Archive for the ‘Applied Physics Letters’ Category

Posted by Kenneth Burch On January - 28 - 2016 Comments Off on Local phonon mode in thermoelectric Bi2Te2Se from charge neutral anti-sites

Local modes caused by defects play a significant role in the thermal transport properties of thermoelectrics. Of particular interest are charge-neutral defects that suppress thermal conductivity, without significantly reducing electrical transport. Here, we report a temperature dependent Raman study that identifies such a mode in a standard thermoelectric material, Bi2Te2Se. One of the modes observed, whose origin has been debated for decades, was shown most likely to be an antisite defect induced local mode. The anomalous temperature independent broadening of the local mode is ascribed to the random arrangement of Se atoms. The temperature renormalization of all modes is well  [ Read More ]

Posted by Kenneth Burch On February - 3 - 2013 Comments Off on Optical properties of SrTiO3 on silicon(100)

Epitaxial buffer layers enable the many functionalities found in perovskites to be integrated with silicon. However, epitaxial growth of SrTiO3 on silicon is tricky and has so far only been achieved by molecular beam epitaxy. Nonetheless, previous investigations of these films were limited by the amorphous layer occurring at the interface. Through a combination of improved interface quality and an improved model, we report the optical properties of SrTiO3 films on Si(100) investigated by spectroscopic ellipsometry. We find that the data are best described by a model with two different SrTiO3 layers, potentially resulting from variations in the oxygen content.  [ Read More ]

Posted by Kenneth Burch On November - 26 - 2012 Comments Off on Structural study of High Tc Superconductor exfoliated nanocrystals

Structural study of Bi2Sr2CaCu2O8+δ exfoliated nanocrystals We demonstrate that structural and spectroscopic information can be obtained on exfoliated nanocrystals as thin as 6nm. This can be achieved by using a combination of micro X-ray fluorescence (lXRF), micro X-ray absorption near-edge spectroscopy (lXANES), and X-ray microdiffraction (lXRD) techniques. Highly focused, tunable X-ray beams available at synchrotron sources enable one to use these non-invasive characterization tools to study exfoliated samples on a variety of substrates. As an example, we focused on exfoliated nanocrystals of the high temperature superconductor Bi2Sr2CaCu2O8þd. lXRF is used to locate the sample of desired thickness; lXANES and lXRD  [ Read More ]

Posted by Kenneth Burch On June - 24 - 2011 Comments Off on Fabrication and characterization of topological insulator Bi2Se3 nanocrystals

In the recently discovered class of materials known as topological insulators, the presence of strong spin-orbit coupling causes certain topological invariants in the bulk to differ from their values in vacuum. The sudden change in invariants at the interface results in metallic, time reversal invariant surface states whose properties are useful for applications in spintronics and quantum computation. However, a key challenge is to fabricate these materials on the nanoscale appropriate for devices and probing the surface. To this end we have produced 2 nm thick nanocrystals of the topological insulator Bi2Se3 via mechanical exfoliation. For crystals thinner than 10 nm  [ Read More ]

Posted by Kenneth Burch On April - 19 - 2010 Comments Off on One-dimensional alignment of nanoparticles via magnetic sorting

R. Bouskila, R. McAloney, S. Mack, D. D. Awschalom, M. C. Goh, K. S. Burch. One-dimensional alignment of nanoparticles via magnetic sorting Applied Physics Letters 96, 163103 (2010)