All-Electrical Determination of Crystal Orientation in Anisotropic Two-Dimensional Materials

Abstract

The crystal orientation of an exfoliated black phosphorous flake is determined by purely electrical means. A sequence of three resistance measurements on an arbitrarily shaped flake with five contacts determines the three independent components of the anisotropic in-plane resistivity tensor, thereby revealing the crystal axes. The resistivity anisotropy ratio decreases linearly with increasing temperature T and carrier density reaching a maximum ratio of 3.0 at low temperatures and densities, while mobility indicates impurity scattering at low T and acoustic phonon scattering at high T.

Emerging in‐plane anisotropic two‐dimensional materials

“…However, the traditional electrical methods need samples have regular shapes or specific information from optical spectra. Recently, Grayson and coworkers developed an all‐electrical technique—conformal five‐contact method, and the in‐plane crystal orientations can be accurately identified without the strict geometric restrictions.…”

“…The rise of in‐plane anisotropic 2D materials began in 2014 with black phosphorus (BP) . Since then, the polarization‐dependent absorption, Raman spectroscopy, photoluminescence, and the in‐plane anisotropic electronic, thermal, and mechanical properties of BP have been intensively studied. Ignited by BP, other in‐plane anisotropic 2D materials, from semimetals (T d WTe 2 , 1 T’ MoTe 2, and ZrTe 5 TaIrTe 4 ,) to semiconductors (group IV monochalcogenides, Ta 2 NiS 5 , GaTe, group IVB trichalcogenides, group IV‐group V compounds, β GeSe 2 , ReS 2, ReSe 2, PdSe 2 , KP 15 , TlSe,) (Table ) and so on were explored.…”

Highly In‐Plane Anisotropic 2D GeAs2 for Polarization‐Sensitive Photodetection

“…Such value is comparable with BP (≈1.5) device,[6a] but less than GeAs (≈4.6–4.8),[13b,c] which may due to the even lower lattice symmetry of GeAs (monoclinic crystal). It should be noted that the obtained mobility ratio dependent on the geometry of the devices in traditional electrical method, recently, Peng et al. developed a conformal five contact method, which can accurately determinate the in‐plane electrical anisotropy with releasing the strict geometric constraints, and the obtained accurate anisotropic ratio of BP is as high as ≈3, much larger than the traditional electrical method.…”

The Optical Properties and Plasmonics of Anisotropic 2D Materials

“…The low lattice symmetry of BP leads to two distinct in‐plane directions: armchair (AC, perpendicular to the pucker) and zigzag (ZZ, along the pucker), as illustrated in Figure a. Previous studies have demonstrated strong anisotropy in electrical, optical, thermal, and mechanical properties, distinguishing BP from graphene and TMDCs.…”