摘要:

In the present letter electron diffraction contrast imaging (EDCI) computations for strain characterization on the nanometer scale are presented. Using newly developed simulation software for EDCI image interpretation it is demonstrated how the technique can be used in the characterization, with submicron resolution, of localized strain fields in any crystalline material. Strain fields of arbitrary geometrical symmetry can be treated. As a case study, localized strain in an advanced semiconductor laser structure is investigated. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114482

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

(100)‐oriented diamond films have been grown on silicon (100) in a microwave plasma assisted chemical vapor deposition (CVD) tubular system. X‐ray photoelectron diffraction (XPD) has been used to study such oriented polycrystalline films. Comparing the diffractograms of a natural diamond (100) surface and of polycrystalline (100)‐oriented CVD diamond films quite similar features are observed. XPD measurements after 8 min of bias treatment show that the tiny crystals are already preferentially oriented at deposition parameters required for (100)‐oriented film growth. Our measurements indicate a strong need to control the growth parameters very carefully during the first minutes of growth to get an orientation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114483

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

One‐dimensional diffusion of excitons in GaAs quantum wires was observed by using microphotoluminescence measurements at low temperature. The observed diffusion length increased with decreasing wire width from 30 to 15 nm, and decreased from 15 to 7 nm, where maximum diffusion length was about 4 &mgr;m for the 15 nm quantum wire, which is the largest value so far reported. It is considered that the change of diffusion length versus wire width is caused by the competition between one‐dimensional character and the interface fluctuation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114484

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We used local probe techniques to characterize electron beam (e‐beam) induced changes in thin oxides on silicon. Primary effects of the 1 nm wide, 300 keV e beam included the formation of positive charges trapped in the SiO2, physical restructuring in the oxide, and deposition of carbonaceous compounds. Charges remained stable in thicker oxides (460 nm) and appeared as changes in the contact potential or microwave response with widths down to 100 nm. In thinner oxides (20 nm) the amount of charge was smaller and less stable; below 7 nm no charge was detected. Physical changes in the oxide, evident as a swelling of irradiated areas, accounted for the etching selectivity of these regions. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114485

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The structural evolution of epitaxial GaN layers grown on basal plane sapphire has been studied by atomic force microscopy (AFM), x‐ray diffraction, and transmission electron microscopy (TEM). High‐temperature growth (1050–1080 °C) on optimized nucleation layers leads to clear, specular films. AFM on the as‐grown surface shows evenly spaced monatomic steps indicative of layer by layer growth. AFM measurements show a step termination density of 1.7×108cm−2for 5 &mgr;m films. This value is in close agreement with TEM measurements of screw and mixed screw‐edge threading dislocation density. The total measured threading dislocation density in the 5 &mgr;m films is 7×108cm−2. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114486

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Zr41.2Ti13.8Cu12.5Ni10.0Be22.5bulk metallic glasses were prepared by cooling the melt with a rate of about 10 K/s and investigated with respect to their chemical and structural homogeneity by atom probe field ion microscopy and transmission electron microscopy. The measurements on these slowly cooled samples reveal that the alloy exhibits phase separation in the undercooled liquid state. Significant composition fluctuations are found in the Be and Zr concentration but not in the Ti, Cu, and Ni concentration. The decomposed microstructure is compared with the microstructure obtained upon primary crystallization, suggesting that the nucleation during primary crystallization of this bulk glass former is triggered by the preceding diffusion controlled decomposition in the undercooled liquid state. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114487

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Amorphous Ni50Nb50/C multilayers with a repeat period of 2.39 nm, suitable for the water window region of soft x rays, have been prepared by pulsed laser deposition. The interface and in‐plane structure of these multilayers was studied by low angle hard x‐ray diffraction. It was found that the interfaces are very sharp with a typical lateral correlation length of the order of 180 nm. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114488

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have grown high quality epitaxial AlN layers on sapphire substrates by pulsed laser ablation of a stoichiometric AlN target. The AlN films deposited at 800 °C and laser energy densities in the range of 2–3 J/cm2were found to be epitaxial with thecaxis normal to the Al2O3(0001) surface. The x‐ray rocking curve of epitaxial AlN films yielded a full width at half maximum of 0.21°. The selected area electron diffraction patterns and high resolution transmission electron microscopy also revealed that the films were epitaxial with an orientational relationship of AlN[0001]∥Al2O3[0001] and in‐plain alignment of AlN[1¯21¯0]∥Al2O3[01¯10] and AlN[101¯0]∥Al2O3[2¯110]. This is equivalent to 30° rotation in the basal plane of the AlN film with respect to the sapphire substrate. The absorption edge measured by ultraviolet‐visible spectroscopy for the epitaxial AlN film was sharp and the band gap was found to be 6.1 eV. The electrical resistivity of the films was about 5–6×1013ohm cm with a breakdown field of 5×106V/cm. At higher laser energy densities ≥10 J/cm2and lower temperatures ≤650 °C, the deposited films were nitrogen deficient and contained free metallic aluminum, both of which degrade the microstructural, electrical, and optical properties of the AlN films. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114489

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We describe a novel technique for fabricating metallic nanostructures on an arbitrary substrate using an atomic force microscope (AFM). An AFM is used to plow a pattern through the top of two resist layers spun onto a substrate. The resist is then developed to create a mask through which material can be deposited. By changing the applied force, the top resist‐layer thickness, or the development time, the linewidth can be varied. Continuous metallic wires ∼500 A˚×400 A˚×15 &mgr;m have been fabricated on bare substrates and between contact pads. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114731

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A diamond film consisting of almost 100% [001] grains can be synthesized at a fast rate (∼ 3 &mgr;m/h) by a two‐step process. First, the nuclei are formed under −160 V dc bias with 3 mol % CH4/H2at 900 °C substrate temperature and then the films are grown under −100 V dc bias with around 5–6 mol % CH4/H2at the same temperature. The nucleation of the diamond is enhanced by using bias voltage. Theaandbaxis of [001] textured diamond films grown under large bias voltage are aligned withaandbaxes of silicon, viz. (100)diamond∥(100)Siand [110]diamond∥[110]Si. The effect of bias voltage on the growth behavior of the diamond films is accounted for by the suppression of the growth of the non‐[001] grains due to the electron emission under bias. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114732

出版商:AIP    

年代:1995

数据来源: AIP