Hyperfine interactions at dangling bonds in amorphous germanium

T. Graf, T. Ishikawa, K. M. Itoh, E. E. Haller, M. Stutzmann, M. S. Brandt

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Isotope-engineered amorphous germanium (a-Ge) films with73Ge concentrations in the range of 0.1 to 95.6 % have been investigated by electron spin resonance (ESR) and electrically detected magnetic resonance (EDMR) at microwave frequencies between 0.434 and 9.35 GHz. The hyperfine interactions of dangling bond (DB) defects with many73Ge nuclei and their spin localization radius have been extracted from the broadening of the EDMR signals in isotope enriched samples at different73Ge concentrations. Linewidths as low as (Formula presented) have been observed at 0.434 GHz in a sample without73Ge nuclear spins. At low73Ge concentrations, the frequency-dependent linewidth (Formula presented) is determined by g-factor anisotropy and disorder. A frequency-independent linewidth contribution of about 1 G is attributed to dipolar broadening between the DB electronic spins. Over a large range of intermediate concentrations, the statistically distributed nuclear spins of73Ge atoms on sites close to the DB defect atom are responsible for the overall linewidth. The large linewidth (Formula presented) of samples with73Ge concentrations of 95.6% requires a model wave function with a Fermi contact interaction of Aiso = 29 G × gμB at the defect atom, indicating that a fraction of 3.4% of the DB wave function originates from s-like orbitals there. The decay of the rest of the DB wave function can be described with a spin localization radius of 3.5 Å by a numerical model for the statistical hyperfine broadening. The delocalization of the DB spin is much smaller than that of the DB charge density determined in transport measurements.

Original languageEnglish
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume68
Issue number20
DOIs
Publication statusPublished - 2003 Nov 20

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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