ReaxFF molecular dynamics study on oxidation behavior of 3C-SiC: Polar face effects

Abstract

The oxidation of nanoscale 3C-SiC involving four polar faces (C( 100), Si(100), C( 111 ), and Si( 111)) is studied by means of a reactive force field molecular dynamics (ReaxFF MD) simulation. It is shown that the consistency of 3C-SiC structure is broken over 2000 K and the low-density carbon chains are formed within SiC slab. By analyzing the oxygen concentration and fitting to rate theory, activation barriers for C( 100), Si(100), C( 111 ), and Si(111) are found to be 30.1, 35.6, 29.9, and 33.4 kJ•mol −1 . These results reflect lower oxidative stability of C-terminated face, especially along [111] direction. Compared with hexagonal polytypes of SiC, cubic phase may be more energy-favorable to be oxidized under high temperature, indicating polytype effect on SiC oxidation behavior.

Atomic-Level Simulation Study of n-Hexane Pyrolysis on Silicon Carbide Surfaces

“…The hydrogen density profile across the surface also again demonstrates the permeation of hydrogen atoms at high temperature (see Figure c). Our simulation results are consistent with the previous studies of hydrothermal corrosion and asymmetric surface face’s stability of SiC (001) surfaces in the presence of water …”

“…For the simulations in this work, LAMMPS molecular dynamics simulation package (version released on Nov. 17, 2016) was employed with the Si/C/H/O ReaxFF potential developed by van Duin et al for the interactions of hydrocarbon, water and silicon/silicon oxides, which have previously been successfully used to investigate various systems. , The silicon carbide (SiC) surface with the dimension of 3.69 × 3.69 × 4.02 nm 3 was constructed by cleaving β-cristobalite unit cell along the (001) direction and then periodically expanded in x - and y - directions. ,, Due to the highly reactive nature of the silicon carbide surface, hydroxyl groups were used to terminate the dangling bonds on both top and bottom of surface slab, which ensures that, at the beginning of the simulations, all carbon and silicon atoms have their normal coordination number of four, , since the previous studies , suggest it as an important step to make the surface stable. On the Si-face of the surface slab, hydroxyl groups are bonded with exposed silicon atoms, whereas on the C-face, hydroxyl groups are bonded with the surface’s carbon atoms.…”

“…28 Oxidation of silicon carbide (SiC) surfaces has been studied by ReaxFF MD from the atomistic and quantum scales. 4,27,34 It was also found that at higher temperature silicon has higher oxidation potential than carbon. van Duin and co-workers 4 34 Although pyrolysis and combustion have been extensively investigated in many experimental methods, 35−37 there are very limited studies on the detailed reaction mechanism at atomic and molecular levels due to the myriad number of chemical reactions taking place within nanoseconds.…”

“…Standard MD simulations mainly handle physical processes, − whereas ReaxFF MD can handle simulations involving both physical and reactive events at the interface between solid, liquid, and gas phases, due to the transferability of ReaxFF across phases . Oxidation of silicon carbide (SiC) surfaces has been studied by ReaxFF MD from the atomistic and quantum scales. ,, It was also found that at higher temperature silicon has higher oxidation potential than carbon. van Duin and co-workers used ReaxFF to study the oxidation of β-SiC (001) interfaces by pure O 2 , pure H 2 O, and a mixture of both at high temperature.…”

“…Unexpected condensation of large graphene flakes during high-temperature oxidation of SiC has been observed above 2400 K in 1.4 ns by ReaxFF MD simulation, which was validated by ab initio quantum molecular dynamics. Oxidation of SiC surface slab of thickness 2.06 nm with different polar faces was studied by ReaxFF and lower oxidative stability of C-terminated face was observed compared to Si-terminated face …”