The heteroepitaxial growth of gallium phosphide on silicon (GaP/Si) is a useful step towards integration of III-V based devices onto silicon. GaP layers grown on silicon substrates of different orientations using metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were characterized using transmission electron microscopy (TEM) with an attempt to understand the epilayer growth characteristics. Despite the fact that the GaP/Si system has a low misfit (≈0.4 %), a high density of crystal stacking defects was commonly observed. Inversion domain boundaries (IDBs) were another common defect observed in regions where the fault density was reduced.

High-resolution cross-sectional and conventional plan-view transmission electron microscope observations have been carried out for molecular beam epitaxially grown GaAs films on vicinal Si (001) as a function of film thicknesses and observation directions between two orthogonal <110> directions before and after annealing. Two groups of misfit dislocations are characterized by analyzing whether their extra half planes exist in the film and the substrate side. The group I misfit dislocations due to a stress caused by a lattice misfit between GaAs and Si consist of partial and, 60° and 90° complete dislocations in an as-grown state. After annealing partial dislocations almost disappear and 90° perfect dislocations are predominantly observed. The group II misfit dislocations due to a thermal-expansion misfit-induced stress are all of the 60° type complete dislocations, independent of film thickness and annealing.

High-resolution transmission electron microscopy has been used to study formation of interfacial defects related to misfit strain accommodation in Ge/Si heterostructures (mismatch 4%) grown in the two-dimensional mode. Special emphasis is placed on the conditions leading to a two-dimensional (layer-by-layer) growth mode. We discuss general features of a dislocation tangle resulted from glide-limited plastic relaxation, typical for highly mismatched (001)-diamond and zinc-blende heterostructures. The evolution of the dislocation network as a function of film thickness and thermal annealing is controlled by growth instabilities and dislocation interactions. The observed correlation in distribution of parallel misfit dislocations including pairing (at <2 nm) of misfit segments from intersecting glide planes and rearrangements in a nonequilibrium dislocation network driven by elastic interaction between 60° dislocation segments in the almost relaxed heterostructures are discussed in detail. Pairing of the 60° glide dislocations results either in their combination to form pure edge 90° dislocations or in the dissociation into partials. We propose and experimentally verify a model for the latter process involving the formation of extrinsic stacking faults in the heterolayers under compressive strain.

We have investigated anisotropic lattice relaxation and its mechanism of ZnSe epitaxial layer grown on (001) GaAs substrate by MBE. Double-crystal X-ray rocking curves for (004), {115} and {404} reflections were measured as a function of the azimuthal rotation angle of the sample. We observed the sinusoidal oscillation of the FWHM of the epilayer peak for (004) reflections due to the asymmetric dislocation density along two orthogonal <110> directions, and the direction of the maximum FWHM corresponding to high dislocation density is along [110]. In addition, the strain along [110] is smaller than that along [1-10], indicating that the layer suffered anisotropic lattice relaxation. The direction of larger relaxation([l-10]) is not consistent with that of high dislocation density([110]). The results suggest that the asymmetry in dislocation density is not responsible for the anisotropic relaxation of the ZnSe epilayer.

Metastable SiGe films were grown by MBE on Si (001) substrates and annealed to promote varying degrees of partial relaxation. X-ray diffraction reciprocal-space analysis was then used to monitor the structural evolution of the displacement fields of the dislocation array with increasing misfit density. The diffuse-x-ray-scattering patterns of the dislocated heterolayers were compared with lineal-misfit densities determined by defect etching, leading us to develop a geometric model which provides a framework for understanding the early-stage evolution of the displacement fields of the dislocation array, and which also explicitly links diffuse x-ray intensity to misfit density. At low misfit density, the diffuse intensity arises from two-dimensional displacement fields associated with single-nonoverlapping dislocations. As misfit density increases, the displacement fields of individual dislocations increasingly overlap producing three-dimensional displacements. The evolving diffuse intensity reflects the transition from 2-D to 3-D displacement fields. Finally, it is demonstrated that the diffuse x-ray intensity of the strained epilayer can be used to accurately measure lineal misfit-dislocation densities from 400 to 20,000 lines/cm.

Samples of Si1-x-YGexCy were analyzed with a triple axis high resolution x-ray diffractometer to produce reciprocal space maps. Films with compositions of approximately Si0.77Ge0.20C0.01 vvith thicknesses ranging from 120 nm to 750 nm were found to be pseudomorphic with a tetragonal distortion, εT, near 1%. The tetragonal distortion in pseudomorphic samples with compositions near Si0.47Ge0.50C0.03 with thicknesses ranging from 61 nm to 115 nm was found to be near 2%. The strain increased linearly with Ge concentration even though the Ge:C ratio remained nearly constant. The strain in samples with similar compositions was not a function of thickness. These strain measurements correlated well with results from ion channeling analysis.

