Top–down fabrication of sub-nanometre semiconducting nanoribbons derived from molybdenum disulfide sheets

Abstract

Developments in semiconductor technology are propelling the dimensions of devices down to 10 nm, but facing great challenges in manufacture at the sub-10 nm scale. Nanotechnology can fabricate nanoribbons from two-dimensional atomic crystals, such as graphene, with widths below the 10 nm threshold, but their geometries and properties have been hard to control at this scale. Here we find that robust ultrafine molybdenum-sulfide ribbons with a uniform width of 0.35 nm can be widely formed between holes created in a MoS2 sheet under electron irradiation. In situ high-resolution transmission electron microscope characterization, combined with first-principles calculations, identifies the sub-1 nm ribbon as a Mo5S4 crystal derived from MoS2, through a spontaneous phase transition. Further first-principles investigations show that the Mo5S4 ribbon has a band gap of 0.77 eV, a Young’s modulus of 300GPa and can demonstrate 9% tensile strain before fracture. The results show a novel top–down route for controllable fabrication of functional building blocks for sub-nanometre electronics.

MoS2‐Based Nanocomposites for Electrochemical Energy Storage

“…There are two typical methods to prepare MoS 2 : top‐down and bottom‐up. A top‐down method starts from bulk MoS 2 crystals as the raw material, and the bulk MoS 2 crystals can be easily exfoliated to atomically thin layers via mechanical cleavage, high‐energy sonication, and liquid exfoliation or chemical intercalation‐exfoliation methods based on the special feature of MoS 2 (interlayer contacted via the weak van der Waals force) 36, 37, 38, 39. The bottom‐up method can be divided into two approaches: 1) chemical vapor deposition (two‐step thermolysis using ammonium thiomolybdeates or molybodenum trioxide as the precursor followed by sulfidation with sulfur) method with the features of high quality, controllable thickness, and compatible substrates; and 2) wet‐chemical synthesis including hydrothermal and solvothermal ((NH 4 ) 6 Mo 7 O 24 ·4H 2 O and thiourea have been utilized as the precursors), showing relative lower crystal quality yet abundant active sites and easy to form morphologies with various substrates (such as hollow carbon spheres, carbon nanotube/nanofibers, amorphous carbon/conductive polymer coatings, graphene films, and CMK‐3).…”

Single-layer MoS2 nanopores as nanopower generators

“…12). We use our MoS 2 nanopore generator to power a MoS 2 transistor, thus demonstrating a self-powered nanosystem.MoS 2 nanopores have already demonstrated better water-transport behaviour than graphene 13,14 owing to the enriched hydrophilic surface sites (provided by the molybdenum) that are produced following either irradiation with transmission electron microscopy (TEM) 15 or electrochemical oxidation 16 . The osmotic power is generated by separating two reservoirs containing potassium chloride (KCl) solutions of different concentrations with a freestanding MoS 2 membrane, into which a single nanopore has been introduced 13 .…”

Identification of single nucleotides in MoS2 nanopores

“…MoS 2 nanopores are of particular interest as they can be used for extended periods of time (hours, and even days) without the need for any additional functionalization 18 . The sticking of DNA to MoS 2 nanopores is reduced by the Mo-rich region around the drilled pore after irradiation with a transmission electron microcope (TEM) 21 , and their stability can be attributed to their relative thickness (single-layer MoS 2 has a thickness of 0.7 nm). Single-layer MoS 2 also has a direct bandgap of at least 1.8 eV (refs 4, 22), a feature that is essential for electronic base detection with field-effect transistors (FETs) 4,23 .…”

“…Our group has recently shown that a silicon nitride nanopore can be integrated with a graphene nanoribbon transistor, and the translocation of DNA can be simultaneously detected using ionic currents and electrical currents 4 . However, pristine graphene nanopores exhibit strong hydrophobic interactions with DNA 15 , which limits their long-term use because of clogging, so surface functionalization of the graphene is required 16 .Other two-dimensional materials such as boron nitride (BN 21 , and their stability can be attributed to their relative thickness (single-layer MoS 2 has a thickness of 0.7 nm). Single-layer MoS 2 also has a direct bandgap of at least 1.8 eV (refs 4, 22), a feature that is essential for electronic base detection with field-effect transistors (FETs) 4,23 .…”

“…Other two-dimensional materials such as boron nitride (BN 21 , and their stability can be attributed to their relative thickness (single-layer MoS 2 has a thickness of 0.7 nm). Single-layer MoS 2 also has a direct bandgap of at least 1.8 eV (refs 4, 22), a feature that is essential for electronic base detection with field-effect transistors (FETs) 4,23 .…”