Violet phosphorene, a recently determined semiconducting two-dimensional elemental structure, is a promising electronic and optoelectronic material. The nano-tribological properties of violet phosphorene nanoflakes are essential for their micro device applications. A friction anisotropy has been demonstrated for the violet phosphorene nanoflakes by lateral force microscope due to the sub-nanorod components of violet phosphorus. The friction forces of the violet phosphorene nanoflakes have been demonstrated to be valley along sub-nano rod direction and peak across the sub-nanorod direction with a period of 180°, resulting in a fast identification of the surface structure direction of violet phosphorene. The friction of violet phosphorene nanoflakes has also been shown to increase with increasing scanning pressure. However, it is not sensitive to scanning speed or layers. The friction of the violet phosphorene nanoflakes have also been demonstrated to increase when exposure to air for hours. The friction and adhesion features of violet phosphorene nanoflakes provide valuable foundation for violet phosphorene based devices.

Phosphorene is another layered elemental structure after graphene. The mechanical property is an important character for two-dimensional (2D) structures. The 2D Young's modulus (E 2D ), representing the deformation resistance of 2D nanostructures, has been investigated for the black phosphorene (BP) nanoflakes with thicknesses of 6−22 nm (11−43 layers) by an atomic force microscope nanoindentation method. The nanoeffects have also been found to significantly affect the E 2D of BP nanoflakes. The BP E 2D increases as the layers decreasing. The E 2D -layer model for BP nanoflakes has been deduced to follow E 2D (n) = 53.31(1 + 3.30e −0.13n ), where the E 2D of monolayer BP was deduced to be 214 ± 11 N/m. The E 2D analysis model and E 2D -layer model have been well used to deduce the E 2D of BP nanoflakes.

The dielectric screening plays a critical role in determining the fundamental electronic properties in semiconductor devices. In this work, we report a noncontact and spatially resolved method, based on Kelvin probe force microscopy (KPFM), to obtain the inherent dielectric screening of black phosphorus (BP) and violet phosphorus (VP) as a function of the thickness. Interestingly, the dielectric constant of VP and BP flakes increases monotonically and then saturates to the bulk value, which is consistent with our first-principles calculations. The dielectric screening in VP has a much weaker dependence on the number of layers. This could be ascribed to a strong electron orbital overlap between two adjacent layers of VP, resulting in a strong interlayer coupling. The findings of our work are significant both for fundamental studies of dielectric screening and for more technical applications in nanoelectronic devices based on layered 2D materials.