Observation and Origin of Extraordinary Atomic Mobility at Metal-Semiconductor Interfaces at Low Temperatures

Abstract

Extraordinarily high mobility of Si and Ge atoms at semiconductor (Si, Ge)-metal (Al) interfaces is observed at temperatures as low as 80 K during thin metal film deposition. In situ x-ray photoemission spectroscopic valence-band measurements reveal a changed chemical bonding nature of the semiconductor atoms, from localized covalentlike to delocalized metalliclike, at the interface with the Al metal. The resulting delocalized bonding nature of the interfacial semiconductor atoms brings about the observed extreme enhancement of their mobility. The finding opens avenues for tailoring reaction kinetics and phase transformations in nanostructured materials, as functional thin-film systems, at ultralow temperatures by dedicated interfacial design.

Heterogeneous growth of single crystals on polycrystals

“…After growth stagnation of c-Ge at the intersection of an Al GB with the Al surface, it is energetically more preferred that the Ge atoms of the a-Ge on the adjacent Al grain [grain 1 in the drawing of Figs. 4(d) and 4(e)] now diffuse along the a-Ge/c-Al interface [14] towards the c-Ge on grain 0, causing growth of the c-Ge sheet on grain 0 perpendicular to the surface (i.e., thickening) and depletion of a-Ge on Al grain 1, as experimentally observed (Figs. 1 and 3).…”

“…This interface-mediated nucleation of c-Ge has been shown to be possible to occur at the a-Ge/c-Al interface at very low temperatures ( 50 • C) on the basis of interface thermodynamic calculation [9,13]. The critical thickness above which the bulk Gibbs energy overcompensates the increase of the interface energies upon crystallization is smaller than the thickness of a-Ge adjacent to the metal of weakened covalent bonds and thus of increased atomic mobility [14]. Then, as shown in Fig.…”

Melting Point Depression and Fast Diffusion in Nanostructured Brazing Fillers Confined Between Barrier Nanolayers

“…Only very recently it has been demonstrated that nano-scale effects, such as a size-dependent reduction of the melting point (further referred to as Melting Point Depression; MPD) (Ref [1][2][3][4][5][6] and intrinsically high atom mobilities along internal interfaces (i.e., phase and grain boundaries) ( Ref 7,8) can be exploited to meet these opposing technological requirements (Ref 7,9). This recent awareness has resulted in increased research activities in the emerging field of nanojoining, focusing on the development of novel nanostructured metallic filler materials for advanced low-temperature joining applications ( Ref 1,7,[10][11][12][13][14][15][16][17][18][19][20].…”

Interdiffusion at Room Temperature in Cu-Ni(Fe) Nanolaminates

“…High diffusivities are found for semiconductor interfaces at lower temperatures as well. A high atomic mobility of Si and Ge at (Si,Ge)-Al interfaces is reported [37] at only 80 K. Similarly, the diffusion of Hf at 950 • C is reported [38] along linear defects in HfN-ScN nanolaminate; for Cu diffusion at 450 • C [39] along internal interfaces in Cu-AlN nanolaminates; and for Si-Al [40] as well. In these high-temperature studies, high-resolution electron microscopy (HREM) and atom probe methods are used for measuring the effect of solute concentration due to atomic diffusion along dislocations and grain grain boundaries.…”