摘要:

Room temperature 200 keV xenon-ion irradiation of multilayers, designed under interfacial free energy concern, did result in the formation of Mo–Cu metallic glasses only within a narrow Mo-enriched composition range. In addition, some Cu-based alloys of metastable fcc solid solutions were also formed at different irradiation stages. To obtain a possible thermodynamic interpretation, a Gibbs-free-energy diagram was calculated based on the semiquantitative Miedema’s model and the related methods proposed by Alonso. The free energy of the Mo–Cu multilayers including excess interfacial free energy was also estimated and was compared to that of the amorphous state. It turned out that the interfacial free energy stored in the multilayered films could raise the energy level of the multilayers to a state higher than that of the metastable phases and thus played an important part, in comparison to the energy deposited by irradiation, in inducing alloying in this immiscible system. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365744

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have used x-ray absorption spectroscopy to study the formation and dissolution of&thgr;-Al2Cuprecipitates in blanket Al-Cu films. In one series of experiments, we examined films deposited at different temperatures and average Cu concentrations. For a given temperature, there is a Cu concentration above which precipitates form. This effective solvus agrees with the equilibrium solvus at high temperatures, but exceeds the equilibrium values at low deposition temperatures. The formation of precipitates correlates with a pileup of Cu in the part of the film which was deposited first. This pileup is explained by a model involving precipitate growth at grain boundaries and grain growth during deposition. We also measured the kinetics of precipitation formation and dissolution inAl−0.5w/o Cu. In the range 200–270 °C, the precipitation kinetics show an activation energy of 0.54 eV, which is lower than that for grain-boundary diffusion of Cu in Al. Precipitate dissolution over the range 300–400 °C shows an activation energy of 1.37 eV, consistent with lattice diffusion. These results may be useful in designing heat treatments which will minimize the occurrence of precipitates in integrated-circuit interconnects when process corrosion could be a problem, yet leave the material with precipitates before use, when electromigration becomes an issue. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365745

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Deep levels related to iron inn-type silicon have been investigated using thermally stimulated capacitance (TSCAP) combined with minority carrier injection. The TSCAP measurement reveals two traps ofEV+0.31andEV+0.41eV. The trap ofEV+0.41 eV is a donor due to interstitial iron. The trap ofEV+0.31eV, due to a complex of interstitial iron and hydrogen, is observed in the sample etched chemically with an acid mixture containing HF and HNO3and annihilates after annealing at 175 °C for 30 min. It is demonstrated that interstitial3dtransition metals such as vanadium, chromium, and iron tend to form complexes with hydrogen inn-type silicon, and the complexes induce donor levels below the donor levels of the isolated interstitial species. This trend is related to the interaction between the metals and hydrogen in the complexes. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365746

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Undoped liquid encapsulated Czochralski grown GaAs crystals with a transition from semi-insulating to medium-resistivity behavior show unusual low values of the Hall mobility at 300 K in this transition region. Moreover, in samples of this region an anomalous temperature dependence of&mgr;Hcharacterized by an increase of&mgr;Hwith increasing temperature forT<400 Kis observed. By model calculations using a standard effective medium theory it is shown that this anomalous behavior of the Hall mobility is due to the existence of mesoscopic electrical nonuniformities connected with the cellular structure of dislocations. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365747

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Semi-insulating Fe-doped InP was annealed under different conditions and investigated by Hall effect, extrinsic photocurrent mapping, chemical etching, and optical microscopy. The resistivity is increased for any treatment, particularly in wafer-annealed InP. This result is probably due to strong losses of shallow donors. Remarkable differences exist between the structural properties of the wafer and ingot annealed material; wafer annealing produces a quick elimination of growth striations and decoration microdefects while ingot-annealed InP still retain these microdefects, both along dislocations and in the matrix. The photocurrent maps indicate that the thermal treatments normally improve the doping uniformity (especially the short-range fluctuations). The best uniformity is achieved for the long annealing time(⩾50 h),while a slow cooling rate improves the mobility. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365748

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The influence of electron energy width in the hot electron double-slit experiment is investigated quantitatively. The required condition on the Fermi level in the emitter and the slit-spacing is derived for the experiment. In order to achieve a coherent electron source, a single-barrier graded emitter structure is discussed and its characteristics are considered. For application to the hot electron double-slit experiment, the graded emitter diode is fabricated and the current–voltage relation is measured in a supplementary experiment. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365749

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In the present study we calculate the energy values and the spatial distributions of the bound electronic states in some diffused quantum wells. The calculations are performed within the virtual crystal approximation,sp3s*spin dependent empirical tight-binding model and the surface Green function matching method. A good agreement is found between our results and experimental data obtained for AlGaAs/GaAs quantum wells with thermally induced changes in the profile at the interfaces. Our calculations show that for diffusion lengthsLD=0−20Å the optical transition between the ground electron and hole states is less sensitive to theLDchanges than the optical transitions between the excited electron and hole states. For diffusion lengthsLD=20−100Å, the optical transition between the second excited states is not sensitive to the diffusion length, but the other optical transitions display large “blue shifts” asLDincreases. The observed dependence is explained in terms of the bound states spatial distributions. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365750

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Quantum well potentials are engineered to control the energy level shifts induced by semiconductor alloy intermixing. A few monolayers of a semiconductor with a different band gap can be inserted at the node or at the crest of wavefunctions with different parities to enhance the interdiffusion-induced interband transition energy-shifts, or to manipulate the intersubband transition energies. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365751

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effects of Group III and Group V interdiffusions with a varied as-grown well width and P concentration in the quaternary InGaAsP quantum well material have been theoretically studied. Interesting features of multiple mini-well profiles, generated by interdiffusion induced compressive and tensile strains, have been obtained and varying envelope overlapping of the electron-hole wave functions has been observed. The results show that the interdiffusion of the Group III elements with a well width of 10 nm offers a wide adjustability of the operation wavelength, enhances Stark shift, and reduces absorption loss, although they bear the shortcomings of low electro-absorption and contrast ratio. Several methods are proposed here to recover the contrast ratio with a maximum improvement of 66&percent;. For the Group V interdiffusion of a 10-nm-wide as-grown well, a low absorption loss and a large Stark shift will result, while that of a narrowed well can widen the band-edge wavelength adjustability with a large electro-absorption. These results are important for the development of electro-absorptive InGaAsP/InP diffused quantum well modulators. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365752

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The photoluminescence (PL) intensity of free excitons in a GaInAsSb/GaAlAsSb single quantum well structure is investigated as a function of excitation intensity and lattice temperature. The relationship between PL intensity of free excitons and excitation intensity as well as lattice temperature was developed for the quantitative descriptions of the experimental data. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365689

出版商:AIP    

年代:1997

数据来源: AIP