Thursday, June 20, 2019

Enhancement of the quality of InAsSb epilayers using InAsSb graded and InSb buffer layers grown by hot wall epitaxy

We have investigated the structural and electrical properties of InAsxSb1−x epilayers grown on GaAs(0 0 1) substrates by hot wall epitaxy. The epilayers were grown on an InAsSb graded layer and an InSb buffer layer. The arsenic composition (x) of the InAsxSb1−x epilayer was calculated using x-ray diffraction and found to be 0.5. The graded layers were grown with As temperature gradients of 2 and 0.5 °C min−1. The three-dimensional (3D) island growth due to the large lattice mismatch between InAsSb and GaAs was observed by scanning electron microscopy. As the thicknesses of the InAsSb graded layer and the InSb buffer layer are increased, a transition from 3D island growth to two-dimensional plateau-like growth is observed. The x-ray rocking curve measurements indicate that full-width at half-maximum values of the epilayers were decreased by using the graded and buffer layers. A dramatic enhancement of the electron mobility of the grown layers was observed by Hall effect measurements.



Source:IOPscience

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Friday, June 14, 2019

Epitaxial InSb(111) layers on Sb(111) substrates characterised by Raman spectroscopy

InSb overlayers on Sb, obtained by UHV deposition of In onto heated substrates, are analysed by Raman spectroscopy. Well defined peaks from the InSb phonons are observed already at five monolayers coverage. The phonon frequencies of the overlayer as well as the substrate show shifts which reveal the following strain; compressive in the InSb overlayer and tensile in the Sb substrate top region. Also, the InSb LO intensity shows an anomalous behaviour for thin coverages, possibly due to the gradual development of the InSb electronic band structure.



Source:IOPscience

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Wednesday, June 5, 2019

High resolution LT-STM imaging of PTCDA molecules assembled on an InSb(001) c(8 × 2) surface

The self-assembling of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) molecules deposited on an InSb(001) c(8 × 2) surface at sub-monolayer quantities has been investigated at low temperature (77 K) using scanning tunnelling microscopy. Sub-molecular resolution was obtained on PTCDA molecules. The results reveal that individual PTCDA molecules are arranged on the substrate in chains parallel to the [110] crystallographic direction, correlated with characteristic features of the low temperature InSb(001) c(8 × 2) surface electronic structure. A structural model for PTCDA molecules adsorbed on InSb is proposed.


Source:IOPscience

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