摘要:

We have used the perturbed angular correlation technique to measure the orientation of the electric‐field gradients (EFGs) due to vacancy trapping by substitutional indium donors in the II‐VI semiconductor Hg0.79Cd0.2Te. Previously, two hyperfine interaction frequencies were measured and were attributed to the trapping of a metal vacancy at a next nearest‐neighbor site to the indium atom in bulk solid‐state recrystallized materials. In the present experiments, measurements are done on thin‐film samples to find the principal axes of the EFGs. Both EFGs are found to have principal axes parallel to a ⟨111⟩ crystal axis, despite the fact that a simple point charge model supports a ⟨110⟩ EFG for this ⟨110⟩‐oriented In‐VHgcomplex. A similar situation exists for indium‐vacancy pairing in other II‐VI semiconductors. We propose that the ⟨111⟩ EFG orientation arises from the electric dipole moments of the highly polarized Te ions in the region of the vacancy.  

ISSN:0021-8979    

DOI:10.1063/1.354331

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The characteristic ionization energies, barriers associated with capture, energy levels, and introduction rates of the various electron and hole traps introduced by electron irradiation inn‐type GaP are determined using deep level transient spectroscopy. The same traps are created after 4 or 300 K irradiation. Their introduction rates correspond to those expected for primary displacements. From the similarity to the case of GaAs, we conclude that the corresponding defects are intrinsic defects (isolated vacancies and vacancy interstitial pairs) associated with the P (electron traps) and Ga (hole traps) sublattices.  

ISSN:0021-8979    

DOI:10.1063/1.354332

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Ablation is the main phenomenon which occurs on a polymer surface when a pulse of ultraviolet radiation is absorbed. The front edge of the radiation pulse is absorbed by a volume which eventually vaporizes and the rest is partially blocked by the ablation plume of products and partially transmitted to the new surface left behind after ablation. Most of this transmitted energy is transformed into heat and raises the temperature of the surface sometimes above the melting point of the polymer. Due to the transient character of the irradiation which lasts 25 ns, a rapid cooling occurs. For semicrystalline polymers like poly(ethylene terephthalate) the surface is left in an amorphous state by this cooling. In this work the amorphous depth was measured by monochromatic ellipsometry as a function of the pulse energy. It is shown that amorphization has a threshold fluence (7 mJ/cm2at 193 nm) which is lower than the ablation threshold (17 mJ/cm2). The ablation depth reaches a maximum of 850 A˚ at 193 nm when the ablation threshold is reached. Similarly the ablation depth measured at 248 nm is 1600 A˚. The amorphization depths are proportional to the radiation penetration depths in the materials.

ISSN:0021-8979    

DOI:10.1063/1.354333

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The crystallization of coevaporated, amorphous CoSi2with and without ion irradiation has been studied. Without ion irradiation, the crystallization of amorphous CoSi2is characterized by three‐dimensional growth from preexisting nuclei. The crystallization kinetics, described by the Avrami equation, are retarded by irradiating the as‐deposited CoSi2with either Si or Kr ions at liquid nitrogen temperature. The dose dependence of the crystallization kinetics can be divided into two regions. In the low dose regime, the crystallization kinetics decrease sharply with increasing dose, while the mode of crystal growth changes continuously from three‐dimensional to two‐dimensional growth. In the high dose regime, the crystallization kinetics are only slightly dependent on the irradiation dose. Nucleation occurs throughout the crystallization process and two‐dimensional growth dominates.

ISSN:0021-8979    

DOI:10.1063/1.354334

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Textured TlBaCaCuO superconducting thin films identified by electron microscopy as consisting of a mixture of TlBa2Ca2Cu3O9and Tl2Ba2Ca2Cu3O10layers with no long range crystalline order normal to the basal planes have been prepared. The Tl1+xBa2Ca2Cu3O9+xthin films yield complex x‐ray diffraction patterns with a nonrational series of basal reflections. In order to further understand the structure of this material, a statistical model for x‐ray diffraction by partially disordered layered structures was formulated for a material consisting of a random mixture of two types of layers in which both the layer thickness and scattering power of the layers differ. The scattering equation was solved computationally for x‐ray scattering from the basal planes of layered materials consisting of random mixtures of TlBa2Ca2Cu3O9and Tl2Ba2Ca2Cu3O10layers. The results were applied to the modeling of the x‐ray diffraction scattering intensity for 1.0‐&mgr;m‐thick textured thin films of TlBa2Ca2Cu3O9, Tl2Ba2Ca2Cu3O10, and Tl1+xBa2Ca2Cu3O9+x. The computational results support the identification of one such Tl1+xBa2Ca2Cu3O9+xthin film as consisting predominantly of a nearly random mixture of 50% TlBa2Ca2Cu3O9and 50% Tl2Ba2Ca2Cu3O10layers (x&bartil;0.5). The model was also used to examine the effect of intergrowth layers in TlBaCaCuO compounds on the intensity, location, and width of the basal plane reflections.

