共查询到20条相似文献,搜索用时 46 毫秒
1.
Hisashi Masui Samantha C. Cruz Shuji Nakamura Steven P. DenBaars 《Journal of Electronic Materials》2009,38(6):756-760
Inclined crystallographic planes of the wurtzite structure were investigated in comparison with the zincblende structure in
terms of surface geometry characteristics. The ball–stick model indicates that the semipolar surface possesses a surface polarity resembling the anion polarity, which agrees with the common experimental observations
of epitaxial growth preference for the cation-polarity surface over the surface. The wurtzite surface was found to share geometrical similarities with the zincblende {100} surface uniquely among the possible semipolar
planes. This finding encourages epitaxial growth on the plane of wurtzite semiconductors, e.g., GaN, with the potential of avoiding atomic step formations typically associated with
off-axis crystallographic planes. 相似文献
2.
J.D. Benson R.N. Jacobs J.K. Markunas M. Jaime-Vasquez P.J. Smith L.A. Almeida M. Martinka M.F. Vilela U. Lee 《Journal of Electronic Materials》2008,37(9):1231-1236
X-ray diffraction full-width at half-maximum (XRD FWHM), reflection high-energy electron diffraction (RHEED), and atomic force
microscopy (AFM) indicate a mosaic structure for molecular-beam epitaxy (MBE) (211)B CdTe/Si. AFM measurements indicate long,
thin, small-angle-disoriented grains for CdTe/Si epilayers. These disoriented grains are ~1 μm in the [] direction and are ~40 nm in the [] direction. The RHEED pattern in the [] direction depicts nearly ideal single-crystal periodicity. The RHEED pattern in the [] direction is indicative of small-angle-disoriented crystalline grains. Scanning electron microscopy (SEM), AFM, and XRD
measurements all indicate an approximate factor of 10 increase in the Everson etch pit density (EPD) over standard Nomarski
microscopy Everson EPD determination. 相似文献
3.
C. André D. Vasilevskiy S. Turenne R. A. Masut 《Journal of Electronic Materials》2009,38(7):1061-1067
Thermoelectric (TE) generator modules for a number of waste heat recovery applications are required to operate between room
temperature and 500 K, a temperature range for which the composition of bismuth-telluride-based alloys needs to be adjusted
to optimize performance. In particular n-type alloys do not perform as well as p-type and require a more systematic study. We have produced, by mechanical alloying followed by hot extrusion, alloys, within the range with fixed carrier concentration () to optimize their TE performance in the temperature range 300 K to 420 K. The optimum composition has been identified to
be and which is very close to the composition that also maximizes the ratio of the electron mobility to the lattice component of
the thermal conductivity. The optimized alloy performance can be further increased by adjusting the carrier concentration. 相似文献
4.
S.K. Chan S.K. Lok G. Wang Y. Cai N. Wang I.K. Sou 《Journal of Electronic Materials》2008,37(9):1344-1348
Nanotrenches are induced by thermal annealing Au droplets on ZnSe surfaces. High-resolution scanning electron microscopy studies
of the nanotrench structures reveal that the preferred migration directions of the catalyst droplets are along the direction family. On a ZnSe(111)B surface, each of the trenches is along one of the six directions while on a nonvicinal ZnSe(100) surface, the trenches are along a pair of antiparallel directions. Based on the results obtained from atomic force microscopy surface profiling and electron energy-loss spectroscopy
chemical analysis techniques, a model is proposed to describe the possible formation mechanisms of the␣observed nanotrenches.
The highly parallel nanotrenches induced on the Au/ZnSe(100) structure as revealed in this study are potentially useful as
a template for in situ fabrication of ordered one-dimensional nanostructures (such as nanowires) of many materials. 相似文献
5.
