‘Direct writing’ nanodiamond patterns from graphite

November 6, 2014

This illustration depicts a new technique that uses a pulsing laser to create synthetic nanodiamond films and patterns from graphite, with potential applications from biosensors to computer chips. (Credit: Purdue University/Gary Cheng)

Purdue University researchers have developed a method to instantly create synthetic nanodiamond films and patterns from graphite using a pulsing laser, with potential applications from biosensors to computer chips.

“The biggest advantage is that you can selectively deposit nanodiamond on rigid surfaces without the high temperatures and pressures normally needed to produce synthetic diamond,” said Gary Cheng, an associate professor of industrial engineering at .

“We do this at room temperature and without a high temperature and pressure chamber, so this process could significantly lower the cost of making diamond.”

The method also allows the researchers to selectively “write” lines of diamond on surfaces, which could be practical for applications including biosensors, quantum computing, fuel cells,  and next-generation computer chips.

The technique works by using a multilayered film that includes a layer of graphite topped with a glass cover sheet. Exposing this layered structure to an ultrafast-pulsing laser instantly converts the graphite to an ionized plasma and creates a downward pressure. Then the graphite plasma quickly solidifies into diamond. The glass sheet confines the plasma to keep it from escaping, allowing it to form a nanodiamond coating.

“These are super-small diamonds and the coating is super-strong, so it could be used for high-temperature sensors,” Cheng said.

Research findings are detailed in a paper that appeared online in the open-access Nature journal Scientific Reports.

The research team confirmed that the structures are diamond using a variety of techniques including transmission electron microscopy, X-ray diffraction, and measurement of electrical resistance.

A U.S. patent application has been filed on the concept through the Purdue Office of Technology Commercialization. More research is needed to commercialize the technique, Cheng said.


Abstract of Direct Laser Writing of Nanodiamond Films from Graphite under Ambient Conditions

Synthesis of diamond, a multi-functional material, has been a challenge due to very high activation energy for transforming graphite to diamond, and therefore, has been hindering it from being potentially exploited for novel applications. In this study, we explore a new approach, namely confined pulse laser deposition (CPLD), in which nanosecond laser ablation of graphite within a confinement layer simultaneously activates plasma and effectively confine it to create a favorable condition for nanodiamond formation from graphite. It is noteworthy that due to the local high dense confined plasma created by transparent confinement layer, nanodiamond has been formed at laser intensity as low as 3.7 GW/cm2, which corresponds to pressure of 4.4 GPa, much lower than the pressure needed to transform graphite to diamond traditionally. By manipulating the laser conditions, semi-transparent carbon films with good conductivity (several kΩ/Sq) were also obtained by this method. This technique provides a new channel, from confined plasma to solid, to deposit materials that normally need high temperature and high pressure. This technique has several important advantages to allow scalable processing, such as high speed, direct writing without catalyst, selective and flexible processing, low cost without expensive pico/femtosecond laser systems, high temperature/vacuum chambers.