ТЕОРЕТИЧНА МОДЕЛЬ ФОРМУВАННЯ ОДНОВИМІРНИХ НАНОСТРУКТУР ОКСИДУ МІДІ В УМОВАХ ПЛАЗМОВОГО СЕРЕДОВИЩА

Abstract

The work is devoted to the development of a theoretical model of the formation of 1D nanostructures of copper oxide under conditions of action on a copper sample of elevated temperatures and fluxes of charged particles. One of the promising methods for obtaining copper oxide nanowires is the use of plasma to activate the sample surface and heat it. Although the thermal growth is the most applied, plasma methods have a number of advantages, such as process rate (tens of minutes compared to several hours – for thermal methods), better process control (the ability to use ions with specified energy), low cost on electricity, environmental safety, etc. However, plasma methods have some disadvantages, like relatively small aspect ratio (the characteristic value ranges from 20 to 40, while for thermal methods – 60 to 100), as well as rapid achieving of the saturation mode in length. To synthesize a new technology that combines the advantages of both methods and eliminates their disadvantages, a developed theoretical basis is necessary, which, unfortunately, is absent today. The proposed model of formation of oxide nanostructures considers the dynamics of growth of oxide layers (Cu2O and CuO) on the surface of the copper sample, as well as the formation of nanowires on the surface of the oxide exposed to the gas phase. The model takes into account the temperature of the sample, the gas pressure in the chamber, and the energy of the plasma ions. It was found that although the diffusion rate increases significantly with increasing the sample temperature, the main factors limiting the growth process are: the rate of CuO formation and the intensity of surface sputtering due to the ion bombardment; limited supply of copper atoms to the top of the nanowire, as well as their unlimited supply to the base of the nanowire. Uneven spraying of the nanowire material along its surface is also an important factor: the ion current density on the side surface of the nanowire is much lower compared to the density on its top, because ions bombard the side surface at a very small angle. Thus, the increased energy of the ions can prevent the formation of nanowires at a significant electric potential of the sample.