Molecular Nanostructures at Surfaces - Jan Čechal
CEITEC BUT CEITEC BUT
Molecular Nanostructures at Surfaces - Jan Čechal
For spintronics and energy conversion

Join our team

Are you are interested to join our research team as postdoc, PhD, master or internship student? Contact Jan Čechal at cechal@fme.vutbr.cz.


The official call for PhD positions opens in Decemer 2019 and May 2020. You are wellcome to contact PI if you are interested. We offer state-of-the-art equipment of CEITEC Nano core facility, motivating international environment and funding adequate to Brno area. Folowing topics are open:


Remote graphene doping

The possibility to tune the graphene transport properties, i.e., type and concentration of charge carriers makes graphene an attractive candidate for electronic devices, sensors, and detectors. In this context, various approaches for providing graphene with controlled doping were developed. The original approach – application of an external electric field provided by the voltage between the graphene and a gate electrode – was followed by deposition of atoms or molecules featuring as charge donors or acceptors in direct contact with graphene. Remote graphene doping based on charge trapping in gate dielectric by visible-, UV-, and X-ray radiation was only recently established. In parallel, the effect of electron beam (e-beam) irradiation on graphene devices was evaluated and the e-beam also entered the group of techniques capable of providing graphene with remote doping.

The goal of PhD is to reveal the mechanism of electron beam induced graphene doping, assess the role of defects in dielectric layer and develop a theoretical model describing the kinetics of the process.

Our current understanding suggests that the key mechanism here is a charging of defects in an oxide dielectric layer and a p-/n- doping is achieved depending on possibility of formation of electron-hole pairs in the dielectric layer by electron irradiation. We envision the utilization of the project outputs in adaptive electronics and fabrication of graphene devices, in general.


Organic semiconductors on oxide electrode surfaces

Studies of model oxides with well-defined surfaces provide detailed information important for a understanding of adsorbate−oxide interactions. Indium oxide is the prototypical transparent contact material that is extensively used in a wide range of applications, most prominently in optoelectronic technologies especially if doped with tin; then is commonly referred to as indium tin oxide (ITO). The performance of an organic semiconductor devices is determined by the geometric alignment, orientation, and ordering of the organic molecules. Despite its technological importance, surprisingly little is known about the fundamental surface properties of and the organic semiconductor/ITO (In2O3) interface.

The goal of PhD is to reveal the structure and morphology of organic semiconductors (para-hexaphenyl, pentacene, PTCDA) and describe kinetics of its growth by real-time LEEM.

This will be complemented atomic/molecular scale investigation by STM/AFM and area integrated XRD and XPS. The PhD is a part of of our collaboration with TU Wien in the framework of SINNCE project.


Externally tunable magnetic coupling between arrays of molecular quantum bits at surfaces

Single molecular magnets (SMM) are molecular entities bearing nonzero magnetic moment. In addition to the magnetic properties SMM provide one important attribute: they represent two-state system that can be in superposition state, i.e., SMM represent quantum bits (qubits). Recent developments pushed the coherence properties of individual magnets to the range required for competitive qubits. However, for any future application the molecular qubits should be processable as thin films. Moreover, the individual qubits should be mutually interacting.

The goal of PhD study is to prepare long-range ordered arrays of molecular magnets/qubits on solid surfaces and reveal the possibility to externally steer their magnetic interaction.

The experimental research within the PhD study aims at the understanding of deposition/self-assembly phenomena of organic compounds containing magnetic atoms on metallic and graphene surfaces. A special focus will be given to graphene surfaces that provide means to control their electronic properties (by intercalation or external gate voltage) and, hence, mutual interaction of individual spins. The spin coherence properties will be investigated by cooperating partners at CEITEC and University of Stuttgart. Project is also supported by running GAČR project.


Kinetics of growth and phase transformations in self-assembled molecular systems

Self-assembly is a promising route to fabricate nanostructures with atomic precision. Targeted design of molecular precursors allows to program nanostructures with desired functional properties. To implement these structures into functional devices it is necessary to understand the kinetics of the grow as it defines the fabrication procedures. However, only little is known about kinetics of the growth/transformation processes near thermodynamic limit.

The goal of Ph.D. study is to study the growth kinetics and phase transformation in self-assembled molecular systems and formulate suitable model describing the surface processes.

The experimental research within the PhD study aims at the understanding the kinetics deposition/self-assembly phenomena of organic molecular compounds on metallic surfaces. Low-Energy Electron Microscopy presents an ideal technique for monitoring real time evolution of surface growth in both real and reciprocal space. These data will be complemented with chemical composition by X-ray photoelectron spectroscopy and atomic level structure by scanning tunneling microscopy available within the UHV system.


Infrared spectroscopy of self-assembled molecular systems on surfaces

Self-assembly is a promising route to fabricate nanostructures with atomic precision. Targeted design of molecular precursors allows to program nanostructures with desired functional properties. The basic functional units form extended long-range ordered assemblies, the structure of which is a result of delicate interplay of molecule-molecule and molecule-substrate interactions. Infrared spectroscopy can be an important method to asses the type of bonding within the self-assembled or metal-organic networks.

The goal of Ph.D. study is to develop the infra-red spectroscopy methodology to be capable of routine measurement of self-assembled systems and determine the binding in them.

The experimental research within the PhD study aims at development of methodology of surface sensitive infrared spectroscopy on an UHV PM-IRAS setup for molecular systems at surfaces. The IR analysis results are combined with low-energy electron microscopy and diffraction, X-ray photoelectron spectroscopy, and scanning tunneling microscopy, which are available within the UHV system; the experimental measurements can be complemented by DFT description available in the group. This should provide a detailed view on the nature of intermolecular bonding. One of the questions to answer within the Ph.D. is the nature of carboxylate bonding to the benzene ring of neighboring molecule: is it ionic-hydrogen- or substrate-mediated bonding?


See details on CEITEC PhD school here.