摘要:

The effects of hydrostatic pressure on the solid‐phase epitaxial growth (SPEG) ratevof intrinsic Ge(100) and undoped and doped Si(100) into their respective self‐implanted amorphous phases are reported. Samples were annealed in a high‐temperature, high‐pressure diamond anvil cell. Cryogenically loaded fluid Ar, used as the pressure transmission medium, ensured a clean and hydrostatic environment.vwas determined byinsitutime‐resolved visible (for Si) or infrared (for Ge) interferometry.vincreased exponentially with pressure, characterized by a negative activation volume of −0.46&OHgr; in Ge, where &OHgr; is the atomic volume, and −0.28&OHgr; in Si. The activation volume in Si is independent of both dopant concentration and dopant type. Structural relaxation of the amorphous phases has no significant effect onv. These and other results are inconsistent with all bulk point‐defect mechanisms, but consistent with all interface point‐defect mechanisms, proposed to date.A kinetic analysis of the Spaepen–Turnbull interfacial dangling bond mechanism is presented, assuming thermal generation of dangling bonds at ledges along the interface, independent migration of the dangling bonds along the ledges to reconstruct the network from the amorphous to the crystalline structure, and unimolecular annihilation kinetics at dangling bond ‘‘traps.’’ The model yieldsv= 2 sin(&thgr;)vsnr exp[(&Dgr;Sf+ &Dgr;Sm)/k] exp− [(&Dgr;Hf+ &Dgr;Hm)/kT], where &Dgr;Sfand &Dgr;Hfare the standard entropy and enthalpy of formation of a pair of dangling bonds, &Dgr;Smand &Dgr;Hmare the entropy and enthalpy of motion of a dangling bond at the interface,vsis the speed of sound, &thgr; is the misorientation from {111}, andnris the net number of hops made by a dangling bond before it is annihilated. It accounts semiquantitatively for the measured prefactor, orientation dependence, activation energy, and activation volume ofv, and the pressure of a ‘‘free‐energy catastrophe’’ beyond which the exponential pressure enhancement of SPEG cannot continue uninterrupted due to a vanishing barrier to dangling bond migration. The enhancement ofvby doping can be accounted for by an increased number of charged dangling bonds, with no change in the number of neutrals, at the interface. Quantitative models for the doping dependence ofvare critically reviewed. At low concentrations the data can be accounted for by either the fractional ionization or the generalized Fermi‐level‐shifting models; methods to further test these models are enumerated. Ion irradiation may affectvby altering the populatio

ISSN:0021-8979    

DOI:10.1063/1.350243

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Using a simulation experiment, transient optical 30‐Hz elements which respond to dc signal changes in thin‐film transistor liquid‐crystal display are investigated. After dc voltage is applied, even without dc voltage, the 30‐Hz element appears and decays to the level in the steady state. This is explained by the generation of an electric double layer. The generation mechanism of the layer is described by an equation with a creation time constant &tgr;1and a disappearance time constant &tgr;2, and these values are estimated to be approximately 1400 and 500 s, respectively. The relaxation process is described by the empirical model in which relaxation time constant is initially 60 s and increases as a function of time.

ISSN:0021-8979    

DOI:10.1063/1.350244

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Using angle‐resolved Auger electron spectroscopy, we show, nondestructively, a sequential variation of the composition from the outermost layer to the second layer of a Cu0.81Pt0.19alloy and provide new evidence for ion bombardment‐induced Gibbsian segregation in that alloy when it was sufficiently bombarded with 2.8‐keV Ar ions at 10 and −80 °C.

ISSN:0021-8979    

DOI:10.1063/1.350215

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The screening effect of dc voltage in a nematic liquid‐crystal cell having polyimide alignment layers is studied experimentally and theoretically. The transmitted intensity of light passing through a liquid‐crystal sample exhibits a dip arising from dc screening effects, which are never observed with ac voltage application. The dc screening effect is produced by two kinds of ionic charges in the boundary layer. One is adsorbed on the orientation film and the other compensates the adsorbed charges. The two kinds of charge model account quantitatively for the observed dip in transmission making its origin clear, and explain well the ionic conduction processes accompanying the application of dc voltage to a liquid‐crystal sample.

ISSN:0021-8979    

DOI:10.1063/1.350216

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Shock initiated chemical reaction experiments have been performed on a 1:1 atomic ratio mixture of 20‐ to 45‐&mgr;m nickel and −325 mesh crystalline silicon powders. It has been observed that no detectable or only minor surface reactions occur between the constituents until a thermal energy threshold is reached, above which the reaction goes to completion. The experiments show the energy difference between virtually no and full reaction is on the order of 5 percent. Differential scanning calorimetery (DSC) of statically pressed powders shows an exothermic reaction beginning at a temperature which decreases with decreasing porosity. Powder, shock compressed to just below the threshold energy, starts to react in the DSC at 621 °C while powder statically pressed to 23% porosity starts to react at about 30 °C higher. Tap density powder starts to react at 891 °C. The DSC reaction initiation temperature of the shock compressed but unreacted powder corresponds to a thermal energy in the powder of 382 J/g which agrees well with the thermal energy produced by a shock wave with the threshold energy (between 384 and 396 J/g). (Thermal energies referenced to 20 °C.) A sharp energy threshold and a direct correlation with DSC results indicates that the mean thermal energy determines whether or not the reaction will propagate in the elemental Ni+Si powder mixture rather than local, particle level conditions. From this it may be concluded that the reaction occurs on a time scale greater than the time constant for thermal diffusion into the particle interiors.

