Current Seminars
​​​Friday, February 27, 2015
  • ​1 ​PM​, Dow Science Complex 102
  • Dr. Remi Beaulac - Department of Chemistry, Michigan State University
  • Rethinking the Quantum Dot: Bringing Nitrides into the Quantum Confined Regime
Group III-nitrides form a particularly interesting class of materials for photoemissive applications, as evidenced by the tremendous impact that GaN-based blue light-emitting diode (LED) technologies have had over the last decade and which was recognized by the 2014 Nobel Prize in Physics to Akasaki, Amano, and Nakamura.[1] The use of indium nitride has been comparatively hindered in large part due to challenges associated with its synthesis. Nevertheless, InN is a rather intriguing material: not only does it have a much smaller bandgap (0.7 eV) than expected on the basis of simple electronic structure considerations, but it also has a anomalously low conduction band energy, associated with an exceptionally large electron affinity of 6 eV.[2] This feature is obviously associated with clear challenges in the preparation of pristine and stable InN materials. We describe here a new approach to synthesize indium nitride that yields colloidal nanoparticles matching the quality of II-VI nanomaterials obtained through state-of-the-art hot-injection approaches. An interesting aspect of these new materials is that they clearly do not exhibit any features of impurity-based doping that are prevalent in other forms of nanocrystalline InN previously studied, as seen from the absence of the large Burstein-Moss shifts and surface plasmon resonance signatures that have always been associated with previous forms of this materials.[3,4] Instead, as expected for pristine semiconductor nanomaterials, the samples obtained through our approach exhibit unambiguous size-dependent electro-optical effects that are consistently explained by the trend expected from Brus equation for strong-confinement regimes, with effective optical bandgaps that can be tuned from 0.7 eV to above 1.0 eV for quantum dot diameters varying between 3 nm and 10 nm. These samples furthermore are bright emitters in the near-infrared, with microseconds recombination lifetimes and photoluminescence quantum yields around 10%, making them attractive candidates for imaging and detection applications.[5]

References

  1. "The Nobel Prize in Physics 2014". NobelPrize.org. Nobel Media AB 2014. Web. 31 Dec 2014. <http://www.nobelprize.org/nobel_prizes/physics/laureates/2014/>
  2. Ager III JW, Miller NR (2012) Taming transport in InN. Eur. Mater. Res. Soc. (E-MRS) 2011 Spring Meeting, Nice, France, May 9-13, 2011. Lawrence Berkeley National Laboratory. LBNL Paper LBNL-5208E.
  3. Hsieh JC, Yun DS, Hu E, Belcher AM (2010). J. Mater. Chem. 20, 1435-1437.
  4. Palomaki PKB, Miller EM, Neale, NR. J. Amer. Chem. Soc. 135, 14142-14150.
  5. Chakraborty B, Beaulac R. "Colloidal Quantum-Confined Indium Nitride Nanocrystals," submitted.​
​​Friday, March 20, 2015
  • 1 PM, Dow Science Complex 102
  • Dr. Xiaoquing Pan, Dept. of Materials Science & Engineering, University of Michigan
​​Friday, April 10, 2015
  • ​1 PM, Dow Science Complex 102
  • Dr. Sadagopan Krishnan, Department of Chemistry, Oaklahoma State University
​​Friday, April 17, 2015
  • 1 PM, Dow Science Complex 102
  • Dr. Anuja Datta, Department of Physics, University of South Florida
​​Friday, April 24, 2015
  • 1 PM, Dow Science Complex 102
  • Dr. Vladimiro Mujica, Department of Chemistry and Biochemistry, Arizona State University