Surface Morphology and Defect Formation Mechanisms for HgCdTe (211)B Grown by Molecular Beam Epitaxy 总被引:1,自引:0,他引:1
Yong Chang C.R. Becker C.H. Grein J. Zhao C. Fulk T. Casselman R. Kiran X.J. Wang E. Robinson S.Y. An S. Mallick S. Sivananthan T. Aoki C.Z. Wang D.J. Smith S. Velicu J. Zhao J. Crocco Y. Chen G. Brill P.S. Wijewarnasuriya N. Dhar R. Sporken V. Nathan 《Journal of Electronic Materials》2008,37(9):1171-1183
The surface morphology and crystallinity of HgCdTe films grown by molecular beam epitaxy (MBE) on both CdZnTe and CdTe/Si
(211)B substrates were characterized using atomic force microscopy (AFM), as well as scanning (SEM) and transmission (TEM)
electron microscopy. Crosshatch patterns and sandy-beach-like morphologies were commonly found on MBE (211) HgCdTe epilayers
grown on both CdZnTe and CdTe/Si substrates. The patterns were oriented along the , , and directions, which were associated with the intersection between the (211) growth plane and each of the eight equivalent HgCdTe
slip planes. This was caused by strain-driven operation of slip in these systems with relative large Schmid factor, and was
accompanied by dislocation formation as well as surface strain relief. Surface crater defects were associated with relatively
high growth temperature and/or low Hg flux, whereas microtwins were associated with relatively low growth temperature and/or
high Hg flux. AFM and electron microscopy were used to reveal the formation mechanisms of these defects. HgCdTe/HgCdTe superlattices
with layer composition differences of less than 2% were grown by MBE on CdZnTe substrates in order to clarify the formation
mechanisms of void defects. The micrographs directly revealed the spiral nature of growth, hence demonstrating that the formation
of void defects could be associated with the Burton, Cabrera, and Frank (BCF) growth mode. Void defects, including microvoids
and craters, were caused by screw defect clusters, which could be triggered by Te precipitates, impurities, dust, other contamination
or flakes. Needle defects originated from screw defect clusters linearly aligned along the directions with opposite Burgers vector directions. They were visible in HgCdTe epilayers grown on interfacial superlattices.
Hillocks were generated owing to twin growth of void or needle defects on (111) planes due to low growth temperature and the
corresponding insufficient Hg movement on the growth surface. Therefore, in addition to nucleation and growth of HgCdTe in
the normal two-dimensional layer growth mode, the BCF growth mode played an important role and should be taken into account
during investigation of HgCdTe MBE growth mechanisms. 相似文献
6.
P. Kale P. Padmini J. Dou L. Navarrete M. Shamsuzzoha R. Schad R. K. Pandey 《Journal of Electronic Materials》2007,36(9):1224-1228
The ilmenite–hematite (1 − x) FeTiO3 · xFe2O3 solid solution system is considered to be a novel material for spin-electronics, microelectronics, high-temperature electronics,
and radhard electronics. This paper focuses on thin films of composition x = 0.33 grown on (100) MgO single-crystal substrates using pulsed-laser deposition (PLD) under different argon–oxygen mixtures.
The surface of the MgO was found to possess MgO2 crystals, yielding an orientation relationship, [001] MgO ∥ [011] MgO2 and (00)MgO ∥ (10) MgO2. The structural characterizations show that the films are crystalline and homogeneous without any secondary phase. The films
show a weak and inclined (110) growth epitaxy. A bandgap of 3.4–3.7 eV was obtained for these films from optical measurements carried out in the UV–visible
region. Electrical measurements confirmed the semiconducting behavior. However, the resistivity was found to increase substantially
on the slightest addition of oxygen into the chamber. 相似文献
7.
Maskless Lateral Epitaxial Growth of Gallium Nitride Using Dimethylhydrazine as a Nitrogen Precursor
Lateral epitaxial growth (LEG) is a key technology to improve the lifetime of III-V nitride-based laser diodes (LDs) by reducing
the dislocation density in the materials. To increase the area of low dislocation density, the lateral growth rate needs to
be increased. In addition, suppression of the vertical growth is strongly desired to avoid unnecessarily thick growth, which
would result in cracks in the epitaxial film. This paper reports the maskless LEG of GaN with extremely high lateral-to-vertical
growth rate ratio using dimethylhydrazine as a nitrogen precursor. The lateral growth only occurs from the sidewalls of the
etched mesa stripes without any dielectric masks. The lateral growth rate toward the direction is extremely high, as high as 10 μm/h, while no vertical growth is observed on the top of unmasked mesa. The cross-sectional transmission electron microscopic
image shows that the threading dislocations in the wing region extend only toward the lateral direction. Note that almost smooth coalescence between the wing regions is confirmed by atomic force microscopy. X-ray diffraction
measurements reveal that this maskless LEG drastically improves the crystallographic twist down to 97 arc-s, which is as comparably
low as that of a free-standing GaN substrate. The presented maskless LEG is advantageous for optical device applications. 相似文献
8.