Using Transmission Electron Microscopy, we examine the defect structure of Cu-rich and In-rich CuInSe2 films grown by Molecular Beam Epitaxy on GaAs (100) substrates. A surprisingly high density of cation sublattice stacking faults on (001) planes are observed in the Cu-rich films. Because these stacking faults are extremely flat and extend thousands of Ångstroms over the surface, and because they are not observed in other, non-Cu-rich films, we argue that they are a consequence of a surface structural change during growth, induced by the excess Cu. Two other types of defects are also observed: near the CuInSe2/GaAs interface, there is a high concentration of dislocations, stacking faults and domain boundaries. In the In-rich films, stacking faults and twin-type defects on {112} planes extend throughout the thickness of the grown film.

In this paper we report on the morphology of InSb layers grown by atomic layer molecular beam epitaxy (ALMBE) onto InP substrates at low temperatures (330<T<400°C), comparing the nature and densities of defects with those found in ALMBE InSb films grown over InSb/InP buffer layers grown by molecular beam epitaxy (MBE). The main types of defects for ALMBE direct layers are threading dislocations and stacking faults with similar defect densities along both á110ñ directions. The inclusion of the intermediate InSb/InP MBE grown buffer layers leads to lower threading dislocation densities but higher and anisotropic stacking fault distribution. Moreover, different types of three-dimensional defects appear, which are associated with pyramidal or truncated pyramidal hillocks on the surface. These defects, consisting in twins associations are originated at the InSb/InP MBE interface and they are induced by an anomalous growth of InSb layers. In all the cases, the strain caused by the large lattice mismatch is accommodated by means of a pure edge-type misfit dislocation network placed at the interface.

X-ray diffraction spectra of CdTe epilayers grown with and without ZnTe buffer layers on <211> Si substrates by molecular beam epitaxy consist of 422 and 331 reflections. We interpret these as evidence for the existence of twins within the volume of a <211> oriented epilayer and show that twin volume is dependent on the ZnTe buffer layer and substrate misorientation.

Structure of stacking faults in a ZnSe epitaxial layer grown on a GaAs(001) buffer layer was determined with transmission electron microscopy. Two stacking faults were formed in pairs on (111) and (111) planes with the same polarity and met at a point which is a few atomic layers away from the interface between ZnSe and GaAs. Partial dislocations were found to be the Shockley type ones with a Burgers vector of 1/6<211>. Atomic force microscopy showed that hillocks were formed in pairs at a surface where the pair of stacking faults existed in the layer. Moreover, it was observed that the pair of stacking faults elongated along the <110> direction by gliding on the {111} faulted planes under annealing at 200°C for 30min. Formation mechanisms of the pair of stacking faults have been discussed.

An in-situ annealing process, which is conducted in the growth chamber by exposing the film to a Se beam immediately after film deposition, is developed to control defect structures in CuGaSe2 epitaxial films. TEM observations showed that the films annealed at a temperature above 450°C could completely remove anti-phase domain boundaries and effectively annihilate threading dislocations. The annealing process also changes the distributions of intrinsic point defects in the film. Photoluminescence (PL) may reflect the microstructure improvement in the films. A suppress of the donor-to-acceptor transitions caused by antisite defects and an enhancement in the PL intensity were found in a annealed film.

We have calculated the effective cluster interactions (ECI) which govern the ordering of Ir adatoms on the Ir(111) surface. The computations are based on a tight-binding Hamiltonian in which no adjustable or experimentally determined parameters were introduced. Both atoms adsorbed in ‘bulk’ sites (i.e. continuing the fee lattice) and those in ‘surface’ sites (i.e. producing hep stacking) are considered. We use this formalism to determine the relative stability of various adsorption sites and cluster shapes at zero temperature. The overall trends are in excellent agreement with the experimental results found by Ehrlich and co-workers. Next, we employ these ECI in Monte Carlo simulations of the kinetics of domain growth and evolution. Specifically we analyze the effect of diffusion barriers and the competition between the ordering tendencies of the system and entropic effects. Typical ‘snapshots’ in a range of temperatures and coverages are discussed.

