Figure 1
Left: Illustration of the FED-setup for the conductivity measurement during RXR and XAS measurements. The measurements were performed in a 4-point van der Pauw-setup in constant current mode at \(\pm 10\mu\)A. Right: (a) FED-initialization at \(T=11\) K. Cycling of gate voltage in dark (red curve) and the corresponding hysteretic response of the sheet resistance (black curve). Hollow dots highlight the non-reversible growth of \(R_{sheet}\) at zero \(V_G\) after every increased value of the positive voltage. (b) Effect of X-ray irradiation: Temporal evolution of the sheet resistance at \(T=11\) K and \(V_G=-150\) V under illumination with 490 eV X-rays. These data have been taken after a previous exposure to X-rays. Hence the initial sheet resistance differs from the initialization measurement in (a) done before X-ray exposure. This hysteretic effect can also be seen in the inset, where the influence of X-ray irradiation on the electrical conductivity versus V\(_G\) is shown.
