Prof. Cheshnovsky Ori
|Affiliation:||School of chemistry
|Postal Address:||School of chemistry|
Tel Aviv University
Tel Aviv 69978
Nanoscale Optics in STM Junctions. Electronic Properties of Clusters.
1. Light, tunneling junctions and nanoparticles:
In this new project, we study the correlation between the electrical properties and the optical properties of isolated nanocrystals or polymeric films. The sample, deposited on a surface, will be studied using scanning Tunneling Microscope (STM). The transport properties of the sample will be measured using I-V spectroscopy. In parallel, on the same particle, light emission induce by inelastic tunneling will be monitored. A dedicated STM head is coupled to a high collection efficiency mirror is developed for this project. A major virtue of the project is that the optical and electrical measurements will be performed on the same single isolated nanoparticle. The same methods will serve in studying the relation between the morphology segregation and light emission in multi-chromophor polymeric films.
STM measurement of a single CdSe nanocrystal on Au substrate. I.) Surface topography II.) Photon emission map revealing high emission intensity at the apparent location of the nanocrystal.
The long controversial problem of a critical size in which clusters of bivalent metals approach bandgap closure(metallic behavior) was addressed by us. By using PES of negatively charged clusters we showed that the band gap closes at the cluster-size of ~400 atoms. At smaller sizes mercury clusters behave as semiconductors with band gap varying for 3 eV (Hg4) to 0.2 eV (Hg28O). Electron-hole pairs could be efficiently excited in semiconductor mercury clusters. Their thermalization and recombination via Auger electron ejection is the focus of our current research. The understanding of the dynamics of these processes may offer ways to improve the performance of semiconductor based nano-devices.
By detaching an electron from negatively charged cluster, a wide rang of mass-selected neutral donor acceptor ion-pairs can be generated. Using this technique, we study ion-pair solvation and dipole-bound staes in clusters.