# Graphene Raman layer checker: monolayer, few-layer or multilayer

> Check graphene layer number from Raman: 2D width and I(2D)/I(G) against the NPL monolayer criteria, 2D line shape, and D-band defect hints. Free.

URL: https://www.labcanvas.com/tools/graphene-raman-layer-calculator

Monolayer graphene on Si/SiO₂ has a single-Lorentzian 2D band with a full width at half maximum of 35 cm⁻¹ or less and a 2D peak at least twice as high as the G peak: these are the UK National Physical Laboratory (NPL) criteria. Enter the 2D width, the I(2D)/I(G) ratio and the 2D line shape from your fit, and the checker compares them with the NPL criteria and the published layer trends. It is an indication, not proof.

## Quick answer

- **What it does:** Checks a graphene Raman spectrum against the NPL monolayer criteria from the 2D width, I(2D)/I(G) and 2D line shape, with notes on defects from the D band.
- **Formula:** Monolayer (NPL, Si/SiO₂): single-Lorentzian 2D with FWHM(2D) ≤ 35 cm⁻¹ and I(2D)/I(G) ≥ 2; defect type from I(D)/I(D′) ≈ 13 sp³, 7 vacancy, 3.5 boundary.
- **Example:** A single-Lorentzian 2D band with FWHM 28 cm⁻¹ and I(G)/I(2D) = 0.28 (I(2D)/I(G) = 3.57) meets both criteria: consistent with monolayer graphene.

Free, in the browser, no account needed. Updated 2026-11-08.

## Features

- Checks the NPL monolayer criteria: \(\mathrm{FWHM(2D)} \le 35\ \mathrm{cm^{-1}}\) and \(I(\mathrm{2D})/I(\mathrm{G}) \ge 2\)
- Whether the 2D band is stronger than G, seen below five layers
- The 2D line shape: one Lorentzian, or several components as in bilayers and graphite
- Enter the ratio as I(2D)/I(G) or I(G)/I(2D)
- Reference values from published spectra: a single layer at 532 nm and a CVD monolayer map
- D-band notes from I(D)/I(G), and the likely defect type from I(D)/I(D′)
- A one-line summary to copy into your notes; nothing is uploaded

## How to use it

1. **Fit your spectrum**: Fit the G and 2D peaks (and D and D′ if present) with Lorentzians in your Raman software, and note whether one Lorentzian describes the 2D band.
2. **Set the measurement**: Choose the laser wavelength and the substrate. The criteria were set for graphene on Si/SiO₂ measured at 532 nm.
3. **Enter the 2D and G values**: Type the 2D FWHM in cm⁻¹ and the peak-height ratio, as I(2D)/I(G) or I(G)/I(2D), and the 2D line shape.
4. **Add the defect bands**: Optionally enter I(D)/I(G) and I(D)/I(D′) to get notes on defects.
5. **Read the indication**: See which criteria are met and what they suggest, then confirm the layer number with optical contrast, AFM or a Raman map.

## At a glance

| | |
| --- | --- |
| Monolayer criteria | \(\mathrm{FWHM(2D)} \le 35\ \mathrm{cm^{-1}}\) and \(I(\mathrm{2D})/I(\mathrm{G}) \ge 2\) (NPL, Si/SiO₂) |
| Layer trend | 2D stronger than G below five layers (Gupta et al. 2006) |
| Input | 2D FWHM, I(2D)/I(G) or I(G)/I(2D), 2D line shape; optional I(D)/I(G) and I(D)/I(D′) |
| Output | Criteria met or not, and what they suggest; not a layer count |
| Defects | D-band notes; defect type from I(D)/I(D′) (Eckmann et al. 2012) |
| Limits | Doping, strain, defects, substrate, stacking and laser all change the numbers |

## How it works

$$\begin{aligned} &\text{Monolayer (NPL, Si/SiO}_2\text{):} \\ &\mathrm{FWHM(2D)} \le 35\ \mathrm{cm^{-1}}\ \text{and} \\ &I(\mathrm{2D})/I(\mathrm{G}) \ge 2 \end{aligned}$$

**Monolayer criteria.** The UK National Physical Laboratory proposed a 2D full width at half maximum of 35 cm⁻¹ or less and an I(2D)/I(G) ratio of at least 2 to identify monolayer graphene on Si/SiO₂, as applied at 532 nm by Muñoz-Vargas et al. (2025). Both numbers are sensitive to other things: I(2D)/I(G) falls with doping and defects, and the 2D width grows with adlayers and with strain variations below the laser spot. A turbostratic (randomly stacked) multilayer can also give a single-Lorentzian 2D narrower than 35 cm⁻¹. Their CVD monolayer averaged 26.2 ± 1.7 cm⁻¹ and 2.4 ± 0.7 over 1024 spectra.

**Layer trends.** The 2D band changes in shape, width and position with the number of layers (Ferrari et al. 2006). On Si/SiO₂ at 514.5 nm, the 2D band is more intense than G for fewer than five layers (Gupta et al. 2006). At 532 nm, Qiu et al. (2016) measured a single-layer 2D at 2675 cm⁻¹ with a FWHM of about 28 cm⁻¹, and I(G)/I(2D) rising from 0.28 for a single layer to more than 1.4 for multilayers; graphite (HOPG) shows two 2D components near 2680 and 2720 cm⁻¹. The 2D band of AB-stacked bilayer graphene is made of four peaks (Mafra et al. 2012). The checker reports which of these apply to your numbers; it does not claim a layer count.

