Oxidation Pattern of Small Silicon Oxide Clusters:  Structures and Stability of Si₆O_n (n = 1−12)

Abstract

We have performed systematic ab initio calculations to study the structures and stability of Si(6)O(n)() clusters (n = 1-12) in order to understand the oxidation process in silicon systems. Our calculation results show that oxidation pattern of the small silicon cluster, with continuous addition of O atoms, extends from one side to the entire Si cluster. Si atoms are found to be separated from the pure Si cluster one-by-one by insertion of oxygen into the Si-O bonds. From fragmentation energy analyses, it is found that the Si-rich clusters usually dissociate into a smaller pure Si clusters (Si(5), Si(4), Si(3), or Si(2)), plus oxide fragments such as SiO, Si(2)O(2), Si(3)O(3), Si(3)O(4), and Si(4)O(5). We have also studied the structures of the ionic Si(6)O(n)(+/-) (n = 1-12) clusters and found that most of ionic clusters have different lowest-energy structures in comparison with the neutral clusters. Our calculation results suggest that transformation Si(6)O(n)+(a) + O --> Si(6)O(n+1)+(a) should be easier.

Theoretical prediction of atomic and electronic structure of neutral Si6Om (m=1–11) clusters

“…Figure 8 shows that the best Si 6 O 6 isomer is the less stable among these silicon-oxide systems, as we can see from the BE I curve. This observation was also reported by Zang et al 39 We study some fragmentation pathways and the corresponding energies for the most stable structures of the series Si 6 Figure 9 shows a similar behavior for the LUMO-HOMO gap and the fragmentation energy against the number of oxygen atoms for the most stable isomer of the series Si 6 O m ͑m =1-11͒, except Si 6 O 5 . Clusters with high minimum fragmentation energy are particularly stable while large LUMO-HOMO gaps are indicative of chemical inertness.…”

“…This global search assures that Si 6 O m isomers are produced from a full exploration of the MSINDO/DFT potential energy, without the limitations of DFT relaxed structures obtained by adding m oxygen atoms, one by one, to different Si 6 isomers. In an attempt to understand better the electronic properties in the formation of these clusters, 39,40 we studied two series: ͑i͒ Si 6 O m ͑m =2,3,4,5,6͒, which can be thought as small Si n clusters plus small oxide fragments and ͑ii͒ Si 6 O m ͑m =9,10,11͒, clusters rich in oxygen, which show that the more stable ones are those for which the silicon atoms are more coordinated to oxygen ones.…”

First Principles Study on Sino (N=14-18) and Si10-Mom(M=1-8) Clusters

“…Zhang and co-workers reported that the binding energies per O atom for Si 6 O n (n=1-12) increased with the numbers of O atoms at first, and then decreased when n>8 [19]. The similar tendency also was found in Si 7 O n (n=1-14) clusters [20].…”

“…In recent years, the oxide silicon was investigated in both experiment [1,4,5,[10][11][12][13] and theory [10][11][12][13][14][15][16][17][18][19][20][21] for its broad prospect in the application. Desjardin and co-workers [1] studied oxidation of Si (111)-(7×7) surface by STM.…”

“…Kinds of Si-O clusters such as SimOn (m, n=1-8) [10,11], SinOn (n=3-5) [12], Si m O n (m=1-5, n=1, 2m+1) [14], Si n O n (n>=5) [17], Si 6 O n (n=1-12) [19], Si 7 O n (n=1-14) [20] and SiO n (1<n≤6) [21] were studied by first principle calculations. Many new possible structures of these clusters were drawn and numerous unfamiliar features of them were investigated.…”