It is found that the change of threshold voltage value fits in exponential law with absorbed dose, which is caused by the effect of space charge and interface charge.

• 产生这种现象的原因是场效应管氧化物中的空间俘获电荷与吸收剂量近似成线性变化，对阈值电压变化和吸收剂量有近似线性的改变；