fall2017

Where are hot carriers created in plasmonically enhanced semiconductor substrates?

  • By Burcu Ozden
  • 5 December 2017

PQI members Hrvoje Petek, Jin Zhao and their colleagues investigated a less known fact about the microscopic details of how the combined optical, electronic and chemical properties of metal/semiconductor interfaces define the coupling of light into the electronic reagents on their recent paper published in Nature Photonics. In this study, they investigated the coherence and hot electron dynamics in a prototypical Ag nanocluster/TiO2 heterojunction via ultrafast two-photon photoemission (2PP) spectroscopy, scanning tunneling microscopy (STM) and density functional theory (DFT).  The silver nanoclustors used in this study were grown via e-beam evaporation of Ag on top of TiO2 surface.They have shown that the plasmon excitation, dephasing and hot electron processes that are related to plasmonically enhanced photocatalysis involve complex physical and chemical interactions, with strong interfacial character involving the chemical and plasmonic coupling of Ag nanoclusters and the TiO2 substrate that cannot be predicted by the properties of the component materials, but rather require an understanding of their interactions. They found that the dephasing of the perpendicular and parallel plasmons by the dielectric screening response of the TiO2 substrate generates hot electrons with anisotropic and non-thermal distributions.

Emergent Phenomena at Oxide Interfaces

Speaker(s): 
Dennis Christensen
Dates: 
Friday, December 8, 2017 - 3:00pm

The plethora of fascinating properties observed in oxide heterostructures has attracted a lot of interest. Most noticeably, the confined electron gas formed at the interface between the two insulators LaAlO3 and SrTiO3 features e.g. gate-tunable superconductivity, ferromagnetism and non-volatile memory effects. Numerous studies have been devoted to understanding the origin of the conductivity along with enhancing its properties. Recently, we found that substituting LaAlO3 with γ-Al2O3 can produce a confined electron gas with an electron mobility exceeding 100,000 cm2/Vs. Here, I show that...

On systems with and without excess energy in environment

Speaker(s): 
Lorenz Cederbaum 
Dates: 
Monday, November 20, 2017 - 11:00am

How does a microscopic system like an atom or a small molecule get rid of the excess electronic energy it has acquired, for instance, by absorbing a photon? If this microscopic system is isolated, the issue has been much investigated and the answer to this question is more or less well known. But what happens if our system has neighbors as is usually the case in nature or in the laboratory? In a human society, if our stress is large, we would like to pass it over to our neighbors. Indeed, this is in brief what happens also to the sufficiently excited microscopic system. A new mechanism of...