摘要:

A general methodology is developed to experimentally characterize the spatial distribution of occupied traps in dielectric films on a semiconductor. The effects of parasitics such as leakage, charge transport through more than one interface, and interface trap charge are quantitatively addressed. Charge transport with contributions from multiple charge species is rigorously treated. The methodology is independent of the charge transport mechanism(s), and is directly applicable to multilayer dielectric structures. The centroid capacitance, rather than the centroid itself, is introduced as the fundamental quantity that permits the generic analysis of multilayer structures. In particular, the form of many equations describing stacked dielectric structures becomes independent of the number of layers comprising the stack if they are expressed in terms of the centroid capacitance and/or the flatband voltage. The experimental methodology is illustrated with an application using thermally stimulated current (TSC) measurements. The centroid of changes (via thermal emission) in the amount of trapped charge was determined for two different samples of a triple‐layer dielectric structure. A direct consequence of the TSC analyses is the rigorous proof that changes in interface trap charge can contribute, though typically not significantly, to thermally stimulated current.

ISSN:0021-8979    

DOI:10.1063/1.354291

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Electron injection at high field and moderate fluence into the gate oxide ofP‐channel metal–oxide–semiconductor transistors creates net positive charges and related interfacial states as it has often been reported. A threshold electric field at around 7.2 MV/cm is found for the generation of positive charges. For this same oxide field the interfacial state density increases abruptly. For an average oxide field in the 8–9‐MV/cm range, the densities of positive charges and interfacial states increase linearly with the fluence forF<1016e/cm2and saturate forF≳1017e/cm2. The positive charge density is more important near the channel edges. The interfacial state density seems to be homogeneously distributed along the channel. The density of electron traps is negligible for the studied dry gate oxide except in the overlaps above drain and source and in some cases near the channel edges. The negative space charge, resulting from electron trapping in these regions, reduces the length of the electron injection and in some cases the surface of the channel which contributes to the charge pumping current. Two types of relaxation have been observed.

ISSN:0021-8979    

DOI:10.1063/1.354292

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The doping effect of N in hydrogenated amorphous silicon (a‐Si:H) is studied. The absence of a thickness dependence of the conductivity of N‐doped samples provides convincing evidence that the doping effect of N ina‐Si:H is a bulk property. The similarity between the effect of N doping and that of P doping found in the conductivity and the photoconductivity decay indicates that N can act as an effective donor ina‐Si:H and that N doping is also of substitutional type; however, the solid‐phase doping efficiency of N is estimated to be at least three orders of magnitude lower than that of P.

ISSN:0021-8979    

DOI:10.1063/1.354293

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We have focused our attention on the dependence of Ba1−xRbxBiO3(BRBO) film composition ratio and film properties on rubidium‐beam‐flux intensity. BRBO films were deposited on MgO(100) substrates by molecular‐beam epitaxy (MBE) using distilled ozone. Systematic measurements showed that the rubidium content was nearly independent of rubidium‐beam‐flux intensity in a wide beam‐flux range. Therefore, it can be concluded that some degree of self‐control of rubidium stoichiometry is actually possible in BRBO film growth by MBE. This study also revealed that the BRBO film properties had strong dependences on rubidium‐beam‐flux intensity even in the range for self‐control of rubudium stoichiometry. Our study also clarified that rubidium‐beam flux affects the barium content in the BRBO film.

ISSN:0021-8979    

DOI:10.1063/1.354294

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We have prepared a bulk Y0.8Ho0.2Ba2Cu3Oysuperconductor by the powder melting process method and investigated its magnetization curves and magnetic relaxation in the temperature range 55–77 K at different fields. TheJcvalues at a certain temperature and field is estimated by Bean’s model. It is found thatJcdecreases with the magnetic field according to a power law, whereas it drops exponentially with temperature. The dependence on temperature of the maximum diamagnetization fieldHpand the remanent magnetizationMremis discussed. The magnetic relaxation indicates that the magnetizationMvaries logarithmically with time. The relaxation ratedM/d ln tis also studied.

