Hafnium(IV) oxide

Names
IUPAC name

Hafnium(IV) oxide

Other names

Hafnium dioxide
Hafnia

Identifiers

CAS Number

* 12055-23-1 Y

3D model (JSmol)

* Interactive image

ChemSpider |

* 258363 Y

EC Number |

* 235-013-2

PubChem CID

* 292779

UNII |

* 3C4Z4KG52T Y

InChI

* InChI=1S/Hf.2O Y

Key: CJNBYAVZURUTKZ-UHFFFAOYSA-N Y

* InChI=1/Hf.2O/rHfO2/c2-1-3

Key: CJNBYAVZURUTKZ-MSHMTBKAAI

SMILES

* O=[Hf]=O

Properties

Chemical formula

| HfO2
Molar mass | 210.49 g/mol
Appearance  | off-white powder
Density | 9.68 g/cm3, solid
Melting point |  2,758 °C (4,996 °F; 3,031 K)
Boiling point |  5,400 °C (9,750 °F; 5,670 K)

Solubility in water

| insoluble

Magnetic susceptibility (χ)

| −23.0·10−6 cm3/mol
Hazards
Flash point | Non-flammable
Related compounds

Other cations

| Titanium(IV) oxide
Zirconium(IV) oxide

Related compounds

| Hafnium nitride

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is YN ?)
Infobox references

Hafnium(IV) oxide is the inorganic compound with the formula HfO2. Also known as hafnium dioxide or hafnia, this colourless solid is one of the most common and stable compounds of hafnium. It is an electrical insulator with a band gap of 5.3~5.7 eV.[1] Hafnium dioxide is an intermediate in some processes that give hafnium metal.

Hafnium(IV) oxide is quite inert. It reacts with strong acids such as concentrated sulfuric acid and with strong bases. It dissolves slowly in hydrofluoric acid to give fluorohafnate anions. At elevated temperatures, it reacts with chlorine in the presence of graphite or carbon tetrachloride to give hafnium tetrachloride.

## Structure

Hafnia typically adopts the same structure as zirconia (ZrO2). Unlike TiO2, which features six-coordinate Ti in all phases, zirconia and hafnia consist of seven-coordinate metal centres. A variety of other crystalline phases have been experimentally observed, including cubic fluorite (Fm3m), tetragonal (P42/nmc), monoclinic (P21/c) and orthorhombic (Pbca and Pnma).[2] It is also known that hafnia may adopt two other orthorhombic metastable phases (space group Pca21 and Pmn21) over a wide range of pressures and temperatures,[3] presumably being the sources of the ferroelectricity observed in thin films of hafnia.[4]

Thin films of hafnium oxides deposited by atomic layer deposition are usually crystalline. Because semiconductor devices benefit from having amorphous films present, researchers have alloyed hafnium oxide with aluminum or silicon (forming hafnium silicates), which have a higher crystallization temperature than hafnium oxide.[5]

## Applications

Hafnia is used in optical coatings, and as a high-κ dielectric in DRAM capacitors and in advanced metal–oxide–semiconductor devices.[6] Hafnium-based oxides were introduced by Intel in 2007 as a replacement for silicon oxide as a gate insulator in field-effect transistors.[7] The advantage for transistors is its high dielectric constant: the dielectric constant of HfO2 is 4–6 times higher than that of SiO2.[8] The dielectric constant and other properties depend on the deposition method, composition and microstructure of the material.

Hafnium oxide (as well as doped and oxygen-deficient hafnium oxide) attracts additional interest as a possible candidate for resistive-switching memories[9] and CMOS-compatible ferroelectric field effect transistors (FeFET memory) and memory chips.[10][11][12][13]

Because of its very high melting point, hafnia is also used as a refractory material in the insulation of such devices as thermocouples, where it can operate at temperatures up to 2500 °C.[14]

Multilayered films of hafnium dioxide, silica, and other materials have been developed for use in passive cooling of buildings. The films reflect sunlight and radiate heat at wavelengths that pass through Earth's atmosphere, and can have temperatures several degrees cooler than surrounding materials under the same conditions.[15]

