Graphene vs Silicon: Properties, Band Gap and Real Uses

Key takeaways

• Graphene is a single layer of carbon atoms. It conducts electrons far faster than silicon and is stronger and more thermally conductive than any bulk material.
• It has no band gap, so a graphene transistor cannot be switched fully off. That one property keeps it out of digital logic.
• In 2024 a team grew semiconducting epitaxial graphene on silicon carbide with a 0.6 eV band gap and room-temperature mobility above 5,000 cm²/V·s, a lab result, not a product.
• Today graphene is used as an additive in composites, coatings and batteries, and in research for radio-frequency and photonic devices. Silicon still runs every processor.

Graphene is a sheet of carbon one atom thick, with the atoms arranged in a hexagonal honeycomb. Andre Geim and Konstantin Novoselov isolated it at the University of Manchester in 2004 by peeling layers off graphite with adhesive tape, work that won the 2010 Nobel Prize in Physics. The Nobel committee described it as the thinnest material ever made and also the strongest (Nobel Prize, popular information).

Since then graphene has been promoted as silicon’s successor. The numbers explain the excitement, and one number explains why it has not happened.

Graphene vs silicon: the properties side by side

Two of these rows deserve a comment. The mobility figure is a ceiling set by lattice vibrations: graphene encapsulated in boron nitride reaches room-temperature mobility close to that phonon limit (Wang et al. 2013), but graphene grown on large wafers is far lower. The areal mass follows from the lattice: two carbon atoms per 0.0524 nm² unit cell give about 0.76 mg per square metre, so a sheet covering a 105 × 68 m football pitch would weigh about 5.4 g.

Why no band gap means no graphene processor

A digital transistor must conduct strongly when on and almost not at all when off. Silicon’s 1.12 eV band gap makes that possible, with on/off current ratios of a million or more. Graphene’s conduction and valence bands touch, so a graphene transistor keeps conducting even at its minimum, and its on/off ratio at room temperature is small. Logic built that way would leak power continuously.

Methods that open a gap, such as cutting graphene into nanoribbons or chemically modifying it, have generally destroyed the high mobility that made it attractive. That trade-off is why the field reads the 2024 result from Georgia Tech and Tianjin University carefully: semiconducting epitaxial graphene grown on silicon carbide showed a 0.6 eV band gap with room-temperature mobilities above 5,000 cm²/V·s, which the authors put at ten times silicon’s (Zhao et al., Nature 2024). It is a single-group laboratory demonstration on silicon carbide substrates, and it has not yet produced circuits that compete with silicon.

Where graphene already works

• Radio-frequency transistors. Analogue amplifiers do not need to switch fully off, so the missing band gap matters less. IBM reported graphene transistors with a 100 GHz cutoff frequency on wafer-scale epitaxial graphene in 2010 (Lin et al.).
• Transparent conductors. One layer absorbs only 2.3% of light while conducting, which makes graphene a candidate for touch screens, displays and solar cells.
• Composites and coatings. Small amounts of graphene flakes added to polymers improve stiffness, conductivity and barrier properties; this is where most commercial graphene is sold today.
• Batteries and supercapacitors. The large surface area of graphene flakes helps electrodes store charge.
• Photonics. Graphene absorbs across a wide band from visible to infrared, and its absorption can be tuned with voltage, which suits fast photodetectors and modulators on silicon photonic chips.

The pattern is that graphene complements silicon. It adds speed, transparency or strength where those matter, while silicon keeps digital logic. Two-dimensional semiconductors with natural band gaps, such as molybdenum disulfide, are now the more likely successors for the smallest transistor channels.

Manufacturing is the other bottleneck

Exfoliated flakes give the best graphene but only in micrometre pieces. Chemical vapour deposition on copper foil produces large films that must be transferred to the target substrate, which adds wrinkles, tears and contamination. Growth on silicon carbide avoids the transfer but needs expensive SiC wafers. Liquid-phase exfoliation is cheap and scalable but yields small, defective flakes, adequate for inks and composites and not for electronics. Matching laboratory properties at wafer scale and low cost is still the main barrier to graphene electronics.

For a related beyond-CMOS approach that uses the electron’s spin, see our explainer on spintronics and MRAM.

References

1. Nobel Prize in Physics 2010, popular information. nobelprize.org
2. J.-H. Chen et al., “Intrinsic and extrinsic performance limits of graphene devices on SiO2”, Nature Nanotechnology 3, 206 (2008). doi
3. L. Wang et al., “One-dimensional electrical contact to a two-dimensional material”, Science 342, 614 (2013). doi
4. A. A. Balandin et al., “Superior thermal conductivity of single-layer graphene”, Nano Letters 8, 902 (2008). doi
5. C. Lee et al., “Measurement of the elastic properties and intrinsic strength of monolayer graphene”, Science 321, 385 (2008). doi
6. R. R. Nair et al., “Fine structure constant defines visual transparency of graphene”, Science 320, 1308 (2008). doi
7. A. H. Castro Neto et al., “The electronic properties of graphene”, Rev. Mod. Phys. 81, 109 (2009). doi
8. J. Zhao et al., “Ultrahigh-mobility semiconducting epitaxial graphene on silicon carbide”, Nature 625, 60 (2024). doi
9. Y.-M. Lin et al., “100-GHz transistors from wafer-scale epitaxial graphene”, Science 327, 662 (2010). doi
10. Ioffe Institute, Silicon: basic, band structure and electrical parameters. ioffe.ru