Defect sizing, separation, and substrate effects in ion-irradiated monolayer two-dimensional materials

Abstract

Precise and scalable defect engineering of 2D nanomaterials is acutely sought-after in contemporary materials science. Here we present defect engineering in monolayer graphene and molybdenum disulfide (MoS2) by irradiation with noble gas ions at 30 keV. Two ion species of different masses were used in a gas field ion source microscope: helium (He + ) and neon (Ne + ). A detailed study of the introduced defect sizes and resulting inter-defect distance with escalating ion dose was performed using Raman spectroscopy. Expanding on existing models, we found that the average defect size is considerably smaller for supported than freestanding graphene and that the rate of defect production is larger. We conclude that secondary atoms from the substrate play a significant role in defect production, creating smaller defects relative to those created by the primary ion beam. Furthermore, a similar model was also applied to supported MoS2, another promising member of the 2D material family. Defect yields for both ions were obtained for MoS2, demonstrating their different interaction with the material and facilitating comparison with other irradiation conditions in the literature.

Large Photothermal Effect in Sub‐40 nm h‐BN Nanostructures Patterned Via High‐Resolution Ion Beam

“…Second, Ne + ion interstitials within the plane or between the h‐BN layers could further modify the vibrational modes. These conclusions are supported since recent work has shown that exposure of supported graphene to a helium and neon ion beam broadens and reduces the intensity of the E 2g phonon mode due to increased disorder . Although h‐BN consists of two different atoms and layered stacks, we expect that these previous results on a similar E 2g phonon mode inform our measured reduction of the Raman peak in h‐BN.…”

“…Previous work that studied the ion beam patterning of 2D materials, has primarily focused on the sputtering of monolayer graphene via a gallium ion beam, control of defects and electronic doping in encapsulated graphene via a helium ion beam, nanoscale patterning of monolayer graphene, and nanoscale patterning and electrical‐tuning of few‐layer molybdenum disulfide (MoS 2 ) . Recent work has reported the effects of both helium and neon irradiation at 30 keV on monolayer graphene and MoS 2 . However, the sub‐50 nm patterning of multi‐layer and insulating vdW crystals such as h‐BN is even more challenging due to strong charging effects and is yet to be demonstrated.…”

Recent Progress on Irradiation-Induced Defect Engineering of Two-Dimensional 2H-MoS2 Few Layers

“…Maguire et al [92] also irradiated CVD-grown MoS 2 mono-layers with Ne + ions with an energy of 30 keV. With increasing Ne + ion doses, the A 1g and E 2g modes were quenched and broadened, indicating the growing disorder induced by the Ne + ions.…”

“…Maguire et al [92] grew MoS 2 mono-layers on SiO 2 substrates by a CVD technique and irradiated them with He 2+ at an energy of 30 keV and an angle of incidence of 0 • . These irradiation doses ranged from 1 × 10 13 ions/cm 2 to 1 × 10 17 ions/cm 2 .…”

Effect of localized helium ion irradiation on the performance of synthetic monolayer MoS2 field-effect transistors

“…Energetic light ions are known to preferentially sputter chalcogen atoms from TMDs while retaining an adequate micrometer-scale structural integrity for irradiation doses up to approx. 10 16 ions cm −2 [13][14][15][16][17], as well as good electrical conductivity for up to approx. 10 18 ions cm −2 [9,10,18].…”