fig1

Figure 1. Images of pristine-STO and Nb-doped STO substrate and related dI/dV spectra. (A) Image of pristine STO surface (60 × 60 nm²) with U_B: +1.0 V and I_T: 20 pA; (B) Image of Nb-doped-STO surface (50 × 50 nm²) with U_B: +1.0 V and I_T: 50 pA. Inset: High resolution image of 2×2 reconstructed Nb-doped-STO surface (14 × 14 nm²); (C) dI/dV curves taken on the clean surfaces of the pristine STO (cyan) and Nb-doped STO (black) substrate, respectively. All STS measured with V_B:1.2V, I_T:10 pA and bias modulation of 20 mV at 4.2 K; (D) Imageof C₆₀ deposited on the pristine STO substrate (50 × 50 nm²) with U_B: +1.0 V and I_T: 20 pA; (E) Image of C₆₀ deposited on the Nb-doped STO substrate. Image size is 40 × 40 nm² with U_B: +1.0 V and I_T: 20 pA. STO: SrTiO₃; C₆₀: fullerene.