WG 8 - TC 113/WG 8

IEC TS 62607-6-7:2023 establishes a method to determine the key control characteristics sheet resistance RS [measured in ohm per square (Ω/sq)], by the van der Pauw method, vdP.
The sheet resistance RS is derived by measurements of four-terminal electrical resistance performed on four electrical contacts placed on the boundary of the planar sample and calculated with a mathematical expression involving the two resistance measurements.
The measurement range for RS of the graphene samples with the method described in this document goes from 10−2 Ω/sq to 104 Ω/sq.
The method is applicable for CVD graphene provided it is transferred to quartz substrates or other insulating materials (quartz, SiO2 on Si), as well as graphene grown from silicon carbide.
The method is complementary to the in-line four-point-probe method (4PP, IEC 62607-6-8) for what concerns the measurement of the sheet resistance and can be applied when it is possible to reliably place contacts on the sample boundary, avoiding the sample being scratched by the 4PP.
The outcome of the van der Pauw method is independent of the contact position provided the sample is uniform, which is typically not true for graphene at this stage. This document considers the case of samples with non-strictly uniform conductivity distribution and suggests a way to consider the sample inhomogeneity as a component of the uncertainty on RS.

IEC TS 62607-6-8:2023 establishes a method to determine the key control characteristic sheet resistance RS [measured in ohm per square (Ω/sq)], by the in-line four-point probe method, 4PP.
The sheet resistance RS is derived by measurements of four-terminal electrical resistance performed on four electrodes placed on the surface of the planar sample.
The measurement range for RS of the graphene samples with the method described in this document goes from 10−2 Ω/sq to 104 Ω/sq.
The method is applicable for CVD graphene provided it is transferred to quartz substrates or other insulating materials (quartz, SiO2 on Si, as well as graphene grown from silicon carbide.
The method is complementary to the van der Pauw method (IEC 62607-6-7) for what concerns the measurement of the sheet resistance and can be useful when it is not possible to reliably place contacts on the sample boundary.

IEC TS 62607-6-17:2023 establishes a standardized method to determine the key control characteristic order parameter for graphene-based material and layered carbon material by X-ray diffraction (XRD) and transmission electron microscopy.
The order parameter is analysed from two perspectives: z-axis and x-y-axis. In the z-axis the order parameter is derived from the full width at half maximum (FWHM) of peak (002) in the XRD spectrum. In the x-y-axis, it is derived from the FWHM of peak (100) corresponding to diffraction patterns obtained by SAED (selected area electron diffraction) technique, which is routinely performed on most transmission electron microscopes in the world.
The method is applicable for graphene-based material and layered carbon material including graphite, expanded graphite, amorphous carbon, vitreous carbon or glassy carbon, the structures of which are clarified by other characterization techniques.
The method is applicable for differentiating few-layer graphene or reduced graphene oxide from layered carbon material.
Typical application area is quality control in manufacturing to ensure batch-to-batch reproducibility.
NOTE Graphene oxide, one type of graphene-based material, is not within the scope of this document.

IEC TS 62607-6-18:2022(E) establishes a standardized method to determine the chemical key control characteristic
functional groups  for functionalized graphene-based material and graphene oxide by
thermogravimetry analysis (TGA) coupled with Fourier transform infrared spectroscopy (FTIR), referred to as TGA-FTIR.  The content of functional groups is derived by changes in mass of the sample as a function of temperature using TGA. Materials evolved during these mass changes are then analysed using coupled FTIR to identify functional groups.
The functional groups determined according to this document will be listed as a key control characteristic in the blank detail specification for graphene IEC 62565-3-1 for graphene powder.
The method is applicable for functionalized graphene powder and graphene oxide that can be pyrolysed and gasified with elevated temperature during TGA.
Typical application areas are quality control for graphene manufacturers, and product selection for downstream users.

IEC TS 62607:2022 establishes a standardized method to determine the key control characteristic
carrier concentration  for semiconducting two-dimensional materials by the
field effect transistor (FET) method.  For semiconducting two-dimensional materials, the carrier concentration is evaluated using a field effect transistor (FET) test by a measurement of the voltage shift obtained from transfer curve upon doping process. The FET test structure consists of three terminals of source, drain, and gate where voltage is applied to induce the transistor action. Transfer curves are obtained by measuring drain current while applying varied gate voltage and constant drain voltage with respect to the source which is grounded.

IEC TS 62607-2-5:2022 specifies the protocols for determining the mass density of vertically-aligned carbon nanotubes (VACNTs) by X-ray absorption method. This document outlines experimental procedures, data formats, and some case studies. These protocols are applicable to VACNT films with thickness larger than several tens of micrometres. There are no limitations in materials for substrate.

