Self-organized hexagonally ordered quantum dot patterns are produced on GaSh (100) and InSb (100) surfaces by low energy Ar+-ion sputtering at normal angle of incidence. The QDs are crystalline, exhibiting narrow size distributions with diameters from 17–80 nm depending on sputter conditions, densely packed with densities as high as 2 × 1011 cm−2. The origin of the QD formation is attributed to the interplay of two surface processes during ion bombardment: ion induced surface roughening, provoked by the curvature dependent sputter yield and balanced by surface diffusive processes. The observed QD patterns obtained at different sputter conditions show that the formation mechanism can be described by the Kuramoto-Sivashinsky equation. The dominant diffusive process emerges to be effective ion induced without any mass transport on the surface, inherent to the sputtering process.

We discuss a recent investigation of adatom behavior on the AlSb(001) surface using first-principles electronic structure methods based on the density functional theory. For Al and Sb adatoms, we find a number of novel adatom structures that differ dramatically from previous results for the superficially similar group-III arsenides. In particular, we conclude that it is energetically favorable for an Al adatom to incorporate substitutionally into the outermost layer of the AlSb surface. This observation helps motivate a proposed new reconstruction for the AlSb(001) surface. Finally, we argue that the unusual adatom behavior identified for this surface probably results from the presence of a dimer row composed of a double layer of group-V atoms in the reconstruction, and therefore, it should be generic to all of the antimonides, as well as, the c(4 × 4) reconstruction of the arsenides and phosphides.

Metal-based silicides on silicon substrates are a widely used material system for infrared detection. PtSi/p-Si infrared Schottky barrier detectors (IRSBD) have become one of the most successful photoemisive infrared detectors. Till now, most of the efforts have been focused on the design of two dimensional PtSi-SBD arrays for the infrared (IR) camera. In this paper, we discussed the formation conditions of PtSi. Qualities are compared for PtSi films prepared at different conditions including different annealing sequences, annealing time, film thickness, and annealing ambient using pulsed laser deposition on various temperature substrates. Film structures and compositions, phase's formation using different processes are analyzed. By studying the kinetics of PtSi formation during various annealing processing, preferable preparing conditions are proposed to form the continuous PtSi ultra-thin film on Si substrate by PLD.

Three-dimensional islands of InP have been reproducibly grown in the Stranski-Krastanow growth mode on Si (001) and (111) by using metal-organic vapor phase epitaxy in order to obtain nanometer-scale quantum dots. Atomic-force microscopy was used to determine the morphology of the samples and to evaluate the dimensions of the islands. Formation of three-dimensional islands with densities as high as 2.5×1010 cm−2 and small sizes have been observed. The evolution of island morphology is explained in terms of strain-relaxing mechanisms at the first stages of InP/Si heteroepitaxy.

Thermal stability has been evaluated for ALE-grown Si/Ge interfaces by co-axial impact collision ion scattering spectroscopy. The IML-thick Si layer on Ge was stable only at less than 360°C. The 2ML-thick Si layer on Ge, however, was stable up to 550°C, and Si layers could be also ALE-grown successively on the 2ML-thick Si layer on Ge, while keeping the interface abrupt, since the Si-ALE growth temperature was about 530°C.

Strain and compositional modulation in AlxGa1−xAs layers grown by metalorganic vapour phase epitaxy (MOVPE) over a sinusoidally shaped GaAs (001) surface grating were studied by scanning electron microscopy (SEM), X-ray grazing-incidence diffraction (GID) and photoluminescence (PL). Two growth temperatures and two compositions were chosen to realize planar overlayers. By SEM a periodic reduction in Al-content was found at the valley positions of the GaAs grating. The appearance of such vertical quantum wells (VQWs) has been explained by the growth rate anisotropy between high-index and (001) planes and a curvature-induced capillarity flow of Ga. Estimated from PL energies a larger reduction of the Al-concentration in the VQW and also at the high-index sidewall facets was found than compared to predictions from the capillarity flow theory. Using depth-resolved GID we show that the formation of VQWs is accompanied by a periodic lateral strain field. Therefore we assume, that the formation of the VQWs is influenced by strain induced diffusion due to the interaction of opposite sidewall facets.

The influence of surface roughness on the initial V-grooved substrate on the interface uniformity of V-shaped AIGaAs/GaAs quantum wires (QWRs) is investigated by direct atomic force microscopy observation of V-groove surface. We found that roughness on the initial V-grooved substrate induced during V-groove preparation processes can severely affect the interface uniformity of QWRs grown on it. We also found that roughness on the initial substrate can be greatly reduced by a simple etching treatment using a NH4OH:H2O2:H2O=1:3:50 solution, and this resulted in significant improvement of QWR interface quality.

