Self organization during Pulsed Laser Deposition
Pulsed Laser Deposition (PLD) is a tool which is well suited for the fabrication of high quality complex oxide thin-films of only a few nanometers thick. By using PLD, we are able to make stacks of 2 dimensional sheets made up from a vast range of materials, all with different properties. For example by creating a stacking of BaCuO2/(Sr,Ca)/CuO2, which is superconducting using specific deposition conditions. Artificially fabricated structures can give rise to new or enhanced properties. Within this project we seek to create such structures by using materials which show self-organization during fabrication.
One method to achieve such self-organization is to use starting templates which has to types of surface areas. For example DyScO3 (Figure 1a) single crystals showing well ordered areas of both DyO and ScO2 at the surface in a striped fashion (Figure 1b). These areas can be as small as 50 nanometer in width, while their length spans a few millimeter. During PLD growth of metallic SrRuO3 on these double terminated DyScO3 substrates a pattern resembling the template is formed. In the case of a striped template, high aspect ratio nanowire arrays are formed. (Figure 1c). An example Scanning Tunneling Microscopy (STM) image is depicted in Figure 2, showing 100 nm wide and 6 nm high nanowires after PLD growth.
Another interesting case of self-organization is the formation of arrays of nanorods during the growth of mutually immiscible oxide composite mixtures, as for perovskite-type BaTiO3 and spinel-type CoFe2O4, which are technologically relevant high-k dielectric and paramagnetic phases, respectively. Both types of growth can be modeled by a diffusion process, for example using kinetic Monte Carlo simulations. This type of model provides a guide to optimize growth conditions and control the dimensions of the nanostructures.
Within this project contributions can be made both on the experimental side, including PLD growth, AFM, STM, SEM and X-Ray analysis and on the growth simulations and more fundamental understanding of the mechanisms behind the self-organization. For example by tuning growth conditions to control the size of the nanostructures or their properties, or by changing to a different material system. For more information, please contact Bouwe Kuiper: firstname.lastname@example.org.