過去のニュース ( 2014年5月まで JAIST在籍時)
過去のセミナー (2014年5月まで JAIST在籍時)
- 8th Simulation Science Seminar
- 演題: Understanding the STM and AFM contrast in graphene, reducible oxides and biomolecules
- 演者: Ruben Perez (Professor, Autonomous University of Madrid, SPAIN)
- 日時: 2013 11/18 15:00-16:30
- 要旨: We’ll review the computational tools and protocols developed in our group in order to study the mechanical
and transport properties of materials, and its application to the understanding of
the atomic-resolution images obtained with the scanning tunneling (STM)
and the force microscope (AFM) by different experimental groups on technologically relevant materials.
Firstly, we’ll focus on tuning of the electronic properties of graphene through the creation of defect
and edge states, looking, in particular, to the connection of graphene with metal surfaces.
Combining high resolution STM experiments and DFT calculations,
we have unambiguously unveiled the atomic structure of the boundary between a graphene zigzag edge
and a Pt(111) step. The graphene edges minimize their strain by inducing a 3-fold edge-reconstruction
on the metal side. We have shown the existence of an unoccupied electronic state
exclusively localized in the C-edge atoms of a particular graphene sublattice,
which could be used to develop new dual-channel devices.
Metal oxides play a key role in a wide range of technological applications.
While in many cases the same FM-AFM image can be explained by different models,
and even different underlying tip-sample interactions, we show here that the combination
of force spectroscopy (FS) measurements and first-principles simulations
can provide an unambiguous identification of the tip structure and the image contrast mechanism
in rutile TiO2 (110) and anatase TiO2 (101) surfaces. In the case of STM,
we have made a comprehensive study of the (2√2x√2)R45゜ missing row reconstruction
of the Cu(100) surface, using different tips and systematically varying bias voltage
and tip sample distance, to explore the rich variety of image contrasts observed in the experiments.
Our results achieve a conclusive understanding of fundamental STM imaging mechanisms
and provide guidelines for experimentalists to achieve chemically selective imaging
by selecting imaging parameters.
Finally, we’ll present our recent work on the structure and functionality of biological systems
in their native liquid environment. We’ll discuss the application of large-scale steered
Molecular Dynamics simulations, based on classical potentials developed by the molecular biology community
and the use of GPUs as processing units, provide insight into the protein-graphene biocompatibility,
the flexibility map of human antibodies, and the hydration properties of self-assembled monolayers
of single-stranded DNA and its possible use as a label-free DNA sensor.