摘要:

We report on measurements of fractal dimension for ultrathin cobalt films deposited onto silicon substrates. A new method has been used for the fractal dimension measurements, which involves an image processing of transmission electron microscopy (TEM) bright field image of the ultrathin film structure. The TEM image is digitized by 512×512 pixels with intensity levels from 0 to 255, and topographic contour lines which connect the same intensity levels are obtained from the digitized image. The fractal dimension (D) of the ultrathin film structure is calculated from the contour lines by using a relation (L=AD/2) between the areas (A) and perimeters (L) for each of the closed lines as suggested by Mandelbrot [FractalGeometryofNature(Freeman, New York, 1982), Chap. 12]. Results of the measurements indicate that the Co‐Si interfacial dimension is increased from 2.0 to near 2.5 as the reaction is progressed. The results are compared with the fluctuating fractal dimension calculated from the noise exponent data.

ISSN:0003-6951    

DOI:10.1063/1.100802

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The formation of an interfacial AlN layer was observed in an Al/Si3N4thin‐film system immediately after electron beam deposition of Al, employing Auger electron spectroscopy, x‐ray diffraction, and transmission electron microscopy. Heat treatments up to 600 °C resulted in growth of this layer. The Si liberated by the direct reaction between Al and Si3N4was found to crystallize into small islands of peculiar fractal‐like shape. The AlN layer acted as a diffusion barrier for diffusion of Al into Si3N4.

ISSN:0003-6951    

DOI:10.1063/1.101418

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Wide optical gap (2.0 eV) boron‐doped hydrogenated amorphous silicon carbide films were prepared by the plasma‐assisted chemical vapor deposition technique from a SiH4+CH4+BF3+H2gas mixture for the first time. The film showed a photoconductivity of 1×10−5S/cm under 1 sun illumination, which was higher by a factor of 5 than the films doped with B2H6.

ISSN:0003-6951    

DOI:10.1063/1.100803

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A potential origin for the reported discrepancies on the low‐temperature photosensitivity of particle‐induced anion antisites in GaAs is revealed by a systematic study of the relative fraction of photoquenchable paramagnetic As4+Gacenters as a function of neutron fluence and annealing temperature. The electron paramagnetic resonance data show that the As4+Gacenters can be split into two subsets.

ISSN:0003-6951    

DOI:10.1063/1.100804

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The selective epitaxy of GaAs was demonstrated in the metalorganic vapor phase epitaxy of GaAs utilizing diethylgallium chloride [Ga(C2H5)2Cl] and AsH3. No GaAs will deposit on SiO2, Si3N4, or SiONxunder normal growth conditions, i.e., 600–800 °C at 0.1 atm reactor pressure. Unlike other forms of selective epitaxy, there is no enhanced growth rate at the edge of the selectively grown regions. The selectivity is a result of the reduced adsorption of the growth precursor, probably GaCl, on the masking material relative to the exposed GaAs areas. Similar selectivity should be possible for Al and In containing semiconductors using an analogous growth chemistry.

ISSN:0003-6951    

DOI:10.1063/1.100805

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The stability of strained‐layer AlyGa1−yAs‐GaAs‐InxGa1−xAs single quantum well heterostructures against thermal processing is examined using transmission and scanning electron microscopy. A self‐aligned impurity‐induced layer disordering process employing Si‐O diffusion is used to produce buried heterostructure stripe geometry lasers with a pseudomorphic InxGa1−xAs quantum well active region. The 2‐&mgr;m‐wide stripe laser diodes exhibit high efficiency (&eegr;∼41%/facet), low threshold (Ith=7 mA), and high output power (Pout>20 mW/facet).

ISSN:0003-6951    

DOI:10.1063/1.100806

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Enhanced diffusion of B is observed during the growth of ion bombarded epitaxial layers by Si molecular beam epitaxy. Ion‐assisted methods are generally required for high levels ofn‐type doping, and we find that the damage caused by the low‐level ion bombardment is responsible for the enhanced diffusion of B. Furthermore, the concentration profiles of as‐grown and post‐growth annealed samples show that the diffusion is a transient effect that occurs at the growth temperature of 600–700 °C. Simulation of the diffusion process demonstrates that nearly all of the B is participating in the diffusion and that the built‐in electric field at thep‐njunction leads to a further smearing of the B profile.

ISSN:0003-6951    

DOI:10.1063/1.100807

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Recent experimental studies of ballistic electron transport have pushed the transit time well into the subpicosecond dynamical regime. By applying the quantum dynamical theory to study ultrafast transient transport, we report results that are dramatically different from those predicted by the classical Boltzmann theory.

ISSN:0003-6951    

DOI:10.1063/1.100808

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Single and multiple quantum wells of GaSb/GaInSb were grown by metalorganic vapor phase epitaxy. X‐ray diffraction on an 80 A˚ single well confirmed the Ga1−xInxSb composition to bex=0.15, for which the lattice mismatch is ≊1.0%. Photoluminescence and photoconductivity from this sample both showed a signal due to carriers in the well, the position of which was in good agreement with the calculated band diagram. Shubnikov–de Haas oscillations in the transverse magnetoresistance (&rgr;xx) of a four‐period multiquantum well, and the associated quantum Hall effect, indicated that a two‐dimensional hole gas was present in one of the wells. Unusually, the strongest oscillations were seen for occupancy of an odd number of (spin split) Landau levels (&ngr;=1,3,5,...,etc.) This sample also showed luminescence peaks at 738 and 755 meV which were attributed to recombination in the wells.

ISSN:0003-6951    

DOI:10.1063/1.100809

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We show how strained‐layer relaxation via misfit dislocation introduction varies significantly in GexSi1−x/Si (100) epitaxy as a function of the strain in this system. It is found that for samples grown by molecular beam epitaxy at a substrate temperature of 550 °C, structures with lower strain (x=0.15) are highly metastable, relaxing most of their excess stress on annealing to temperatures ∼650–750 °C. Structures with higher strain (x=0.25) are observed to relax far more gradually over the temperature range 550–900 °C.Insituelectron microscope observations explain this behavior in terms of misfit dislocation interactions in the relaxing material.

ISSN:0003-6951    

DOI:10.1063/1.100810

出版商:AIP    

年代:1989

数据来源: AIP