Figure 4. Decay behavior of resistance variation after light off.

(a) Normalized resistance variation as a function of time after switching off the illumination of 325 nm laser at different temperatures. The decay curves are well fitted by Kohlrausch stretched exponential expression △R ~ exp[-(t/τ)^β]. Here τ and β are decay time constant and exponent. (b) ln τ vs the reciprocal of temperature (1/T).