Tungsten Diselenide Patterning and Nanoribbon Formation by Gas‐Assisted Focused‐Helium‐Ion‐Beam‐Induced Etching

Abstract

A gas‐assisted focused‐helium‐ion beam‐induced etching (FIBIE) process is introduced, which accelerates direct‐write patterning of WSe2 relative to standard ion milling. The etching process utilizes the XeF2 precursor molecule to provide a chemical assist for enhanced material removal relative to ion sputtering. The FIBIE process enables high‐fidelity patterning of WSe2 with doses 5× lower than standard He+ milling. This enables the formation of high‐resolution WSe2 nanoribbons with dimensions less than 10 nm. The WSe2 nanoribbons demonstrate high Raman anisotropy and nanoribbon electrical measurements are reported for the first time. The normalized on‐currents of field‐effect transistors reveal that the electron and hole currents are both suppressed and scale with the nanoribbon width, with the electron transport experiencing more degradation. However, on‐currents of nanoribbons created by the FIBIE process remain orders of magnitude greater than nanoribbons formed by standard He+ milling. Scanning transmission electron microscopy and complementary Monte Carlo ion–solid simulations reveal that the reduced currents are partially due to ion‐induced damage in the WSe2.

Electrical and geometrical tuning of MoS2 field effect transistors via direct nanopatterning

“…[37][38][39] It is well known that sulfur vacancies are a strong p-dopant due to a charge transfer mechanism in sulfur deficient MoS 2 , 40,41 making this vacancy process a plausible scenario. Some groups have studied the interaction of TMDCs with helium ion beams, observing the creation of vacancies, 25,28 what supports our hypothesis.…”

“…Helium ion beam etching has also shown the viability of creating new geometries. 27,28 For example, high-quality MoS 2 ribbons down to 10 nm were fabricated to induce a change in the semiconducting phase of the material. 27 One of the advantages of pulsed-focused electron beam induced etching (PFEBIE) compared with other studies is that the energy of the electron beam is much lower.…”

Emerging nanofabrication and quantum confinement techniques for 2D materials beyond graphene

“…Focused helium ion beam-induced etching (IBIE) with XeF 2 precursor gas has been used to directly etch sub-10 nm nanoribbons in WSe 2 . 76 Analogous to the EBIE process, the ion irradiation drives dissociation of the XeF 2 precursor gas, and both chemical and physical mechanisms contribute synergistically to etch the WSe 2 film. A schematic of this process is shown in Fig.…”

Lithographically patterned metallic conduction in single-layer MoS2 via plasma processing

“…12,13 Atomic vacancies, interstitials, and grain boundaries have been extensively studied in MoS 2 . Of particular relevance to this work, sulfur vacancies are generally present in single-layer MoS 2 upon synthesis, 14 and they can be induced by processes such as ion beam exposure, [15][16][17][18][19] plasma exposure, [20][21][22][23][24][25] and annealing, 26 to name a few. The chalcogen vacancies in MoS 2 behave like highly localized n-type dopants, which are nearly dispersionless.…”