Saturday, March 28, 2015

Brown University uses silicon telluride to produce multilayered two-dimensional semiconductor materials


 
 By adjusting the fabrication technique, researchers can make different semiconductor structures, including nanoplates that lie flat or stand upright. Koski lab/Brown University
 
A Silicon-Based Two-Dimensional Chalcogenide: Growth of Si2Te3 Nanoribbons and Nanoplates
Sean Keuleyan , Mengjing Wang , Frank R. Chung , Jeffrey Commons , and Kristie J. Koski
Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
Nano Lett., Article ASAP
DOI: 10.1021/nl504330g

Abstract Image

We report the synthesis of high-quality single-crystal two-dimensional, layered nanostructures of silicon telluride, Si2Te3, in multiple morphologies controlled by substrate temperature and Te seeding. Morphologies include nanoribbons formed by VLS growth from Te droplets, vertical hexagonal nanoplates through vapor–solid crystallographically oriented growth on amorphous oxide substrates, and flat hexagonal nanoplates formed through large-area VLS growth in liquid Te pools. We show the potential for doping through the choice of substrate and growth conditions. Vertical nanoplates grown on sapphire substrates, for example, can incorporate a uniform density of Al atoms from the substrate. We also show that the material may be modified after synthesis, including both mechanical exfoliation (reducing the thickness to as few as five layers) and intercalation of metal ions including Li+ and Mg2+, which suggests applications in energy storage materials. The material exhibits an intense red color corresponding to its strong and broad interband absorption extending from the red into the infrared. Si2Te3 enjoys chemical and processing compatibility with other silicon-based material including amorphous SiO2 but is very chemically sensitive to its environment, which suggests applications in silicon-based devices ranging from fully integrated thermoelectrics to optoelectronics to chemical sensors.