Modeling of Catalytic Centers Formation Processes during Annealing of Multilayer Nanosized Metal Films for Carbon Nanotubes Growth

Abstract

The paper presents a theoretical model of the catalytic centers formation processes during annealing of multilayer nanosized metal films for carbon nanotubes growth. The approach to the description of the model is based on the mass transfer processes under the influence of mechanical thermoelastic stresses, which arise due to the difference in the thermal expansion coefficients of the substrate materials and nanosized metal layers. The thermal stress gradient resulting from annealing creates a drop in the chemical potential over the thickness of the film structure. This leads to the initiation of diffusion mass transfer between the inner and outer surfaces of the films. As a result, the outer surface begins to corrugate and fragment, creating separate islands, which serve as the basis for the catalytic centers formation. Experimental research on the formation of catalytic centers in the structure of Ni/Cr/Si was carried out. It is demonstrated that the proposed model allows to predict the geometric dimensions of the catalytic centers before growing carbon nanotubes. The results can be used to create micro-and nanoelectronics devices based on carbon nanotube arrays.

Piezoelectric Energy Harvester Based on LiNbO3 Thin Films

“…This indicates a transition from the evaporation mode to ablation ( Figure 7 ). The structural changes of fabricated films deposited at different laser pulse energies can be attributed to the diffusion character of incident particles on the substrate [ 39 , 44 ].…”

“…The deposition of CNTs took place in a plasma obtained at low pressure by means of a direct current electric discharge only on previously prepared catalytic structures with a structure suitable for CNT synthesis. Previously [ 38 , 39 ], we carried out the necessary studies of the growth modes of CNTs by PECVD, which made it possible to determine the optimal technological parameters of their growth. CNTs were grown on Si (100) samples coated with contact V or Cr (50 nm) and catalytic Ni layers (10 nm).…”

“…This indicates a transition from the evaporation mode to ablation (Figure 7). The structural changes of fabricated films deposited at different laser pulse energies can be attributed to the diffusion character of incident particles on the substrate [39,44]. An increase in the grain size can be related to an increase in the kinetic energy of the ablated particles and the intensification of coalescence processes ( Figure 5) [37].…”

“…This indicates a transition from the evaporation mode to ablation (Figure 7). The structural changes of fabricated films deposited at different laser pulse energies can be attributed to the diffusion character of incident particles on the substrate [39,44]. Increasing the laser pulse energy from 180 to 220 mJ results in a decrease of charge carrier concentration from 8.6 × 10 15 to 1.0 × 10 13 cm −3 .…”

“…This indicates a transition from the evaporation mode to ablation (Figure 7). The structural changes of fabricated films deposited at different laser pulse energies can be attributed to the diffusion character of incident particles on the substrate [39,44]. The dependencies of polarization on the field strength exhibit hysteresis, which characterizes these films as ferroelectric with spontaneous polarization.…”