INSTRUMENTATION • ELECTRONICSSECTION TITLE
The laser-based slicing technique can successfully slice a diamond to produce smooth wafers
Focusing the energy of a laser beam into a small volume of a diamond sample creates tiny modifi ed regions
can be used to cleanly slice a diamond along the optimal crystallographic plane to produce smooth wafers. According to the researchers, their fi ndings will help in making diamonds cost-eff ective semiconductors for highly effi cient power conversion in EVs and high-speed communication technologies. T e properties of most crystals, including diamonds, vary along diff erent crystallographic planes – imaginary surfaces containing the atoms that make up the crystal. For instance, a diamond can easily be sliced along the (111) surface. However, slicing (100) is challenging because it also produces cracks along the (111) cleavage plane, increasing kerf loss. To prevent the propagation of these undesirable cracks, the researchers
developed a diamond processing technique that focuses short laser pulses onto a narrow cone-like volume within the material. “Concentrated laser illumination transforms diamond into amorphous carbon, whose density is lower that that of diamond,” says Professor Hidai. “Hence, regions modifi ed by laser pulses undergo a reduction in density and crack formation.” By shining these laser pulses onto the
transparent diamond sample in a square grid pattern, the researchers created a grid of small crack-prone regions inside the material. If the space between the modifi ed regions in the grid and the number of laser pulses used per region are optimal, all modifi ed regions connect to each other through small cracks that preferentially propagate along the (100) plane. As a result, a smooth wafer with (100) surface can be easily separated from the rest of the diamond block by simply pushing a sharp tungsten needle against the side of the sample.
NEXT-GENERATION SEMICONDUCTORS T e Chiba University team believes
its technique off ers a pivotal step towards making diamonds a suitable semiconductor material for future technologies, particularly those that will aid in creating a more sustainable future. “Diamond slicing enables the
production of high-quality wafers at low cost and is indispensable in fabricating diamond semiconductor devices,” says Professor Hidai. “T erefore, this research brings us closer to realising diamond semiconductors for various applications in our society, such as improving the power conversion ratio in EVs and trains.”
For more information, read the full paper ‘Laser slicing of a diamond at the (100) plane using an irradiation sequence that restricts crack propagation along the (111) plane,’ published in the Diamond & Related Materials Journal:
www.doi.org/10.1016/ j.diamond.2023.110045
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