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Tin monoxide

SnO

Also called stannous oxide, litharge-type SnO

van der Waals crystal semiconductor

Almost every useful oxide semiconductor conducts electrons, not holes, because oxygen’s 2p states make a flat, heavy valence band. SnO is the exception that works: the tin 5s2 lone pair mixes with those oxygen states and lifts the top of the valence band, so holes can move. That makes it one of the best-studied p-type oxides, the missing half of an all-oxide circuit, and it happens to be layered.

Crystal structure

  • O
  • Sn
Cell
Square, a = 3.80 Å
Atoms per cell
4
Sn–O bond
2.22 Å
Height
2.31 Å between the outer atom centres
A square net of oxygen with tin atoms alternately above and below it, each tin capping four oxygens like the apex of a pyramid. Each tin carries a lone pair of electrons that points outward, away from the layer, and it is these lone pairs that face each other across the van der Waals gap – which is why SnO can be thinned like a 2D material, and part of why it conducts holes. One layer of bulk SnO (Pannetier and Denes, Acta Crystallographica B 36, 2763, 1980; COD 9011217): a = 3.80 Å, tin 1.15 Å above and below the oxygen plane.

Key properties

  • A rare p-type oxide semiconductor: the tin 5s2 lone pair hybridises with oxygen 2p and gives a dispersive valence band
  • Epitaxial films show Hall mobilities of ~2.4 cm2 V−1 s−1 and p-channel transistors with field-effect mobilities of ~1.3 cm2 V−1 s−1
  • Ambipolar behaviour is possible, which is why it is studied for complementary oxide circuits
  • The same lone pair that gives p-type conduction also makes the structure layered, with the lone pairs facing the gap
  • SnO is metastable: heating disproportionates it into tin and SnO2, which limits processing temperatures

How it is made

  • Pulsed-laser deposition or sputtering of epitaxial and polycrystalline films, with tight control of oxygen pressure to avoid SnO2
  • Solution and vapour routes to nanosheets
  • Post-growth annealing in a narrow window, because too little oxygen leaves tin and too much gives SnO2

Uses, and how close they are

  • p-channel oxide thin-film transistors, the missing half of oxide CMOSlab
  • Transparent and back-end-of-line electronicslab
  • Battery anodes and gas sensinglab

Readiness runs lab → prototype → pilot → deployed.

Open problems

  1. Can hole mobility be pushed from a few cm2 V−1 s−1 to something competitive with n-type oxides like IGZO?
  2. How can films be made phase-pure and stable when the compound itself is metastable?
  3. What limits hole doping, and can acceptors be introduced without wrecking the lattice?
  4. Do thin, exfoliated or grown SnO layers keep the bulk valence-band structure?

Going deeper

Short notes for specialists. Choose a lens in the header and yours comes first.

For theoreticians · your lens

The textbook case for lone-pair chemistry in a band picture: calculations show the asymmetric electron density around tin comes from Sn 5p mixing with the antibonding combination of Sn 5s and O 2p, not from a simple stereochemical lone pair sitting on the cation. That mixing raises and disperses the valence band, which is the whole reason holes move. Getting the indirect and direct gaps right needs a functional that handles this s–p coupling, and defect calculations have to contend with a phase that is thermodynamically metastable to begin with.

For experimentalists · your lens

Phase purity is the measurement: X-ray diffraction and XPS should both be reported, since SnO, SnO2 and metallic tin coexist easily and each shifts the transport. Quote the oxygen partial pressure and the annealing history with every mobility. For transistors, report whether the behaviour is p-channel or ambipolar, and at what gate range.

For engineers · your lens

The reason to care is complementary oxide electronics: n-type oxides are mature, and SnO is the most credible p-type partner. What stands in the way is mobility of a few cm2 V−1 s−1, a metastable phase that narrows the process window, and device stability rather than any exotic physics.

In the research tracks

Readiness assessments

Recent news

The newest items tagged SnO, from the news feed updated 5 Oct 2026.

Preprintnot yet peer reviewed arXiv

Polarizing ultrathin ferroelectric BaTiO3 films through interfacial layer polarization

An important requirement for the integration of ferroelectric thin films into devices is deterministic control of the polarization state in films of only a few unit cells in thickness. Here, we utilize the charged atomic planes of (001)-oriented SmNiO3 (SNO) buffer layers as a polarizing template to stabilize the…

TheorySnO
Preprintnot yet peer reviewed arXiv

Dilute Magnetism and Edge-State Engineering in Monolayer SnO

Tin monoxide (SnO) is a p-type oxide semiconductor whose electronic properties can be widely modified via atomic-scale engineering. Using density functional theory, we investigate the electronic and magnetic properties of transition-metal (TM = Mn, Fe, Co and W) doped SnO monolayer within a large supercell. We find…

TheorySnO

All 5 items tagged SnO in the news feed  ·  RSS feed for SnO

Key references

  1. Electronic structures of rocksalt, litharge, and herzenbergite SnO by density functional theoryWalsh & Watson · Physical Review B 70, 235114 (2004)cited by 134doi:10.1103/PhysRevB.70.235114
  2. Thermal disproportionation of SnO under high pressureGiefers et al. · Solid State Ionics 176, 1327 (2005)cited by 18doi:10.1016/j.ssi.2005.03.003
  3. p-channel thin-film transistor using p-type oxide semiconductor, SnOOgo et al. · Applied Physics Letters 93, 032113 (2008)cited by 688doi:10.1063/1.2964197
Oxides and hydroxides Oxide nanosheets 2D oxides and oxide nanosheets nanosheet
type
depends on form
thickness
~0.7 nm per α-MoO₃ layer
band gap
2.3–8 eV
most mature
deployed
Clay–polymer nanocomposites and gas-barrier coatings Other layered chalcogenides SnSe, GeSe Tin and germanium monochalcogenides van der Waals crystal
type
semiconductor
thickness
~0.55–0.6 nm per layer
band gap
0.9–1.6 eV
most mature
prototype
Thermoelectric generators (bulk SnSe) Mixed-anion layers BiOCl, BiOBr, BiOI Bismuth oxyhalides van der Waals crystal
type
semiconductor
thickness
~0.74 nm per BiOCl layer
band gap
1.8–3.2 eV
most mature
deployed
Pearlescent pigments in cosmetics (BiOCl) Oxides and hydroxides LaAlO₃/SrTiO₃ Oxide interface electron gases an interface, not a sheet
type
depends on form
thickness
Electron gas confined within roughly 1–10 nm of the interface
most mature
lab
Oxide electronics, spin–charge conversion and gate-tunable superconducting devices