Charge doping in graphene on thermodynamically preferred BiFeO₃(0001) polar surfaces

Abstract

For graphene/ferroelectric hybrid structures, the atomistic and electronic details of the interfaces are of crucial importance for charge doping in graphene. In this paper, we choose thermodynamically stable BiFeO(0001) surfaces to explore the adsorption behavior and charge doping effect in a graphene/BiFeO system. By performing first-principles calculations, we find that both the adsorption behavior and charge doping effect show distinct characteristics for graphene adsorbed on the oppositely polarized BiFeO(0001) surfaces. We predict that n-type doping and p-type charge doping occur in graphene on the positive and negative BiFeO(0001) surfaces, respectively. The carrier density is estimated to be 10 cm orders of magnitude. Our results reveal that the graphene/BiFeO hybrid system is an intriguing candidate to make graphene-based field-effect transistors, whose p-n junctions can be made by patterning the domain structure of the BiFeO substrate. Moreover, the graphene/BFO hybrid structure may display an outstanding photovoltaic effect due to the combination of the bulk photovoltaic effect of the BFO substrate and the optical transparency of the graphene electrode.

Large Band Offset in Monolayer MoS2 on Oppositely Polarized BiFeO3(0001) Polar Surfaces

“…The calculated binding energies for MoS 2 /BFO Z− and MoS 2 / BFO Z+ hybrid systems are 0.60 and 0.51 J/m 2 , respectively, which are the same order of magnitude as the reported graphene/BFO(0001) hybrid structure. 47 The weak binding energy is consistent with the physisorption mechanism and implies that the vdW bonding is the dominant interaction between the MoS 2 monolayer and the BFO(0001) substrate. Next, we inspect the effect of the MoS 2 monolayer adsorption on the electrostatic potential of the oppositely polarized BFO(0001) surfaces.…”

“…Therefore, the n-type charge doping effect in the MoS 2 monolayer on the BFO Z+ surface is consistent with our previous results. On the basis of Bader’s topological charge analysis, the carrier density is quantitatively estimated to be 3.97 × 10 12 /cm 2 , which is an order of magnitude lower than graphene on the BFO Z+ substrate . Another character to be pointed out is that the band structure of the MoS 2 monolayer on the BFO Z– surface exhibits a considerable perturbation compared to the MoS 2 /BFO Z+ system and that an obvious spin splitting occurs in the d z 2 valence-band edges at the Γ point of the primitive-cell Brillouin zone.…”

“…With regard to the BFO Z+ substrate, the effect of the MoS 2 overlayer on the surface PDOS is manifested by a remarkable upward shift in energy (about 0.5 eV) with respect to the bare BFO Z+ surface (Figure d). According to previous reports on the graphene/ferroelectric hybrid structures, , if we want to obtain reliable quantitative information about the electronic properties of the 2D materials from the DOS calculation, a more dense k -point mesh is necessary. Taking graphene on the 2 × 1 LiNbO 3 (0001) surface unit cell as an example, a k -point mesh reaching up to 30 × 60 × 1 is needed to quantitatively evaluate the charge doping effect in the graphene sheet .…”

“…The multiferroic BiFeO 3 (BFO), with the coexistence of G-type antiferromagnetic order and large ferroelectric polarization (∼90 μC/cm 2 ) well above room temperature, has received intensive investigations in the past decade. − The bulk BFO belongs to the rhombohedral space group of R 3 c with ferroelectric polarization along the four-index [0001] direction, which is the [111] direction in the pseudocubic notation. , For the BFO(0001) polar surfaces, the surface chemistry and thermodynamic stability have been determined by performing first-principles DFT calculations in our previous reports. , Under most environmental conditions, we found that the clean BFO(0001) positive (Z+) and negative (Z−) surfaces should be respectively terminated with −Fe–O 3 –Bi and −Bi–O 2 , which were in agreement with experimental observations at the BFO/La x Sr 1– x MnO 3 and BFO/CoFeB interfaces. By employing the thermodynamically preferred BFO(0001) positive and negative surfaces, we have studied the charge doping effect in the graphene/BFO(0001) hybrid system . Here, we report on the first-principles calculations concerning the effect of BFO(0001) surfaces on the electronic properties of the MoS 2 monolayer.…”

“…By employing the thermodynamically preferred BFO(0001) positive and negative surfaces, we have studied the charge doping effect in the graphene/BFO(0001) hybrid system. 47 Here, we report on the first-principles calculations concerning the effect of BFO(0001) surfaces on the electronic properties of the MoS 2 monolayer. The computational method is detailed in the Supporting Information.…”