Nickel (Ni) single crystal substrate is a type of metallic substrate made of a single crystal of nickel. Single crystal nickel substrates are used in various applications, including electronics and optoelectronics. The high electrical and thermal conductivity of nickel make it an attractive material for use as a substrate in electronic devices, especially for high-temperature applications. Additionally, nickel is also known for its resistance to corrosion, which makes it a suitable material for use in harsh environments. However, the high melting point and low ductility of nickel can make it difficult to process and handle, which can present some challenges in the fabrication of devices.