Environmental effects in mechanical properties of few-layer black phosphorus

Abstract

We report on the mechanical properties of few-layer black phosphorus (BP) nanosheets, in high vacuum and as a function of time of exposure to atmospheric conditions [1]. BP flakes with thicknesses ranging from 4 to 30 nm suspended over circular holes are characterized by nanoindentations using an atomic force microscope tip. From measurements in high vacuum an elastic modulus of 46±10 GPa and breaking strength of 2.4±1 GPa are estimated. Both magnitudes are independent of the thickness of the flakes. Our results show that the exposure to air has substantial influence in the mechanical response of flakes thinner than 6 nm but small effects on thicker flakes. Figure 2. Indentation curves and E3D of BP drumheads in high vacuum. (a) Force versus indentation (F(δ)) curves (coloured lines) performed in HV in five BP drumheads with different thickness (4.5, 7.5, 13.3, 17 and 29 nm) and their cubic polynomial fit to Eq. (1) (thin black lines). (b) Histogram of the E3D values obtained from the cubic polynomial fit of F(δ) curves performed in 39 BP drumheads, following the first method described in the main text. The fit of the data of the histogram to a normal distribution yields E3D= 41±15 GPa. (c) Elastic constant versus t 3 /R 2 measured for 29 BP drumheads, and their linear fit to the Expression [2] (red solid line). This method yields E3D= 52±6 GPa.

Black phosphorus as a new lubricant

“…The ideal elastic moduli of zigzag and armchair BP nanoribbons are approximately 65 and 27 GPa, respectively [26]. Morenomoreno et al [67] investigated the effects of environmental conditions on the mechanical properties of few-layer BP, and the results indicated that the elastic modulus and the breaking strength of BP nanosheets were 46 ± 10 GPa and 2.1 ± 1 GPa, respectively. The in-plane Young's modulus of single-layer BP was 41.3 GPa in the direction perpendicular to the pucker and 106.4 GPa in the parallel direction, and the ideal strains were 0.48 and 0.11 in the perpendicular and parallel directions, respectively [68].…”

Optical Identification of Few-Layer Antimonene Crystals

“…[6][7][8][9] Theoretical calculations predict different interesting properties for this material: an electronic structure with a bandgap in the ultrafast optoelectronics applications range, 6,10,11 high carrier mobilities, 12,13,14 topological behavior 15,16 and optical properties 17,18 that would make antimonene suitable for numerous optoelectronics applications, ranging from solar cell and light-emitting devices to touch screens and photodetectors, [17][18][19][20][21] but without the above mentioned instability of isolated layers of black phosphorus, which are highly hygroscopic (they tend to take up moisture from air) degrading in a few hours of exposition, which limits their application. 22,23 Recent studies have shown both experimentally and theoretically that insights into the optical properties of few-layer antimonene based on Raman spectroscopy are hampered. 6,7 Tsai et al…”

Two-dimensional layered materials: from mechanical and coupling properties towards applications in electronics

“…115 When compared to other 2DLMs with similar honeycomb structures, such as graphene, 4 graphane, 111 WS 2 , 84 MoS 2 69 and h-BN, 133 the weaker P-P bond strength and compromised dihedral angles made the ideal Young's modulus of phosphorene (0.166 TPa in the zigzag direction and 0.044 TPa in the armchair direction) at 0 K much smaller. Besides, the pretension of few-layer black phosphorus was determined experimentally to be in the range of 0.05-0.44 N m −1 , 83,93 and thicker nanosheets had smaller values because of their stronger structural stiffness. Interestingly, phosphorene has a negative Poisson's ratio of −0.027 in the out-of-plane direction when the strain is applied in the zigzag direction due to the coupling hinge mechanism where the hinge θ 546 and θ 214 in Fig.…”

“…Similarly, the deformation consists of linear elastic response under small loads and nonlinear elastic response under larger loads. Thus the effective spring constant of 2D nanosheets under small loads could also be used for the extraction of E and T. 85,92,93 When taking the size of the indenter into consideration, the force-displacement equation could be further modified. 50 In addition to Young's modulus and pretension, breaking strength can also be derived from the model of a clamped circular membrane under a point load.…”

“…120 In this part, recent progress of both the elastic properties and failure mechanisms of different 2DLMs will be analyzed. The critical mechanical constants 4,53,54,61,62,72,74,76,[81][82][83][84][85]87,89,92,93,103,108,109,[111][112][113]116,117,119,120,122,125,126,128,132,134,135,141,142,[144][145][146]148, have been summarized in Fig. 14.…”