摘要:

A single-crystalline cubic boron nitride(c-BN)(111) surface has been studied by atomic force microscopy with simultaneous measurements of normal atomic force (constant height mode and constant force mode) and lateral (friction) force in air. On the friction force mode the different two domains observed can be attributed to the termination of the surface; boron (Aside) or nitrogen (Bside). 2.6 Å periodicity corresponding to the1×1surface unit cellasofc-BN(111)(as=a0/&sqrt2;=2.56 Å,wherea0is the lattice constant, 3.62 Å) has been observed also on the friction force mode, which is in agreement with our low-energy electron diffraction measurement. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122573

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We demonstrate that the morphology of crystalline surfaces during ion sputtering and thermal annealing can be monitoredin situwith an oblique-incidence polarization-modulated optical reflectance difference technique. Such a technique is effective under high ambient pressures as well as ultrahigh vacuum. We studied the Ne ion sputtering and thermal annealing of Ni(111) from 623 to 823 K. We found that the rate-limiting step (with an activation energy of 1.1 eV/atom) during annealing is most likely to be direct evaporation of Ni atoms from step edges. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122574

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The grain morphology ofSi0.7Ge0.3depends on the number of the primary noncoplanar twin variants formed at the early stage of solid-phase crystallization. The grain with major twin bands of a single twin variant parallel to a {111} plane develops an elongated shape, owing to the preferential growth in a ⟨112⟩ direction along twins. When the grain has major twin bands of two or more noncoplanar twin variants, the growth front between noncoplanar twin bands develops as fast as the ⟨112⟩ direction along twins propagates, because such a growth front is formed from a {111} ledge. As results, the grain becomes more or less equiaxed due to the increasing number of primary, noncoplanar twin variants. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122575

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Uncapped InGaAs quantum dots (surface quantum dots) on a GaAs substrate emit photoluminescence at a long wavelength of 1.53 &mgr;m at room temperature. When the surface dots are covered by a GaAs cap layer, the emission energy of the dots increases by 287 meV. This large energy shift is mainly caused by inducing compressive stress from the cap layer. In segregation on the surface led to greater photoluminescence intensity in the surface quantum dots even at room temperature due to the suppression of nonradiative surface recombination.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122576

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A range of La–Ca–Mn–O films have been grown using pulsed-laser deposition on hot Si substrates. The composition of the films is found to be strongly dependent on substrate temperature(Ts)with the calcium and oxygen content being significantly reduced at highTs(>700 °C). The kinetic energies of the various ions in the laser generated plume are found to be distributed in the 10–100 eV range, high enough to induce resputtering from deposited films. Surface segregation was also observed in the films grown at highTs(>700 °C), resulting in a Ca-rich surface. Preferential resputtering of these surface Ca-rich segregated samples, driven by a mixture of high energy ion irradiation and thermally activated processes, is proposed to explain the observed phenomena. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122577

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Electromigration threshold has been measured for unpassivated damascene Al(Cu) interconnects by drift experiments on Blech-type test structures, and results are compared to equivalent plasma-etched lines. When using a damascene implementation, the critical product of current density and stripe length increases significantly. As a result, the incubation period, needed for Cu depletion beyond a critical length, is increased over a wide temperature range (155–230 °C). This is shown to be an intrinsic effect, directly controlling the relative electromigration performance of both metallization schemes. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122578

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Density-functional-theory calculations have been performed to study the effect of doping and growth stoichiometry on the core structure of a threading edge dislocation in GaN. Four candidate structures were examined and their formation energies were found to depend strongly on Fermi level and growth stoichiometry. A structure having gallium vacancies at the dislocation core is predicted to be most stable inn-type material grown under nitrogen-rich conditions, while a structure without vacancies is most stable inp-type material grown under these conditions. In material grown under gallium-rich conditions, a structure having nitrogen vacancies at the dislocation core is predicted to be most stable inp-type material, whereas a variety of core structures should be present inn-type material. Edge dislocations are predicted to behave as electron traps inn-type material and may act as hole traps inp-type material depending on the growth conditions. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122579

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Epitaxial films of TiC and VC can be deposited at low temperatures on Mg(001) substrates by coevaporation of the metals withC60in a ultrahigh vacuum system. This process was used to deposit TiC/VC (001) superlattices on MgO(001) at 400 °C. The superlattice structure was characterized with low electron energy diffraction, x-ray diffraction, and transmission electron microscopy (TEM). Cross-sectional high-resolution TEM showed good registry between the different carbide layers. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122580

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report laser emission from Be-doped Ge lasers at high repetition rates of up to 45 kHz which is one order of magnitude higher than previously reported. Laser radiation was detected from Ge:Be crystals with volumes as small as0.5 mm3and with intercontact distances down to 1 mm. We present a thermal analysis and derive the design parameters for continuous wave Ge lasers.

ISSN:0003-6951    

DOI:10.1063/1.122581

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Modulation-dopedIn0.5Ga0.5As/In0.5Al0.5Asquantum well structures grown by molecular beam epitaxy on GaAs substrates using a relaxed AlGaAsSb buffer showed carrier mobilities of8500 cm2/V sfor a sheet concentration of3.5×1012 cm−2at room temperature. The crystallinity of the quaternary buffer layer was verified by x-ray diffractometry. Transistors with0.25×100 &mgr;m2gates demonstrated transconductance values as high as 800 mS/mm. S-parameter measurements revealed a cutoff frequencyfTof 87 GHz and a maximum oscillation frequencyfMAXof 140 GHz (both extrinsic values). ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.122582

出版商:AIP    

年代:1998

数据来源: AIP