Research project P6/42 (Research action P6)
The study of clusters and nanowires is a very important subfield in the area of nanoscience where the nanosize control of materials structures is realized in at least two dimensions. Nanoscience involves the understanding of physical and chemical phenomena at the atomic and molecular level. Nanotechnology provides the ability to precisely manipulate matter and energy at molecular scales. Based on unique electrical, magnetic, optical and structural properties of nanomaterials it will revolutionize existing architectures of computers or optical devices and lead to fundamentally new applications in, e.g., biomedicine and catalysis. Just as antibiotics, silicon transistors and plastics affected nearly every aspect of the society in the 20th century, nanotechnology will have profound influences in the 21st century.
The central objective is to design and control the structural, optical, magnetic, electrical and reactive properties through nano-engineering of the size, shape, structure, and composition of clusters and nanowires. Through the confinement of charges and spins a coherent control of the quantum mechanical states of the nano-device will be realized to achieve the desired physical properties for different applications.
Some key questions which we want to address are:
• What is the influence of size and composition on structure and stability?
• How can the fundamentals of magnetism be understood (in particular ferromagnetism and superparamagnetism) through the investigation of very small magnets?
• What is the relation between structure (including the confinement geometry) and the functional properties (in particular optics, magnetism, electrical transport including superconductivity)?
• How can hybrid systems, where clusters and wires with different properties are combined at nanometer scale, be used in order to (i) understand these properties through their confrontation and (ii) create extra functionalities (e.g., magnetism and semiconducting behavior, superconductivity and magnetism)?
• To which extent does the chemical/physical environment of a cluster/nanowire modify its properties?
Our main effort will be centered on clusters and nanowires consisting of metal (e.g., magnetic and superconducting or metals with different chemical properties), semiconductor, carbon and combinations of these materials (these are the so-called hybrid systems). The focus will be on the bottom-up approaches such as laser vaporization, ion implantation, electrochemical and vapor deposition (both physical vapor deposition, in particular molecular beam epitaxy and chemical vapor deposition) and self-assembly driven by chemical interactions to produce nanostructures, although the top-down (electron beam lithography) approach will not be discarded.
Structural, chemical and electronic (including optical, magnetic and transport) characterization on different length scales (from nanometer to atomic size) are essential parts in the study. We will use high-resolution electron microscopy, nuclear techniques with atomic probes, different types of local probe microscopy and field ion microscopy along with local chemical probing, SQUID based magnetometry, laser spectroscopy, X-ray reflectometry and others.
Computational studies will be an important part in order to interpret the experimental observations on the one hand and to provide feedback for an improved design and control of the physical properties of the systems on the other hand. Different modeling techniques are available in the proposed consortium, ranging from Monte Carlo and molecular dynamics simulations, finite element and finite difference techniques to ab initio approaches with different levels of sophistication. Genetic and other global optimization algorithms as well as multi-scale approaches are also important techniques which will be used.
A single laboratory is not able to realize this program and an integrated effort is obviously necessary. In the previous IUAP/PAI V program on “Quantum size effects in nanostructured materials” the nanosize control of materials structures was realized in at least one dimension. In the new network we go one fundamental step further and aim at realizing this control in at least two and, finally, three dimensions.
