摘要:

The structural characterization of ZnS epilayers grown by hydrogen transport vapor‐phase epitaxy on (100)‐oriented GaAs substrates is reported. X‐ray‐diffraction measurements in both double‐axis (DA) and single‐axis modes were performed to determine the residual strain tensor and the strain temperature dependence of the epilayer in the range between 25 and 650 °C. From the analysis of the data obtained by DA measurements of several symmetric Bragg reflections at different azimuth angles and several asymmetric reflections recorded in different geometries, an orthorhombic distortion of the ZnS lattice was found. The crystallographic symmetry could be explained by an asymmetric distribution of the misfit dislocation density in the interface plane along the [011] and [01¯1] directions. The temperature dependence measurements of the strain tensor components between room temperature and the growth temperature (650 °C) allowed determination of the thermal misfit between ZnS and GaAs and the linear thermal‐expansion coefficient of ZnS. Finally, triple‐crystal diffractometry and secondary‐ion‐mass spectrometry were used to investigate the chemical nature of the ZnS‐GaAs interface. The results indicate the presence of an interdiffused ZnS‐GaAs interface region, whose occurrence turns out to be associated with the initial defect structure of the substrate surface before the growth. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358769

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

CoSi2exhibits the features of low resistivity and stability at elevated temperatures which make it interesting to employ for metallization on GaAs. The interfacial reactions in GaAs samples with thin film overlayers of Si and Co [Si(220 nm)/Co(50 nm)/(⟨100⟩‐GaAs)] were studied using x‐ray diffraction, scanning electron microscopy, x‐ray photoelectron spectroscopy, and mass and energy dispersive recoil spectrometry. Samples were vacuum furnace annealed for time periods between 1 and 8 h at temperatures ranging from 300 to 700 °C. It was found that a CoSi2layer formed without observable reaction with the substrate at 500 °C and above. The excess Si (Si/Co atomic ratio of 2.41) remained near the surface as elemental Si and as SiO2for the 500 and 600 °C annealings. For the 700 °C annealing the excess near‐surface Si was not observed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358770

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present a simple method for calculating strain distributions in structures containing an arbitrary number and combination of strained layers of finite length buried in an infinite medium. This method is used to calculate the strain distributions for a quantum‐well stack containing four compressive layers separated by barriers of different thicknesses and states of strain. It is found that the in‐plane strain is relaxed along a significant length of each compressive layer if the barriers are unstrained. In contrast, if the barriers are in tension, the compressive strain is retained over most of the length of the layer. It is concluded that the judicial use of compressive and tensile layers in device structures would substantially reduce the region over which the strain is relaxed and possibly minimize the adverse effects of modified band structure or atomic diffusion arising due to the relaxation of strain. It is also confirmed that strain relaxation reduces the average strain within the square cross section of a single quantum wire to about one tenth of the misfit strain. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358771

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Equilibrium geometries of 60° dissociated misfit dislocations are considered theoretically using elasticity theory. The prediction of equilibrium dissociation width and the position of each partial with respect to the interface is given. The experimental results are in excellent agreement with the theory. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358772

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The interfacial energy of interconnect‐metal/barrier‐metal interfaces in ultralarge‐scale integrations have been investigated numerically by assuming a simple additive interaction potential within a rigid‐lattice approximation. The calculation gave some noteworthy results: Al prefers the (111) orientation on a TiN(111) plane, but Cu did not have such a strong preference. Al(111) can be expected to show strong epitaxial growth on VNx(111), as did Cu on Nb(110). On the basis of the calculations, a Cu/Nb bilayered structure was sputter deposited sequentially by dc magnetron sputtering and examined for crystalline orientation by x‐ray‐diffraction analysis. Cu exhibited strong (111) orientation preference, and a narrow full width at half‐maximum in (111) rocking angle around the substrate normal. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358773

