The influence of localized states charging on 1/f^{\alpha} tunneling   current noise spectrum
  We report the results of theoretical investigations of low frequency tunneling current noise spectra component (1/f^{\alpha}). Localized states of individual impurity atoms play the key role in low frequency tunneling current noise formation. It is found that switching "on" and "off" of Coulomb interaction of conduction electrons with one or two charged localized states results in power law singularity of low-frequency tunneling current noise spectrum 1/f^{\alpha}. Power law exponent in different low frequency ranges depends on the relative values of Coulomb interaction of conduction electrons with different charged impurities. 
V.N. Mantsevich, N.S. Maslova