## References

1. ↑ Bersch, Eric (2008). "Band offsets of ultrathin high-k oxide films with Si". Phys. Rev. B 78 (8): 085114. doi:10.1103/PhysRevB.78.085114. Bibcode: 2008PhRvB..78h5114B.
2. ↑ Table III, V. Miikkulainen (2013). "Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends". Journal of Applied Physics 113 (2): 021301–021301–101. doi:10.1063/1.4757907. Bibcode: 2013JAP...113b1301M.
3. ↑ T. D. Huan; V. Sharma; G. A. Rossetti, Jr.; R. Ramprasad (2014). "Pathways towards ferroelectricity in hafnia". Physical Review B 90 (6): 064111. doi:10.1103/PhysRevB.90.064111. Bibcode: 2014PhRvB..90f4111H.
4. ↑ T. S. Boscke (2011). "Ferroelectricity in hafnium oxide thin films". Applied Physics Letters 99 (10): 102903. doi:10.1063/1.3634052. Bibcode: 2011ApPhL..99j2903B.
5. ↑ J.H. Choi (2011). "Development of hafnium based high-k materials—A review". Materials Science and Engineering: R 72 (6): 97–136. doi:10.1016/j.mser.2010.12.001.
6. ↑ H. Zhu; C. Tang; L. R. C. Fonseca; R. Ramprasad (2012). "Recent progress in ab initio simulations of hafnia-based gate stacks". Journal of Materials Science 47 (21): 7399–7416. doi:10.1007/s10853-012-6568-y. Bibcode: 2012JMatS..47.7399Z.
7. ↑ Intel (11 November 2007). "Intel's Fundamental Advance in Transistor Design Extends Moore's Law, Computing Performance". https://www.intel.com/pressroom/archive/releases/2007/20071111comp.htm.
8. ↑ Wilk G. D., Wallace R. M., Anthony J. M. (2001). "High-κ gate dielectrics: Current status and materials properties considerations". Journal of Applied Physics 89 (10): 5243–5275. doi:10.1063/1.1361065. Bibcode: 2001JAP....89.5243W. , Table 1
9. ↑ K.-L. Lin (2011). "Electrode dependence of filament formation in HfO2 resistive-switching memory". Journal of Applied Physics 109 (8): 084104–084104–7. doi:10.1063/1.3567915. Bibcode: 2011JAP...109h4104L.
10. ↑ Imec (7 June 2017). "Imec demonstrates breakthrough in CMOS-compatible Ferroelectric Memory". https://www.imec-int.com/en/articles/imec-demonstrates-breakthrough-in-cmos-compatible-ferroelectric-memory.
11. ↑ The Ferroelectric Memory Company (8 June 2017). "World's first FeFET-based 3D NAND demonstration". https://ferroelectric-memory.com/2017/06/08/worlds-first-fefet-based-3d-nand-demonstration/.
12. ↑ T. S. Böscke, J. Müller, D. Bräuhaus (7 Dec 2011). "Ferroelectricity in hafnium oxide: CMOS compatible ferroelectric field effect transistors". 2011 International Electron Devices Meeting (IEEE): 24.5.1–24.5.4. doi:10.1109/IEDM.2011.6131606. ISBN 978-1-4577-0505-2.
13. ↑ Nivole Ahner (August 2018) (in de). Mit HFO2 voll CMOS-kompatibel. Elektronik Industrie.
14. ↑ Very High Temperature Exotic Thermocouple Probes product data, Omega Engineering, Inc., retrieved 2008-12-03
15. ↑ "Aaswath Raman | Innovators Under 35 | MIT Technology Review". August 2015. http://www.technologyreview.com/lists/innovators-under-35/2015/pioneer/aaswath-raman/.

* v
* t
* e

Hafnium compounds

Hf(II)|

* HfB2

Hf(IV)|

* HfC
* HfBr4
* HfCl4
* HfF4
* HfI4
* Hf(C5H7O2)4
* HfO2
* HfSiO4
* HfS2
* Ta4HfC5

* v
* t
* e

Oxides

Mixed oxidation states|

* Antimony tetroxide (Sb2O4)
* Cobalt(II,III) oxide (Co3O4)
* Europium(II,III) oxide (Eu3O4)
* Iron(II,III) oxide (Fe<sub>3O4)
* Lead(II,IV) oxide (Pb3O4)
* Manganese(II,III) oxide (Mn3O4)
* Silver(I,III) oxide (Ag2O2)
* Triuranium octoxide (U3O8)
* Carbon suboxide (C3O2)
* Mellitic anhydride (C12O9)
* [[Chemistry:Praseodymium(III,IV) Praseodymium(III,IV) oxide]] (Pr6O11)
* Terbium(III,IV) oxide (Tb4O7)