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Several monolayers thick hydrogenated carbon films, C:H, were prepared by ion beam deposition from hydrocarbon process gases onto Pt and monolayer C covered Pt single crystal surfaces and investigated with Auger electron and thermal desorption spectroscopies in an UHV environment. Efficient deposition was achieved at ion energies in the 160–300 eV range. The deposited thickness and H/C ratio of the films depend on both, target temperature and H/C ratio of the process gas. It is shown that the C monolayer is crucial for efficient on‐top deposition. Irrespective of the process gas used for deposition, the films grow as a C network and assume a constant H/C ratio at thicknesses greater than ∼ 3 monolayers. The H/C ratio of the films scale with the H content of the hydrocarbon process gas, a H/C ratio of 0.4 was obtained for ethane at 350 K substrate temperature. Upon thermally activated decomposition the films release molecular hydrogen as the major gaseous species and various hydrocarbons as minority species. The latter products signal chemical erosion of the film. It is shown that the rate determining step towards erosion via methane is a C–C bond breaking event which releases methyl radicals from the C network in the film. The activation energies for this step are determined as a 10 kcal/mol wide Gaussian distribution centered at 56 kcal/mol. Transport through the film is found to be so fast that it does not contribute to the observed gas release rates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358774

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The kinetics of a low‐temperature silicide formation have been investigated in experiments on the solid‐phase interaction between Cr and amorphous Si (a‐Si). For the Cr/plasma‐enhanced chemical‐vapor‐depositeda‐Si:H system, it was found that amorphous interlayer was formed at the interface at RT. The compositional ratio of Cr to Si in the amorphous interlayer formed at RT was found to be about 5%. On the other hand, for the Cr/sputtereda‐Si system at RT, an interfacial amorphous layer with negligible thickness seemed to exist. From the experimental results and from the results previously reported, the kinetics of the low‐temperature interaction were discussed and a new model of an internal‐field‐assisted interaction was proposed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358775

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Low (keV) and high (MeV) energy Al and B implants were performed into n‐type 6H‐ and 3C‐SiC at both room temperature and 850 °C. The material was annealed at 1100, 1200, or 1400 °C for 10 min and characterized by secondary ion mass spectrometry, Rutherford backscattering (RBS), photoluminescence, Hall and capacitance‐voltage measurement techniques. For both Al and B implants, the implant species was gettered at 0.7 Rp(where Rpis the projected range) in samples implanted at 850 °C and annealed at 1400 °C. In the samples that were amorphized by the room temperature implantation, a distinct damage peak remained in the RBS spectrum even after 1400 °C annealing. For the samples implanted at 850 °C, which were not amorphized, the damage peak disappeared after 1400 °C annealing. P‐type conduction is observed only in samples implanted by Al at 850 °C and annealed at 1400 °C in Ar, with 1% dopant electrical activation. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358776

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence (PL) measurements at 10 K were performed in order to investigate the influence of electric fields on the exciton states in Al0.4Ga0.6As/GaAs asymmetric coupled multiple quantum wells (ACMQW) grown by molecular‐beam epitaxy. The coupling of the electronic energy levels in the wells led to an enhancement of the quantum‐confined Stark effect. The PL intensity decreased as the electric field increased. Calculated values of the intersubband transition energies were in good agreement with the experimental values for the ACMQW, and these values showed a similar behavior as those for the step quantum well. When the external applied field was very strong, Stark‐ladder transitions were observed, and the measured dependence of the field‐induced energy shifts of the Stark‐ladder transitions for the ACMQW agreed with theory. These results indicate that the Stark effect and the Stark‐ladder transitions in a unique ACMQW based on the AlxGa1−xAs/GaAs structure were observed simultaneously. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358777

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The electrical and optical properties of defects due to ion implantation of ruthenium in silicon have been studied by means of junction space‐charge techniques. Two energy levels were observed with energy positions atEc−0.184 eV (A‐level) andEV+0.265 eV (B‐level), respectively, at 77 K. The changes in enthalpy due to the capture of electrons and holes were −8 meV (A‐level) and 1 meV (B‐level). Gibb’s free energies at different temperatures were calculated for both levels. Good agreement with the corresponding optical threshold energy was found for theB‐level suggesting a small Frank–Condon shift. A tentative model for the origin of the observed defects is discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358778

出版商:AIP    

年代:1995

数据来源: AIP