Krill Prize 2014
Dr. Roie Yerushalmi (ד”ר רועי ירושלמי)
Molecular design of hybrid nanometric building blocks
My research focus at the interface of chemistry and materials science, combining the expertise I gained in my PhD studies and in my post-doctoral research. My main research interests relate to nanostructured materials and surface chemistry at nanoscale interfaces. My goal as independent researcher is to advance our understanding of chemical reactivity and physical processes at nanostructured interfaces. The laboratory that I have formed provide a comprehensive and synergistic research environment combining the various research disciplines in order to open new avenues for the basic understanding of chemical and physical processes at nanostructure interfaces. We study the emerging complexity of interacting nanostructure-molecular hybrids at various scales. In addition to funding from the ISF, MOST, and Academia Sinica, I received the Career Development Award by the Human Frontier Science Program Organization and the young investigator ERC starting grant from the EU, for “Large Scale Architectures with Nanometric Structured Interfaces for Charge Separation, Transport and Interception”.
The research performed in my lab integrates concepts and methods gained during my accumulated research experience into the systematic study of nanostructures at interfaces by implementing leading edge spectroscopic, synthetic, and assembly techniques in an innovative way.
Design of hybrid nanometric structures and study of their photocatalytic activity
We presented for the first time the transformation of organic-inorganic hybrid layers formed by solvent-free Molecular Layer Deposition to highly active photocatalytic films. We presented the formation of thin films as well as formation of highly controlled nanotube structures using nanowire templates. The new hybrid materials show unique photocatalytic properties as well as unique physical properties that are now being further studied in the context of direct water splitting. One of the unique properties of the active layers is molecular level permeability that is playing a major role in the adsorption of molecules to the whole film volume rather surface are alone, adsorption of dopants and control of the electronic structure of the films, and formation of new class of noble metal-metal oxide hetero structures. These results are now being summarized in several manuscripts, including the report of direct photocatalytic formation of hydrogen peroxide without the use of sacrificial compounds.
Controlled doping of nanostructures
We developed a new approach we termed Monolayer Contact Doping, for the introduction of dopant atoms into nanostructures. A unique feature of the MLCD method is that the monolayer used for doping is formed on a separate substrate (donor substrate) that is distinct from the interface intended for doping (acceptor substrate). Surface contact doping of Si wafers and silicon nanowires is demonstrated and characterized. Using Kelvin probe force microscopy (KPFM) we were able to demonstrate the highly uniform longitudinal distribution of dopant atoms using MLCD in comparison with in situ doped nanowires (by CVD). This achievement relies on the extensive development of wide range of metal oxide surface chemistries and new doping methodologies for the nanometric scale.
Tuning of semiconductor electronic properties by molecular design of interface properties
By systematic study of oxide surface chemistry and development of non-covalent metal oxide surface modification approach we were able to gain new understanding of the tuning mechanism of the electronic structure of the silicon/silicon dioxide/molecular layer interfaces.
The general and facile non-covalent surface modification approach developed in my group relying on polar head group interactions with the polar surface groups of the oxide interface enabled us to systematically study the role of molecular polarizability in addition to the well established role of molecular dipole at the interface. We present a model that extends the Helmholtz ideal capacitor model to include the role of molecular polarizability in tuning the electronic structure of molecule-semiconductor interfaces. The insights obtained in this study have wide implications for an array of fields ranging from fundamental physical understanding of the electronic structure to opening future possibilities for new sensing mechanisms and identification of molecules based on the fine electronic structure properties.