+1 oxidation state|

* Copper(I) oxide (Cu<sub>2O)
* Caesium oxide (Cs2O)
* Dicarbon monoxide (C2O)
* Dichlorine monoxide (Cl2O)
* Gallium(I) oxide (Ga2O)
* Lithium oxide (Li2O)
* Potassium oxide (K2O)
* Rubidium oxide (Rb2O)
* Silver oxide (Ag2O)
* Thallium(I) oxide (Tl2O)
* Sodium oxide (Na2O)
* Water (hydrogen oxide) (H2O)

+2 oxidation state|

* Aluminium(II) oxide (AlO)
* Barium oxide (BaO)
* Beryllium oxide (BeO)
* Cadmium oxide (CdO)
* Calcium oxide (CaO)
* Carbon monoxide (CO)
* Chromium(II) oxide (CrO)
* Cobalt(II) oxide (CoO)
* Copper(II) oxide (CuO)
* Europium(II) oxide (EuO)
* Germanium monoxide (GeO))
* Iron(II) oxide (FeO)
* Lead(II) oxide (PbO)
* Magnesium oxide (MgO)
* Manganese(II) oxide (MnO)
* Mercury(II) oxide (HgO)
* Nickel(II) oxide (NiO)
* Nitric oxide (NO)
* Palladium(II) oxide (PdO)
* Silicon monoxide (SiO)
* Strontium oxide (SrO)
* Sulfur monoxide (SO)
* Disulfur dioxide (S2O2)
* Thorium monoxide (ThO)
* Tin(II) oxide (SnO)
* Titanium(II) oxide (TiO)
* Vanadium(II) oxide (VO)
* Zinc oxide (ZnO)

+3 oxidation state|

* Aluminium oxide (Al<sub>2O3)
* Antimony trioxide (Sb2O3)
* Arsenic trioxide (As2O3)
* Bismuth(III) oxide (Bi2O3)
* Boron trioxide (B2O3)
* Cerium(III) oxide (Ce2O3)
* Dibromine trioxide (Br2O3)
* Chromium(III) oxide (Cr2O3)
* Dinitrogen trioxide (N2O3)
* Dysprosium(III) oxide (Dy2O3)
* Erbium(III) oxide (Er2O3)
* Europium(III) oxide (Eu2O3)
* Gadolinium(III) oxide (Gd2O3)
* Gallium(III) oxide (Ga2O3)
* Holmium(III) oxide (Ho2O3)
* Indium(III) oxide (In<sub>2O3)
* Iron(III) oxide (Fe2O3)
* Lanthanum oxide (La2O3)
* Lutetium(III) oxide (Lu2O3)
* Manganese(III) oxide (Mn2O3)
* Neodymium(III) oxide (Nd2O3)
* Nickel(III) oxide (Ni2O3)
* Phosphorus trioxide (P4O6)
* Praseodymium(III) oxide (Pr2O3)
* Promethium(III) oxide (Pm2O3)
* Rhodium(III) oxide (Rh2O3)
* [[Chemistry:Samarium(III) Samarium(III) oxide]] (Sm2O3)
* Scandium oxide (Sc2O3)
* Terbium(III) oxide (Tb2O3)
* Thallium(III) oxide (Tl2O3)
* Thulium(III) oxide (Tm2O3)
* Titanium(III) oxide (Ti2O3)
* Tungsten(III) oxide (W2O3)
* Vanadium(III) oxide (V2O3)
* Ytterbium(III) oxide (Yb2O3)
* Yttrium(III) oxide (Y2O3)

