Holmium growth on Si(001): Surface reconstructions and nanowire formation

Abstract

Holmium deposition on the Si͑001͒ surface at elevated temperature results in the formation of Ho silicide islands coexisting with a Ho reconstructed substrate surface. At metal coverages below a monolayer, most of the islands are highly elongated nanowires. Structural details of both the reconstructions and the nanowires derived from scanning tunneling microscope data are presented. In addition, scanning tunneling spectroscopy shows that the nanowires are more metallic than either the reconstructed surface, or large silicide islands.

Formation of ytterbium silicide film on Si(001) by solid-phase epitaxy

“…A close inspection of this STM image reveals that the islands are preferably elongated in the either [1 1 0] or ½1 1 0 direction. This is reminiscence of the growth of hexagonal RE silicide nanowires on Si(0 0 1) with the epitaxial relationship of ½1 1 2 0RESi 2Àx J[1 1 0] or ½1 1 0Si [6][7][8][9][10][11][12][13][14]. As remarked above, due to a rather good lattice match along one silicide axis and a poor match along the other, the anisotropic strain of hexagonal Yb silicide can indeed favor the preferable growth along one of these Si directions.…”

“…It is not clear enough whether such a structure can be compatible with AlB 2 and Th 3 Pd 5 structures found for silicon-rich Yb disilicides [21]. However, it is different from the 1 Â 1 reconstruction on the top of hexagonal Yb silicide nanowires [16] as well as the c(2 Â 2) and 2 Â 1 reconstructions on the top of other hexagonal RE silicide nanowires [8,9,[12][13][14]. Therefore, we can presume that 3D clusters crystallize in distinct structure, as compared to that of hexagonal Yb silicide nanowires.…”

“…It was shown that the formation of such nanowires is favored by epitaxial relationship of hexagonal silicide and Si(0 0 1) surface lattices, where the ½1 1 % 2 0 and [0 0 0 1] silicide axes lie in the substrate surface plane and are aligned along the [1 1 0] Si directions. In particular, the long nanowires were reported recently for Dy [6,[8][9][10], Er [7,[10][11][12], Ho [8,13], and Gd [10,14] that provide a very low lattice mismatch along the [11][12][13][14][15][16][17][18][19][20] axis (about 1% or below) and much larger mismatch along the [0 0 0 1] axis (about 7%). In contrast, Nd silicide is poorly matched with Si(0 0 1) along the both axes, yielding the formation of compact 3D islands [15].…”

Synthesis of very long ErSi2 nanowires on Si substrates

“…But the average length of those wires was in the range of 100 nm, which making such wires in device applications difficult. Indeed, most of the reports focused on the formation mechanism and investigation in vacuum such as by using a scan tunneling microscope [1][2][3][4][5]. Most of the studies confined to surface physics are more correct.…”

“…The synthesis of rare-earth silicide nano-structures on Si substrate has been an interesting topic because of their potential in forming low-dimensional devices [1][2][3]. One approach for fabricating such nanostructures is a self-assembled growth in an ultra-high vacuum (UHV) system.…”