Most electronic memory storage devices require the ability to trap large numbers of electrons for each bit of memory. In an ideal world, however, it would take only one electron. This would reduce space requirements and power consumption for devices. Now, a team in China has realized this goal with an ultrathin device capable of minimizing the stray capacitance that plagued earlier attempts. The new study, published in Science, describes how this novel device has overcome challenges in implementing the single-electron design.
The capacitance problem
In theory, each time an electron is added or removed, it should create a distinct, step-like change in a transistor’s switching voltage. However, in practice, electrical effects can blur those steps and make it difficult to distinguish these additions and removals. Single-electron memories have been created before, but they struggled to produce states that were both clearly distinguishable and stable at room temperature.
When the number of electrons was decreased in conventional devices, stray electrical coupling, referred to as fringe capacitance, weakened the one-electron signal. This was partially overcome in the design of a nanoscale polysilicon dot that was shown to produce a detectable voltage at room temperature, but this lasted only five seconds. The challenge of creating a single-electron device was to find a way to ensure the signal was detectable by limiting fringe capacitance at room temperature—and to make sure these states lasted long enough to be useful for storage.
Achieving a useful single-electron memory device
The team involved in the new study found a way to overcome these challenges by engineering an ultrathin graphene-based transistor with a coplanar drain-channel-source layout. The atomically thin materials and edge contacts were able to minimize stray capacitance near the memory region. When tested, the device detected the addition or removal of one electron as a 0.5-volt threshold-voltage step at room temperature. The device retained its distinct states for at least 5,000 seconds in direct measurements. However, the team’s analysis suggested that the states could potentially last for up to 10 years, although that remains to be tested.
The device also exhibited a state-removal mechanism that the researchers call “density-of-states scissors” that can be used to manipulate individual quantum memory states. This was shown in a second, low-temperature device design, in which an otherwise expected memory state was deliberately skipped. One state-skipping result was measured at 10 kelvin, which is far below everyday operating temperatures.
The study authors write, “This prediction was verified through experiments, which demonstrated that our theoretical and technological framework can support the precise manipulation of even a single quantum state. Our findings pave the way for discovering emerging quantum phenomena, suggesting that the integration of diverse semiconductors with customized zero-DOS regions as the storage layer can effectively clip a specific number of quantum states.”
While this study offers a design strategy for making individual-electron states easier to discern at room temperature, there is still work to be done before the design can become a truly manufacturable memory array. Future work will need to show room-temperature versions of the state-skipping effect and scale the devices into dense, reliable arrays.
https://phys.org/news/2026-07-2d-quantum-memory-device-electron.html
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