IEC TS 62607-6-22:2022 establishes a standardized method to determine the key control characteristic
ash content  of powder and dispersion of graphene-based material by
incineration.  The ash content is derived by residue obtained after incineration under the operating conditions specified in this document, being divided by the mass of the dried test portion.
The method is applicable for graphene, graphene oxide and reduced graphene oxide in forms of both dry powder and dispersion. This document can be used as reference for graphite oxide and other modified graphene.
Typical application areas of this method are research, manufacturer and downstream user to guide material processing and quality control.

IEC TS 62607-6-20:2022 (EN) IEC TS 62607 establishes a standardized method to determine the chemical key control characteristic
- metallic impurity content
for powders of graphene-based materials by
- inductively coupled plasma mass spectrometry (ICP-MS).
The metallic impurity content is derived by the signal intensity of measured elements through MS spectrum of ICP-MS.
- The method is applicable for powder of graphene and related materials, including bilayer graphene (2LG), trilayer graphene (3LG), few-layer graphene (FLG), reduced graphene oxide (rGO) and graphene oxide (GO).
– The typical application area is in the microelectronics industry, e.g. conductive pastes, displays, etc., for manufacturers to guide material design, and for downstream users to select suitable products.

IEC TS 62607-6-21:2022 establishes a standardized method to determine the chemical key control characteristics
- elemental composition, and
- C/O ratio
for powders of graphene-based materials by
- X-ray photoelectron spectroscopy (XPS).
The elemental composition (species and relative abundance) is derived by the elemental binding energy and integral peak area at corresponding portion of XPS spectrum.
- The elemental composition refers to main elements in graphene powders, typically including carbon (C), oxygen (O), nitrogen (N), sulfur (S) , chloride (Cl) and silicon (Si).
- This document is applicable to graphene powders consisting of graphene, bilayer graphene (2LG), trilayer graphene (3LG), few-layer graphene (FLG), graphene nanoplate (GNP), reduced graphene oxide (rGO), graphene oxide (GO), and functionalized graphene powders.
- Typical application areas are the microelectronics and thermal management industries, e.g. batteries, integrated circuits, high-frequency electronics. This document can be used by manufacturers in research and development and by downstream users for product selection.

IEC TS 62607-6-19:2021(E) establishes a standardized method to determine the chemical key control characteristic
• elemental composition
for powder consisting of graphene-based material by
• CS analyser and ONH analyser.
The method as described in this document determines the content of carbon (C), sulfur (S), oxygen (O), nitrogen (N) and hydrogen (H).
The carbon (C) and sulfur (S) content in graphene powder is derived by the content of converted CO, CO2 and SO2, which is determined by infrared gas detector (IGD) using a non-dispersive infrared adsorption method in CS analyser.
The content of oxygen (O), nitrogen (N) and hydrogen (H) in graphene powder is derived by ONH analyser using pyrolysis method. The O content is obtained according to the content of converted CO and CO2, which is determined by IGD using a non-dispersive infrared adsorption method. The N content is obtained according to the content of converted N2, which is determined by a thermal conductivity detector (TCD) method. The H content is obtained by measuring converted H2 or H2O, corresponding to TCD or IGD method.
• The method is applicable for graphene, graphene oxide (GO) and reduced graphene oxide (rGO) in powder form.

IEC TS 62607-6-10:2021(E) establishes a standardized method to determine the electrical key control characteristic
– sheet resistance (Rs)
for films of graphene-based materials by
– terahertz time domain spectroscopy (THz-TDS).
In this technique, a THz pulse is sent to the graphene-based material. The transmitted or reflected THz waveform is measured in the time domain and transformed to the frequency domain by the fast Fourier transform (FFT). Finally, the spectrum is fitted to the Drude model (or another comparable model) to obtain the sheet resistance.
• This non-contact inspection method is non-destructive, fast and robust for the mapping of large areas of graphene films, with no upper sample size limit.
• The method is applicable for statistical process control, comparison of graphene films produced by different vendors, or to obtain information about imperfections on the microscale such as grain boundaries and defects, etc.
• The method is applicable for graphene grown by chemical vapour deposition (CVD) or other methods on or transferred to dielectric substrates, including but not limited to quartz, silica (SiO2), silicon (Si), sapphire, silicon carbide (SiC) and polymers.
• The minimum spatial resolution is in the order of 300 µm (at 1 THz) given by the diffraction limited spot size of the THz pulse.