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The evolution of polytypism during GaAs nanowire growth was investigated by in situ X-ray diffraction. The growth of nanowires was found to start with the formation of zincblende structure, followed by the growth of wurtzite structure. The growth process was well reproduced by a simulation based on a layer-by-layer nucleation model. The good agreement between the measured and simulated results confirms that nucleation costs higher energy for the stackings changing the crystal structure than for those conserving the preceding structure. The transition in prevalent structure can be accounted for by the change of local growth conditions related to the shape of a triple phase line rather than by the change in supersaturation level, which quickly reaches steady state after starting growth.

This paper describes the development of a high-speed three-dimensional reciprocal-space mapping method designed for the real-time monitoring of the strain relaxation process during the growth of heterostructure semiconductors. Each three-dimensional map is obtained by combining a set of consecutive images, which are captured during the continuous rotation of the sample, and calculating the reciprocal-space coordinates from the detector coordinate system. To demonstrate the feasibility of this rapid mapping technique, the 022 asymmetric diffraction of an InGaAs/GaAs(001) thin film grown by molecular beam epitaxy was measured and the procedure for data calibration was examined. Subsequently, the proposed method was applied to real-time monitoring of the strain relaxation process during the growth of a thin-film heterostructure consisting of In0.07Ga0.93As and In0.18Ga0.82As layers consecutively deposited on GaAs(001). The time resolution of the measurement was 10 s. It was revealed that additional relaxation of the first In0.07Ga0.93As layer was induced by the growth of the second In0.18Ga0.82As layer within a short period of time corresponding to the deposition of only two monolayers of InGaAs.

The InSb(111)A surface is prepared by molecular beam epitaxy and investigated by reflection high-energy electron diffraction (RHEED). The complete two dimensional diffraction pattern is mapped out by azimuthal RHEED (ARHEED). Two reconstructions are identified and additionally a set of new symmetries is observed. At low temperature a 2 3 × 2 3 pattern is observed which changes to the (2 × 2) pattern at high temperature. In contrast to the GaSb(111)A surface the observed 2 3 × 2 3 structure is not stabilized by configurational entropy.

The molecular-beam epitaxial growth processes of GaAs on Si(001) were investigated using in situ synchrotron X-ray diffraction. Three-dimensional X-ray intensity distributions around the Si and GaAs 022 Bragg points in reciprocal space were measured during growth using combination of an area detector and one-axis scans. During the initial stage of growth, the average radius of GaAs islands was found to follow a second power law function of the growth time, in accordance with the growth being limited by the binding of Ga with As at step edges. With increasing GaAs thickness, streaky scattering extending from the GaAs 022 peak in the 〈 111 〉 directions was observed, indicating the development of plane defects.

The polytypism of GaAs nanowires was investigated by in situ X-ray diffraction under different growth conditions. The growth of nanowires was found to start with the formation of the zincblende structure, followed by the growth of the wurtzite structure. The observed growth process of nanowires was well reproduced by simulations based on a layer-by-layer nucleation model. At a low growth temperature and a high growth rate, stacking faults were found to be frequently introduced owing to the reduction in energy barrier. As a result, the zincblend and wurtzite segments in nanowires were highly fragmented and the wurtzite structure was formed in the early stage of growth.

A ternary Fresnel zone plate (FZP) has been fabricated and installed at the beamline 11XU of SPring-8, in the aim of in situ studies on the growth of semiconductor nanostructures. The FZP is designed for an X-ray energy of 9.5 keV for the first-order diffraction, which is isolated by an order sorting aperture (OSA) inserted 450 mm after the FZP. The focal length of this FZP is 650 mm. The full width at half maximum of the focused beam profile was estimated to be 1.17 μm (H) × 1.38 μm (V) by the dark-field knife-edge scan. Using this FZP, micro-beam diffraction of an as-grown single InAs NW was carried out to show the feasibility of in situ study during growth.

In-situ monitoring of the crystal structure formation during Ga-assisted GaAs nanowire growth on Si(111) substrates has been performed in a combined molecular beam epitaxy growth and x-ray characterization experiment. Under Ga rich conditions, we show that an increase in the V/III ratio increases the formation rate of the wurtzite structure. Moreover, the response time for changes in the structural phase formation to changes in the beam fluxes is observed to be much longer than predicted time scales of adatom kinetics and liquid diffusion. This suggests that the morphology of the growth interface plays the key role for the relative growth structure formation rates.