Self-assembly, dynamics, and structure of Si magic clusters

Abstract

We demonstrate the preferential formation and self-assembly of monodisperse Si magic clusters ͑X 4 ͒ of size ϳ13.5Ϯ 0.5 Å on Si͑111͒-͑7 ϫ 7͒ surface using scanning tunneling microscope. The growth process is observed to occur via a stepwise assembly of planarized Si tetramers ͑X 1 ͒ formed from Si adatoms deposited at room temperature, leading to Si tetraclusters ͑X 2 ͒ ͑size ϳ4.6Ϯ 0.5 Å͒ and culminating in tetracluster dimer ͑X 3 ͒ and trimer ͑X 4 ͒ formations as the surface is being annealed progressively to 150°C. The respective cluster species density distribution at each annealing temperature also shows the preferential formation of X 1 → X 2 → X 3 → X 4 at higher temperatures, which we describe using surface reaction schemes; X 1 → X 2 , X 2 + X 2 → X 3 , and X 2 + X 3 → X 4 . We determine the activation and formation energies for respective cluster species and elucidate the formation energetics and dynamics of tetraclusters which function unequivocally as fundamental building blocks in the self-assembly of stable Si magic clusters. Finally, we resolve the structure of the Si magic cluster to comprise three tetraclusters or n = 12 Si atoms taking into consideration ͑i͒ cluster symmetry and alignment, ͑ii͒ close packing, and ͑iii͒ minimization of dangling bonds.

Graphene Growth on C and Si-Face of <i>4H</i>-SiC – TEM and AFM Studies

“…These strong bonds are most likely responsible for the honeycomb nanomesh called 6R3 pattern which is superimposed on the 1x1 graphene structure. The 6R3 pattern has been extensively characterized by STM experimental [12][13][14][15][16][17][18] and theoretical studies [9][10][11]18].…”

Starting Point of Cluster-Derived Silicon Nanowires

“…On the other hand, as the diameter of small sized SiNW is close to that of the medium-sized silicon cluster, cluster-derived SiNW (CDSiNW) is also concerned of as a possible structural model to study the SiNW in theory. The latter has been supported as the assembly of silicon clusters on silicon surfaces confirmed with Scanning Tunneling Microscopy (STM) in experiments [19,20]. The possibility of silicon clusters congregating and forming a wire-like structure was focused in this work.…”