Atomistic computer simulations and anisotropic elastic theory are employed to determine the elastic fields of surface steps and vicinal surfaces. The displacement field of and interaction energies between <100> steps on an {001} Ni surface are determined using atomistic simulations and EAM potentials. The step-step interaction energy found from the simulations is consistent with a surface line force dipole elastic model of a step. We derive an anisotropic form for the elastic field associated with a surface line force dipole using a two dimensional surface Green tensor for a cubic elastic half-space. Both the displacement fields and step-step interaction energy predicted by the theory are shown to be in excellent agreement with the simulations.

We have investigated Si (100) homoepitaxy in variety of different temperature regimes. In the high temperature step flow regime, the growth properties of the different steps play an important role. The binding sites and diffusion barriers for a Si adatom moving over the buckled Si(100) surface and single-height steps were investigated with the ab initio Car-Parrinello scheme. The SA step edge was found to be a relatively poor sink for adatoms. By contrast, growth takes place much more rapidly at the SB step edges, so that one can understand the relatively fast growth observed at the ends of dimer rows. We have also investigated Si(100) homoepitaxy with classical molecular dynamics simulations at very low temperatures, where typically an amorphous deposit forms. By tuning the energy of the incoming atomic beams, one can lower the temperature of the amorphous to crystalline transition considerably and thereby enhance epitaxial growth.

Competing desorption during the epitaxial growth of Cu on the W(110) surface has been studied with low energy electron microscopy (LEEM). Direct imaging of a structural transformation from pseudomorphic (1×1) to relaxed (15×1) periodicity which occurs at a coverage of θCu = 2.13 monolayers is used as a very accurate, local probe of coverage during deposition. The desorption energy E = 3.67 eV and attempt frequency v = 2.15 × 1015 s−1 are determined by examining the balance condition when the incident and desorption fluxes are equal. A step-flow-like growth morphology occurs when the supersaturation is significantly reduced by competing desorption. An island nucleation and coalescence growth morphology results at higher supersaturation.

Results from X-ray diffraction studies of the morphology of the growing Si(001 )/SiO2 interface are presented. We show the evolution of the root mean square roughness as a function of the growth variables, and we try to go beyond the root mean square parametrization of the interface by measuring the spectral distribution of interface fluctuations. Within our current experimental sensitivies we cannot resolve any fluctuations with a finite in-plane momentum transfer.

Success in incorporating single crystal, epitaxial metal layers into semiconductors will have a significant impact on electronic and optical devices. The growth of GaAs on (001) pseudomorphic NiAl/GaAs by molecular beam epitaxy has been studied using transmission electron microscopy. The island growth of GaAs on pseudomorphic (lattice matched) NiAl is the origin of the formation of stacking faults and microtwins in the GaAs overlayer. The GaAs islands are considered to be due to heterogeneous nucleation, which occurs more easily at the corner of a step on a strained metal film. Growth of almost twin free In0.25Al0.75As on thick, lattice relaxed, epitaxial NiAl films has been achieved, which supplying useful information for the investigation of the possible factors causing poor quality of GaAs overlayers.

Molecular beam epitaxy was used to grow EuTe(x)/PbTe(y) short period superlattices with x=1-4 EuTe(111) monolayers alternating with y≈3x PbTe monolayers. The superlattices were characterized by transmission electron microscopy and high resolution x-ray diffraction. Regions with double periodicity were observed coexisting with areas of nominal periodicity. The sample with x=3.5 and y=9, for example, contains regions with double periodicity of x=7 and y=17. X-ray diffraction measurements confirm the formation of the double periodicity in these samples by the appearance of weak satellites in between the satellites of the nominal periodicity. The double periodicity in the superlattice is believed to result from interdiffusion during the growth. A model for this process is presented.

A series of CuInSe2 thin films of varying thicknesses were grown on both GaAs(001) substrates and nominally lattice-matched In0.29Ga0.71As (001) linearly graded buffers by MBE at 450°C. Transmission electron microscopy and high resolution x-ray diffraction measurements revealed the presence of a second phase with chalcopyrite symmetry strained to the CuInSe2 thin film in-plane lattice constant for CuInSe2 films grown on GaAs substrates. Further examination confirmed that the second phase possessed chalcopyrite symmetry. No second phase was observed in films grown on nearly lattice-matched In0.29Ga0.71As (001) linearly graded buffers. Secondary ion mass spectrometry confirmed the presence of interdiffusion from of Ga from the substrate into the CuInSe2layer. It is speculated that this diffusion is related to the state of stress due to heteroepitaxial misfit.