Steven C. Erwin

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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(More)
Doping--the intentional introduction of impurities into a material--is fundamental to controlling the properties of bulk semiconductors. This has stimulated similar efforts to dope semiconductor nanocrystals. Despite some successes, many of these efforts have failed, for reasons that remain unclear. For example, Mn can be incorporated into nanocrystals of(More)
We report on the epitaxial growth of a group-IV ferromagnetic semiconductor, Mn(x)Ge(1-x), in which the Curie temperature is found to increase linearly with manganese (Mn) concentration from 25 to 116 kelvin. The p-type semiconducting character and hole-mediated exchange permit control of ferromagnetic order through application of a +/-0.5-volt gate(More)
If magnetic semiconductors are ever to find wide application in real spintronic devices, their magnetic and electronic properties will require tailoring in much the same way that bandgaps are engineered in conventional semiconductors. Unfortunately, no systematic understanding yet exists of how, or even whether, properties such as Curie temperatures and(More)
By incorporating spin-dependent properties and magnetism in semiconductor structures, new applications can be considered which go beyond magnetoresistive effects in metallic systems. Notwithstanding the prospects for spin/magnetism-enhanced logic in semiconductors, many important theoretical, experimental, and materials challenges remain. Here we discuss(More)
We demonstrate that our tight-binding method { which is based on tting the energy bands and the total energy of rst-principles calculations as a function of volume { can be easily extended to accurately describe carbon and silicon. We present equations of state that give the correct energy ordering between structures. We also show that quantities that were(More)
A reversible structural transition is observed on Si(553)-Au by scanning tunneling microscopy, triggered by electrons injected from the tip into the surface. The periodicity of atomic chains near the step edges changes from the 1×3 ground state to a 1×2 excited state with increasing tunneling current. The threshold current for this transition is reduced at(More)
A stable high-index surface of silicon, Si(5 5 12), is described. This surface forms a 2 x 1 reconstruction with one of the largest unit cells ever observed, 7.7 angstroms by 53.5 angstroms. Scanning tunneling microscopy (STM) reveals that the 68 surface atoms per 2 x 1 unit cell are reconstructed only on a local scale. A complete structural model for the(More)