GaP islands grown on selected surfaces of Si and their coalescence behavior have been investigated by transmission electron microscopy. These layers were grown by chemical beam epitaxy. A number of significant observations emerge from this study. First, planar defect formation has been shown to be related to stacking errors on the smaller P-terminated {111} facets of GaP islands. Amongst the four orientations, (111) epilayers have a higher density of stacking faults and first order twins because of more P-terminated {111} facets per island. Second, multiple twinning on exposed {111} facets can produce tilt boundaries and irregular growths when islands coalesce. Third, inversion domain boundaries lying on {110} planes have been shown to form during GaP island coalescence across monatomic steps on (001) Si. Image simulations have been performed to show that these boundaries can be seen in high resolution lattice images and the observed contrast is attributed to the presence of wrong Ga-Ga and P-P bonds at the inversion boundary.

We have investigated the influence of MOVPE growth parameters on the surface morphology of InAs nanostructures grown on 0.2° misoriented (001)InP substrates. Thin layers of nominal thickness of about 3 and 6 ML were deposited at 500°C with V/Ill flux ratios ranging from 50 to 240. The samples were cool down from 500 to 350°C during 6 minutes under either arsine or phophine atmosphere. The influence of this step has been found to greatly determine the surface morphology of the nanostructures observed by atomic force microscopy. Dots self-aligned along the steps and forming a non continuous strip, regularly spaced every 3-4 terraces have been obtained. The morphology of the strips can be varied with the growth conditions (V/III flux ratio). In this work, we will propose a mechanism for the formation of the strips observed during the cooling under phosphine atmosphere taking into account an As » P exchange.

The growth of Si1−yCy on Si(001) and Si(118) surfaces is investigated experimentally and theoretically. A step instability is found on (118) surfaces leading to step bunching, under low C-concentrations. This behavior is explained by increased diffusivity of Si dimers in the vicinity of carbon. Self adjusting step bunches are found in kinetic Monte Carlo simulations with ordering of the carbon along nearly (001) planes. Experimental parameters (i.e., temperature, flux rate, and tilt angle of the substrate), which are controllable experimentally, can be used to adjust the length scale of the step bunching.

Both the wafer fusion and the heteroepitaxy technology were used successfully to obtain high quality GaAs layer on the InP substrate where the lattice mismatch was 3.7 %. The enhancement of the lateral growth rate was a crucial factor for the formation of high quality QWR in the patterned fusion layer. This technique can provide a way of overcoming the limitation of heteroepitaxy caused by misfit problems and its subsequent quality degradation. It is expected that the overgrowth technique on the patterned fusion layer can be applicable to the photonic device fabrication on the other substrate such as Si.

We consider several approaches to control morphology of self-organized quantum dot (QD) nanostructures. (i) We study effects of temperature and of temperature ramping on formation of QD arrays. The theory of equilibrium distribution of island volumes is developed predicting an entropy-driven decrease of island volume at higher temperatures. Experiments on InAs/GaAs(001) obtained both at submonolayer deposition and in Stranski-Krastanow (SK) growth mode reveal the decrease of island volume with temperature increase that agrees with the thermodynamic picture of island formation. (ii) We show a reversibility of temperature-driven changes in island volume, shape, and density for SK InAs/GaAs(001) islands and a new possibility to control QDs. (iii) We consider an advanced way of formation of complex QD structures. For multisheet arrays of strained islands a transition between correlation and anticorrelation driven by the spacer thickness is predicted theoretically and confirmed experimentally. (iv) The overgrowth of InAs/GaAs islands by an InGa(Al)As alloy leads to alloy phase separation in the capping layer and an effective increase of both the lateral size and the height of the QDs. These complex growth approaches enable us to tune efficiently electronic spectra of the QD systems.

This paper discusses structural and optical data taken on a series of MBE grown samples where n monolayers of CdSe (0.5< n < 2.6) was deposited on (and subsequently capped by) ZnSe. The cross-sectional scanning transmission electron microscopy (STEM) images observed on samples with lowest CdSe coverages reveal the co-existence of 2D ZnCdSe platelets and 3D islands, showing clearly that the platelets act as precursors for the formation of the 3D islands. The STEM data also present direct graphic evidence that interdiffusion plays an important role in the dynamics of CdSe quantum dot formation. The macro- and micro-photoluminescence results fully confirm the STEM data. For coverages below 1.5 monolayers, photoluminescence data show only the emission characteristic of 2D platelets, while for coverages between 1.5 and 1.9 monolayers simultaneous emissions from 2D and 3D islands are observed. The sample obtained by depositing the highest (2.6 monolayer) CdSe coverage shows only the emission characteristic of 3D islands.

