摘要:

Metal‐silicon dioxide‐silicon capacitors were irradiated with soft x rays to 40 krads (SiO2) with different biases (−3 to +12 V) at 83 K. The number of interface states generated after samples were warmed was found to bear a linear relation with the flatband voltage shift measured before warm up. A one‐to‐one relationship was observed between the number of interface states generated in the central 0.7‐eV portion of the Si band gap during a one year storage at room temperature and the number of holes that moved to the Si–SiO2interface during warm up. Annihilation of the x‐ray‐generated holes by photoinjection of electrons before warm up prevented the generation of interface states. Both experiments support a cause‐and‐effect relationship between holes in the oxide and interface states generated in the metal‐oxide semiconductor structure.

ISSN:0021-8979    

DOI:10.1063/1.332169

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We describe a new technique for the study of high‐field transport at semiconductor–insulator interfaces. In this technique, we observe the time‐of‐flight of discrete charge packets introduced by a pulsed laser. The packets drift in a region of uniform applied tangential field at the interface. We present data on the room temperature drift velocity of electrons at the interface between (100) silicon and thermally grown silicon dioxide as a function of both tangential and normal electric fields. We observe velocities near saturation of 8.9×106cm/s at a tangential field of 4 V/&mgr;m and a normal field of 9 V/&mgr;m, and extrapolate to a saturation velocity of 9.2×106cm/s independent of normal field. This value is more than 40% higher than reported by early workers, and is close to the saturation velocity observed in bulk silicon.

ISSN:0021-8979    

DOI:10.1063/1.332170

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We have compared the generation of radiation‐inducedPb(‘‘trivalent silicon’’) centers at the Si/SiO2interface with the radiation‐induced buildup of interface states. We observe a strong correlation between the density ofPbcenters and radiation‐induced interface state density (Dit) and similar annealing behavior of radiation‐inducedPbandDit. Furthermore, thePbresonance intensity is strongly bias dependent; this indicates that the charge state of thePbdefect is bias dependent. We conclude thatPbdefects account for a very large portion of radiation‐induced interface states.

ISSN:0021-8979    

DOI:10.1063/1.332171

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Raman scattering, infrared absorption, conductivity measurements, electron microprobe, and secondary ion mass spectrometry (SIMS) were used to characterize boron and phosphorus doped hydrogenated amorphous silicon (a‐Si:H) films prepared by Homogeneous Chemical Vapor Deposition (HOMOCVD). HOMOCVD is a thermal process which relies upon the gas phase pyrolysis of a source (silane containing up to 1.0% diborane or phosphine) to generate activated species for deposition upon a cooled substrate. Doped films prepared at 275 °C by this process were found to contain ∼12‐at. % hydrogen as determined by infrared absorption. We examined dopant incorporation from the gas phase, obtaining values for a distribution coefficientCD(film dopant content/gas phase dopant concentration, atomic basis) of 0.33≤CD≤0.63 for boron, while 0.4≤CD≤10.75 in the limits 3.3×10−5≤PH3/SiH4≤0.004. We interpret the data as indicative of the formation of an unstable phosphorus/silicon intermediate in the gas phase, leading to the observed enhancements inCDat high gas phase phosphine content. HOMOCVD films doped at least as efficiently as their prepared counterparts, but tended to achieve higher conductivities [&sgr;≥0.1 (&OHgr; cm)−1for 4.0% incorporated phosphorus] in the limit of heavy doping. Raman spectra showed no evidence of crystallinity in the doped films. Film properties (conductivity, activation energy of of conduction) have not saturated at the doping levels investigated here, making the attainment of higher ‘‘active’’ dopant levels a possibility. We attribute the observation that HOMOCVD appears more amenable to high ‘‘active’’ dopant levels than plasma techniques to the low (∼0.1 eV) thermal energy at which HOMOCVD proceeds, versus ∼10–100 eV for plasma techniques. Low substrate temperature (75 °C) doped films were prepared with initial results showing these films to dope as readily as those prepared at high temperature (T∼275 °C).

ISSN:0021-8979    

DOI:10.1063/1.332172

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Silicon epitaxial growth on the Si‐Ge buffer layer at a low substrate temperature by the rf plasma chemical vapor deposition using SiH4and GeH4has been investigated. The electron Hall mobility of the homoepitaxial layer grown at 750 °C with a growth rate of 14 A˚/sec coincides with that of bulk Si, but for a high growth rate of 33 A˚/sec, the mobility was limited to within half the value of bulk Si. However, a small amount of Ge introduced in an initial stage of growth to form the Si‐Ge buffer layer improved the crystalline quality of the ensuing Si epitaxial layer with a high growth rate. The electron Hall mobility of the Si layer grown on the Si‐Ge buffer layer was a similar value of bulk Si in a low carrier concentration of 6×1015cm−3. The crystalline quality of the grown Si layers was examined by the combination of Rutherford backscattering spectrometry and transmission electron microscopy.

