Nanoscale probing of surface potential landscape at MoS₂/BP van der Waals p–n heterojunction

Abstract

2D van der Waals heterostructure paves a path towards next generation semiconductor junctions for nanoelectronics devices in the post silicon era. Probing the band alignment at a real condition of such 2D contacts and experimental determination of its junction parameters is necessary to comprehend the charge diffusion and transport through such 2D nano-junctions. Here, we demonstrate the formation of the p-n junction at the MoS2/Black phosphorene (BP) interface and conduct a nanoscale investigation to experimentally measure the band alignment at real conditions by means of measuring the spatial distribution of built-in potential, built-in electric field, and depletion width using the Kelvin probe force microscopy (KPFM) technique. We show that optimization of lift scan height is critical for defining the depletion region of MoS2/BP with nanoscale precision using the KPFM technique. The variations in the built-in potential and built-in electric field with varying thicknesses of MoS2 are revealed and calibrated.

Facet Engineering by Sculpting Artificial Edges on 2D Black Phosphorus for Localized and Selective Piezoelectric Response

“…Additionally, the loops have shown the shift from the zero bias in Figure c,d, which can be elucidated by the difference in work function between the top (AFM tip: Pt/Cr) and bottom electrodes (sample: BP). The built-in electric field originates at the interface of Pt-coated conducting AFM tip and the BP flake due to the difference in work functions of the materials (Figure g), which forms the potential barrier between the semiconducting BP flake and the Pt-coated AFM tip (Figure g) and leads to the self- polarized condition as reflecting in the offset in hysteresis loop at zero bias. , Hence, the electric dipoles of the flake may perhaps tends to prealign due to the existence of an built-in electric field at the interface of conducting AFM tip and semiconducting flake, which signifies the intrinsic polarization of the BP flake, observed locally at the contact point of the AFM tip and flake at a zero bias . Consequently, a higher tip bias becomes necessary to overcome the polarization state induced by the built-in field within the flake, causing a switching of the polarization.…”

“…To gain a comprehensive understanding of the lateral (in-plane) and vertical (out-of-plane) piezoelectric response variation across the facets, such as basal plane and edges of the BP flake, a computational analysis has been carried out in the framework of the first-principles-based DFT − using the plane-wave basis PAW , method. The BP is a noncentrosymmetric system, with the bond angle in the ZZ direction measuring 96.0°, with an adjacent P–P bond length of 2.22 Å.…”