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”]
- Graphene in Biomedicine: Opportunities and Challengeson March 25, 2024 at 5:00 pm
Graphene, whose discovery won the 2010 Nobel Prize in physics, has been a shining star in the material science in the past few years. Owing to its interesting electrical, optical, mechanical and ...
- A bioelectronic mesh capable of growing with cardiac tissues for comprehensive heart monitoringon March 21, 2024 at 8:47 am
A team of engineers led by the University of Massachusetts Amherst and including colleagues from the Massachusetts Institute of Technology (MIT) recently announced in Nature Communications that they ...
- Graphene - where is our promised wonder material?on February 29, 2024 at 3:44 pm
Graphene is considered one of the most important breakthroughs in material science since its discovery. This “wonder material” was widely overhyped, and still hasn’t lived up to its potential.
- ‘Wonder material’ graphene makes huge step towards practical useon February 16, 2024 at 2:19 am
Graphene, a “wonder material” that could help solve some of humanity’s deepest problems, has cleared a major hurdle towards practical uses. Graphene is the world’s thinnest, super-strong ...
- ‘Graphene will change the world’: the boss using the ‘supermaterial’ in the global microchip waron December 19, 2023 at 6:18 am
Simon Thomas knew the periodic table by heart at six. Now the Cambridge firm’s co-founder is putting his scientific brain behind graphene’s power to help us compete with China The first thing ...
- Why Graphene Batteries Might Be The Next Big Breakthrough In The EV Industryon December 8, 2023 at 3:12 pm
As car manufacturers continue to throw research funding at solid-state batteries, graphene has emerged as the next technology that might “revolutionize,” “reinvent,” or “redefine” the ...
- News tagged with grapheneon November 25, 2023 at 7:08 am
Think big. Despite its research topic, this could well be the motto of the Graphene Flagship, which was launched in 2013: With an overall budget of one billion Euros, it was Europe's largest ...
- Graphene Oxide In Pfizer Covid-19 Vaccines? Here Are The Latest Unsupported Claimson July 10, 2021 at 1:54 pm
One example of such a claim was an Instagram post that stated: “99% Graphene Oxide in Pfizer V4X? Spanish scientists obtain vial of Pfizer v4xin3 and find that 98-99%.” In this case ...
- How impermeable is the impermeable graphene?on August 5, 2020 at 10:00 am
New experiments by researchers at The University of Manchester have placed the best limits yet on impermeability of graphene and other two-dimensional materials to gases and liquids. The work has also ...
- Graphene Desalinates Sea Wateron March 8, 2019 at 4:03 pm
Researchers at the University of Manchester have found a way to improve a graphene-based filter mechanism that could help convert sea water to potable water. Pure graphene can do the job ...
via Google News and Bing News