Category Physics

Schematic of the epitaxial growth procedure of ZnSe/GaAs heterostructure growth using either light-start or dark-start growth procedures. (a) Prior to ZnSe epilayer growth, the GaAs epilayer was grown in a dedicated III-V MBE chamber and was covered with an amorphous arsenic film prior to transferring it to a dedicated II-VI chamber. (b) The amorphous arsenic film was then thermally desorbed and the interface growth was initiated with a Zn pre-treatment under either a light-start or dark-start condition. During light-start sample growth, UV light was directed onto the growth surface from the beginning of Zn pre-treatment until the end of the ZnSe growth (f–h). During dark-start sample growth, UV light was directed onto the growth surface only during ZnSe epilayer growth (c–e).

1. The selective solar absorber (SSA) developed by the researchers appears black, and thus absorptive, under sunlight (as shown on the photograph on the left). However, for thermal radiation, it behaves like a non-emissive metal mirror (reflecting the dark blue sky, as shown on the thermograph on the right), and prevents the absorbed solar energy from being radiated away and lost.
—Figure courtesy of Jyotirmoy Mandal and Yuan Yang/Columbia Engineering
2. The researchers make their SSAs using a dip-and-dry technique which is considerably simpler than common manufacturing methods for SSAs.
—Photo courtesy of Jyotirmoy Mandal and Yuan Yang/Columbia Engineering

Sandia National Laboratories’ Guillaume Loisel poses with Sandia’s Z machine, where hands-on experiments contradicted a long-standing assumption about the X-ray spectra from the vicinity of black holes in space. Loisel is the lead author of a paper on the experimental results, published in Physical Review Letters. Credit: Randy Montoya, Sandia National Laboratories

The perovskite material changes size when exposed to light. Reproduced with permission from reference 1.© 2017 WILEY‐VCH Verlag GmbH & Co.