Nanostructured surfaces

A role of fluctuations of the adsorbate flux in nanostructured thin films growth during deposition
Dvornichenko A.V., Shchokotova O.M., Manko N.N.
Sumy State University.
Rimskogo-Korsakova str., 2,Sumy-40007, Ukraine. 
E-mail:alina.dvorni4enko@ukr.net

We derive the stochastic model of plasma-condensate system by introducing fluctuations of the adsorbate flux composed of ordinary diffusion flux and the flux related to interaction of adatoms. The model is used to study pattern formation on an intermediate layer of multi-layer plasma-condensate system with anisotropy in transference of adatoms between neighbor layers induced by the electrical field nearby substrate. 
In the framework of the stability analysis and by numerical simulations it will be shown that an increase in the fluctuation's intensity leads to homogenization of the adsorbate distribution in the system leading to layer-by-layer growth. We will show that in the case of weak fluctuations an increase in the flux fluctuations intensity leads to: (i) an acceleration of pattern formation processes, (ii) a delaying dynamics of the mean adsorbate islands growth, (iii) a decrease in the linear size of separated spherical-shaped adsorbate islands. At elevated values of the fluctuation's intensity it’s increasing leads to the transformation of the surface morphology from separated adsorbate islands on the substrate towards separated holes inside adsorbate matrix. 
By performing statistical analysis of the surface we will show that the introduced fluctuations result in abnormal adsorbate islands growth law with the power-law asymptotic, comparing to the deterministic case. It will be shown that the distribution of adsorbate islands over sizes remains universal at different time instants in the stage of islands growth. It will be shown that in the quasi-stationary limit an increase in the fluctuation's intensity provides transformations of the islands size distribution from unimodal for spherical-shaped adsorbate islands, through bimodal distribution of adsorbate islands of different form and bimodal distribution of holes of different form, towards unimodal distribution of spherical-shaped holes, which are fitted well by the Lorenz-like distributions.