Transistors based on carbon nanostructures: what sounds like a futuristic dream could be reality in just a few years’ time. An international research team working with Empa has now succeeded in producing nanotransistors from graphene ribbons that are only a few atoms wide, as reported in the current issue of “Nature Communications”.
Graphene ribbons that are only a few atoms wide, so-called graphene nanoribbons, have special electrical properties that make them promising candidates for the nanoelectronics of the future: while graphene – a one atom thin, honeycomb-shaped carbon layer – is a conductive material, it can become a semiconductor in the form of nanoribbons. This means that it has a sufficiently large energy or band gap in which no electron states can exist: it can be turned on and off – and thus may become a key component of nanotransistors.
The smallest details in the atomic structure of these graphene bands, however, have massive effects on the size of the energy gap and thus on how well-suited nanoribbons are as components of transistors. On the one hand, the gap depends on the width of the graphene ribbons, while on the other hand it depends on the structure of the edges. Since graphene consists of equilateral carbon hexagons, the border may have a zigzag or a so-called armchair shape, depending on the orientation of the ribbons. While bands with a zigzag edge behave like metals, i.e. they are conductive, they become semiconductors with the armchair edge.
This poses a major challenge for the production of nanoribbons: if the ribbons are cut from a layer of graphene or made by cutting carbon nanotubes, the edges may be irregular and thus the graphene ribbons may not exhibit the desired electrical properties.
Empa researchers in collaboration with the Max Planck Institute for Polymer Research in Mainz and the University of California at Berkeley have now succeeded in growing ribbons exactly nine atoms wide with a regular armchair edge from precursor molecules. The specially prepared molecules are evaporated in an ultra-high vacuum for this purpose. After several process steps, they are combined like puzzle pieces on a gold base to form the desired nanoribbons of about one nanometer in width and up to 50 nanometers in length.
These structures, which can only be seen with a scanning tunneling microscope, now have a relatively large and, above all, precisely defined energy gap. This enabled the researchers to go one step further and integrate the graphene ribbons into nanotransistors. Initially, however, the first attempts were not very successful: Measurements showed that the difference in the current flow between the “ON” state (i.e. with applied voltage) and the “OFF” state (without applied voltage) was far too small. The problem was the dielectric layer of silicon oxide, which connects the semiconducting layers to the electrical switch contact. In order to have the desired properties, it needed to be 50 nanometers thick, which in turn influenced the behavior of the electrons.
However, the researchers subsequently succeeded in massively reducing this layer by using hafnium oxide(HfO2) instead of silicon oxide as the dielectric material. The layer is therefore now only 1.5 nanometers thin and the “on”-current is orders of magnitudes higher.
Another problem was the incorporation of graphene ribbons into the transistor. In the future, the ribbons should no longer be located criss-cross on the transistor substrate, but rather aligned exactly along the transistor channel. This would significantly reduce the currently high level of non-functioning nanotransistors.
Learn more: A nanotransistor made of graphene
The Latest on: Graphene nanotransistor
[google_news title=”” keyword=”graphene nanotransistor” num_posts=”10″ blurb_length=”0″ show_thumb=”left”]
- Accurate rapid tests made from smart graphene paperon March 27, 2023 at 11:12 am
The basis for this invention is the use of a laser to convert the sugar polymers that make up the cellulose in the paper into graphene. This special form of carbon is conductive and is considered ...
- Graphene grows—physicists find a way to visualize iton March 24, 2023 at 1:27 pm
Graphene is one of the strongest materials. On top of that, it is exceptionally good at conducting heat and electrical currents, making it one of the most special and versatile materials we know.
- New Way to Recycle Waste Plastic Into Grapheneon March 21, 2023 at 5:01 pm
Researchers at Rice University have come up with a new and useful way to repurpose plastic waste into a carbon-based material that has numerous uses in scientific and commercial applications—graphene.
- Graphene smart contact lenses could give you thermal infrared and UV visionon February 1, 2023 at 8:39 pm
A breakthrough in graphene imaging technology means you might soon have a smart contact lens, or other ultra-thin device, with a built-in camera that also gives you infrared "heat vision." ...
- The rise of grapheneon January 13, 2023 at 1:25 pm
Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic ...
- If Graphene Batteries Do Everything Scientists Say, They Could Be a Gamechangeron January 7, 2022 at 8:17 am
Imagine you're cruising down the freeway in your new electric car, equipped with the latest graphene battery. You notice you're running low on juice, so you pull over at a rest stop, plug it in ...
- Graphene and fullereneson March 26, 2018 at 5:07 am
Like graphite, graphene conducts electricity well because it has delocalised electrons that are free to move across its surface. These properties make graphene useful in electronics and for making ...
- We May Finally Have a Way of Mass Producing Grapheneon January 28, 2017 at 3:18 pm
Hailed as the future's 2D miracle material, graphene has remarkable applications. Graphene is essentially a one-atom thick graphite layer, made from elemental carbon. Graphene's unique properties ...
- Graphene makes rubber more rubberyon May 19, 2016 at 10:20 pm
Graphene can make thin rubber films up to 50% more stretchy Rubber films are used in a variety of household objects, from gloves to condoms In an article published in Carbon, Dr Aravind Vijayaraghavan ...
- Graphene paints a corrosion-free futureon September 11, 2014 at 7:43 am
A thin layer of graphene paint can make impermeable and chemically resistant coatings which could be used for packaging to keep food fresh for longer and protect metal structures against corrosion, ...
via Google News and Bing News