Strain Oscillations Probed with Light

Abstract

We show that reflectance difference spectroscopy (RDS) is sensitive to the inhomogeneous surface and thin film strain which builds up during hetero- and homoepitaxial growth. The RDS signal is affected by the local, mean square atomic displacements in the substrate resulting from the stress relaxation of strained adlayer islands. For layer-by-layer growth an oscillatory variation of the RDS intensity is observed. These results demonstrate the potentiality of RDS to probe the growth kinetics on structurally anisotropic surfaces.

Effects of ion bombardment on the optical and electronic properties of Cu(110)

“…8,9 At room temperature, the lower-lying surface state resides at ϳ0.4 eV below E F , 10 and the unoccupied state resides at ϳ1.8 eV above E F . 11 It is this unoccupied surface state that has been the focus of the IPE study by Heskett et al 4 RAS has been used to monitor the behavior of these surface states upon molecular adsorption 8,9,12 and alkali metal deposition. 13,14 Features in the RA response of Cu͑110͒ in the region 4 -5 eV have been assigned to surface-modified bulk band transitions at L. 15 RAS can therefore be used to investigate the effects of ion bombardment on the surface states at Ȳ and transitions at L. In addition to probing surface electronic structure, RAS has been found to be sensitive to surface morphology.…”

Effects of laser irradiation on the morphology of Cu(110)

“…13,15 It is known that the intensity at 4.3 eV strongly depends on the surface strain field and is modified by higher order terms of the spatial strain distribution even if the average strain ͑bending͒ of the surface is zero. 16 In similar experiments on the Cu͑100͒ surface performed by Ernst et al, 9 STM revealed that laser irradiation induces adatom and vacancy islands as well as edge dislocations along the fcc easy glide system. 10 According to this, the quenching of the surface state related features at 2.1 and 3.9 eV can be attributed to scattering and quenching of the surface states by surface defects and by step edges formed at the surface as a consequence of the formation of subsurface dislocation lines.…”

“…As already mentioned, the RD signal at this energy is sensitive to the changes in the spatial strain distribution. 16 Therefore, the saturation of the RD signal at 4.3 eV could just mark the point where the dislocation lines have reached a critical density at which their individual strain fields start to overlap.…”

Reflectance‐anisotropy study of the dynamics of molecular beam epitaxy growth of GaAs and InGaAs on GaAs (001)

“…Oscillations in the RA amplitude has been also observed during the epitaxial growth of Cu, thus showing that these oscillations is a phenomenon not exclusive to semiconductors [6]. Metals, nevertheless, are isotropic for (001) surfaces and RA oscillations are observed only for lower symmetry surfaces such as (110).…”

“…Oscillations in the optical reflectance-anisotroy (RA) response during the growth of GaAs and AlAs by both MBE and MOCVD are also known to occur [2][3][4][5][6]. The RA response is obtained by taking the difference is sample reflectivity for two mutually orthogonal polarizations ductor in nominally isotropic, it is surface-specific [9].…”