We investigated the morphological evolution of InSb grown on InAs (001) substrates (lattice mismatch = 6.9%) as a function of film thickness. Due to the very large lattice mismatch, growth proceeded via the Volmer-Weber mode. The morphological evolution of highly strained InSb films proceeds through several regimes as a function of thickness. The films initially nucleate isolated 3D islands even in the earliest stages of growth. The islands then coarsen and coalesce at slightly higher thicknesses, with some evidence of cooperative nucleation, or the sequential nucleation of islands and pits. Once the islands coalesce, the morphology evolves into long ridges aligned along the [110], however, those films are still discontinuous. At a thickness =100nm, the films finally become completely continuous and 2D growth proceeds via step flow of growth spirals present on the surface.

Atomic force microscopy (AFM) reveals that InAs islands grown on InP (111)A, as they grow in size, undergo a shape transition. Below a critical size of around 30 nm, round-shaped quantum dots form, while above this size they grow in the shape of triangles, reflecting the symmetry of the (111) substrates. The edges of triangular islands are aligned along the three equivalent {110} directions of the InP (111) surface. The triangular islands grow laterally much faster than vertically, indicating the aspect ratio decrease of the islands with increasing InAs coverage. Our results provide a better understanding of the self-organization behaviors of InAs on InP (111)A.

The formation of carbon-induced Ge islands has been studied using low-pressure chemical vapour deposition (LPCVD) of Ge on Si(001) at temperatures between 600°C and 700°C. Propane (C3 H8 ) diluted in He was used as a carbon source. The experiments show that the influence of carbon was most significant for deposition at low growth temperature of the Ge island layer. Small-sized islands with a narrow size distribution could be achieved using a carbon adsorption layer. Compared to a sample grown without this layer, the size distribution was significantly smaller. An enhancement of the growth rate of Ge, as seen from Rutherford backscattering spectroscopy (RBS) will be discussed.

We have investigated the stability of ensembles of Ge/Si(100) islands by annealing at their growth temperature. Islands grown by molecular beam epitaxy at temperatures of 450, 550, 600 and 650°C were annealed for times between 5 and 120 minutes. Small, pure Ge hut clusters, bound by {105} facets appear to be extremely stable structures, surviving the longest anneals with no apparent coarsening. Dome clusters, however, coarsen. Large alloyed hut clusters, apparent in as-grown samples only for growth temperatures greater than 600°C, appear during annealing at 450 and 550°C. During anneals at 550 and 650°C, we observe novel coarsening behavior. Arrays of crystallographically oriented, alloyed hut clusters are formed which result from the dissolution of large, alloyed dome clusters.

SiGe island layers have been created by post growth anneal on supercritical layers grown at low temperatures (500°C) and high hydrogen pressures (40 Torr). The epitaxial growth has been performed in a commercially available single wafer RPCVD reactor using SiH2Cl2 and GeH4 as precursor gasses. SiGe layers grown under these conditions exceed the critical thickness for the onset of elastic relaxation reported for lower hydrogen pressures as well as the critical thickness for plastic relaxation by more than one order of magnitude. A subsequent anneal step is used to form the islands. This procedure allows some degree of control in the formation of SiGe islands. High island densities and uniform size distributions were achieved. Photoluminescence as well as electroluminescence measurements of these layers show strong emission from SiGe.

To fabricate nanometer-sized Ge dots on Si(100), we have investigated multi-step procedure, involving low temperature deposition of a Ge layer, a sub-monolayer C on a Ge wetting layer, a Ge top layer for three-dimensional (3D) dot formation and post-annealing. Effects of each procedure were discussed on the basis of an atomic force microscope study. 10nm-sized Ge dots with a high number density in the order of 1011 cm−2 were grown on the Si(100) substrate by combining each procedure and optimizing experimental conditions, such as deposition temperature, the C layer thickness and post-annealing temperature.

We have used in-situ scanning tunneling microscopy (STM) to study the formation and evolution of InAs islands on an InP (001) surface. The InAs islands are produced by (i) exchange of P-atoms with As-atoms or by (ii) direct deposition of In and As. In both cases InAs nanowires arem elongated along the [ī 10] direction with a length over 1 µm. We observe these nanowires to be stable under an arsenic environment while unstable with no arsenic flux, and eventually transform into a rectangular-based pyramid with a truncated top. These observations indicate that surface reconstruction can play a role in the selection of quantum wire or dot growth.