TY - JOUR
T1 - Al coverage of AlN(0001) surface and Al vapor pressure – Thermodynamic assessment based on ab initio calculations
AU - Strak, Pawel
AU - Ahmad, Ashfaq
AU - Kempisty, Pawel
AU - Piechota, Jacek
AU - Sakowski, Konrad
AU - Nowak, Grzegorz
AU - Kangawa, Yoshihiro
AU - Łażewski, Jan
AU - Krukowski, Stanislaw
N1 - Funding Information:
The research was partially supported by Poland National Science Centre [grant number DEC-2016/23/B/ST5/02278 and DEC- 2017/27/B/ST3/01899] and partially by Japan JST CREST [grant number JPMJCR16N2] and by JSPS KAKENHI [grant number JP16H06418]. This research was carried out with the support in part of the Interdisciplinary Centre for Mathematical and Computational Modelling at the University of Warsaw (ICM UW) under grants no GB77-29, GB84-23 and in part of PLGrid Infrastructure.
Publisher Copyright:
© 2021
PY - 2022/2/15
Y1 - 2022/2/15
N2 - Ab initio calculations were used to determine physical properties of AlN(0001) surface under Al coverage. It was shown that Al atoms are adsorbed in T4 sites for very low Al coverage, up to θAl=1/4 monolayers (ML). For higher Al coverage, θAl=1/4ML up to θAl=1ML the adlayer becomes disordered and corrugated vertically. In this coverage range (0<θAl≤1ML) the Al bonding energy is independent on the coverage and equal to EadsDFT≅5.0eV. For higher coverage, 1ML≤θAl≤7/6ML, the Al adlayer becomes ordered and atomically flat. The Al adsorption energy in this range is EadsDFT≈6.0eV, i.e. much higher. For higher coverage, θAl>1.25ML, the Al adatoms are located in the second layer. The adsorption energy is reduced to EadsDFT=3.97eV at θAl=1.25ML and linearly increasing to EadsDFT=4.88eV for the coverage increase up to θAl=2ML. Full thermodynamic analysis identified two regions in equilibrium with Al vapor: first at very low pressures where θAl≤10-3ML and the second for higher pressures which is 1ML≤θAl≤7/6ML. The second region is relevant for physical vapor transport (PVT) AlN growth. The nitrogen adsorption process, important for PVT AlN growth, takes place at single or double Al layer covered AlN(0001) surface.
AB - Ab initio calculations were used to determine physical properties of AlN(0001) surface under Al coverage. It was shown that Al atoms are adsorbed in T4 sites for very low Al coverage, up to θAl=1/4 monolayers (ML). For higher Al coverage, θAl=1/4ML up to θAl=1ML the adlayer becomes disordered and corrugated vertically. In this coverage range (0<θAl≤1ML) the Al bonding energy is independent on the coverage and equal to EadsDFT≅5.0eV. For higher coverage, 1ML≤θAl≤7/6ML, the Al adlayer becomes ordered and atomically flat. The Al adsorption energy in this range is EadsDFT≈6.0eV, i.e. much higher. For higher coverage, θAl>1.25ML, the Al adatoms are located in the second layer. The adsorption energy is reduced to EadsDFT=3.97eV at θAl=1.25ML and linearly increasing to EadsDFT=4.88eV for the coverage increase up to θAl=2ML. Full thermodynamic analysis identified two regions in equilibrium with Al vapor: first at very low pressures where θAl≤10-3ML and the second for higher pressures which is 1ML≤θAl≤7/6ML. The second region is relevant for physical vapor transport (PVT) AlN growth. The nitrogen adsorption process, important for PVT AlN growth, takes place at single or double Al layer covered AlN(0001) surface.
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U2 - 10.1016/j.commatsci.2021.111159
DO - 10.1016/j.commatsci.2021.111159
M3 - Article
AN - SCOPUS:85121908596
VL - 203
JO - Computational Materials Science
JF - Computational Materials Science
SN - 0927-0256
M1 - 111159
ER -