About surface science and nanomaterials

Surface science and nanoscience are closely connected research areas. The research in these areas is presently focused on two main topics: 

• carbon-based nanomaterials like carbon nanotubes, graphene and nanofibers,
• low-dimensional and nanoscale structures on semiconductor surfaces, primarily metallic layers and self-organized molecular layers.

The research on carbon nanostructures is led by docent Krister Svensson. It has been enabled by the development of new research instruments. By joining scanning probe microscopies with electron microscopy, we were able to, for the first time, both image and manipulate materials on the nanometer level simultaneously. The various production methods and their after-treatments have been shown to greatly influence material properties and this threatens to hamper commercialisation due to the inferior properties of mass-produced fibre materials. 

We have access to a variety of commercial materials as well as small-scale lab-production materials through international collaborators.  We are now investigating electrical properties, such as electron mean free path and contact resistance, in relation to the crystallinity of the materials. This will aid the development of material standards, which are vital for the global commercialisation of nanomaterials.

The surface science research is led by docent Hanmin Zhang. The research has a long history back to the beginning of the material physics group in Karlstad University. Various types of funds have been granted for the different projects. These projects started with semiconductor surfaces, metal/semiconductor reconstructions, and developed into low-dimensional systems. 

The research is mainly of fundamental physics character, but several of the systems may have an important impact on the development of applications in ambient environment. We are in particular interested in materials and structures that are relevant for technological applications in e.g. electronics, spintronics, and photovoltaic devices. The main earlier research projects have been:

• Growth and properties of self-assembled monolayers (SAM) formed in solution on Au surfaces. We studied aromatic molecules with thiolate headgroups and specially designed end groups.
• Studies of metal-induced reconstructions on Si and Ge surfaces. We were especially interested in the 3x1 reconstructions formed on Si(111) and Ge(111) by several different metal atoms.
• We have studied growth of small aromatic molecules on differently prepared Si surfaces, to investigate how the surface reactivity and periodicity influenced the growth and self-organisation of the molecules PTCDA and, more recently PTCDI.
• We have investigated the structure, electronic and magnetic properties of Mn-Si and Mn-Ge alloys grown by solid phase epitaxy on Si and Ge substrates.

For the present status, the studies of semiconductor surfaces and nanostructures have been focused on quantum well states in ultrathin silver layers on Si and Ge surfaces, as well as topological effects in the metal-semiconductor interfaces. We use a combination of spectroscopy and microscopy methods: photoelectron spectroscopy, X-ray absorption, circular dichroism and scanning tunneling microscopy (STM), combined with ab initio density-functional theory (DFT) calculations to get a complete understanding of the system under study. Synchrotron radiations at MAX IV in Sweden and ELETTRA in Italy are primarily used for the spectroscopy studies.