ISSN:0021-8979    

DOI:10.1063/1.354295

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A system composed of two Josephson junctions connected by a transmission line has been studied by means of electronic analog simulation. Under external current bias, the resistive component of the coupling induces frequency locking between the two junctions at commensurate ratios. The resonant modes of the transmission line give rise to steps in theI‐Vcharacteristics of the system.

ISSN:0021-8979    

DOI:10.1063/1.354296

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Detailed measurements of voltage‐current (V‐I) curves and magnetoresistance (R‐H) for Bi(2223) thick film were carried out for various temperatures and magnetic fields. The results indicate that a flux lattice melting transition takes place as the temperature and the field are raised. This transition boundary in the (H,T) phase diagram was found to follow the irreversibility line described by the function ofH=H0(1−T/Tc)3/2. Above this line, theV‐Icurves display a flux‐flow‐like character. Temperature and magnetic field dependencies of flow resistanceRf‐TandRf‐Hshow a varied viscosity in different temperature and field ranges. Below this line,V‐Icurves in the low voltage region present a thermally activated flux creep property. TheR‐Hmeasurements indicate that the fields at the onset and the midpoint of the magnetoresistive transition also follow a (1−T/Tc)3/2dependence.

ISSN:0021-8979    

DOI:10.1063/1.354297

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Cubic Laves phase alloys of Ho0.85Tb0.15Fe2−xNix(0≤x≤2) were prepared and the lattice parameters, evaluated as a function ofxat room temperature, show deviation from Vegard’s law. This was attributed to the presence of a magnetovolume effect and charge transfer. Magnetization measurements were performed in the temperature range 77–700 K. The results suggest that the system undergoes a gradual transition from ferri‐ to ferromagnetic with increasingx. This has been explained based on the 3dband model. Furthermore, a monotonic decrease in Curie temperature withxwas observed. Electrical resistivity studies were carried out in the temperature range 16–700 K. An anomaly was found in the vicinity of the Curie temperature forx=2 which has been attributed to the existence of the long‐range nature of the critical fluctuations due to short‐range spin ordering.

ISSN:0021-8979    

DOI:10.1063/1.355287

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Films of Fe0.79Ge0.21with thicknesses of 300 nm were synthesized by ion beam sputtering, and were annealed at temperatures from 200 to 550 °C. The materials were characterized by x‐ray diffractometry, Mo¨ssbauer spectrometry, vibrating sample magnetometry, ferromagnetic resonance spectrometry, and electrical resistivity measurements. The as‐prepared materials comprised chemically disordered bcc crystallites of sizes less than 20 nm, and were found to have a distribution of internal strains. Upon annealing at temperatures of 250 °C and below, there occurred strain relaxation, some evolution of short range chemical order, and an improvement in soft magnetic properties. The coercive field was a minimum for the sample annealed at 250 °C. Crystallite growth occurred at higher annealing temperatures, accompanied by a transition in several measured parameters from those of ultrafine grained materials to those typical of polycrystalline materials. This trend can be explained with the random anisotropy model. Mo¨ssbauer and magnetization measurements indicated that the Ge atoms behave as magnetic holes. The57Fe hyperfine magnetic field distribution, and its change during chemical ordering, can be calculated approximately with a model of magnetic response. The large local isomer shifts at57Fe atoms near Ge atoms suggest that a local depletion of 4sconduction electron density should be incorporated into the model.

ISSN:0021-8979    

DOI:10.1063/1.354298

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A study was made of the structure and magnetic properties of Fe‐Co alloy films produced by dc magnetron sputtering at an oblique angle of incidence. The films obtained in this manner showed uniaxial magnetic anisotropy in the film plane, with an easy axis of magnetization perpendicular to the incident direction of the sputtered particles. The anisotropy field increased with increasing sputtering gas pressure and with increasing Co content at high pressures. The structure of the film surfaces also changed with sputtering Ar gas pressure, and elongated grains were observed in the intermediate Ar pressure range. The texture was essentially isotropic in the film plane over the whole pressure range. It is suggested that the observed uniaxial anisotropy was due mainly to a magnetoelastic effect.

ISSN:0021-8979    

DOI:10.1063/1.354299

出版商:AIP    

年代:1993

数据来源: AIP