The Post-Moore Era

Could Molecular Electronics Keep the Pace?

Molecular electronics could continue semiconductor advances in a post-Moore era. Here we break down how molecular diodes, wires, and logic gates work, examine recent commercial breakthroughs, and look at the feasibility of integrating molecular components into existing semiconductor workflows. Can molecules really take us beyond the limits of lithography, or is this just another lab-bound dream?

This theory was never meant to last forever. In fact, Moore himself predicted that it would only continue for around 10 years (up to 1975). In reality, Moore’s law has continued to hold true right up into the 21st century and has been a driving force for development within the semiconductor industry, with Apple’s 2025 ARM-based M3 Ultra SoC containing a staggering 184 billion transistors.

Despite this, we’re now starting to see signs that we’re fast approaching a post-Moore era. Silicon-based transistors can only get so small before the laws of physics start to get in the way. We’re already measuring transistors on the atomic scale, with the smallest commercially available transistor measuring at 3 nanometers (only slightly wider than a strand of human DNA, which is roughly 2.5 nanometers wide). There’s still some room to go smaller, and IBM recently announced their 2 nanometer chip, but progress is slow and understandably expensive. [1]

As traditional transistors approach their physical and quantum limits, the search for a viable successor to silicon-based electronics has intensified. Molecular electronics, where individual molecules perform the functions of diodes, transistors, or memory units, has emerged as a potential candidate. This field poses an interesting question at the heart of post-Moore’s Law innovation: Can molecules do what shrinking transistors no longer can?

Moore’s Law Breakdown: Current Challenges

As previously mentioned, Moore’s Law predicts that the number of transistors on a chip will double approximately every two years (Figure 1), implying increasingly smaller semiconductor components. However, transistors can only get so small, and as they approach atomic dimensions, they encounter fundamental physical limitations. At this scale, quantum effects begin to dominate, creating challenges for the continued miniaturization of devices.

On the quantum level, electrons no longer behave purely as particles but also exhibit wave-like properties. This gives them the ability to tunnel through barriers, leading to unintended current flow and reduced device reliability. This effect is negligible in conventional circuits, but when features are only a nanometer apart—the direction we’re headed for in the next generation of semiconductors—it becomes significant, allowing electrons to tunnel between wires and effectively exist at two locations simultaneously. This makes the precise control of electronic behavior incredibly difficult in nanoscale circuits.

These quantum effects are a particular challenge within silicon, the material most used within the semiconductor industry. As a result, there’s now a drive towards exploring alternative materials (gallium nitride and graphene, for example) which have better electronic properties including higher electron mobility and better thermal conductivity.

The manufacturing processes involved with shrinking transistors are also challenging. Currently, commercial transistors, commonly made with silicon, are created via photolithography, a technique that uses light to transfer patterns from a mask onto a wafer. Smaller transistors require extreme precision during the manufacturing and characterisation process, using sensitive semiconductor probing setups to ensure they work as intended. [2] Industries have already developed extreme ultraviolet (UV) lithography which can produce finer patterns with greater accuracy, but this technique is very specialised and expensive to implement.

What is Molecular Electronics?

Molecular electronics summarizes the field of research in which molecules are used as building blocks to create electronic components, including transistors, capacitors, and diodes. [3] It operates at distances less than 100 nanometers, meaning that quantum effects are particularly important and the transfer of a single electron can have a significant impact on the system. Despite this, molecular electronics is very advantageous, as being able to control properties on the molecular scale gives us a better understanding of the overall processes in an electronic device.

The difference between molecular electronics and conventional electronics largely comes down to the manufacturing approaches used for each. Conventional electronics uses bulk materials that are formed into transistors via a top-down approach, meaning that a large piece of material is broken down into the nanoscale dimensions needed. This is how silicon semiconductors are made, with a standard 300mm silicon wafer creating around 300 chips, each containing billions of transistors.

On the other hand, molecular electronics uses individual molecules and a bottom-up approach, in which chemical synthesis and assembly is used to create and order transistors (Figure 2). As such, molecular electronics have many advantages over conventional electronics. The most obvious of these is that the use of single molecules makes extreme miniaturization possible, further extending the limits of Moore’s Law.

Additionally, molecular electronics can be used to avoid the negative quantum effects that occur when using bulk materials like silicon. This is because molecules already operate on the quantum scale, and so quantum effects such as tunnelling can be harnessed as an advantage rather than a negative.

Molecules designed for molecular electronics can also be capable of self-assembly, therefore avoiding the challenge of manufacturing at the atomic scale. Here, molecules find their own way into a highly ordered structure without the need for expensive manufacturing tools. This phenomenon is spontaneous and does not require human input. Instead, it is driven by the interactions between molecules in which they seek out a minimum energy state.

