Diamond single crystal, method for producing the same, and single crystal diamond tool

A diamond single crystal produced by gas-phase synthesis,

• wherein the diamond single crystal includes two or more diamond monocrystalline layers having different absorption coefficients for light having a wavelength of 350 nm,
• one of the diamond monocrystalline layers having one main surface has an absorption coefficient of less than 25 cm−1 for light having a wavelength of 350 nm, and another of the diamond monocrystalline layers having the other main surface has an absorption coefficient of 25 cm−1 or more and 80 cm−1 or less for light having a wavelength of 350 nm, and
• any of the two or more diamond monocrystalline layers has an absorption coefficient of 80 cm−1 or less for light having a wavelength of 350 nm.

A method for producing a diamond single crystal, comprising:

• implanting an ion other than carbon into a main surface of a diamond single crystal seed substrate and thereby decreasing the transmittance of light having a wavelength of 800 nm, the main surface having an off-angle of 7 degrees or less with respect to a {100} plane;
• and
• homoepitaxially growing a diamond single crystal on the ion-implanted main surface of the seed substrate using a chemical vapor synthesis method under synthesis conditions where the ratio NC/NH of the number of carbon-containing molecules NC to the number of hydrogen molecules NH in a gas phase is 10% or more and 40% or less, the ratio NN/NC of the number of nitrogen molecules NN to the number of carbon-containing molecules NC in the gas phase is 0.1% or more and 10% or less, and the seed substrate temperature T is 850° C. or more and less than 1000° C.

A single crystal diamond tool, comprising a diamond single crystal joined to a shank of the tool, wherein the diamond single crystal includes an ion-implanted layer formed by ion implantation into a crystal face on a side of the diamond single crystal to be joined to the shank.