A method for coating temperature-sensitive substrates with polycrystalline diamond by a hot-wire CVD method, in which hydrogen and at least one carbon carrier gas are fed into a coating chamber. The fed gases are split at an electrically heated wire in such a way that carbon is formed and deposits on the temperature-sensitive substrate in the form of the diamond modification thereof. The substrate is arranged in the coating chamber, which is at a reduced pressure, and electrical power to electrically heat the wire is adjustable. The method is performed cyclically in respect of the electrical power that is fed to electrically heat the wire. A basic power is fed as lower threshold value for a predetermined time (basic load phase) and is increased for a further predetermined time to a maximum power as an upper threshold value (pulse phase) and is then reduced again to the basic power.

A method for manufacturing diamond substrate of using source gas containing hydrocarbon gas and hydrogen gas to form diamond crystal on an underlying substrate by CVD method, to form a diamond crystal layer having nitrogen-vacancy centers in at least part of the diamond crystal, nitrogen or nitride gas is mixed in the source gas, wherein the source gas is: 0.005 volume % or more and 6.000 volume % or less of the hydrocarbon gas; 93.500 volume % or more and less than 99.995 volume % of the hydrogen gas; and 5.0×10.sup.−5 volume % or more and 5.0×10.sup.−1 volume % or less of the nitrogen gas or the nitride gas, and the diamond crystal layer having the nitrogen-vacancy centers is formed. A method for manufacturing a diamond substrate to form an underlying substrate, a diamond crystal having a dense nitrogen-vacancy centers (NVCs) with an orientation of NV axis by performing the CVD.

A method is disclosed for manufacturing lab grown diamond material by plasma enhanced chemical vapour deposition (PECVD). A substrate is exposed to a plasma containing carbon species while supported within a recess in a holder, resulting in a single crystal diamond (SCD) growing on the substrate while polycrystalline diamond (PCD) is deposited on the substrate holder. The relative rate of growth of the single crystal diamond on the substrate and the polycrystalline diamond on the surface of the holder is set, by control of at least one of the applied energy, cooling of the substrate holder and the chemical composition of the process gases, such that the single crystal diamond grown on the substrate protrudes above the surface of the holder and is constrained not to increase or to reduce in cross sectional area with increased distance from the surface of the holder by simultaneous growth of a polycrystalline diamond layer on the surface of the holder.

A tool with a through hole includes a base and a diamond component held by the base, and when the length of the diamond component along a center line of the through hole is denoted as L1 and the maximum value of a diameter of a circle having the same area as a region surrounded by an outer edge of the diamond component in a cross section having the center line as a normal line is denoted as M1, the ratio L1/M1 between L1 and M1 is 0.8 or more.

The invention relates to a diamond-based gem. The diamond-based gem may include, at least one first portion comprising one of: a single crystal diamond and a transparent polycrystal diamond; and at least one second portion comprising opaque polycrystal diamond. Further are disclosed several methods for manufacturing such a diamond-based gem.

A method for manufacturing diamond substrate of using source gas containing hydrocarbon gas and hydrogen gas to form diamond crystal on an underlying substrate by CVD method, to form a diamond crystal layer having nitrogen-vacancy centers in at least part of the diamond crystal, nitrogen or nitride gas is mixed in the source gas, wherein the source gas is: 0.005 volume % or more and 6.000 volume % or less of the hydrocarbon gas; 93.500 volume % or more and less than 99.995 volume % of the hydrogen gas; and 5.0×10.sup.−5 volume % or more and 5.0×10.sup.−1 volume % or less of the nitrogen gas or the nitride gas, and the diamond crystal layer having the nitrogen-vacancy centers is formed. A method for manufacturing a diamond substrate to form an underlying substrate, a diamond crystal having a dense nitrogen-vacancy centers (NVCs) with an orientation of NV axis by performing the CVD.

There is provided a novel stack that includes a single-crystal diamond substrate having a coalescence boundary, yet effectively uses the coalescence boundary. A stack comprising at least a semiconductor drift layer stacked on a single-crystal diamond substrate having a coalescence boundary, wherein the coalescence boundary of the single-crystal diamond substrate is a region that exhibits, in a Raman spectrum at a laser excitation wavelength of 785 nm, a full width at half maximum of a peak near 1332 cm.sup.1 due to diamond that is observed to be broader than a full width at half maximum of the peak exhibited by a region different from the coalescence boundary, the coalescence boundary has a width of 200 m or more, and the semiconductor drift layer is stacked on at least the coalescence boundary.

A method for coating temperature-sensitive substrates with polycrystalline diamond by a hot-wire CVD method, in which hydrogen and at least one carbon carrier gas are fed into a coating chamber. The fed gases are split at an electrically heated wire in such a way that carbon is formed and deposits on the temperature-sensitive substrate in the form of the diamond modification thereof. The substrate is arranged in the coating chamber, which is at a reduced pressure, and electrical power to electrically heat the wire is adjustable. The method is performed cyclically in respect of the electrical power that is fed to electrically heat the wire. A basic power is fed as lower threshold value for a predetermined time (basic load phase) and is increased for a further predetermined time to a maximum power as an upper threshold value (pulse phase) and is then reduced again to the basic power.

A diamond coating includes a first diamond layer made of minute diamond particles and a second diamond layer made of coarse diamond particles: in a flank-face side diamond coating, a mean coat thickness d2 is not less than 3 m and not more than 25 m, a first diamond layer is formed on a surface side and a second diamond layer is formed on a tool base side: a rake-face side diamond coating is in a smaller range of 50 m or 1/10 of a tool diameter from a tip of a base cutting-edge part; in the rake-face side diamond coating, a mean coat thickness d1 is a smaller one in a range not less than 0 m and not more than 5.0 m or a range less than d2: and a boundary part between the first diamond layer and the second diamond layer.

A single-crystal diamond includes n types of regions different in total concentration of an impurity, the n types of regions being observed in an observed surface being in parallel to a (110) face. Each of the n types of regions has an area not smaller than 0.1 m.sup.2. At least one of a first line, a second line, and a third line on the observed surface crosses a boundary between the n types of regions at least four times. The first line, the second line, and the third line are in parallel to a <110> direction and have a length of 1 mm. A midpoint of the first line corresponds to the center of gravity of the observed surface. The second line and the third line are distant from the first line by 300 m in a <001> direction and a <001> direction, respectively.