A single crystal diamond material comprising: neutral nitrogen-vacancy defects (NV.sup.0); negatively charged nitrogen-vacancy defects (NV.sup.−); and single substitutional nitrogen defects (N.sub.s) which transfer their charge to the neutral nitrogen-vacancy defects (NV.sup.0) to convert them into the negatively charged nitrogen-vacancy defects (NV), characterized in that the single crystal diamond material has a magnetometry figure of merit (FOM) of at least 2, wherein the magnetometry figure of merit is defined by (I) where R is a ratio of concentrations of negatively charged nitrogen-vacancy defects to neutral nitrogen-vacancy defects ([NV.sup.−]/[NV.sup.0]), [NV.sup.−] is the concentration of negatively charged nitrogen-vacancy defects measured in parts-per-million (ppm) atoms of the single crystal diamond material, [NV0] is a concentration of neutral nitrogen-vacancy defects measured in parts-per-million (ppm) atoms of the single crystal diamond material, and T.sub.2′ is a decoherence time of the NV.sup.− defects, where T.sub.2′ is T.sub.2* for DC magnetometry or T.sub.2 for AC magnetometry.

A group-III nitride substrate includes: a base material part of a group-III nitride including a front surface, a back surface, and an inner layer between the front surface and the back surface, wherein the carbon concentration of the front surface of the base material part is higher than the carbon concentration of the inner layer.

A method for preparing suspended graphene support film by selectively etching growth substrate is disclosed in present invention. The transfer process of graphene is avoided. The process of present invention is efficient and low in cost, suspended graphene support film can be prepared in a single etching step. The prepared graphene support film does not need any support by polymer film and polymer fiber. The prepared graphene support film has controllable number of layers and high intactness (90%-97%), large suspended area (diameter is 10-50 μm), wide clean area (>100 nm) and can be mass-produced. In addition, the graphene support film can be directly used as transmission electron microscope support film, and can be used to achieve high resolution imaging of nanoparticles.

An evaluation method of a silicon epitaxial wafer, including using a photoluminescence (PL) measuring apparatus to measure a PL spectrum of the mirror wafer and adjusting the apparatus so emission intensity of a TO-line becomes 30000 to 50000 counts, irradiating the silicon epitaxial wafer with an electron beam, measuring PL spectrum from an electron beam irradiation region, and sorting out and accepting a silicon epitaxial wafer which has emission intensity resulting from a C.sub.iC.sub.s defect of the PL spectrum being 0.83% or less of the emission intensity of the TO-line and from a C.sub.iO.sub.i defect being 6.5% or less of the emission intensity of the TO-line.

A group III nitride crystal, wherein the group III nitride crystal is doped with an N-type dopant and a germanium element, the concentration of the N-type dopant is 1×10.sup.19 cm.sup.−3 or more, and the concentration of the germanium element is nine times or more higher than the concentration of the N-type dopant.

A group III nitride crystal, wherein the group III nitride crystal is doped with an N-type dopant and a germanium element, the concentration of the N-type dopant is 1×10.sup.19 cm.sup.−3 or more, and the concentration of the germanium element is nine times or more higher than the concentration of the N-type dopant.

A group III nitride crystal, wherein the group III nitride crystal is doped with an N-type dopant and a hydrogen element, and the concentration of the N-type dopant is 1×10.sup.20 cm.sup.−3 or more, and the concentration of the hydrogen element is 1×10.sup.19 cm.sup.−3 or more.

A group III nitride crystal, wherein the group III nitride crystal is doped with an N-type dopant and a hydrogen element, and the concentration of the N-type dopant is 1×10.sup.20 cm.sup.−3 or more, and the concentration of the hydrogen element is 1×10.sup.19 cm.sup.−3 or more.

Provided is a method of producing an epitaxial silicon wafer, which is excellent in productivity and prevents the formation of a backside haze in consecutive single-wafer processing epitaxial growth procedures on a plurality of silicon wafers without cleaning a process chamber after each epitaxial growth procedure. The method of producing an epitaxial silicon wafer includes: a step of loading a silicon wafer; a step of forming a silicon epitaxial layer; a step of unloading the silicon wafer; and a cleaning step. The cleaning step is performed before and after repeating a predetermined number of times a series of growth procedures including the silicon wafer loading step, the silicon epitaxial layer formation step, and the silicon wafer unloading step.

Provided are a GaN crystal used in a substrate for a nitride semiconductor device having a horizontal device structure such as GaN-HEMT, and a substrate used for production of a nitride semiconductor device having a horizontal device structure such as GaN-HEMT. The Gab crystal has a (0001) surface having an area of not less than 5 cm.sup.2, the (0001) surface having an inclination of not more than 10° with respect to the (0001) crystal plane, wherein the Fe concentration is not less than 5×10.sup.17 atoms/cm.sup.3 and less than 1×10.sup.9 atoms/cm.sup.3, and wherein the total donor impurity concentration is less than 5×10.sup.16 atoms/cm.sup.3.