Recent Breakthroughs

Breakthroughs in recent years have taken molecular electronics from theory to experimental reality. New advances in single-molecule transistors, quantum-enabled single-molecule field-effect transistors (SMFETs), and molecular logic components are laying the groundwork for computing beyond silicon.

Single-molecule transistors: Single-molecule transistors are fundamentally different to conventional bulk transistors due to the way they operate. In a bulk transistor, the gate determines the conductance between the source and drain electrode by controlling the density of charge carriers between them. In a single-molecule transistor, however, the gate controls the possibility of a single electron to jump on or off of the molecule by altering the energy of the molecular orbitals. Because of this, single-molecule transistors can be thought of as binary systems.

In 2024, scientists at the S. N. Bose National Centre created a transistor using single molecules which could be controlled by mechanical forces rather than conventional electrical signals. [4] Here, they used a piezoelectric stack to create a sub-nanometer gap in a macroscopic metal wire that is precisely sized to fit a single ferrocene molecule. This technique is known as a mechanically controllable break junction (MCBJ) and makes it possible to manipulate molecules with precision. Ferrocene (an iron atom between two cyclopentadienyl rings) exhibits altered electrical behaviour when it is mechanically stimulated, making it a suitable candidate for molecular electronics. Interestingly, the performance of the transistor was impacted by the orientation of the molecule, with both amplification and attenuation possible depending on how it was aligned.

The University of Lancaster has also demonstrated a single molecule transistor that could operate at room temperature, showing real-world feasibility. [5] The molecule was able to switch in both directions under ambient conditions, remained stable for a long period of time in both the bright and dark state, and spontaneously formed highly ordered layers that were only one molecule thick—the first example of a molecule capable of all features. Many promising molecules for molecular electronics currently require cryogenic conditions to function, making this a particularly exciting discovery.

Molecular diodes and logic gates: One of the most exciting areas within molecular electronics surrounds the development of molecular diodes and logic gates, which are core components of digital circuits. Shrinking these down to the scale of single molecules could change how computation is performed by enabling ultra-dense, low-power, and biocompatible computing architectures.

A major breakthrough has been the fabrication of robust, single-molecule diodes that exhibit high rectification ratios. The molecular diodes achieve this through asymmetric molecular structures. Here, molecules are carefully designed to have opposing electron-donating and electron-withdrawing ends, creating inherent electronic polarity which facilitates directional electron flow. These molecules are not just functional, but also highly integrable and offer a realistic path towards molecular-scale circuits.

Molecular logic gates are also a reality, and can perform fundamental computational operations such as AND, OR, and XOR. These gates operate by responding to a combination of chemical, optical, and electrical inputs, essentially translating environmental stimuli into logical outputs.

At the University of Cambridge, researchers have built self-assembled protein-based circuits that perform basic logic operations. [6] Because these circuits are built from proteins, they are inherently renewable and show potential integrating with living systems, further pushing the boundaries of what we consider to be computing platforms.

SMFETs and Quantum Effects: At the quantum dimensions used within molecular electronics, the behaviour of electrons is not governed by classical mechanics, but instead by a series of complex quantum interactions.

Unlike conventional field-effect transistors (FETs), SMFETs operate with a single molecule acting as the active channel, as the name suggests. Charge transport in these devices is not only determined by the molecular structure, but also by interfacial coupling between the molecule and the metal electrodes.

Quantum effects can actually be exploited within molecular electronics. For example, the Coulomb blockade effect allows single-electron transistors (SETs) to operate at the scale of individual charge events. [7] In SMFETs, researchers are able to design molecules with specific redox properties and weak coupling to electrodes to observe discrete charging events, essentially turning a molecule into a quantized capacitor.

Another example is with the Kondo effect, which occurs when the magnetic moment of a molecule containing an unpaired electron can interact with conduction electrons in nearby electrodes. This leads to an unexpected increase in conductance at low temperatures, counteracting the Coulomb blockade. Researchers are now trying to use this effect to develop components for molecular spintronics, where information is stored and manipulated via the electron’s spin rather than its charge. [8]

Real-world Applications

We are still a long way from seeing molecular electronics replace traditional silicon in mainstream computing, but there are several near-future use cases being explored.

Sensors: One of the most promising areas for molecular electronics lies in the development of highly sensitive sensors, particularly for chemical detection. Molecular transistors are able to respond to subtle electronic changes that happen during chemical reactions, making them well-suited for identifying minute quantities of substance, far beyond the capability of our current sensing technologies.

