A survey will be given on recent advances in the investigation of semiconductor epilayers, heterostructures and superlattices using reciprocal space mapping techniques based on triple-axis diffractometry. It is shown that X-ray reciprocal space mapping yields quantitative information on strain, strain relaxation, as well as composition in such structures. These data are obtained from analyses of the isointensity contours of scattered X-ray intensity around reciprocal lattice points. Further analysis of the diffuse scattering yields also information on defect distribution in the epilayers.
ZnO nanowires doped with Mg have been successfully prepared on Au-coated Si (111) substrates using chemical vapor deposition method with a mixture of ZnO, Mg, and activated carbon powders as reactants at 850°C. The structural, compositional, morphological and optical properties of the samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectroscopy. The nanowires are single crystalline in nature and preferentially grow up along [0001] direction with the average diameter and length of about 60 nm and several hundred micrometers, respectively, thinner and longer than the results of literature using the similar method. Room temperature photoluminescence spectroscopy shows a blueshift from the bulk band gap emission, which can be attributed to Mg doping that were detected by energy dispersive X-ray analysis EDX in the nanowires. Finally, the possible growth mechanism of crystalline ZnO nanowires is discussed briefly.
The vibrational dynamics of water around glycine was investigated by using Raman spectroscopy and inelastic neutron scattering. Experiments of deuterated glycine versus deuterium were performed as comparison. The study shows that for glycine, the exchange of proton-deuteron on the active NH_3^+ side was easy, whereas there was hardly exchange on the CH_2 side. Comparing different proportion of glycine vs. water molecules we obtained that the presence of water hardly changes the main features of glycine illustrating its hydrophobic character. The intralayer hydrogen bonds of glycine crystal are difficult to be replaced due to its stronger bond than water.
We demonstrate the imaging of the extended defects in Si materials using a focused ion beam instrument. Since Ga-ion beam has small penetration depth and high channeling character compared with electron beam, the secondary electron signal of focused ion beam is more sensitive to the surface morphology and crystallinity. We have tried to use this secondary electron imaging of focused ion beam for observation of various extended defects in Si materials for photovoltaic and semiconductor devices. As for the texture of multicrystalline Si, some grains are imaged darker than the others. It suggests that the crystal orientation gives different channeling effect on the primary Ga-ion beam, resulting in the different secondary electron yield. The grain boundaries and lineage in multicrystalline Si are shown as bright lines and patterns in the image. Although it may reflect the surface morphologies, these contrasts may be attributed to the channeling contrast due to lattice displacement or distortion. The contrast mechanism of FIB imaging is discussed.
Epitaxial manganite La_{0.67}Sr_{0.33}MnO₃ (LSMO) layers, with a thickness of 20-50 nm, are prepared on single crystal (001) SrTiO₃ (STO) substrates by pulsed laser deposition technique. Structural characterization (composition analysis, surface morphology), investigated by the Rutherford backscattering spectroscopy and atomic force microscopy, reveals the growth of stoichiometric LSMO films with a smooth surface (root-mean-square value of 0.21-1.6 nm). The prepared LSMO films possess high Curie temperature ( ≈ 412 K), low room temperature resistivity (1-2 mΩ cm) and maximum of temperature coefficient of resistivity TCR = 2.7% K¯¹ at 321 K.