X-ray micro-beam characterization of lattice rotations and distortions due to an individual dislocation.

Understanding and controlling the behaviour of dislocations is crucial for a wide range of applications, from nano-electronics and solar cells to structural engineering alloys. Quantitative X-ray diffraction measurements of the strain fields due to individual dislocations, particularly in the bulk, however, have thus far remained elusive. Here we report the first characterization of a single dislocation in a freestanding GaAs/In0.

Ga droplet morphology on GaAs(001) studied by Lloyd's mirror photoemission electron microscopy.

We apply Lloyd's mirror photoemission electron microscopy (PEEM) to study the surface shape of Ga droplets on GaAs(001). An unusual rectangular-based droplet shape is identified and the contact angle is determined in situ. It is shown that quenching does not appreciably affect droplet shape and ex situ measurements of the contact angle by atomic force microscopy are in good agreement with Lloyd's mirror PEEM.

Imaging surface topography using Lloyd's mirror in photoemission electron microscopy.

We use Lloyd's mirror to modulate electron photoemission in photoemission electron microscopy. This results in the projection of Lloyd's fringes on to three-dimensional (3D) surface objects. An iterative reconstruction method is used to correct for distortions in the fringe pattern due to the cathode immersion lens, thereby providing a quantitative interpretation of surface shape.

Surface reactions of 1-propanethiol on GaAs(100).

The adsorption and decomposition pathways of 1-propanethiol on a Ga-rich GaAs(100) surface have been investigated using the techniques of temperature programmed desorption, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS). 1-Propanethiol adsorbs dissociatively on a clean GaAs(100) surface to form propanethiolate and hydrogen. Further reactions of these species to form new products compete with the recombinative desorption of molecular propanethiol.

Selective photon-stimulated desorption of hydrogen from GaAs surfaces.

Photon-stimulated desorption of H(+) from hydrogenated GaAs (110) and (100) surfaces was studied as a function of photon energy. Distinct peaks, observed around As 3d core-level binding energy for desorption from the GaAs (100) surface and in the As 3d and Ga 3p region for desorption from the GaAs (110) surface, show a striking similarity with the fine structure (spin-orbit splitting) measured in the photoemission from As 3d and Ga 3p levels. These results provide clear evidence for direct desorption processes and represent a basis for selective modification of hydrogenated GaAs surfaces.