The Synthesis of Needle‐Like Monocrystalline Diamonds with a High Aspect Ratio up to 14

Abstract Diamond exhibits nontrivial hardness and abrasion, ultra‐high thermal conductivity, and light transmission over a wide wavelength range. All these properties are anisotropic. There is considerable literature on the synthesis of large‐sized monocrystalline diamonds but the synthesis of highly oriented monocrystalline diamonds is limited. Here, [100] oriented monocrystalline needle‐like diamonds are successfully synthesized with an aspect ratio of up to 14 by controlling the temperature gradient and carbon concentration gradient using FeCo alloy as the catalyst at ≈5.8 GPa and 1473 K. The distinctive morphology and microstructure of needle‐like diamonds are characterized using Scanning Electron Microscopy, X‐ray diffraction, and Focused Ion Beam‐Transmission Electron Microscopy. A four‐stage growth model is established to elucidate the growth mechanism along the [100], which sheds light on the synthesis of diamonds with predetermines crystal orientations. Increasing the aspect ratio of needle‐like diamonds further may enable the development of diamond fibers and assist in the fabrication of laser diamonds with specific orientation requirements.