium crystals produced a peak inJcat applied magnetic fields of strengthHc2, the upper critical field. The peaks inJcwere removed by annealing the crystals in the recovery range. The critical current density was increased both below and aboveHc2by producing a dislocation substructure in the crystals. Small additions of oxygen also causedJcto increase above and belowHc2. The upper critical field, however, was relatively insensitive to structure, varying only through the structure sensitivity of the bulk GLAG parameters.

ISSN:0021-8979    

DOI:10.1063/1.1714227

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Both static atomic displacements (resulting from vacancies) and vibration amplitudes, were measured in specimens having the compositions TiN0.59, TiN0.78, and TiN0.95. The static displacements for titanium (and nitrogen) in the first two specimens were about 5.5% of the first neighbor distance and were comparable to the dynamic displacements at 250°C. Static displacements were not observed for TiN0.95. The specimen of intermediate nitrogen concentrations, TiN0.78, had smaller dynamic displacements and thermal expansions than the other two specimens, indicating the existence of a minimum in these thermal properties.

ISSN:0021-8979    

DOI:10.1063/1.1714228

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The coefficient of linear thermal expansion (&agr;) for NaCl has been determined from 50°C to near the melting point (800°C) with an automatic recording dilatometer. The results confirmed the authors' suspicions that the values of &agr; reported by Eucken and Danno¨hl are systematically high above 450°C. The experimental data are not satisfactorily represented by polynomial curves from the first through the eighth order as there is a decided increase in the thermal expansion above 600°C. Consequently, two second‐order polynomials are employed to adequately fit the data. The difference (&Dgr;&agr;) at constant temperature between the high‐temperature polynomial and the extrapolation of the low‐temperature polynomial behaves logarithmically with respect to 1/Tat high temperatures. The slope of this curve corresponds to a formation energy of 1.916 eV, which compares favorably with the energy required to form a pair of isolated positive and negative ion vacancies within the crystal (a Schottky defect).

ISSN:0021-8979    

DOI:10.1063/1.1714229

出版商:AIP    

年代:1965

数据来源: AIP