4 research outputs found
Understanding the impact of heavy ions and tailoring the optical properties of large-area Monolayer WS2 using Focused Ion Beam
Focused ion beam (FIB) has been used as an effective tool for precise
nanoscale fabrication. It has recently been employed to tailor defect
engineering in functional nanomaterials such as two-dimensional transition
metal dichalcogenides (TMDCs), providing desirable properties in TMDC-based
optoelectronic devices. However, the damage caused by the FIB irradiation and
milling process to these delicate atomically thin materials, especially in the
extended area, has not yet been elaboratively characterised. Understanding the
correlation between lateral ion beam effects and optical properties of 2D TMDCs
is crucial in designing and fabricating high-performance optoelectronic
devices. In this work, we investigate lateral damage in large-area monolayer
WS2 caused by the gallium focused ion beam milling process. Three distinct
zones away from the milling location are identified and characterised via
steady-state photoluminescence (PL) and Raman spectroscopy. An unexpected
bright ring-shaped emission around the milled location has been revealed by
time-resolved PL spectroscopy with high spatial resolution. Our finding opens
new avenues for tailoring the optical properties of TMDCs by charge and defect
engineering via focused ion beam lithography. Furthermore, our study provides
evidence that while some localised damage is inevitable, distant destruction
can be eliminated by reducing the ion beam current. It paves the way for the
use of FIB to create nanostructures in 2D TMDCs, as well as the design and
realisation of optoelectrical devices on a wafer scale
Understanding the impact of heavy ions and tailoring the optical properties of large-area monolayer WS2 using focused ion beam
Abstract Focused ion beam (FIB) is an effective tool for precise nanoscale fabrication. It has recently been employed to tailor defect engineering in functional nanomaterials such as two-dimensional transition metal dichalcogenides (TMDCs), providing desirable properties in TMDC-based optoelectronic devices. However, the damage caused by the FIB irradiation and milling process to these delicate, atomically thin materials, especially in extended areas beyond the FIB target, has not yet been fully characterised. Understanding the correlation between lateral ion beam effects and optical properties of 2D TMDCs is crucial in designing and fabricating high-performance optoelectronic devices. In this work, we investigate lateral damage in large-area monolayer WS2 caused by the gallium focused ion beam milling process. Three distinct zones away from the milling location are identified and characterised via steady-state photoluminescence (PL) and Raman spectroscopy. The emission in these three zones have different wavelengths and decay lifetimes. An unexpected bright ring-shaped emission around the milled location has also been revealed by time-resolved PL spectroscopy with high spatial resolution. Our findings open up new avenues for tailoring the optical properties of TMDCs by charge and defect engineering via focused ion beam lithography. Furthermore, our study provides evidence that while some localised damage is inevitable, distant destruction can be eliminated by reducing the ion beam current. It paves the way for the use of FIB to create nanostructures in 2D TMDCs, as well as the design and realisation of optoelectrical devices on a wafer scale
Strong exciton-photon coupling in large area MoSe2 and WSe2 heterostructures fabricated from two-dimensional materials grown by chemical vapor deposition
Two-dimensional semiconducting transition metal dichalcogenides embedded in optical microcavities in the strong exciton-photon coupling regime may lead to promising applications in spin and valley addressable polaritonic logic gates and circuits. One significant obstacle for their realization is the inherent lack of scalability associated with the mechanical exfoliation commonly used for fabrication of two-dimensional materials and their heterostructures. Chemical vapor deposition offers an alternative scalable fabrication method for both monolayer semiconductors and other two-dimensional materials, such as hexagonal boron nitride. Observation of the strong light-matter coupling in chemical vapor grown transition metal dichalcogenides has been demonstrated so far in a handful of experiments with monolayer molybdenum disulfide and tungsten disulfide. Here we instead demonstrate the strong exciton-photon coupling in microcavities composed of large area transition metal dichalcogenide/hexagonal boron nitride heterostructures made from chemical vapor deposition grown molybdenum diselenide and tungsten diselenide encapsulated on one or both sides in continuous few-layer boron nitride films also grown by chemical vapor deposition. These transition metal dichalcogenide/hexagonal boron nitride heterostructures show high optical quality comparable with mechanically exfoliated samples, allowing operation in the strong coupling regime in a wide range of temperatures down to 4 Kelvin in tunable and monolithic microcavities, and demonstrating the possibility to successfully develop large area transition metal dichalcogenide based polariton devices