+4 oxidation state|

* Americium dioxide (AmO2)
* Carbon dioxide (CO2)
* Carbon trioxide (CO3)
* Cerium(IV) oxide (CeO2)
* Chlorine dioxide (ClO2)
* Chromium(IV) oxide (CrO<sub>2)
* Dinitrogen tetroxide (N2O4)
* Germanium dioxide (GeO<sub>2)
* [[Chemistry:Hafnium(IV) Hafnium(IV) oxide]] (HfO2)
* Lead dioxide (PbO2)
* Manganese dioxide (MnO2)
* Neptunium(IV) oxide (NpO2)
* Nitrogen dioxide (NO2)
* Osmium dioxide (OsO2)
* Plutonium(IV) oxide (PuO2)
* Praseodymium(IV) oxide (PrO2)
* Protactinium(IV) oxide (PaO2)
* Rhodium(IV) oxide (RhO2)
* Ruthenium(IV) oxide (RuO<sub>2)
* Selenium dioxide (SeO2)
* Silicon dioxide (SiO2)
* Sulfur dioxide (SO2)
* Tellurium dioxide (TeO<sub>2)
* [[Chemistry:Terbium(IV) Terbium(IV) oxide]] (TbO2)
* Thorium dioxide (ThO2)
* Tin dioxide (SnO2)
* Titanium dioxide (TiO<sub>2)
* Tungsten(IV) oxide (WO2)
* Uranium dioxide (UO2)
* Vanadium(IV) oxide (VO2)
* Zirconium dioxide (ZrO2)

+5 oxidation state|

* Antimony pentoxide (Sb2O5)
* Arsenic pentoxide (As2O5)
* Dinitrogen pentoxide (N2O5)
* Niobium pentoxide (Nb2O5)
* Phosphorus pentoxide (P2O5)
* Protactinium(V) oxide (Pa2O5)
* Tantalum pentoxide (Ta2O5)
* Vanadium(V) oxide (V2O5)

+6 oxidation state|

* Chromium trioxide (CrO3)
* Molybdenum trioxide (MoO3)
* Rhenium trioxide (ReO3)
* Selenium trioxide (SeO3)
* Sulfur trioxide (SO3)
* Tellurium trioxide (TeO3)
* Tungsten trioxide (WO3)
* Uranium trioxide (UO3)
* Xenon trioxide (XeO3)
* Iridium trioxide (IrO3)

+7 oxidation state|

* Dichlorine heptoxide (Cl2O7)
* Manganese heptoxide (Mn2O7)
* [[Chemistry:Rhenium(VII) Rhenium(VII) oxide]] (Re2O7)
* Technetium(VII) oxide (Tc2O7)

+8 oxidation state|

* Osmium tetroxide (OsO4)
* Ruthenium tetroxide (RuO4)
* Xenon tetroxide (XeO4)
* Iridium tetroxide (IrO4)
* Hassium tetroxide (HsO4)

Related|

* Oxocarbon
* Suboxide
* Oxyanion
* Ozonide
* Peroxide
* Superoxide

Oxides are sorted by oxidation state. Category:Oxides

* v
* t
* e

Oxygen compounds

* AgO
* Al2O3
* AmO2
* Am2O3
* As2O3
* As2O5
* Au2O3
* B2O3
* BaO
* BeO
* Bi2O3
* BiO2
* Bi2O5
* BrO2
* Br2O3
* Br2O5
* CO
* CO2
* C2O3
* CaO
* CaO2
* CdO
* CeO2
* Ce3O4
* Ce2O3
* ClO2
* Cl2O
* Cl2O3
* Cl2O4
* Cl2O6
* Cl2O7
* CoO
* Co2O3
* Co3O4
* CrO3
* Cr2O3
* Cr2O5
* Cr5O12
* CsO2
* Cs2O3
* CuO
* D2O
* Dy2O3
* Er2O3
* Eu2O3
* FeO
* Fe2O3
* Fe3O4
* Ga2O
* Ga2O3
* GeO
* GeO2
* H2O
* H218O
* H2O2
* HfO2
* HgO
* Hg2O
* Ho2O3
* I2O4
* I2O5
* I2O6
* I4O9
* In2O3
* IrO2
* KO2
* K2O2
* La2O3
* Li2O
* Li2O2
* Lu2O3
* MgO
* Mg2O3
* MnO
* MnO2
* Mn2O3
* Mn2O7
* MoO2
* MoO3
* Mo2O3
* NO
* NO2
* N2O
* N2O3
* N2O4
* N2O5
* NaO2
* Na2O
* Na2O2
* NbO
* NbO2
* Nd2O3
* OF2
* O2F2
* O3F2
* O4F2
* O2PtF6

Chemical formulas

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