S.M. Bishop C.L. Reynolds Jr. Z. Liliental-Weber Y. Uprety J. Zhu D. Wang M. Park J.C. Molstad D.E. Barnhardt A. Shrivastava T.S. Sudarshan R.F. Davis 《Journal of Electronic Materials》2007,36(4):285-296
The polytype and surface and defect microstructure of epitaxial layers grown on 4H(), 4H(0001) on-axis, 4H(0001) 8° off-axis, and 6H(0001) on-axis substrates have been investigated. High-resolution x-ray diffraction
(XRD) revealed the epitaxial layers on 4H() and 4H(0001) 8° off-axis to have the 4H-SiC (silicon carbide) polytype, while the 3C-SiC polytype was identified for epitaxial
layers on 4H(0001) and 6H(0001) on-axis substrates. Cathodoluminescence (CL), Raman spectroscopy, and transmission electron
microscopy (TEM) confirmed these results. The epitaxial surface of 4H() films was specular with a roughness of 0.16-nm root-mean-square (RMS), in contrast to the surfaces of the other epitaxial
layer-substrate orientations, which contained curvilinear boundaries, growth pits (∼3 × 104 cm−2), triangular defects >100 μm, and significant step bunching. Molten KOH etching revealed large defect densities within 4H() films that decreased with film thickness to ∼106 cm−2 at 2.5 μm, while cross-sectional TEM studies showed areas free of defects and an indistinguishable film-substrate interface for 4H() epitaxial layers. 相似文献
9.
Organometallic vapor phase epitaxial growth of GaAs on 320 nm high mesas was used to study the dependence of lateral growth
upon the substrate misorientation from (100) and the mesa wall orientation on the substrate. GaAs (100) substrates were misoriented
by 3° toward eight major crystallographic directions, consisting of the four nearest [111] and [110] directions. The mesa
sidewalls were oriented either parallel to the 〈011〉 and 〈01
〉 directions or rotated by 45° to be parallel to the 〈001〉 and 〈010〉 directions. GaAs films were grown with TMGa and TBA at
T=575°C. The lateral growth rates were up to 25 times higher than the vertical growth rate of 1.3 μm/hour. Optical microscopy
and atomic force microscopy (AFM) showed that under the given growth conditions lateral growth off mesa sidewalls is most
rapid in the 〈011〉 and/or 〈0
〉 directions and less in the perpendicular 〈01
〉 and 〈0
1〉 directions (lateral growth anisotropy). By raising the temperature to 625°C lateral growth in the 〈01
〉 -〈0
1〉 directions increased while it remained almost constant in the 〈011〉 -〈0
〉 directions. Published results show that the partial pressure of As also affects lateral growth. Differences in the lateral
growth rates in the 〈011〉 and its opposite 〈0
〉 directions result from substrate misorientation but not from the orientation of the mesa walls on the substrate. Anisotropic
lateral growth rates in different crystallographic directions appear to be caused by both, (1) 1-dimensional Ga diffusion
defined by surface reconstruction, and (2) a relatively low energy barrier to atoms flowing over high-to-low terrace steps.
A lateral growth model is proposed that describes anisotropic lateral growth at mesa sidewalls in terms of growth conditions
and substrate misorientations. The model also explains the difference in the preferential lateral growth directions between
MBE and OMVPE. 相似文献
10.
Lawrence H. Friedman 《Journal of Electronic Materials》2007,36(12):1546-1554
Heteroepitaxial self-assembled quantum dots (SAQDs) will allow breakthroughs in electronics and optoelectronics. SAQDs are
a result of Stranski–Krastanow growth, whereby a growing planar film becomes unstable after an initial wetting layer is formed.
Common systems are and For applications, SAQD arrays need to be ordered. The roles of crystal anisotropy, random initial conditions and thermal
fluctuations in influencing SAQD order during early stages of SAQD formation are studied through a simple stochastic model
of surface diffusion. Surface diffusion is analyzed through a linear and perturbatively non-linear analysis. The role of crystal
anisotropy in enhancing SAQD order is elucidated. It is also found that SAQD order is enhanced when the deposited film is
allowed to evolve at heights near the critical wetting surface height that marks the onset of non-planar film growth. 相似文献
11.
