How to cut atom-sized 2D materials

(Nanowerk News) 2D materials with a thickness of a few nanometres or less have entered the spotlight in recent years thanks to their distinct properties like layered structure, high-surface area and variation of chemical compositions. These features make them potential substitutes for different conventional materials with applications in field-effect transistors, electrochemical sensors and physical sensors. Such materials are used in wearable electronics, optoelectronics and semiconductor technology.
For most applications with 2D materials, functional nanostructures need to be patterned by lithography, which can be a challenging process as the deployment of aggressive chemicals or accelerated electrically charged particles, like electrons and ions, can damage the material’s properties. To address this challenge, a team of researchers has developed a technology that utilises a miniature scalpel to accurately and directly cut 2D materials.
Supported by the EU-funded MEMS 4.0 project, the team used a new nanoscale structuring technique called thermal scanning probe lithography (t-SPL), which works in a similar way to an atomic force microscope.
The researchers published their findings in the journal Advanced Materials ("Thermomechanical Nanocutting of 2D Materials").
“Here, a thermomechanical indentation technique is demonstrated, which allows for the direct cutting of 2D materials using a heated scanning nanotip. Arbitrarily shaped cuts with a resolution of 20 nm are obtained in monolayer 2D materials, i.e. molybdenum ditelluride (MoTe2), molybdenum disulfide (MoS2), and molybdenum diselenide (MoSe2), by thermomechanically cleaving the chemical bonds and by rapid sublimation of the polymer layer underneath the 2D material layer.”

Various applications

Study author Dr Ana Conde Rubio comments: “We use heat to modify the substrate and make it more flexible and, in some cases, even turn it into a gas. We can then more easily carve into the 2D material.” Study author Dr Samuel Tobias Howell adds: “We use a computer-driven system to control the ultra-fast heating and cooling process and the position of the tip. This enables us to make pre-defined indents to create, for instance, the nanoribbons that are used in nanoelectronic devices.”
The technique could be beneficial for applications in nanoelectronics, nanophotonics and nanobiotechnology, “as it will help to make electronic components smaller and more efficient,” according to Dr Xia Liu, another author of the study.
In the next stage, the research will focus on looking at a wider range of materials and finding combinations that will work in integrated nanosystems. Future activities will also revisit the design of the cantilever and nanotip for improved nano-cutting performance.
Prof. Jürgen Brugger explains: “Polymer-based microelectromechanical systems (MEMS) have a lot of potential electronic and biomedical applications. But we’re still in the early stages of developing techniques for designing functional polymers in 3D microsystems.”
Prof. Brugger “hopes to push the boundaries and find new materials and processes for MEMS by focusing on the stencil, the printing process, the directed self-assembly of nanomaterials, and localized thermal processing.”
The MEMS 4.0 (Additive Micro-Manufacturing for Plastic Micro-electro-Mechanical-Systems) project that provided funding for the study will run until September 2022. “MEMS 4.0 in analogy with the industry 4.0 concept, aims to perform concerted research in additive manufacturing at the micro/nanoscale and associated key techniques,” as noted in the project factsheet.
Source: Cordis
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