The first issue of "Science" in 2021: stretch the diamond to extremely uniform elastic deformation!

Diamond is not only the hardest material in nature, but also an extreme electronic material with ultra-wide band gap, special carrier mobility and thermal conductivity. Generally, diamonds are considered inflexible, but thin samples can actually deform elastically.
 
Recently, researchers from the City University of Hong Kong, Alice Hu and Lu Yang, Harbin Institute of Technology Zhu Jiaqi, and MIT Li Ju, prepared a single crystal diamond bridge structure with a length of ~1 micron with a width of ~100 nanometers, and edged it at room temperature [ Uniaxial tensile loads in 100], [101] and [111] directions have obtained uniform elastic strain across the sample width. A related paper entitled "Achieving large uniform tensile elasticity in microfabricated diamond" was published in the top international journal Science on January 1, 2021.
 
Paper link:
https://science.sciencemag.org/content/371/6524/76
 
 
Diamond, because of its ultra-high thermal conductivity, dielectric breakdown strength, carrier mobility and ultra-wide band gap, has become the Mount Everest of electronic and photonic materials. A serious obstacle to the realization of diamond-based electronic and optoelectronic devices is the doping challenge brought by its large band gap and its crystal structure. One possible solution is to apply elastic lattice strain, which can fundamentally change the properties of the material. Recently, by bending the nano-diamond needle, super elastic deformation was proved. The local tensile elastic strain reaches more than 9% in the range of tens of nanometers, and the strength is close to the theoretical limit of diamond. This finding indicates that deep elastic strain engineering (ESE) may fundamentally change the physical properties of diamond, that is, induce very high (>5%) tensile and/or shear elastic strains in diamond.
 
However, people need precise control in a large enough capacity to take full advantage of the very large-scale industrial integration of deep ESE. In the past attempts to strain diamond, the strain was often limited by bending to make the strain in a small sample volume, resulting in uneven strain distribution. These samples are difficult to control and the high strain field generated is highly localized. The large uniform elastic strain is usually the ideal initial state of the deep ESE of the device array. This scenario is difficult to experiment with micron-scale samples, such as in a clean wafer, because of the well-known trend of "smaller, stronger", which indicates that increasing the size will weaken the sample.
 
Here, the researchers demonstrated the extremely large, reversible and uniform elastic deformation of the microcrystalline single crystal diamond bridge under tensile load. In order to obtain a stretched sample with a length of ~1μm, a width of 300 nm, and a clear geometry and crystal orientation, the researchers used an advanced microwave plasma-assisted chemical vapor deposition method to obtain a bulk single crystal diamond micromachining process. The process developed by the researchers can produce high-quality diamond structures in micrometer sizes, which is a major candidate material for microelectromechanical systems (MEMS), quantum and photonic devices, strain-engineered transistor arrays, and other applications. In addition, the researchers also demonstrated the deep elastic strain of the diamond microbridge array. Studies have shown that the super-large, highly controllable elastic strain can fundamentally change the diamond body band structure, including the calculation of the band gap eigenvalue, which reduces as much as 2eV.
 
 
The micron-sized single crystal diamond bridge structure is very suitable for the scale of MEMS, photonic devices, quantum information processors, and microelectronic or nanoelectronic device arrays. The large and uniform elastic strain should drive the change of the band gap. The researchers proved this by DFT simulation and EELS measurement. At the same time, the research highlights the huge application potential of deep elastic strain engineering in photonics, electronics and quantum information technology.


Related items & useful information

Carbon Sputtering Target