ISSN:0021-8979    

DOI:10.1063/1.332173

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Specific heat measurements have been used to study the electronic excitation spectrum of the Cu regions ofinsituprepared Cu‐Nb and Cu–Nb3Sn composites having filament dimensions comparable to the superconducting coherence distance. At very low temperatures the major contribution toCpcomes from the electrons in the Cu regions so the excitation spectrum in Cu is easily accessible by this technique. Measurements show that the specific heat is far smaller than that expected if the Cu were normal, indicating that there is a well developed superconducting order parameter of about the size predicted from the de Gennes boundary conditions, i.e., about 0.3 meV. With the application of only a few millitesla, this gap is reduced by at least a factor of 10.

ISSN:0021-8979    

DOI:10.1063/1.332174

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The critical current forinsituprepared Cu‐Nb3Sn microfilamentary composites has been measured as a function of both temperature and magnetic field in order to determine the suitability of these materials for superconducting magnets which operate above 4.2 K, either continuously or in brief excursions. A rather simple relation,Jc=AB−1/2(Bc2−B)2whereA=860 A cm−2T−3/2, describes the data very well. The temperature dependence ofBc2is the dominant factor controllingJc(T). Values ofBc2determined both from low current resistive transitions and from Kramer plot extrapolations giveBc2=B0(1−t2), whereB0is approximately 19 T. Scaling applies in these materials and the volume flux pinning force goes asB5/2c2as predicted if the flux line shear modulus controls the flux pinning. The data show that a magnet designed to operate at 4.2 K and 12 T also will operate well at 10 K and 7 T.

ISSN:0021-8979    

DOI:10.1063/1.332175

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The powder‐metallurgical process for the preparation of filamentary Nb3Sn and V3Ga microcomposites is described and compared to alternative processing techniques. Investigations of the thermal stability of the submicron size filamentary structure show that the thickness of the ribbonlike filaments should be in the range between 0.1 and 1 &mgr;m for a typical wire diameter of 0.2–0.4 mm to avoid a spheroidization of the filaments during the diffusion treatment. The superconducting properties are comparable to the optimized values of other techniques. Overall critical current densitiesJcof a Cu‐30 wt. % Nb+Sn composite wire amount to 109and 1.6×108A/m2at fields of 10 and 15 T, respectively, whereas values up to 4×108A/m2at 16 T are observed for Cu‐30 wt. % V+Ga composites. The mechanical behavior such as tensile strength, and the dependence of the superconducting current carrying capability on tensile stress and strain show a favorable behavior in light of a technical application.

ISSN:0021-8979    

DOI:10.1063/1.332176

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Sets of magnetoelastic equations in the quasi‐magnetostatic approximation and in the absence of dissipation are deduced for uniaxial antiferromagnets of the easy‐axis type on the basis of a previously set forth fully nonlinear, rotationally invariant, thermodynamically admissible theory of deformable ferrimagnets. The equations are obtained for three typical initial magnetic configurations where the bias field is either parallel or orthogonal to the easy axis and depending on whether this field is weak, moderate or strong relatively to some combinations of material parameters. In each case, the linearization about the initial configuration (which is automatically endowed with initial fields and internal stresses) is performed by means of the so‐called Lagrangian variation of the nonlinear field and constitutive equations. In the process of linearization, all elastic, magnetic, and magnetoelastic coefficients evaluated at the initial state are given a thermodynamical definition. The linearization about a finite initial state allows one to exhibit the various influences of this state on the linearized equations and the alterations brought on the material‐coefficient tensors (stiffening of the elasticity coefficients, symmetry breaking by the bias magnetic field, magnetoelastic coupling at any order since the linearization is made with a fully nonlinear theory as starting point).

ISSN:0021-8979    

DOI:10.1063/1.332177

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Magnetoacoustic resonance between transverse phonons and magnons is studied analytically on the basis of a set of linearized equations previously deduced from a fully nonlinear, rotationally invariant, thermodynamically admissible theory of uniaxial antiferromagnets of the easy‐axis type. The present paper concerns the case where the bias magnetic field is relatively weak and aligned with the axis of symmetry. Various types of dispersion are exhibited depending on whether disturbances propagate along the symmetry axis in the positive or negative direction or orthogonally to this axis. In the first situation, two magnetoacoustic regions are placed in evidence (forward travelling modes), which correspond to the interaction between, or the entanglement of, either left‐circularly polarized transverse phonons and the upper magnon branch or right‐circularly polarized transverse phonons and the lower magnon branch. The resulting dispersion is thoroughly discussed in an analytical manner in terms of a small parameter which represents globally magnetoelastic couplings. The accompanying magnetoacoustic Faraday effects are also exhibited. In the second situation, longitudinal and slow‐transverse phonons propagate independently of magnons, while fast transverse phonons couple by resonance with both upper and lower magnon branches, which provides a direct analogy with resonance phenomena in purely mechanical theories, such as vibrations in rods.

ISSN:0021-8979    

DOI:10.1063/1.332178

出版商:AIP    

年代:1983

数据来源: AIP