We have carried out RHEED measurements and Monte Carlo simulations of the growth on GaAs(001), AlAs(001) grown on GaAs(001), and InAs(001) to address the common features of the growth near the transition to step flow. For a fixed V/IIl ratio, the cation flux and misorientation-angle dependencies of the transition temperature on AlAs(001) and InAs(001) follow the same pattern as on GaAs(001). The same anisotropic behavior was also obtained, in that the transition temperature on a surface misoriented toward [110] is higher than that on a surface misoriented toward [110]. Unlike the case of GaAs(001), however, the surface reconstruction could not be kept constant near the growth mode transition for AlAs(001) and InAs(001). Therefore, we cannot compare simulations with experiments in as much detail as we have done for GaAs(001). Nevertheless, we can still estimate the effective surface migration barrier for Al adatoms on AlAs(001) as approximately 1.74eV and for In adatoms on InAs(001) as at most 1.23eV. This value should be compared with the value of 1.58eV obtained for GaAs(001).

High temperature (≥ 650°C) MBE growth of AlAs and AlAs/GaAs superlattices on (100) GaAs is shown to lead to quasi-periodic facetting. We demonstrate that the facetting is only due to the AlAs layers, and growth of GaAs on top of the facets replanarizes the surface. We show that the roughness between the AlAs and GaAs layers increases with increasing number of periods in the superlattice. The roughness increases to form distinct facets, which rapidly grow at the expense of the (100) surface. Within a few periods of the initial facet formation, the (100) surface has disappeared and only the facet planes are visible in cross-sectional transmission electron micrographs. At this point, the reflection high-energy electron diffraction pattern is spotty, and the specular spot is a distinct chevron. We also show that the facetting becomes more pronounced as the substrate temperature is increased from 620°C to 710°C. Atomic force micrographs show that the valleys enclosed by the facets can be several microns long, but they may also be only several nanometers long, depending on the growth conditions.

Step bunching during epitaxial growth results in the transformation of a vicinal surface into a periodic array of micro-facets. Molecular beam epitaxial growth on the vicinal GaAs (110) surface exhibits this phenomenon which has primarily been characterized by electron microscopy. GaAs quantum wells with AlAs barriers were grown on GaAs(110) substrates vicinal 0.5-2· towards [010]. The faceting on the vicinal surface creates two distinct quantum well thicknesses. While most of the quantum well is 96Å thick, it broadens at the faceted regions. This thickness modulation produces two distinct luminescence peaks. By using temperature dependent photoluminescence, we have observed trends in exciton mobility. The exciton mobility decreases at low temperatures for the 1.0° and 2.0° samples, indicating a scattering mechanism. We will discuss interface roughness and other sources of scattering.

Epitaxial growth of Cu thin films on atomically cleaned (111)Si has been studied by transmission electron microscopy (TEM), x-ray diffractometry (XRD) and Auger electron spectroscopy (AES). An interface compound, CuSix with x= 11.2 to 14 at.%, was observed to be present at the Cu/Si interface. Interfacial dislocations at the silicide/Si interface were identified to be of edge type with 1/2<110> Burgers vectors. η“-Cu3Si was found to form in samples annealed at 200 °C for 1 h. Solid phase epitaxial growth of silicon on (111)Si was observed to occur at a temperature as low as 200 °C. Polycrystalline η”-Cu3Si is the only phase present in samples annealed at 200–800 °C. In samples annealed at or higher than 850 °c, a mixture of η′-Cu3Si and η“-Cu3Si were found to be present.

The heteropitaxial growth of (111) Pt on (0001) sapphire and of (0001) Co on (111) Pt on (0001) sapphire has been observed in-situ using grazing incidence x-ray scattering (GIXS). The in-plane lattice parameters of the Pt and Co phases have been measured as a function of film thickness in the regime from two monolayers to 200 monolayers, Relaxation of elastic strain with thickness has been quantified. X-ray reflections consistent with stacking faults in the Co films have been observed and monitored as a function of thickness, giving a measure of the stacking fault density. A distinct Co phase was observed at two monolayers of Co on a thick Pt layer, indicating an incoherent interface between the Co and Pt, even at this very early stage of deposition.

