Newswise — Silicon-based materials are currently the top choice for semiconductors. However, scientists worldwide are actively searching for better alternatives for future electronics and high-power systems. Surprisingly, diamonds show great promise for applications like fast telecommunications, power conversion in electric vehicles, and power plants.
Diamonds have appealing properties for the semiconductor industry, but their applications are limited because efficient techniques to slice them into thin wafers are lacking. Consequently, diamond wafers must be individually synthesized, leading to high fabrication costs that are not feasible for most industries.
A research team led by Professor Hirofumi Hidai from Chiba University in Japan has found a solution to the limitation in diamond wafer fabrication. They developed a novel laser-based slicing technique, as reported in a recent study available online on May 18, 2023, and published in Diamond & Related Materials in June 2023. This technique allows for clean slicing of diamonds along the optimal crystallographic plane, resulting in smooth wafers. The study's co-authors include master's student Kosuke Sakamoto from the Graduate School of Science and Engineering at Chiba University and former Ph.D. student Daijiro Tokunaga, who currently serves as an Assistant Professor at the Tokyo Institute of Technology.
Most crystals, including diamonds, have varying properties along different crystallographic planes, which are imaginary surfaces containing the crystal's atoms. Diamonds, for example, can be easily sliced along the {111} surface. However, slicing along the {100} surface is challenging because it results in cracks along the {111} cleavage plane, leading to increased kerf loss. Kerf loss refers to the material wasted during the slicing process.
To address the issue of undesirable cracks during slicing, the researchers devised a diamond processing technique using short laser pulses directed at a narrow cone-like volume within the material. This concentrated laser illumination causes the diamond to transform into amorphous carbon, which has a lower density than diamond. Consequently, the regions modified by the laser pulses experience a reduction in density, preventing crack formation, as Prof. Hidai explains.
The researchers utilized the laser pulses on a transparent diamond sample, arranging them in a square grid pattern. This process resulted in a grid of small regions inside the material, which were prone to cracking. By carefully controlling the spacing between the modified regions in the grid and the number of laser pulses used per region, all the modified regions connected to each other through small cracks that predominantly propagated along the {100} plane. As a result, a smooth wafer with a {100} surface could be easily separated from the rest of the diamond block by applying gentle pressure with a sharp tungsten needle against the side of the sample.
The proposed technique represents a significant advancement in making diamonds a viable semiconductor material for future technologies. Prof. Hidai emphasizes that diamond slicing allows the production of high-quality wafers at a lower cost and is crucial for fabricating diamond semiconductor devices. As a result, this research brings us closer to realizing diamond semiconductors for various applications in society, including enhancing the power conversion efficiency in electric vehicles and trains. This development holds the potential to revolutionize the semiconductor industry and pave the way for more efficient and powerful electronic devices.
We can hope that this highly valued crystal grants us an advantage in our pursuit of advanced technological advancements, particularly those that contribute to a more sustainable future!
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