Using ultrafast X-ray diffraction, we study the coherent picosecond lattice dynamics of photoexcited thin films in the two limiting cases, where the photoinduced stress profile decays on a length scale larger and smaller than the film thickness. We solve a unifying analytical model of the strain propagation for acoustic impedance-matched opaque films on a semi-infinite transparent substrate, sh...

Dispersions of nanoscale Pb particles embedded in Si, Al, and Cu matrices have been synthesized by ion implantation and subsequent annealing. The melting transitions of the embedded Pb nanocrystals with epitaxial particle/matrix interfaces were investigated by means of in situ high-temperature X-ray diffraction. Due to different levels of lattice mismatch, the Pb nanoprecipitates experience a d...

This paper aims to investigate the light output power (LOP) of InGaN-based light-emitting diodes (LEDs) grown on patterned sapphire substrates (PSSs) with different symmetry. The GaN epitaxial layers grown on the hexagonal lattice arrangement PSS (HLAPSS) have a lower compressive strain than the ones grown on the square lattice arrangement PSS (SLAPSS). The quantum-confined Stark effect (QCSE) ...

An ab initio study of nitride-based heteroepitaxial interfaces that uses norm-conserving pseudopotentials and explicitly treats the strain due to lattice mismatch is presented. Strain effects on the band offsets range from 20% to 40%. The AlN/GaN/InN interfaces ~with AlN in-plane lattice constant! are all of type I, while the Al 0.5Ga0.5N/AlN zinc-blende ~001! interface is of type II. Further, ...

We explore the InSb-semiconductor lattice dynamics after excitation of high density electron-hole plasma with an ultrashort and intense laser pulse. By using time resolved x-ray diffraction, a sub-mÅ and sub-ps resolution was achieved. Thus, a strain of 4% was measured in a 3 nm thin surface layer 2 ps after excitation. The lattice strain was observed for the first 5 ps as exponentially decayin...

Interfacial roughness parameters and lattice strain of Si0.4Ge0.6 films with varying thickness epitaxially grown on Si~100! were determined using the techniques of grazing-incidence x-ray scattering and diffraction. The roughness of both the buried interface and sample surface follows a similar power-law scaling behavior with an exponent b around 0.71 for films below the critical thickness, and...

We have investigated detailed structural properties of epitaxial BiFeO3 thin films grown on 001 , 110 , and 111 SrTiO3 substrates in thicknesses up to 1 m. X-ray reciprocal space mappings reveal that the fabricated films have crystal structures and the strain relaxation dictated by the substrate orientation. The rhombohedral structure, which is observed in the bulk form, is maintained only when...

Three different film systems have been systematically investigated to understand the effects of strain and substrate constraint on the phase transitions of perovskite films. In SrTiO3 films, the phase transition temperature Tc was determined by monitoring the superlattice peaks associated with rotations of TiO6 octahedra. It is found that Tc depends on both SrTiO3 film thickness and SrRuO3 buff...

Electron backscatter diffraction (EBSD) has been used to examine the plastic deformation of an ex-service 316 austenitic stainless steel at 297K and 823K at strain rates 3.5x10 -3 s -1 – 4x10 -7 s -1 . The distribution of local misorientations was found to depend on the imposed plastic strain following a lognormal distribution at true strains < 0.1 and a gamma distribution at strains > 0.1. At ...

First-principles full potential linearized augmented plane wave (FLAPW) calculations have been performed for lattice-mismatched common-atom III-V interfaces. In particular, we have examined the effects of epitaxial strain and ordering direction on the valence band offset in [001] and [111] GaSb/InSb and InAs/InSb superlattices, and found that the valence band maximum is always higher at the InS...