Ab initiocharacterization of transition-metal-doped Si nanocrystals

Abstract

We investigate the influence of transition-metal doping on silicon nanocrystals by means of first-principles calculations within a supercell approach. We focus on the energetic stability of different doping sites and on electronic and magnetic properties of the most stable configurations. Remarkable differences concerning the magnetic moments and the electronic properties are found between iron and manganese and for inclusion of strong electron correlation. In addition, a self-purification effect, which hampers an incorporation of transitionmetal atoms in small nanocrystals, is observed.

Magnetic interaction in pairwise Mn-doped Si nanocrystals

“…Actually the formation energies of isolated substitutional and interstitial Mn crosses at ⌬ Si = −0.4 eV. 14 The difference between the two values ⌬ Si of 0.7 eV may be traced back to the magnetic coupling between two Mn atoms.…”

“…[7][8][9] Meanwhile such studies also exist for Mn-doped III-V semiconductor nanocrystals 8,10-12 and the incorporation of TM atoms into group-IV ͑Si or Ge͒ nanocrystals. 8,[13][14][15] They are driven by experimental findings that, e.g., self-organized Ge 1−x Mn x nanocolumns show high-Curie-temperature ferromagnetism. 16 The understanding of the magnetic and electronic properties of TM-doped nanostructures is related to the central question of interplay of electron confinement and magnetism on a nanoscale.…”

“…The relationship of the electronic and magnetic properties to the different inequivalent sites has been studied for individual Mn dopants and differently sized NCs in detail. [13][14][15] Open questions concern the favored geometrical arrangement of TM atoms for higher dopant concentrations and the accompanying magnetic interactions as well as their modification with the NC size.…”

Theoretical study of the structural and electronic properties of aggregates, wires, and bulk phases formed from M@Si16 superatoms (M = Sc−, Ti, V+)

“…The magnetic properties of the [Cr@Si 12 ] 2 dimer aggregate, both free and supported on Si(111) surfaces, have been studied by Robles and Khanna [19] obtaining a weakening of the Cr-Si bonds as new Si-Si bonds are formed, which facilitate the alignment of Cr spins. Leitsmann and coworkers [20] have investigated the influence of substitutional and interstitial transition metal doping on the electronic and magnetic properties of silicon nanocrystals. They found a large influence from electron-correlation effects by comparing results from a semilocal GGA approach to exchange-correlation with those from a GGA+U treatment.…”

Quantum confined stark effect in wide parabolic quantum wells: real density matrix approach

“…The effects of confinement of carriers overlap with the interaction with the field giving rise to the new phenomenon known as the quantum confined Stark effect (QCSE). First reported for quantum wells by Miller et al [1,2], the QCSE is is still the subject of a vivid interest [3,4]. References are only a small collection of a very large number of papers studying the properties of various nanostructures (quantum wells, quantum dots, quantum rods, superlattices etc.)…”