Due to the absence of the defects associated with grain boundaries, single crystals have unique properties, particularly mechanical, optical, and electrical properties, which can also be anisotropic, depending on the type of crystallographic structure. These properties find wide applications in the fields of optics and electronics. Single crystals are also essential in research, especially for condensed matter physics and materials science, etc.
Monocrystalline silicon is the principal material applied in microelectronic, micro-mechanical, and infrared optical components. Germanium “metal,” i.e., isolated germanium, is used as semiconductor in transistors and various other electronic devices. Germanium’s major end uses in the present are fiber-optic systems and infrared optics. It is also used in solar cell applications. Lithium niobate (LiNbO3) is widely used in a variety of photonic devices due to its high electric-optical, acousto-optic, piezoelectric, and nonlinear optical coefficient. For its low-cost and outstanding physical properties such as high Curie temperature and high rigidity, LiNbO3 has been successfully used in the applications of integrated optics. High-quality electric-optical modulators, optical switches, and rare earth-doped waveguide lasers based on LiNbO3 have been developed.
However, these crystal materials are nominally hard and brittle, which prevents them from manufacturing intricate features and optical quality surfaces (Zhang and Zarudi 2001). It is currently finished by lapping and chemo-mechanical polishing (CMP) (Yan et al. 2001). Many efforts were made to improve the productivity in recent years. Ultra-precision cutting can machine crystals in a ductile mode without the need for subsequent polishing, but the machining scale must be controlled to be in a range of a few tens of nanometers (Fang and Venkatesh 1998).
Nanometric cutting assisted with ion implantation surface modification provides a novel approach for manufacturing brittle monocrystalline materials. The mechanical properties of the surface layer of the material are modified in a depth up to a few micrometers by decrystallization using high-energy ion bombardments so that the brittleness is reduced and the plasticity is enhanced. The productivity is greatly improved by avoiding the fractures during the surface mechanical processing (Fang et al. 2011).