ISSN:0021-8979    

DOI:10.1063/1.354335

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Direct observation of superplastic deformation in shear in a scanning electron microscope in Pb‐62% Sn eutectic alloy at different microstructural levels were performed. The sliding of grains as an entity was observed. Such cooperative grain‐boundary sliding proceeds by means of the sequential shear of grains along shear surfaces, and is accompanied by cooperative grain‐boundary migration. The pattern of shear surfaces at the level of the entire deformed volume is close to one that is predicted by slip‐lines field theory. The processes to accommodate deformation of grain‐boundary sliding include the operation of grain‐boundary migration, intragranular deformation, and grain rotation. A critical analysis of the proposed geometrical models for superplastic flow is given. The model of sequential shear of grains as a result of the movement of cellular dislocations is extended to the case of the two‐phase material, having structure that is typical for superplastic eutectics.

ISSN:0021-8979    

DOI:10.1063/1.354302

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We have measured Raman scattering and high‐resolution x‐ray diffraction from highly strained [(InAs)4(InP)4]Nshort‐period superlattices grown on InP substrates by atomic layer epitaxy at 355 °C. The InAs and InP confined phonons are observed in these highly strained short‐period superlattices. The energy of the InAs confined longitudinal‐optical phonon (LO) modes of a fully strained superlattice (withN=8) is blue shifted by about 10 cm−1compared to the LO phonon of bulk InAs. This effect is explained by the large biaxial strain existing in the InAs layers. The observed frequency shift agrees with the lattice‐mismatch strain given by elasticity theory and independently measured by high‐resolution x‐ray diffraction. No evidence of a frequency shift of the InP confined LO modes in theN=8 fully strained superlattice is observed, indicating that the strain is confined to the InAs layers. We show that in a partially relaxed superlattice (withN=20), the InAs layers are in compression, while the InP layers are in tension. In this case the InP confined LO1phonons are red shifted by about 3 cm−1compared to the InP LO1phonons of theN=8 fully strained superlattice, and the shift of the InAs confined LO phonons with respect to the LO phonons of bulk InAs is also reduced.

ISSN:0021-8979    

DOI:10.1063/1.354303

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The permeation of oxygen through Ag0.05Zr over the temperature range of 300–650 °C under glow‐discharge conditions has been studied and compared to the permeation of thermally dissociated molecular oxygen. A low‐energy dc glow‐discharge in O2has been employed which produced approximately 10% atoms. The permeation rate during the glow discharge was found to be much higher (a factor of ∼10) than without the glow discharge. The small fraction of oxygen atoms generated appears to dominate the permeation because of much higher solution probabilities. Below 500 °C, the activation energy for the permeation with glow discharge was found to be 15.5 kcal/mol compared to 22.0 kcal/mol without glow discharge (molecular oxygen). Above 500 °C, the enhanced permeation with glow discharge gradually diminishes with increasing temperature and approaches that observed without the glow discharge at high temperature; the reason for this is primarily because of the thermal instability of the supersaturated high‐pressure interface where atoms recombine and desorb back into the gas phase.

ISSN:0021-8979    

DOI:10.1063/1.354304

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Probability distributions are evaluated for electromigration induced open failures in narrow, passivated interconnects with a near‐bamboo grain structure. Void formation is initiated at the cathode ends of the polycrystalline line segments or ‘‘grain clusters.’’ If these clusters are longer than a critical sizeLc, they can accommodate enough atoms for voids to reach the critical size to fail the line. Obviously, the critical sizeLcdepends on the thermal stress: a cluster under a tensile stress is able to incorporate more atoms from the void than an unstressed cluster. In the case the clusters are shorter thanLc, atoms from the voids must be distributed also to bamboo sections, outside the clusters, in order for the voids to induce open failures. Based on this physical picture, failure probabilities are evaluated as a function of time. The predicted failure distributions and parametric dependencies compare well with the experiments.

ISSN:0021-8979    

DOI:10.1063/1.354305

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The codiffusion of arsenic and phosphorus implanted in silicon has been investigated after annealing at 900 and 1000 °C for different concentrations of the dopants. Analysis of the profiles was performed using secondary‐ion‐mass spectroscopy, junction staining, and incremental resistivity and Hall measurements. The results do not evidence any direct interaction between the dopants. All the observed anomalous effects of the codiffusion, compared with the diffusion of the single elements by themselves, seem to be justifiable on the basis of the interactions between the dopants and the defects produced by ion implantation. In addition, it has been observed that the presence of a high concentration of As atoms makes the annealing of the implantation damage faster and strongly reduces the P transient‐enhanced diffusion. This effect favors the fabrication of graded shallow junctions with a high‐surface‐carrier concentration.

ISSN:0021-8979    

DOI:10.1063/1.354306

出版商:AIP    

年代:1993

数据来源: AIP