Effect of Hydrogen Plasma Treatment on the Electronic, Optical, Mechanical and Chemical Properties of Mo, Rh, Au, HOPG and Graphene
Event details
| Date | 17.06.2013 |
| Hour | 10:30 › 11:30 |
| Speaker | Baran Eren, Physics Department, Univ. Basel, CH |
| Location |
CRPP, PPB 019
|
| Category | Conferences - Seminars |
We experimentally investigate the properties of molybdenum/hydrogen, rhodium/hydrogen, gold/hydrogen and hydrogenated layered carbon material systems. Investigated transition metals are nanocrystalline coatings prepared by the magnetron sputtering method. Hydrogen introduction into initially pure metals or onto carbon is enabled by interactions of them with low temperature plasma.
Hydrogen in transition metals may act as an electron donor or an acceptor, changing the electronic band structure of its host. It can also result in increased number of lattice distortions, defect sites and inelastic scattering events reducing the optical transitions. Both directly imply that optical properties of these metals are changed. It is shown that hydrogen acts as an electron acceptor in molybdenum, but an electron donor in rhodium. Both cases are investigated with various experimental techniques including photoelectron spectroscopy, spectroscopic ellipsometry, spectroscopic reflectometry, spectrophotometry, specific resistivity and direct surface morphology imaging techniques. Rhodium/hydrogen system is not stable in air due to a catalytic reaction between hydrogen and oxygen, whereas molybdenum/hydrogen system is stable because hydrogen is strongly bound to defect sites. In the case of molybdenum, the research is extended to investigations on the partial delamination of the coated films and kinetic roughening of the surface caused by high flux hydrogen ions. Intense partial buckling of the films is also observed on the gold films, even at very low ion fluxes which is attributed to high compressive stress exerted on the gold films as a result of hydrogen accumulation at the coating interface with the substrate material. It is shown with scanning probe techniques, photoelectron spectroscopy and Raman spectroscopy that hydrogenation of HOPG changes its surface corrugation, valence band structure, surface electron density and vibrational modes. Moreover, it is shown that hydrogenation can be achieved locally and work function changes of the graphene surface can be mapped with Kelvin probe force microscopy. The outcomes of the work are aimed to aid the fusion community in terms of material choice for the light reflecting components considered to be used in new generation reactors, as well as the carbon community in terms of helping the comprehension of properties of hydrogenated graphene.
Hydrogen in transition metals may act as an electron donor or an acceptor, changing the electronic band structure of its host. It can also result in increased number of lattice distortions, defect sites and inelastic scattering events reducing the optical transitions. Both directly imply that optical properties of these metals are changed. It is shown that hydrogen acts as an electron acceptor in molybdenum, but an electron donor in rhodium. Both cases are investigated with various experimental techniques including photoelectron spectroscopy, spectroscopic ellipsometry, spectroscopic reflectometry, spectrophotometry, specific resistivity and direct surface morphology imaging techniques. Rhodium/hydrogen system is not stable in air due to a catalytic reaction between hydrogen and oxygen, whereas molybdenum/hydrogen system is stable because hydrogen is strongly bound to defect sites. In the case of molybdenum, the research is extended to investigations on the partial delamination of the coated films and kinetic roughening of the surface caused by high flux hydrogen ions. Intense partial buckling of the films is also observed on the gold films, even at very low ion fluxes which is attributed to high compressive stress exerted on the gold films as a result of hydrogen accumulation at the coating interface with the substrate material. It is shown with scanning probe techniques, photoelectron spectroscopy and Raman spectroscopy that hydrogenation of HOPG changes its surface corrugation, valence band structure, surface electron density and vibrational modes. Moreover, it is shown that hydrogenation can be achieved locally and work function changes of the graphene surface can be mapped with Kelvin probe force microscopy. The outcomes of the work are aimed to aid the fusion community in terms of material choice for the light reflecting components considered to be used in new generation reactors, as well as the carbon community in terms of helping the comprehension of properties of hydrogenated graphene.
Practical information
- Expert
- Free
Organizer
- Prof. P. Ricci, CRPP
Contact
- Prof. P. Ricci, CRPP