Ohmic contacts to n-type 4H- and 6H-SiC without postdeposition annealing were achieved using an interlayer of epitaxial InN beneath a layer of
Ti. The InN films were grown by reactive dc magnetron sputtering at 450°C, whereas the Ti films were deposited by electron-beam
evaporation at room temperature. The InN films were characterized by x-ray diffraction (XRD), secondary electron microscopy
(SEM), cross-sectional transmission electron microscopy (TEM), and Hall-effect measurements. Both XRD and TEM observations
revealed that the Ti and InN films have epitaxial relationships with the 6H-SiC substrate as follows: (0001)[]Ti∥(0001)[]InN∥(0001)[]6H-SiC. The Ti/InN/SiC contacts displayed ohmic behavior, whereas Ti/SiC contacts (without an InN interlayer) were nonohmic. These
results suggest that InN reduces the Schottky barrier height at the SiC surface via a small conduction-band offset and support previous reports of an electron accumulation layer at the surface of InN. 相似文献
12.
Tsuyoshi Kajitani Kunio Yubuta Xiangyang Huang Yuzuru Miyazaki 《Journal of Electronic Materials》2009,38(7):1462-1467
Single-crystal x-ray diffraction and high-resolution electron microscopy studies were carried out for Co-121 ([Ca2CoO3]
p
CoO2) and Sr-doped Co-121 grown in a KCl flux at 810°C. Typically, the samples were 2 mm × 2 mm × 0.02 mm in size. The single-crystal
diffraction intensities were measured by the use of a four-circle diffractometer. Twinned super reflections, e.g., and were observed in the electron diffraction patterns. These super reflections were not observed in the end-member. Diffuse
scattering was observed in the same reciprocal space by the single-crystal x-ray diffraction study. A discommensurate crystal
model is proposed for the Sr-doped system. 相似文献
13.
Kenji Monden 《Journal of Electronic Materials》2007,36(12):1691-1696
The creep properties of tin-based, lead-free solders, Sn-3.0Ag-0.5Cu and Sn-7.5Zn-3.0Bi, were investigated for the temperature
range from 298 K to 398 K. The creep rupture time decreases with increasing initial stress and temperature. The Omega method
is applied to the analysis of the solder creep curves. The creep rate is expressed by the following formula: , where and Ω are experimentally determined. The parameter , the imaginary initial strain rate, increases with increasing initial stress and temperature. The parameter Ω is temperature dependent, but less dependent on the initial stress. The apparent activation energy for is 108 kJ/mol in Sn-3.0Ag-0.5Cu and 83 kJ/mol in Sn-7.5Zn-3.0Bi. These values are close to the activation energy for the
lattice diffusion of tin. The creep rupture time is calculated using the parameters and Ω. The calculated creep rupture time is in good agreement with the measured creep rupture time. 相似文献
14.
We present evidence that it is the presence or absence of atomic terraces with a specific crystallographic orientation on
the (102) Al2O3 surface that promotes growth of single-crystal (001) CeO2 films over polycrystalline (111) CeO2 films. The CeO2 film nucleates so that the [010] and [100] directions of the film align parallel and perpendicular to the terrace edges.
In the absence of terraces, multidomain (111) CeO2 films result in which the in-plane orientation of the two domains are rotated by 85.71°, so that a [110] CeO2 direction aligns parallel to either the or Al2O3 direction. 相似文献
15.
Giacomo Badano Xavier Baudry Philippe Ballet Philippe Duvaut Alain Million Eric Micoud Sabeur Kaismoune Paul Fougères Sophie Mibord Pierre Tran-Van Arnaud Etcheberry 《Journal of Electronic Materials》2008,37(9):1369-1375
We characterize the surface of molecular-beam epitaxy (MBE)-grown CdTe(211)B/Ge(211) by atomic-force microscopy (AFM), optical interference microscopy, and generalized ellipsometry (GE). We find that, for substrate temperatures above 300°C, the surface is rough and hazy; the AFM root-mean-square roughness is of the order of 150 Å. It appears from GE that the optical response is anisotropic, the principal axes of anisotropy being along the $ [\overline{1} 11] We characterize the surface of molecular-beam epitaxy (MBE)-grown CdTe(211)B/Ge(211) by atomic-force microscopy (AFM), optical
interference microscopy, and generalized ellipsometry (GE). We find that, for substrate temperatures above 300°C, the surface
is rough and hazy; the AFM root-mean-square roughness is of the order of 150 ?. It appears from GE that the optical response
is anisotropic, the principal axes of anisotropy being along the and directions. For a substrate temperature of approximately 300°C, the surface is smooth and mirror-like and the AFM roughness
is as low as 45 ?. The sample is still anisotropic, even though the magnitude of the cross-polarized reflection coefficients
are very small in this case. It appears that the anisotropy originates from the surface roughness, not the bulk. 相似文献
16.
