Beyond luxury: How flexible diamond membranes are set to drive next-generation technological innovation

Diamond is often thought of as a luxury material, with its brilliant lustre and beauty used in jewellery and adornments. Even so, diamond has many practical applications, from industry to electronics, and a recent breakthrough at the University of Hong Kong (HKU) promises to unlock even more.

Led by Zhiqin Chu, associate professor in HKU’s Department of Electrical and Computer Engineering, and Yuan Lin, professor in the Department of Mechanical Engineering, the research looks into the scalable fabrication of ultra-flat diamond films and the material’s potential applications.

“The motivation for our work came from my activity in the diamond quantum sensing field,” explains Chu. “In several of our projects, we needed a very thin diamond film, ideally in a large size. When I initially searched the market, I was surprised to find that such a thing didn’t exist. We wanted to achieve something that simply wasn’t possible with existing methods, specifically aiming for large-scale ultra-thin diamond films."

As Chu and Lin couldn’t rely on the conventional approach of etching and polishing to acquire the ultra-thin diamond films they required, they had to think outside the box. They developed a technique where a thin layer of diamond is grown on a substrate, before a mechanical approach is used to peel away the grown diamond film.

“It is just like peeling a piece of tape off a surface, except the tape is a diamond membrane,” Lin explains. “Normally, people would think this is impossible because diamond is incredibly hard and also extremely brittle. The prevailing assumption was that mechanically peeling or deforming an ultra-thin diamond layer would instantly cause it to fracture.”

Chu adds: "I would emphasise two key features of the samples we are able to obtain through this breakthrough. First is the interfacial surface roughness, which is around one nanometre. This is smooth enough to be directly compatible with existing semiconductor manufacturing. The second is the flexibility. Because these films are so incredibly thin, they exhibit flexible properties rather than the rigid, brittle nature of bulky diamonds. This opens doors to applications where bulk diamond could never be used."

The potential applications that Chu suggests include next-generation electronic and photonic devices, offering novel possibilities in areas like semiconductors, quantum computing and wearables. While diamond semiconductors have been proposed for several years, their commercial applications have been limited due to the difficulty and expense of growing and processing bulk diamond on a mass scale.

“Our ultra-thin diamond membranes provide a major shortcut,” says Lin. “This is fundamentally a platform technology. Previously, when researchers managed to get a diamond surface down to nanometre-scale roughness via chemical etching, the sample sizes were tiny and limited to niche laboratory research. Our method delivers a very large, ultra-smooth surface using a simple, scalable process. This makes high-quality diamond membranes highly accessible to industry partners across various sectors, allowing them to adapt them to their specific needs."

The scalable fabrication of ultra-flat diamond films involves the expertise of material scientists, physicists, chemists and theoreticians to make the innovative leap. Teams specialising in chemical vapour deposition synthesis worked alongside those focusing on quantum sensing and the mechanics of materials. The project sits at the intersection of three or four distinct fields, something that is becoming increasingly common in modern scientific breakthroughs.

Despite the excitement around this collaborative endeavour, a few hurdles remain before ultra-thin diamond film technology can be fully commercialised and adopted at scale. Disrupting the status quo is rarely straightforward.

“The primary hurdle comes from the fact that we are introducing a completely new material modality,” explains Chu. “If you approach a manufacturer with a radically novel material, their initial reaction will be one of caution. To overcome this, we are engaging with industry partners to run collaborative trials, demonstrating the tangible advantages that ultra-thin, flexible diamond membranes bring to their existing components.”

"We are already starting to see industry shifts,” adds Lin. “Given their significant intrinsic advantages in terms of thermal conductivity and unreactivity, I am very confident that our diamond membrane system will rapidly find its way into mainstream electronic and industrial applications in the future."

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