The storage characteristics of nano-crystal Si (NC-Si) devices,especially for MOS capacitors,are studied by cross sectional transmission electron microscopy (TEM) and capacitance-voltage (C-V) measurement under different conditions,including programming and erasing at different temperatures and gate voltages,as well as using +/-bias-temperature (BT) measurements.Physical mechanisms such as carrier trapping,interface state filling,and temperature related deterioration are revealed.The experimental results demonstrate that the degradation of the program window and threshold voltage (VT) shift at high temperature,large voltage sweep range,and bias applied to sweep voltage is strongly related to the type of majority carriers.