John Badding

Solid state and materials chemistry; synthesis of new materials; supercritical fluids; pressure tuning of materials; optoelectronic films and metamaterials; nanoscale reactions; thermoelectric materials.

Materials Chemistry

The Badding group focuses on several areas of inorganic and polymeric materials chemistry, including optoelectronic materials and metamaterials, thermoelectric materials, chemical and physical phenomena in microscale and nanoscale capillaries and orifices, biomedical materials, and polymer nanofibers. A theme running through much of our research is the exploitation of high pressures, which can allow for new phenomena and very useful capabilities not otherwise possible at ambient pressure. High pressure supercritical fluids, for example, can combine the physical transport properties of a gas with the solvating ability and density of a liquid. As a result there is increasing interest in high pressure fluids across a variety of industries and in new technological areas. Chemical and physical behavior at high pressures can be very different in part because mean free paths are up to several orders of magnitude smaller at high pressure (often on the order of 1 nm or less vs 100 nm or more at lower pressures). At the micro and nano scales, the use of high pressures becomes increasingly practical because pressure is force per unit area and the forces involved become very small as the area decreases. The geometric confinement imposed by working in micro/nanoscale spaces also leads to different and in some cases very surprising and nonintuitive behavior. We strive to focus on basic problems that have the potential to have a major technological impact over time and/or open new areas of scientific research.

 We have pioneered the high pressure deposition of micro and nanowires of a broad range of materials in extreme aspect pores. In 2006 we used this approach to demonstrate the first silicon and germanium core optical fibers, thus extending the range of materials that can be exploited in the fiber geometry to unary semiconductors. The geometric perfection of these atomically smooth structures exceeds considerably what is typically possible with planar fabrication methods. Following this work, single crystal silicon wires, and, recently the first crystalline compound semiconductor fiber cores have been demonstrated. The nano/microstructured optical fiber templates we use can be designed to have arbitrary configurations of periodic or aperiodic pores with dimensions from tens of microns less than thirty nanometers. They thus allow for hierarchical organization of materials across many length scales down to nanoscale dimensions, as complex structures can be fabricated within each pore.