Ab-initio and classical molecular dynamics simulations of N2 desorption from TiN(001) surfaces
2014 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 624, 25-31 p.Article in journal (Refereed) Published
Ab initio molecular dynamics simulations based on density functional theory show that N adatoms are chemisorbed in threefold sites close to a N surface atom and between the two diagonally opposed neighboring Ti surface atoms on TiN(001). The most probable N adatom reaction pathway, even in the presence of nearby N adatoms, is for the N adatom and N surface atom pair to first undergo several exchange reactions and then desorb as a N2 molecule, resulting in a surface anion vacancy, with an activation barrier Edes of 1.37 eV and an attempt frequency Ades = 3.4 × 1013 s− 1. Edes is essentially equal to the N adatom surface diffusion barrier, Es = 1.39 eV, while As is only three to four times larger than Ades, indicating that isolated N adatoms migrate for only short distances prior to N2 desorption. The probability of N2 desorption via recombination of N adatoms on TiN(001) is much lower due to repulsive adatom/adatom interactions at separations less than ~ 3 Å which rapidly increase to ~ 2 eV at a separation of 1.5 Å. We obtain good qualitative and quantitative agreement with the above results using the modified embedded atom method potential to perform classical molecular dynamics simulations.
Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 624, 25-31 p.
N2 desorption; Surface diffusion; Nitrides; Molecular dynamics simulations; Density functional theory; Vacancy formation
IdentifiersURN: urn:nbn:se:liu:diva-111791DOI: 10.1016/j.susc.2014.01.007ISI: 000335097900005OAI: oai:DiVA.org:liu-111791DiVA: diva2:760305