Markku Leskelä
Thin films
Thin films form the most important research topic of the group, Atomic Layer Deposition (ALD) being the most widely studied deposition method. Laboratory is worldwide in leading position in developing ALD chemistry.
Atomic Layer Deposition research is a balanced combination of basic and applied topics and covers basically all areas related to ALD: precursor synthesis and characterization, film growth and characterization, and reaction mechanism studies. The emphasis in the ALD research has been in thin film materials needed in future generation integrated circuits. This has resulted in many research projects, a significant part with foreign industry. In addition, applications of ALD in optics and surface engineering are being studied too, for example.
Other thin film deposition techniques studied include electrodeposition, SILAR (successive ionic layer adsorption and reaction), electron beam evaporation (EBE), thermal evaporation and sol-gel.
Other nanostructured materials.
Nanostructured materials are prepared by combining the thin film deposition techniques with various templates (e.g. nanoporous alumina and inverse replicas thereof, as well as man-made and natural nanofibers) and passivation methods (e.g. silylation).
Porous alumina templates are prepared by electrochemical etching of Al sheets and evaporated Al thin films. Inverse replicas of the alumina templates can be formed by electrodeposition of metals in the pores and subsequent dissolution of the template. Polymeric and inorganic nanofibers are prepared by electrospinning. Polymer fibers have been utilized further as templates for nanotubes by depositing inorganic coating on them by ALD and removing the polymer kernel by annealing. Cellulose nanofibers have been used as templates for the preparation of TiO2 replicas as well as photocatalytic TiO2/cellulose composites.
Selective area ALD is studied using silylation as well as other methods to form patterned layers that passivate the surface against ALD growth. Silylation is done by self-assembly of hydrophobic ODS monolayers from gas phase. By forming ODS monolayers on nanostuctured alumina surfaces, also superhydrophobic surfaces have been prepared.
Sculptured metal and oxide thin films are prepared by glancing angle deposition (GLAD). GLAD, i.e., evaporation on a rotating substrate held at oblique angle during the deposition, leads to the formation of nanocolumns with e.g. helical shapes.