**Defects.** The D band needs a defect to appear (Qiu et al. 2016). I(D)/I(G) at a given defect density depends strongly on the laser energy and reaches a maximum at about 3 nm between defects, so one ratio can correspond to two densities; the G width tells them apart (Cançado et al. 2011). The checker therefore does not convert I(D)/I(G) into a defect density. I(D)/I(D′) is about 13 for sp³ defects, 7 for vacancy-like defects and 3.5 for boundaries (Eckmann et al. 2012); the checker names the closest of the three.

Sources: Muñoz-Vargas S et al. *Nanoscale Adv* 2025;7:7382, [doi:10.1039/d5na00668f](https://doi.org/10.1039/d5na00668f). Ferrari AC et al. *Phys Rev Lett* 2006;97:187401, [doi:10.1103/PhysRevLett.97.187401](https://doi.org/10.1103/PhysRevLett.97.187401). Gupta A et al. *Nano Lett* 2006;6:2667–2673, [doi:10.1021/nl061420a](https://doi.org/10.1021/nl061420a). Qiu C et al. *Materials* 2016;9:897, [doi:10.3390/ma9110897](https://doi.org/10.3390/ma9110897). Mafra DL et al. *Nano Lett* 2012;12:2883–2887, [doi:10.1021/nl300477n](https://doi.org/10.1021/nl300477n). Cançado LG et al. *Nano Lett* 2011;11:3190–3196, [doi:10.1021/nl201432g](https://doi.org/10.1021/nl201432g). Eckmann A et al. *Nano Lett* 2012;12:3925–3930, [doi:10.1021/nl300901a](https://doi.org/10.1021/nl300901a).

## Worked examples

**A single layer.** Qiu et al. (2016) report, at 532 nm, a 2D band at 2675 cm⁻¹ with a FWHM of about 28 cm⁻¹ and \(I(\mathrm{G})/I(\mathrm{2D}) = 0.28\) for single-layer graphene. Entered here (\(I(\mathrm{G})/I(\mathrm{2D}) = 0.28\), so \(I(\mathrm{2D})/I(\mathrm{G}) = 3.57\), one Lorentzian), both NPL criteria are met and the 2D is stronger than G: **consistent with monolayer graphene**.

**A multi-component 2D.** With a 2D band that needs several components and \(I(\mathrm{2D})/I(\mathrm{G}) = 1.1\), the 2D is still stronger than G but the shape rules out a monolayer: **not a monolayer**, as for an AB bilayer, whose 2D has four components.

**A defect hint.** \(I(\mathrm{D})/I(\mathrm{D'}) = 7.4\) is closest to the about 7 that Eckmann et al. (2012) found for vacancy-like defects.

## Questions

### How do you tell monolayer graphene from Raman?

Look at the 2D band. For monolayer graphene on Si/SiO₂ it is one Lorentzian, with a full width at half maximum of 35 cm⁻¹ or less, and at least twice as high as the G peak: the UK NPL criteria, \(\mathrm{FWHM(2D)} \le 35\ \mathrm{cm^{-1}}\) and \(I(\mathrm{2D})/I(\mathrm{G}) \ge 2\). Confirm with optical contrast, AFM or a map.

### What are the NPL criteria for monolayer graphene?

\(\mathrm{FWHM(2D)} \le 35\ \mathrm{cm^{-1}}\) and \(I(\mathrm{2D})/I(\mathrm{G}) \ge 2\), proposed by the UK National Physical Laboratory for graphene on Si/SiO₂ and applied at 532 nm by Muñoz-Vargas et al. (2025).

### Can multilayer graphene pass the monolayer test?

Yes. A turbostratic (randomly stacked) multilayer can also give a single-Lorentzian 2D band narrower than 35 cm⁻¹, so a spectrum that meets the criteria is consistent with a monolayer, not proof of one.

### What does I(2D)/I(G) below 1 mean?

The 2D band is weaker than G. Gupta et al. (2006) found the 2D more intense than G for fewer than five layers on Si/SiO₂ at 514.5 nm, so a weaker 2D suggests five layers or more; strong doping or many defects also lower the ratio.

### What does the 2D band of bilayer graphene look like?

Wider than a monolayer’s and made of several components: for AB-stacked bilayer graphene, four peaks (Mafra et al. 2012). Graphite shows two components near 2680 and 2720 cm⁻¹ (Qiu et al. 2016).

### Can I get the defect density from I(D)/I(G)?

Not from the ratio alone. Cançado et al. (2011) showed that I(D)/I(G) for a given defect density depends strongly on the laser energy and peaks at about 3 nm between defects, so one ratio can match two densities; the G width and the laser energy are needed too.

### What does I(D)/I(D′) tell me?

The kind of defect: about 13 for sp³ defects, about 7 for vacancy-like defects and about 3.5 for boundaries (Eckmann et al. 2012).