Intrinsic magnetism at silicon surfaces

Abstract

It has been a long-standing goal to create magnetism in a non-magnetic material by manipulating its structure at the nanoscale. Many structural defects have unpaired spins; an ordered arrangement of these can create a magnetically ordered state. In this article we predict theoretically that stepped silicon surfaces stabilized by adsorbed gold achieve this state by selfassembly, creating chains of polarized electron spins with atomically precise structural order. The spins are localized at silicon step edges having the form of graphitic ribbons. The predicted magnetic state is supported by recent experimental observations, such as the coexistence of double-and triple-period distortions and the absence of edge states in photoemission. Ordered arrays of surface spins can be accessed by probes with single-spin sensitivity, such as spinpolarized scanning tunnelling microscopy. The integration of structural and magnetic order is crucial for technologies involving spin-based computation and storage at the atomic level.

Magnetic Silicon Nanoparticles

“…Similar results have been predicted for stepped silicon surfaces with specific geometry. [7] By assuming only surface atoms contribute to magnetism in Si nanoparticles, the magnetic moment per surface atom is estimated to be ∼0.12 μB, and this trend is consistent with the theory. The experimental value is, however, an order of magnitude smaller than the maximally achievable theoretical magnetic moment (1 μB/surface atom).…”

“…It is conceivable, however, that specific atomic configurations at surfaces support a magnetic moment, and there is experimental as well as theoretical research in this direction. [6,7] However, this paper focuses on Si nanoparticles, whose magnetism has not been investigated in the past. Going from thin films to nanoclusters is likely to enhance the density of moment-carrying defects, because the surface-to-volume ratio is large and because nanoparticles tend to exhibit a broader variety of crystalline imperfections.…”

Current-dependent periodicities of Si(553)-Au

“…However, the transiently doped nature of the 1 2 phase makes this a difficult proposition. adjacent to the step edge [15] is well suited for that purpose. Its structure is not directly affected by the phase transition (compare [1]).…”

Spin Chains and Electron Transfer at Stepped Silicon Surfaces

“…The best studied such example is Si(553)-Au, a stepped surface created when a submonolayer amount of gold is incorporated into the first atomic layer of a silicon substrate [5]. At low temperatures the step edges of Si(553)-Au develop a tripled periodicity which is now understood to arise from the complete spin polarization of every third dangling bond along the step edge [6][7][8][9][10][11][12].The Si(553)-Au system is one member of a family of Au-stabilized Si surfaces miscut from (111) toward or away from the (001) direction. This family is hence collectively denoted as Si(hhk)-Au.…”