Nanomaterials

Nanomaterials research at Boston University is concentrated on exciting work in coatings, composite materials, photo-acoustic microscopy, nanoscale materials, and multi scale modeling. Research, often conducted with industry partners, spans a range of application areas, including developing enhanced materials processing capabilities for opto-electronic applications, advanced engines, power systems and cutting tools

Nanomaterials research involves faculty from various departments within the College of Engineering and College of Arts and Sciences. Scientists in this group share facilities, have collaborative grants, and publish their scientific findings jointly.

Professor Ekinci’s Nanomaterials group studies mechanics and fluid dynamics at the nanoscale. Most experiments are performed on nanometer scale semiconductor mechanical resonators fabricated using top-down approaches (see Figure 1 below).  Among the fundamental phenomena studied using these devices are dissipation, fluctuations and surface effects at the nanometer length scales. The practical aspects of this research involve the design and fabrication of ultra-fast nanomechanical sensors, and development of surface nano-engineering techniques for improved device characteristics.

Ekinci’s group is also interested in the development of ultrasensitive tools for nanoscale characterization. A recent accomplishment is the development of a radio-frequency scanning tunneling microscope (RF-STM) [Nature 450, 85 (2007)] with a bandwidth of ~10 MHz.  This ~100-fold bandwidth improvement upon the state-of-the-art translates into fast surface topography as well as delicate measurements in mesoscopic electronics and mechanics.  Broadband noise measurements across the tunnel junction using this RF-STM have allowed nanoscale thermometry as well as sensitive detection of high-frequency mechanical motion.

Semiconductor nanoscale mechanical resonators.

Figure 1: Semiconductor nanoscale mechanical resonators.

Nanophotonic devices for biosensing and communications: Professor Altug’s group is working on nanoscale photonic structures that can manipulate light and control the light-matter interaction. An example of such structures (photonic crystals nanocavities) is shown in the Figure 2 below. The emphasis is on communications and biotechnology. They are developing high-throughput, ultra sensitive and compact biosensors integrated on chip with microfluidics. The group is also developing nanophotonic devices such as ultrafast lasers, efficient light emitting diodes and structures that can slow down the light on chip. To realize these devices, they are using rigorous numerical methods, advanced nanofabrication and state-of the art optical measurement techniques.

(a) SEM image of a fabricated photonic crystal nanocavity in SOI substrate. (b) Field profile of the cavity mode near 1.58 um shows strong light localization with mode volume less than 0.5 um. (c) Spectrum of cavity shows the resonance modes.

Figure 2: (a) SEM image of a fabricated photonic crystal nanocavity in SOI substrate. (b) Field profile of the cavity mode near 1.58 um shows strong light localization with mode volume less than 0.5 um. (c) Spectrum of cavity shows the resonance modes.