TY - JOUR
T1 - Adsorption and reactions of HN3 on Si(1 0 0)-2 × 1
T2 - A computational study
AU - Wang, Jeng Han
AU - Bacalzo-Gladden, Fe
AU - Lin, M. C.
N1 - Funding Information:
J.H.W. is grateful for the support from the Graduate School of Emory University for this study and M.C.L. acknowledges the support from the R.W. Woodruff Professorship at Emory University and from the National Science Council of Taiwan for a Distinguished Visiting Professorship at the Center for Interdisciplinary Molecular Science, National Chiao Tung University, Hsinchu, Taiwan. The authors are also grateful to the Cherry L. Emerson Center of Emory University, which are in part supported by a National Science Foundation grant (CHE-0079627) and an IBM shared University Research Award, and the National Center for High-performance Computing in Taiwan for the use of their resources. Useful VASP results from Drs. C.M. Wei and Ying-Chieh Sun are very much appreciated.
PY - 2006/3/1
Y1 - 2006/3/1
N2 - We have studied the adsorption and decomposition of HN3 on Si(1 0 0)-2 × 1 surface using the hybrid density functional B3LYP method and effective core potential basis, LanL2DZ, with Si15H16 as a double dimer surface model for cluster calculations. The result shows that the barriers for the dissociative adsorption of HN3 forming HN(a) + N2(g) are quite low by stepwise dissociation processes occurring either on a dimer or across the dimers. The low activation energies are consistent with previous experimental observations that the molecularly adsorbed HN3(a) can undergo decomposition producing HN(a) at low surface temperatures. On the other hand, the predicted activation energies for the N3(a) + H(a) formation processes are all relatively higher. These results also explain the absence of the N3(a) species in HREELS measurements following each annealing experiment. Several selected reaction paths were also confirmed with slab model calculations using an optimization approach coupling the energy and gradient calculations by the slab model with the geometrical optimization using Berny algorithm. In addition, the adsorbate effect was examined for the end-on and side-on molecular configurations. For the side-on adsorption configuration, all possible combinations with 1-4 adsorbates can exist on the four surface Si sites of the double dimers, with adsorption energies lying closely to the multiples of that of a single side-on adsorbate (LM2); i.e., adsorption energies are nearly additive. Interestingly, for the end-on adsorption, only 1 and 2 HN3 molecules can adsorb on a dimer due to the presence of the negative charges on the remaining Si sites in the neighboring dimer. For the two end-on adsorbates on the same dimer, the total adsorption energy is close to two times that of HN3(a) or LM1. For the mixed end-on/side-on configurations, only one of each type can co-exist on a single dimer pair (Si1-Si2 or Si3-Si 4) sites with adsorption energy close to the sum of those of one end-on and one side-on adsorbate. Finally, the predicted reaction routes and vibrational frequencies showed good agreement with previous experimental results. The stabilities of many ad-species involved in these reactions with end-on and/or side-on configurations have been predicted together with the transition states connecting those species.
AB - We have studied the adsorption and decomposition of HN3 on Si(1 0 0)-2 × 1 surface using the hybrid density functional B3LYP method and effective core potential basis, LanL2DZ, with Si15H16 as a double dimer surface model for cluster calculations. The result shows that the barriers for the dissociative adsorption of HN3 forming HN(a) + N2(g) are quite low by stepwise dissociation processes occurring either on a dimer or across the dimers. The low activation energies are consistent with previous experimental observations that the molecularly adsorbed HN3(a) can undergo decomposition producing HN(a) at low surface temperatures. On the other hand, the predicted activation energies for the N3(a) + H(a) formation processes are all relatively higher. These results also explain the absence of the N3(a) species in HREELS measurements following each annealing experiment. Several selected reaction paths were also confirmed with slab model calculations using an optimization approach coupling the energy and gradient calculations by the slab model with the geometrical optimization using Berny algorithm. In addition, the adsorbate effect was examined for the end-on and side-on molecular configurations. For the side-on adsorption configuration, all possible combinations with 1-4 adsorbates can exist on the four surface Si sites of the double dimers, with adsorption energies lying closely to the multiples of that of a single side-on adsorbate (LM2); i.e., adsorption energies are nearly additive. Interestingly, for the end-on adsorption, only 1 and 2 HN3 molecules can adsorb on a dimer due to the presence of the negative charges on the remaining Si sites in the neighboring dimer. For the two end-on adsorbates on the same dimer, the total adsorption energy is close to two times that of HN3(a) or LM1. For the mixed end-on/side-on configurations, only one of each type can co-exist on a single dimer pair (Si1-Si2 or Si3-Si 4) sites with adsorption energy close to the sum of those of one end-on and one side-on adsorbate. Finally, the predicted reaction routes and vibrational frequencies showed good agreement with previous experimental results. The stabilities of many ad-species involved in these reactions with end-on and/or side-on configurations have been predicted together with the transition states connecting those species.
KW - Density functional calculations
KW - Hydrazoic acid
KW - Models of surface chemical reactions
KW - Silicon
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U2 - 10.1016/j.susc.2006.01.002
DO - 10.1016/j.susc.2006.01.002
M3 - Article
AN - SCOPUS:33644615208
SN - 0039-6028
VL - 600
SP - 1113
EP - 1124
JO - Surface Science
JF - Surface Science
IS - 5
ER -