Abstract
We demonstrate the preferential formation and self-assembly of monodisperse Si magic clusters of size on surface using scanning tunneling microscope. The growth process is observed to occur via a stepwise assembly of planarized Si tetramers formed from Si adatoms deposited at room temperature, leading to Si tetraclusters (size ) and culminating in tetracluster dimer and trimer formations as the surface is being annealed progressively to . The respective cluster species density distribution at each annealing temperature also shows the preferential formation of at higher temperatures, which we describe using surface reaction schemes; , , and . 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 Si atoms taking into consideration (i) cluster symmetry and alignment, (ii) close packing, and (iii) minimization of dangling bonds.
1 More- Received 11 February 2009
DOI:https://doi.org/10.1103/PhysRevB.79.235439
©2009 American Physical Society