Identifying the Numbers of Ag Atoms in Their Nanostructures Grown on a Si(111)-(7 × 7) Surface

Abstract

Using scanning tunneling microscopy, we have conducted an in situ study of the room-temperature growth of Ag structures on a Si( 111)-(7 Â 7) surface. By observing the STM images at various Ag coverages, a number of Ag structures were identified in both the faulted and the unfaulted half unit cells. The number of Ag atoms contained in each of these Ag structures was precisely determined through observation of inter-half unit cell diffusion. Transformations between the Ag structures via inter-and intra-half unit cell diffusion provide detailed information for the mechanisms of Ag structure growth. The precision knowledge of the number of atoms in such structures will form a fundamental base for understanding the physical and chemical properties of these structures.

Probing the generalized magicity of Ag nanoclusters constructed on Si(111) by atomic manipulation

“…7,9 Ag clusters could be formed by thermal growth with coverages larger than 0.05 monolayer (ML) (1 ML = 1.38 × 10 15 atoms/cm 2 ). 35 However, this method could neither tell the exact number of atoms of the clusters due to limited resolution of STM images nor provide clean environments for them because of the dense Ag structures on the surface. To precisely identify and quantitatively measure the dynamic processes of the clusters as a function of their sizes, we refer to atomic manipulation to provide such accuracy and clean environments for each cluster.…”

“…36 The Ag clusters are prepared by STM vertical atomic manipulation. We take a faulted-HUC (FHUC) of the (7 × 7) reconstruction as a template trap 35 and use a functionalized STM tip to repetitively transfer single Ag atoms elsewhere to this target FHUC to construct the Ag clusters, one Ag atom at a time. Consequently, the sizes of the clusters can be obtained by counting the number of the Ag atoms used in the assembly.…”

Scanning tunneling microscopy at multiple voltage biases of stable “ring-like” Ag clusters on Si(111)–(7×7)

“…Ming et al recently determined the number of atoms in Ag clusters obtained by deposition at room temperature without annealing [17,18]. While measuring at a bias voltage of + 2 V, they observed three lobes only on clusters with 10 to 13 Ag atoms.…”

“…We present a series of STM images at different bias voltages for the two different "ring-like" clusters. In order to propose a structural model for these clusters, we combined this new insight together with the structure of Au clusters on Si(111)-(7 × 7) studied by Ghose et al [16] as well as the number of Ag atoms determined by comparison with the studies from Ming et al [17,18].…”

Atomically resolved force microscopy

“…Scanning tunneling microscopy (STM), invented in 1981 by Binnig et al, 1 has the ability to image single atoms [2][3][4][5] and intra/intermolecular bonds; 6,7 make measurements of the local density of (electronic) states (LDOS), [8][9][10] spin states, [11][12][13] and standing waves of surface electrons; 14 induce vibration excitation in single molecules (single-molecule vibration spectroscopy), 15 which causes them to dissociate 16 and also causes synthesis 17 (single molecule chemistry); and manipulate individual atoms, [18][19][20][21][22][23][24][25][26] charge, [27][28][29] and spin. 30,31 Thus, STM can be used to fabricate predesigned nanostructures by true bottom-up methods based on atom-by-atom manipulation.…”