With the physical limit approaching, it is widely believed that Moore's Law, the doubling of the number of silicon transistors that can enter an integrated circuit every two years, will expire around 2025.

But researchers at RMIT University in Australia believe the metal-base emitting air channel transistor (ACT) they have developed could sustain Moore's Law for 20 years. ACT devices do not require semiconductors.

Instead, symmetrical metal electrodes (source and drain) are used in both planes to separate air gaps smaller than 35 nm, with metal gates at the bottom to tune the emission field. The nanometer-sized air gap width is smaller than the mean free path of electrons in air, so electrons can pass through air at room temperature without scattering. "Unlike traditional transistors, which require silicon as a base, our parts use a bottom-up fabrication method.

If the optimal air gap can be determined, a complete 3D transistor network can be built. said Shruti Nirantar, lead author of the new transistor paper published in Nano Letters in December. "This means not pursuing miniaturization, but focusing on compact 3D architectures that can use more transistors per unit.

Replacing semiconductors with metal and air as the main components of transistors has many advantages. said Dr Nirantar, a candidate in RMIT's Functional Materials and Microsystems research group. Making a transistor is basically a single-stage process of laying out emitters and collectors, limiting the air gap. The ACT production process uses standard silicon manufacturing processes, but does not require a series of steps such as doping, heat treatment, oxidation, and silicide formation, which greatly reduces production costs.

In addition, replacing silicon with metal means that these ACT components can be fabricated on all dielectric surfaces, and the underlying liner can utilize the bottom metal grid to effectively tune the emission current from source to drain. "ACT devices can be built on ultrathin glass, plastics and elastomers," Niranta said.

"So, it can be applied to wearable devices.

"Solid-state channel transistors for exchange-space circuits are another potential application. Since electrons flow between electrodes, as they would in a vacuum, radiation does not affect channel properties, so ACT devices can be applied in extreme radiation and cosmic environments. Now , the researchers tested multiple sources and leak compositions and obtained theoretical evidence that using more resistant materials to improve part stability and increase efficiency is the next step.

When making the ACT prototype, the researchers used electron beam lithography and thin film deposition, with tungsten, gold, and tungsten being the metals of choice. "The operating voltage also needs to be optimized because the metal ends of the electrodes can be melted locally by a concentrated electric field," Niranta said. "This reduces their clarity and emission efficiency.

Therefore, we are investigating ways to improve collector efficiency and reduce emitter stress. “She believes this will be done within the next two years. Looking ahead, Niranta points out that the theoretical speed of ACT in the terahertz range is about 10,000 times faster than current semiconductor components work.

Therefore, further studies are needed to demonstrate its operational limitations. She added, "In the case of commercialization, Niranta said, access to industrial manufacturing equipment and related support in the industrial sector is a must for scaling 3D transistor networks. With this support and adequate research funding, commercial-grade metal bases launch air channels. Transistors have the potential to be developed within 10 years, which is an approximate time frame. If the right partner is found, it could all happen faster.”