How scientists used Scotch tape to create ultra-thin films of diamond

A welcome accident

The “simple, scalable and reliable method” was discovered by accident when electrical engineer Jing Jixiang of the University of Hong Kong accidentally peeled away a bit of diamond with a misplaced piece of Scotch tape.

Intrigued, Jing and his colleagues decided to experiment further. They first implanted some nano-sized diamonds in a small silicon wafer, and then blew methane gas over it at high temperatures to form a continuous, thin diamond sheet. This is a technique known as chemical vapour deposition, a method very commonly used for creating thin films used in semiconductors.

The challenge was to extract the thin diamond layer from the silicon without damaging it. For this, they cut the wafer to expose the diamond’s edge, and fixed some tape to the diamond. When they peeled the tape back, a thin layer of diamond came with it. Subsequently, they dissolved the tape in a chemical solution to produce a free-standing ultra-thin diamond film.

Scientists have previously used a similar technique (which also utilised Scotch tape) to create thin materials such as graphene, a sheet of graphite made of a single layer of carbon atoms.

Desirable qualities

What excited the scientists were the qualities of the diamond sheet they produced. They were extremely thin while at the same time being smooth enough to allow for the kind of etching techniques used to produce silicon chips, and extremely flexible.

The films’ “flat workable surface, support standard micromanufacturing techniques, and their ultra flexible nature allows for direct elastic strain engineering and deformation sensing applications, which is not possible with their bulky counterpart,” the Nature article said. (‘Scalable production of ultraflat and ultraflexible diamond membrane’).

Diamond is known to possess unique electronic properties. On one hand, it is a good insulator. At the same time, it also allows electrons of certain energies to move without resistance. In theory, this can translate to diamond chips being able to be far more efficient (although likely more expensive) than conventional silicon chip designs.

But so far, creating high-quality, freestanding films of diamond, which can then be fashioned into chips, has been a challenge. This is why the latest development is extremely promising.

“This new edge-exposed exfoliation method will be an enabler for a multitude of device designs and experimental approaches,” physicist Mete Atatüre of the University of Cambridge told NewScientist. One area it could be particularly useful for is offering greater control in quantum devices that use diamonds as sensors, he said.