Noise in Al single electron transistors of stacked design
  We have fabricated and examined several Al single electron transistors whose small islands were positioned on top of a counter electrode and hence did not come into contact with a dielectric substrate. The equivalent charge noise figure of all transistors turned out to be surprisingly low, (2.5 - 7)*10E-5 e/sqrt(Hz) at f = 10 Hz. Although the lowest detected noise originates mostly from fluctuations of background charge, the noise contribution of the tunnel junction conductances was, on occasion, found to be dominant. 
V.A. Krupenin, D.E. Presnov, M.N. Savvateev, H. Scherer, A.B. Zorin   and J. Niemeyer