Proton and Li-Ion Permeation through Graphene with Eight-Atom-Ring Defects

Defect-free graphene is impermeable to gases and liquids but highly permeable to thermal protons. Atomic-scale defects such as vacancies, grain boundaries and Stone-Wales defects are predicted to enhance graphene's proton permeability and may even allow small ions through, whereas larger species such as gas molecules should remain blocked. These expectations have so far remained untested in experiment. Here we show that atomically thin carbon films with a high density of atomic-scale defects continue blocking all molecular transport, but their proton permeability becomes ~1,000 times higher than that of defect-free graphene. Lithium ions can also permeate through such disordered graphene. The enhanced proton and ion permeability is attributed to a high density of 8-carbon-atom rings. The latter pose approximately twice lower energy barriers for incoming protons compared to the 6-atom rings of graphene and a relatively low barrier of ~0.6 eV for Li ions. Our findings suggest that disordered graphene could be of interest as membranes and protective barriers in various Li-ion and hydrogen technologies

Quantum authentication

In secure communication, users must have a method of authenticating the identity of the recipients of their data, and vice versa. This requires the capability of generating a unique yet reproducible signature under a variety of environmental conditions. At present, these unique signatures are widely generated by Physically Unclonable Functions, or PUFs, which use physical characteristics of specific structures containing inherent randomness due to their manufacturing process. These hard to predict physical responses are quantised to generate a unique identity which can be used for authentication. However, these devices are size-limited by their classical design, posing challenges to microelectronic implementation. Here we show that the extensively studied and problematic fluctuations in the current-voltage measurements of Resonant Tunnelling Diodes (RTDs) can be reapplied to function as a PUF without conventional size limitations. This is possible due to quantum-mechanical tunnelling within the RTD, and, on account of these room temperature quantum effects, we term such devices QUFs – Quantum Unclonable Functions. When stimulated with a range of voltages, these devices produce a range of current outputs whilst exhibiting characteristic negative differential resistance in the region where resonant tunnelling takes place. The resultant current-voltage spectra are dependent on the exact atomic structure and composition of the quantum well within the RTD, and so are unique to the device in question. This allows us to create ‘PUF-like’ devices at the on-chip scale which explicitly make use of room-temperature quantum phenomena and subsequently provides a path towards resource-low quantum authentication protocols

Atomic-scale authentication using imperfect semiconductor structures

The unrelenting advancement of modern technology has inadvertently allowed the production of counterfeit components to become increasingly cheaper and easier, undermining the trust of everyday interactions and communications. An emerging solution to this problem is the use of physically unclonable functions1 (PUFs) - physical devices with random characteristics locked into their structure at the point of fabrication. The application of a stimulus to these constructions results in a hard-to-predict response due to the interaction with the complex microstructure of the device. This response is then used as a 'fingerprint' that can be used for a given application. Among others, these include low-cost device identification and authentication, secure key generation and the binding of software to hardware platforms. However, traditional PUFs have various setbacks: they suffer from not being truly unclonable, are susceptible to sophisticated attacks and bear a risk of emulation and simulation. Here we show that quantum physics lends itself to the provision of unique identities in the form of fluctuations in measurements of resonant tunnelling diodes (RTDs) containing various nanostructures. An example of which is a quantum dot, shown in Fig. 1. This provides an uncomplicated measure of identity, without conventional resource limitations or vulnerabilities. The quantum tunnelling spectrum also shown in Fig. 1 is sensitive to the atomic structure within the RTD, with each device providing extreme uniqueness that is presently impossible to clone or simulate. This new class of authentication device, coined the quantum unclonable function (QUF)2, operate with the fewest resources in simple electronic structures operating above 300 K

Author Correction: Ion exchange in atomically thin clays and micas.

From PubMed via Jisc Publications RouterPublication status: aheadofprintFunder: RCUK | Engineering and Physical Sciences Research Council (EPSRC); Grant(s): EP/P009050/1, EP/P00119X/1, EP/M010619/1, EP/S021531/1Funder: EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 European Research Council (H2020 Excellent Science - European Research Council); Grant(s): ERC Synergy Hetero2D project 319277Funder: EC | EU Framework Programme for Research and Innovation H2020 | H2020 European Institute of Innovation and Technology (H2020 The European Institute of Innovation and Technology); Grant(s): 715502, 319277, 71550