17.
J. N. Dai Z. H. Wu C. H. Yu Q. Zhang Y. Q. Sun Y. K. Xiong X. Y. Han L. Z. Tong Q. H. He F. A. Ponce C. Q. Chen 《Journal of Electronic Materials》2009,38(9):1938-1943
In this work, we have comparatively investigated the effects of the GaN, AlGaN, and AlN low-temperature buffer layers (BL)
on the crystal quality of a-plane GaN thin films grown on r-plane sapphire substrates. Scanning electron microscopy images of the a-plane GaN epilayers show that using an AlGaN BL can significantly reduce the density of surface pits. The full-width at half-maximum
values of the x-ray rocking curve (XRC) are 0.19°, 0.36°, and 0.48° for the films grown using Al0.15Ga0.85N, GaN, and AlN BLs, respectively, indicating that an AlGaN BL can effectively reduce the mosaicity of the films. Room-temperature
photoluminescence shows that the AlGaN BL results in lower impurity incorporation in the subsequent a-plane GaN films, as compared with the case of GaN and AlN BLs. The higher crystal quality of a-plane GaN films produced by the Al0.15Ga0.85N BL could be due to improvement of BL quality by reducing the lattice mismatch between the BL and r-sapphire substrates, while still keeping the lattice mismatch between the BL and epitaxial a-plane GaN films relatively small. 相似文献
18.
The ultraviolet (UV) photoelectric characteristics of transitional metal (Cu) doped ZnO nanowires produced by the self-catalytic
vapor–liquid–solid (VLS) method were investigated by performing a series of photoconduction and time-resolved measurements.
The photocurrent voltage characteristics obtained on the nanowires configured as two-terminal metal–semiconductor–metal photodetectors
exhibited a nonmonotonic behavior attributed to the interplay of several limiting mechanisms: Schottky contacts and trapping/detrapping
effects that take place at low and intermediate (pre-avalanche) bias regimes, respectively. In the intermediate biases, the
photocurrent was power-law dependent, i.e., changed with voltage as
and for excitation wavelengths of 365 nm, 302 nm, and 254 nm, respectively. The dependence of the exponent on the wavelength
of the light is analyzed and explained based on the detailed consideration of the contribution of different deep-defect Cu
levels formed within the band gap of ZnO. The study will be important to those working in the area of ZnO-based nanophotodetectors,
optical switches, and sensors. 相似文献
19.
Joseph A. Ball Vladimir Bolotnikov Quanlei Fang 《Multidimensional Systems and Signal Processing》2007,18(4):191-248
It is well known that subspaces of the Hardy space over the unit disk which are invariant under the backward shift occur as
the image of an observability operator associated with a discrete-time linear system with stable state-dynamics, as well as
the functional-model space for a Hilbert space contraction operator. We discuss two multivariable extensions of this structure,
where the classical Hardy space is replaced by (1) the Fock space of formal power series in a collection of d noncommuting indeterminates with norm-square-summable vector coefficients, and (2) the reproducing kernel Hilbert space (often
now called the Arveson space) over the unit ball in with reproducing kernel ). In the first case, the associated linear system is of noncommutative Fornasini–Marchesini type with evolution along a free
semigroup with d generators, while in the second case the linear system is a standard (commutative) Fornasini–Marchesini-type system with
evolution along the integer lattice . An abelianization map (or symmetrization of the Fock space) links the first case with the second. The second case has special
features depending on whether the operator-tuple defining the state dynamics is commutative or not. The paper focuses on multidimensional
state-output linear systems and the associated observability operators; followup papers Ball, Bollotnikov, and Fang (2007a,
2007b) use the results here to extend the analysis to represent observability-operator ranges as reproducing kernel Hilbert
spaces with reproducing kernels constructed from the transfer function of a conservative multidimensional (noncommutative
or commutative) input-state-output linear system.
相似文献