Charge Offset Stability in Si Single Electron Devices with Al Gates
  We report on the charge offset drift (time stability) in Si single electron devices (SEDs) defined with aluminum (Al) gates. The size of the charge offset drift (0.15 $e$) is intermediate between that of Al/AlO$_x$/Al tunnel junctions (greater than 1 $e$) and Si SEDs defined with Si gates (0.01 $e$). This range of values suggests that defects in the AlO$_x$ are the main cause of the charge offset drift instability. 
Neil M. Zimmerman, Chih-Hwan Yang, Nai Shyan Lai, Wee Han Lim, and   Andrew S. Dzurak
cond-mat.mes-hall