ISSN:0021-8979    

DOI:10.1063/1.350217

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Metallizations that incorporate a conductive layer beneath an Al alloy (multilayers) are necessary for the improvement in electromigration performance required by the continued feature size reduction and increased integration of microelectronic devices. Degradation of contact structures that utilize multilayer metallization will result from electromigration‐induced voiding of the Al layer. A detailed understanding of the mechanisms of voiding is required for the accurate prediction of contact reliability. We have examined electromigration voiding in Al‐Si‐Cu/TiNxOy/TiSi2multilayer contacts. Accelerated testing reveals that a TiNxOy/TiSi2layer formed by rapid thermal anneal of Ti is an effective Si diffusion barrier at operating temperatures (<125 °C) and eliminates electromigration‐induced leakage failures. Contact degradation occurs by increased resistance due to voiding of the Al‐Si‐Cu layer. Voiding involves drift‐controlled edge displacement where the Al‐Si‐Cu layer migrates out of positively biased contacts, leaving the TiNxOy/TiSi2layer intact. For 1‐&mgr;m‐diam contacts, the drift velocity has a significant lattice diffusion component and failure times are expected to far exceed operation lifetimes of devices. Additionally, evidence is presented for an electromigation threshold that eliminates voiding degradation for contacts connected by stripes.

ISSN:0021-8979    

DOI:10.1063/1.350218

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The dc self bias voltage developed during CH4/Ar radio frequency plasma‐enhanced vapor deposition of thin films containing polycrystalline diamond grains within ana:C matrix (carbon‐diamond) is found to influence the optical and mechanical properties of the films. In particular it is shown that there is a simultaneous etch deposition process which takes place, and that the dc bias can be used to control this etch rate, and hence the net film growth rate. When a balance between etching and deposition is achieved, the films show increased residual stress and optical density with exposure to Ar+bombardment in the plasma. In addition to the measured dc bias the local electric field developed around the substrate is also found to significantly influence the energy with which ions impinge upon the growing film.  

ISSN:0021-8979    

DOI:10.1063/1.350219

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Surface hydrogen coverage and the surface reconstruction of a silane‐saturated Si(001)2×1 surface were investigated using the thermal‐desorption‐spectroscopy (TDS) and the reflection‐high‐energy‐electron‐diffraction measurements. The TDS spectrum mainly presented a single &bgr;1peak around 520 °C, indicating the predominance of a Si monohydride phase on this surface. This observation agreed with the surface hydrogen coverage (H/Si=1.1–1.4) obtained from the integrated peak area of the TDS spectrum. By a repeated silane‐saturation/thermal‐desorption experiment, it was also clarified that all the hydrogen atoms in the silane molecules adsorb at this room temperature exposure. Adsorption mechanisms of silane molecules onto Si(001) surfaces are discussed and a model is presented based on the result.

ISSN:0021-8979    

DOI:10.1063/1.350220

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Ionized cluster beam (ICB) deposition has received considerable attention since its introduction in 1972 by Takagietal. at Kyoto University because of its potential for low‐temperature film growth. While further investigation of many aspects of ICB deposition is warranted, it is first necessary to determine with some certainty whether large clusters are being produced. A complete analysis of the Eaton ICB source involving computer calculation of the potential fields and computer simulation of the electrons and ions as they react to and influence these fields provides an in‐depth understanding of the dynamics that influence the final ion beam characteristics. A high‐resolution time‐of‐flight mass spectrometer was developed to experimentally investigate the cluster size distribution. No evidence of large clusters was found down to a level more than two orders of magnitude below what the Kyoto University group has reported [T. Takagi,Ionized‐ClusterBeamDepositionandEpitaxy, (Noyes, New Jersey, 1988)]. A computer analysis of the three Kyoto University cluster size experiments that form the foundation of ICB has shown that the potential fields in the ionization areas are critically distorted by either space‐charge effects or design flaws, both of which are serious enough to invalidate the experiments. The theory behind large cluster production and the body of indirect evidence attributed to the presence of large clusters are not convincing by themselves so it is concluded that a Takagi‐type source does not produce large clusters in quantities capable of affecting film growth.

ISSN:0021-8979    

DOI:10.1063/1.350221

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Tungsten deep levels are investigated to clarify energies, which are inconsistent among current research. Hole traps located at 0.41 eV above the top of the valence band are determined to be due to tungsten impurities. The concentration of hole traps is almost one‐third of that of the tungsten impurities in the substrates. Similar hole traps are also found in different silicon substrates in which tungsten impurities are thermally diffused from the surface. These facts indicate that the hole traps are truly due to tungsten impurities.

ISSN:0021-8979    

DOI:10.1063/1.350196

出版商:AIP    

年代:1991

数据来源: AIP