Copyright infringement not intended

Picture Courtesy:  THE HINDU

Context:

Scientists have just achieved a major milestone by creating ultra-thin, two-dimensional (2D) metals, which could revolutionize technologies like super-sensitive sensors, faster computers, and advanced photonic devices.  

What Are 2D Metals?

Regular metals, like the copper in electrical wires, are three-dimensional (3D), their atoms bond in all directions—up, down, left, right, forward, and backward. This 3D structure allows electrons to move freely in all directions.

However, in a 2D metal, the atoms are arranged in a single, flat layer, restricting electron movement to just two directions—left-right and forward-backward. This restriction, called quantum confinement, provides 2D metals unique properties that 3D metals lack.

2D metals like bismuth and tin can act as topological insulators. These materials conduct electricity only along their edges, not through their middle. This property makes them efficient for certain applications, such as creating super-fast, low-power computer chips or sensors that can detect small changes in the environment, useful in fields from medicine to defense.

The Challenge of Making 2D Metals

Unlike carbon atoms in graphene, metal atoms that bond in 3D, forming thick, chunky structures. Scientists have tried various methods over the past decade to force them into a flat, 2D layer, such as:

• Depositing metal atoms carefully onto a surface, hoping they form a thin layer.
• Sandwiching metal slices between other materials to flatten them.
• Hammering metal pieces to make them thinner.

These efforts produced metal sheets a few nanometers thick, but that’s still too thick. To be truly 2D, the sheet must be atomically thin.

Recent discovery

A team of scientists from China, developed a new method to create 2D metals like bismuth, gallium, indium, tin, and lead.

How does it work?

• Start with a pure metal powder, like bismuth, which is a shiny, brittle metal used in alloys and electronics.
• Place the powder on a sapphire plate coated with a single layer of molybdenum disulfide (MoS2), a 2D material known for its strength and smooth surface. This is the “bottom anvil.”
• Heat the setup so the metal powder melts and spreads into a thin droplet on the MoS2 surface.
• Cover the droplet with a top anvil, which is another sapphire plate coated with MoS2, creating a sandwich: sapphire-MoS2-metal-MoS2-sapphire.
• Twist the top anvil slightly and press the two anvils together with a force of about 200 million pascals (unit of pressure)
• Keep the pressure on until the setup cools to room temperature, then remove the anvils.
• Peel off the metal sheet, which is now just 6.3 angstroms thick—about two atoms deep.

This method produced a bismuth sheet so thin that its electrons are confined in 2D, giving it the desired properties. The team also confirmed that the sheet shows a strong field effect (its electrical conductivity changes when an electric field is applied).

Source: 

THE HINDU