The atomic structure of the α-A12O3 (0001)(√31×√31)R±9° reconstruction has been solved by Grazing Incidence X-ray Diffraction. The surface structure is found to be perfectly commensurable with the underlying bulk lattice, with exponential correlation length ∼500 Å. It consists of hexagonal zones of two nearly perfect closed-packed Al(111) planes, separated by a defect of hexagonal periodicity with parameter 26.5 Å. This structure may explain why the reconstruction can be obtained at lower temperature by deposition of a few aluminum layers, and why Al/Al2O3 multilayers remain coherent, with aluminum of (111) orientation.

Thin epitaxial films of β-SiC were grown on (100), (111) and (112) TiC substrates and the interfaces were characterized by HREM. The (111) interface was abrupt and atomically flat, while the (112) interface was composed of {111} facets and steps. The (100) orientation did not result in epitaxial growth of SiC, a phenomenon attributed to the poor match of atomic positions in SiC and TiC on the (100) plane, although the lattice parameters are relatively close. A model for the atomic structure of the stable (111) interface is proposed based on comparison with HREM images of the interfaces.

Epitaxially grown CeO2 layers on (100)Si substrates are studied using the RBS/channeling technique. The crystallographic correlation between the overgrown layers and off-oriented Si substrates is precisely analyzed by means of constructing stereographic projections obtained from the planar channeling dips. From the stereographic projections for the CeO2 layer on the 4° off-oriented Si substrate, it is clearly seen not only that the epitaxial (110)CeO2 layer is single crystal with the direction defined as [001]CeO2 ║ [011]Si, but also that the crystalline quality of (110)CeO2 on (100)Si can be improved by use of the off-oriented substrate. The inclined epitaxial direction is also detected as the depth information.

We present new methods to directly syntesize III-V semiconductor quantum-wire and dot structures based on the evolution of well ordered surface corrugations on non-(100)- oriented substrates and on the controlled step bunching during MBE growth. The distinct electronic properties of these novel structures highlight their potential for fundamental research and advanced device concepts.

For the epitaxial growth of bcc(110) metals on bcc(110) metal substrates, there is a general tendency for roughening by formation of quasi-periodic ridges along [001], with up-and-down staircases in the [110] direction. It can be detected by high angular resolution Spot Profile Analysis (SPA)-LEED, as has been done previously by Hahn et al. for the case of W(110) on W(110). We found this kinetic facetting for Fe(110) on Fe(110), where it can be described by the model of layer restricted diffusion (LRD) epitaxy. We observed the same phenomenon for Fe(110) on W(110), Fe(110) on Cr(110), Cr(110) on W(110) and Cr(110) on Fe(110). In this paper, we present data for Fe(110) on Cr(110). The change between sharp single spots for in-phase energies to double spots for out-of-phase energies documents the staircase facet structure; it can be used to measure a vertical strain in the films.

Molecular beam epitaxial growth on GaAs(110) vicinal surfaces results in the formation of periodic micro-facets. We compare experimental results with computer simulations of a simple one dimensional step-flow growth model. The simulations show that preferential adatom attachment to the down step in a step array results in the destruction of step uniformity. A kinetic limitation due to adatom diffusion length along the terraces leads to stabilization of a periodic array of step-bunches. We extend our simulations to show the effects of the attachment and diffusion parameters on the dynamics of facet evolution.

Dislocations in GaAs are analysed by X-ray topography in order to relate their nature to their efficiency in generating growth steps. The analysis is mainly based on comparing double crystal back reflection images of the defects to calculated misorientations of the crystal surface which are caused at the outcrop. All types of dislocations are equally effective provided their Burgers vector has a component normal to the growth interface. Concentric growth step patterns, which develop in varying numbers on different samples are not caused by substrate dislocations.

Migration enhanced epitaxy (MEE) of GaAs on (001) GaAs substrates was studied by reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). In MEE, Ga and As species are alternately deposited on the growing surface. Ga adatom migration can be enhanced by the low arsenic pressure environment. The STM study was performed ex-situ by the arsenic capping and decapping procedure. We have demonstrated the correlation between the peak RHEED specular intensity during MEE growth and the variation of the lateral step density on the surface, even though the surface stoichiometry changes repetitively during MEE. The peak RHEED intensity during MEE is inversely dependent on the surface step density. The MEE surface exhibited a lower step density than the MBE surface, as shown by both RHEED and STM. However, the MEE surface still exhibited a much higher step density than a well-annealed surface. Consequently we believe that to achieve an atomically flat interface, annealing at high temperature in an arsenic flux is still necessary even if MEE is employed.