Fig. 4
F4TCNQ in PMMA matrix. a Grazing-incidence wide-angle x-ray scattering (GIWAXs) measurements taken on SiC/G with dopant blend and PMMA spacer (inset) (ambient condition, room temperature, 0.15° incident angle). The diffraction ring with radius q = 9.6 nm−1 from PMMA and the absence of F4TCNQ diffraction spots suggests a good molecular solubility in the polymer matrix. The color bar shows the normalized intensity, after a constant diffuse scattering background has been subtracted. The white dotted region denoted over which azimuthal angles the intensity profile in b has been averaged. b The reference sample, without F4TCNQ in the dopant blend displays a clear peak diffraction ring with radius q = 9.6 nm−1; the addition of F4TCNQ molecules enhances the signal twofold. c Stability of doping at low temperature in a device that has been cooled down from room temperature. Starting at T = 300 K we applied a gate voltage VG = +50 V during cool down. Once we reached T = 2 K, the gate terminal is set to VG = 0 V and sample sheet resistance acquires a value of ρXX = 4 kΩ (point A). Thermal excursions to T = 50 K (B), 100 K (C), and 150 K (D) result in reversible ρXX(T) along the black curve. Once temperature exceeds T = 150 K (E), ρXX(T) irreversibly changes to a higher resistive value (red curve), and on cooling down back to T = 2 K, the sample resistance takes a value of ρXX = 5 kΩ (F). In the absence of the gate voltage, the sample resistance remains in the higher resistance ρXX(T) branch