In the healthcare industry, this sensitivity could also be hugely beneficial for early disease detection. Molecular sensors have the potential to identify specific biomarkers at extremely low concentrations, including those that are currently undetectable via existing diagnostic techniques. Many diseases, such as cancers or neurodegenerative disorders, produce unique and specific biomarkers that act as molecular signatures in their early stages. Detecting these biomarkers early could enable faster, more effective treatments, and overall better patient outcomes.

Within security systems, molecular transistors could be used in the next generation of detection systems that can identify trace amounts of hazardous substances. The ability to detect a single harmful molecule could mean preventing threats before they pose real danger.

Beyond this, the integration of molecular electronics into environmental monitoring, industrial safety, and personalised medicine are all real possibilities.

Memory devices: There is an ever-increasing demand for data storage, and traditional silicon-based memory technologies are approaching their physical and performance limits. Molecular electronics could be the alternative that we need, potentially offering dramatically increased storage density, reduced energy consumption, and better durability.

Molecular memory stores data on individual molecules, making it possible to create systems that are significantly smaller than today’s flash storage systems.

By operating at the quantum level, molecular memory devices can exploit quantum mechanical effects to achieve faster data access and better efficiency. Additionally, they offer the potential for non-volatile storage, so information can be retained even when the device is powered off. Though this is already achieved with flash storage, molecular electronics coil makes this possible with higher storage densities.

Niche Computer Parts: Molecular transistors could be very useful in niche computing environments where ultra-low power consumption and extreme miniaturization are needed. Devices such as wearable technology, remote sensors, and embedded systems could benefit from the compact and energy-efficient nature of molecular components.

Naturally, one of the advantages of molecular transistors is their size. By shrinking the active switching element to the molecular scale, it is possible to achieve form factors that are far smaller than what is currently possible with conventional silicon-based transistors.

Miniaturization is particularly relevant in the fast-growing field of quantum computing, where space and quantum coherence are critical. At the core of quantum computing are qubits, which must maintain delicate quantum states to function correctly. Molecular electronics systems containing quantum dots, which are nanoscale semiconductor particles, could be particularly useful for achieving this. Quantum dots can behave as artificial atoms which gives them finely tuneable electronic properties and the potential to be used as qubits or control elements in quantum architectures.

The Road Ahead

Realistically, the applications of molecular electronics are still in their early stages and significantly more work is needed to make them a reliable technology that can compete with silicon on an industrial scale.

The fabrication of molecular electronic devices relies heavily on the ability of molecules to self-assemble into highly organised structures, narrowing down the pool of potential molecules to be used. Without self-assembly, tools with extreme precision would need to be developed to be able to consistently place and align similar molecules—causing more problems than the devices are intended to solve.

The bottom-up synthesis approach of molecular electronics fabrication can clash with the top-down manufacturing approach that is typically used within the tech industry:

• Scale mismatch: Lithographic tools are optimised to create features on the nanometer scale (5-10nm), but molecular electronics operate on an even smaller scale than that (0.1nm range). Currently, conventional lithography lacks the resolution required to define and contact single molecules.
• Alignment: Lithography creates pre-defined patterns by projecting a mask onto a surface coated with photoresist. The features that need to be connected or modified are therefore in known positions. With bottom-up assembly, molecules assemble randomly, making it extremely difficult to align electrodes to a molecule’s exact location.
• Processing Conditions: Individual molecules can be sensitive and may not survive the high temperatures or exposure to solvents that occur during lithographic steps.

Moving forward, for molecular electronics to really be considered a way forward in the post-Moore era, there is still much work to be done. Initially, transitional devices that combine molecular components with conventional silicon technology will go a long way towards demonstrating the feasibility of molecular electronics in the long run. Furthermore, continued research is required to discover or engineer molecules that are stable, reproducible, and multifunctional. 

About the Company 

Ossila is a UK-based supplier that specializes in lab equipment and advanced materials that are used in solar cell and semiconductor research, driving the development of high-efficiency photovoltaics, flexible OLED screens, next-generation semiconductors, and more.

RESOURCES
Osilla | ossila.com

REFERENCES
[1] IBM announced a 2 nanometer chip in 2021
[2] https://www.ossila.com/products/micromanipulator
[3] Molecular electronics
[4] S. N. Bose National Centre
[5] University of Lancaster
[6] University of Cambridge
[7] Coulomb blockade effect
[8] molecular spintronics

PUBLISHED IN CIRCUIT CELLAR MAGAZINE • AUGUST 2025 #421 – Get a PDF of the issue

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