Impurity‐Induced Robust Trionic Effect in Layered Violet Phosphorus

Abstract

such as the strong room-temperature PL and abundant valley-selective excitation of excitonic states in transition metal dichalcogenides (TMDs). [2,[4][5][6][7] Besides, a neutral exciton can capture an additional electron (e) or hole (h) to form a correlated threeparticle state (e-e-h or h-e-h), known as a trion (T), in the presence of excess carriers. [8] It has been demonstrated that trionic effect can strongly affect the PL properties of 2D materials through controlling the excess carriers' population. [9][10][11] However, the small trion binding energy in various TMDs (< 50 meV) greatly hinders the investigation of T emission in 2D systems. Taking the thermal fluctuation and dimensional confinement into account, it is arduous for people to observe T emission in non-monolayer TMDs at room temperature. [12] Recently, the radiative recombination of X 0 and T in black phosphorus (BP) has been studied yet. [13] Robust T emission in monolayer BP was observed at ≈1.63 eV at room temperature with the trion binding energy of ≈100 meV. [14] Although the trion binding energy of BP is considerable, the weak ambient stability, especially for monolayer or bilayer BP, limits its application in future trionic devices. More importantly, subject to the narrow bandgap, the PL emission of BP mainly lies in near-IR range.Violet phosphorus (VP), another allotrope of the elemental phosphorus, was first identified by W. Hittorf in 1865. [15] The subtle van der Waals (vdW) layered phosphorus bi-tubular structure leads to abundant exciton-related phenomena, for example, strong PL emissions in the visible range (from ≈1.67 to ≈2.50 eV) at room temperature. [16][17][18][19][20] Moreover, the thermal stability of VP is higher than that of BP, suggesting that VP and its low-dimensional counterparts are more promising candidates for the research of excitonic physics and optoelectronic applications. [17,21,22] Nevertheless, to the best of our knowledge, the trionic effect in VP have yet to be explored.In this work, we synthesized layered VP crystals by the chemical vapor transport (CVT) method and subsequently studied the trionic effect of the mechanically exfoliated VP flakes comprehensively. We found that a robust T emission contributes to the PL spectra of the VP crystals with a huge trion binding energy of ≈109 meV. Using a mild Ar + plasma post-treatment method, we observed a conversion from T emission to X 0 emission. Trionic effect is a vital excitonic physical phenomenon, which intensively affects the optical and optoelectronic properties of 2D materials. Violet phosphorus (VP) is another allotrope of elemental phosphorus with robust photoluminescence (PL) emission in the visible range. So far, experimental investigations of the excitonic behavior in VP are quite scarce. Herein, the evolution of the PL mechanism in synthesized VP crystals against the Ar + plasma exposure is investigated with emphasis on a conversion from trion to exciton emission. The estimated trion binding energy of VP is ≈109 meV, relatively larger than common la...

Degenerate and non-degenerate all-optical switches using violet phosphorus nanosheets

“…In the last few years, researchers have prepared VP-related nanomaterials and conducted a lot of investigations on their optoelectronic properties. For examples, Zhang et al 4 reported a high yield synthesis of VP crystals; Zhao et al 5 synthesized VP quantum dots and studied their fluorescence properties; Zhang et al 2 investigated the band alignment of few-layer violet phosphorene; Zhang et al 6 explored the phonon properties of VP single crystals; Zhang et al 7 demonstrated the friction anisotropy of violet phosphorene; and Li et al 8 reported the impurity-induced robust trionic effect in layered VP. It is noteworthy that the nonlinear optical properties of BP have been extensively investigated.…”

Few-Layered Violet Phosphorene Nanostructures as Saturable Absorbers for Stable Soliton Mode-Locking Operations in an Ultrafast Fiber Laser

“…These high-frequency intratube modes were due to the majorly localized bond stretching and bending. Furthermore, the complex Raman spectrum reflects a large density of phonon states in VP crystals, indicating a strong light–matter interaction . X-ray diffraction (XRD) analysis was also conducted using an x-ray diffractometer (Ultima IV) to identify the crystallinity and structure of the as-prepared VP nanosheets.…”

“…The excellent resistance to bending deformation is critical for ensuring the compatibility of the material and the performance and service life of the related optoelectronic devices. Additionally, Li et al reported that VP has a strong trionic effect and high trionic binding energy of ∼109 meV at room temperature (higher than that of other common 2D materials, such as graphene and transition-metal sulfides, whose trionic binding energy is <50 meV), confirming that it is a superior system for investigating the interaction between light and matter …”

“…This paved the way to explore the unique properties of violet phosphorene (VP) in-depth and develop its advanced applications. Presently, studies have reported that VP has outstanding physicochemical, mechanical, and optoelectronic properties and shows great potential for photonics applications. − For example, experimental studies have shown that VP has low preparation cost, facile large-scale production methods, high yield synthesis, and better thermal and chemical stability than black phosphorus. , Its surface electronic properties, distinct p-type transport characteristics with a high I on / I off ratio of 10 4 at room temperature (exceeding most of the reported 2D materials), and high carrier mobility (∼7000 cm 2 V –1 s –1 for monolayer, an order of magnitude higher than that of 2D transition-metal dichalcogenides) make VP a very promising optoelectronic material . In terms of mechanical properties, VP with crossed structures possesses the highest resistance to deformation among all of the 2D nanomaterials reported so far (2D Young’s modulus of 1512 N/m for monolayer, which is 4.4 times higher than that of graphene) .…”

Partially Oxidized Violet Phosphorus as an Excellent Lubricant Additive for Tribological Applications

“…19 In 2020, violet phosphorus (VP) was successfully synthesized as a new two-dimensional material 20 with a more stable phosphorus isomer than that of black phosphorus. 21 Because VP possesses many unique properties, 22−24 it has been widely studied in catalysts, 25,26 sensors, 27 and optoelectronic fields 28,29 and has presented great potential for applications in the field of tribology. 30 However, few studies have reported its performance in the macroscale friction field, and VP is expected to replace the other 2D materials as a better lubricant additive.…”