Stretching of Diamonds in Microelectronics

Stretching of microfabricated diamonds pave ways for applications in next-generation microelectronics. Credit: Dang Chaoqun/ City University of Hong Kong

Diamond is the hardest product in nature. A joint research study group led by City University of Hong Kong (CityU) has demonstrated for the first time the large, consistent tensile elastic straining of microfabricated diamond selections through the nanomechanical technique.

The research study was co-led by Dr. Lu Yang, Partner Professor in the Department of Mechanical Engineering (MNE) at CityU and scientists from Massachusetts Institute of Technology ( MIT) and Harbin Institute of Innovation (HIT). Their findings have been just recently published in the prestigious scientific journal Science, entitled “Achieving big uniform tensile elasticity in microfabricated diamond.”

” This is the first time showing the very big, consistent elasticity of diamond by tensile experiments. Our findings show the possibility of establishing electronic gadgets through ‘deep flexible strain engineering’ of microfabricated diamond structures,” said Dr. Lu.

Diamond: “Mount Everest” of electronic products

Well understood for its solidity, commercial applications of diamonds are generally cutting, drilling, or grinding. Diamond is also thought about as a high-performance electronic and photonic material due to its ultra-high thermal conductivity, exceptional electric charge carrier movement, high breakdown strength and ultra-wide bandgap.

Tensile Straining of Diamond Bridges

Illustration of tensile straining of microfabricated diamond bridge samples. Credit: Dang Chaoqun/ City University of Hong Kong

However, the big bandgap and tight crystal structure of diamond make it tough to “dope,” a typical method to regulate the semiconductors’ electronic homes during production, thus hampering the diamond’s industrial application in electronic and optoelectronic devices. It was thought about as “impossible” for diamond due to its extremely high hardness.

Then in 2018, Dr Lu and his collaborators discovered that, surprisingly, nanoscale diamond can be elastically bent with unanticipated large local stress. Based on this, the most current research study revealed how this phenomenon can be used for establishing practical diamond gadgets.

Uniform tensile straining across the sample

The team first of all microfabricated single-crystalline diamond samples from a strong diamond single crystals. The samples remained in bridge-like shape– about one micrometer long and 300 nanometres broad, with both ends larger for grasping (see Fig. 2). The diamond bridges were then uniaxially extended in a well-controlled way within an electron microscopic lense. Under cycles of continuous and manageable loading-unloading of quantitative tensile tests, the diamond bridges demonstrated an extremely consistent, large flexible deformation of about 7.5%stress across the whole gauge area of the specimen, rather than deforming at a localized location in flexing. And they recuperated their initial shape after unloading.

By more enhancing the sample geometry using the American Society for Testing and Products (ASTM) basic, they attained a maximum uniform tensile strain of as much as 9.7%, which even went beyond the optimum regional worth in the 2018 study, and was close to the theoretical elastic limitation of diamond. More notably, to show the strained diamond gadget idea, the group also understood flexible straining of microfabricated diamond selections.

Tuning the bandgap by flexible stress

The team then carried out density practical theory (DFT) calculations to estimate the effect of elastic straining from 0 to 12%on the diamond’s electronic residential or commercial properties. The simulation results suggested that the bandgap of diamond generally decreased as the tensile pressure increased, with the largest bandgap decrease rate down from about 5 eV to 3 eV at around 9%strain along a specific crystalline orientation.

Their estimation outcomes also showed that, interestingly, the bandgap could change from indirect to direct with the tensile strains bigger than 9%along another crystalline orientation. Direct bandgap in a semiconductor means an electron can directly release a photon, allowing numerous optoelectronic applications with higher efficiency.

These findings are an early action in attaining deep flexible strain engineering of microfabricated diamonds. By nanomechanical method, the group demonstrated that the diamond’s band structure can be altered, and more significantly, these modifications can be constant and reversible, allowing different applications, from micro/nanoelectromechanical systems (MEMS/NEMS), strain-engineered transistors, to unique optoelectronic and quantum technologies. “I think a brand-new age for diamond leads us,” stated Dr Lu.

Referral: “Achieving big uniform tensile flexibility in microfabricated diamond” by Chaoqun Dang, Jyh-Pin Chou, Bing Dai, Chang-Ti Chou, Yang Yang, Rong Fan, Weitong Lin, Fanling Meng, Alice Hu, Jiaqi Zhu, Jiecai Han, Andrew M. Minor, Ju Li and Yang Lu, 1 January 2021, Science
DOI: 10.1126/ science.abc4174

Dr. Lu, Dr. Alice Hu, who is also from MNE at CityU, Professor Li Ju from MIT and Professor Zhu Jiaqi from HIT are the corresponding authors of the paper. The co-first authors are Dang Chaoqun, PhD graduate, and Dr. Chou Jyh-Pin, previous postdoctoral fellow from MNE at CityU, Dr. Dai Bing from HIT, and Chou Chang-Ti from National Chiao Tung University. Dr. Fan Rong and Lin Weitong from CityU are also part of the team. Other working together researchers are from the Lawrence Berkeley National Laboratory, University of California, Berkeley, and Southern University of Science and Technology.

The research at CityU was moneyed by the Hong Kong Research Study Grants Council and the National Life Sciences Foundation of China.

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