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Chemistry Seminar

February 27, 2014
Room 114, Smith Hall 11:00 a.m.

Ms. Amanda Landcastle

Silicon d-doping of AlGaN/GaN superlattices to improve near-infrared absorption

Aluminum Gallium Nitride/Gallium Nitride (AlGaN/GaN) semiconducting devices were grown by plasma-assisted molecular-beam epitaxy. The material characteristics were looked at by High Resolution X-Ray Diffraction, Atomic Force Microscopy, and High Resolution Transmission Electron Microscopy. The optical properties were examined by Fourier Transform Infrared Spectroscopy using photoinduced absorption to increase the signal by taking advantage of the intersubband transitions within the quantum wells of the superlattice. Large charge densities are required for the transitions to occur which means that the semiconductor must be doped. This moves the Fermi level closer to the conduction band in order to allow the electrons to make transition from their ground state into the conduction band, ensuing in absorption. An optimal doping scheme is therefore of interest, and is determined through observation of the indirect effects of the doping on the structural properties of the semiconducting devices.

Mr. Nathaniel Burleigh

Constructing Covalent Organic Frameworks via Molecular Tectonics

Covalent Organic Frameworks (COFs) are an interesting class of compounds characterized by extremely high internal surface areas. These compounds exhibit many promising and useful characteristics in such applications as high efficiency gas separation and collection, low pressure gas storage media, re-usable molecular catalysis, as well as enhanced digital storage media, and many other nano-scale engineered products. COFs are also remarkably easily synthesized, generally being made from relatively inexpensive, easily obtained starting materials. Several research groups have studied the synthesis and application of these materials, specifically two dimensional COFs 5, 8, and 10 and three dimensional COFs 102 and 103. COFs 102 and 103 were found to have in internal surface area and methane uptake roughly three times that of activated carbon.