Erbium arsenide
| Names | |
|---|---|
| Other names
Erbium monoarsenide | |
| Identifiers | |
| EC Number |
|
| Properties | |
| ErAs | |
| Molar mass | 242.18 g/mol |
| Appearance | Crystalline solid |
| Density | 8.54 g/cm3 (calculated) |
| Structure | |
| Cubic, rock-salt type | |
| Fm3m, No. 225 | |
a = 0.5732 nm | |
Formula units (Z) |
4 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Erbium arsenide is an inorganic compound of erbium and arsenic with the chemical formula ErAs. It is a semimetal that crystallizes in the cubic rock salt structure type. ErAs has been extensively studied as an epitaxial semimetal in III–V semiconductor heterostructures and as nanoscale inclusions in gallium arsenide.[1][2]
Preparation
[edit]Bulk erbium arsenide can be prepared by direct reaction of elemental erbium and arsenic:
- Er + As → ErAs
ErAs thin films and nanostructures can also be grown by molecular-beam epitaxy. When erbium is incorporated into GaAs above its low solid-solubility limit, ErAs precipitates with the cubic rock-salt structure.[3]
Epitaxial ErAs layers have likewise been grown directly on GaAs and related III–V semiconductor surfaces.[4]
Properties
[edit]Crystal structure
[edit]ErAs crystallizes in the cubic crystal system with the rock-salt structure, space group Fm3m (No. 225), with four formula units per unit cell[5]
and a lattice parameter of a = 5.732 Å.[5] The corresponding calculated density is approximately 8.54 g/cm3.
Er and As occupy alternating sites of the NaCl lattice. The close structural relationship between rock-salt ErAs and zinc-blende III–V semiconductors facilitates epitaxial growth despite their different coordination geometries.
Electronic properties
[edit]ErAs is a semimetal rather than a semiconductor. Experimental and theoretical studies show overlapping electron and hole bands at the Fermi level.[1]
The electronic structure contains strongly localized Er 4f states in addition to broader Er 5d- and As-derived bands. First-principles treatments generally require explicit treatment of the localized 4f electrons to reproduce the observed semimetallic state.[6]
Photoemission and inverse-photoemission measurements on epitaxial ErAs(100) films show dispersive bulk bands broadly consistent with calculated band structures, together with localized erbium multiplet states and surface resonances.[2]
Bulk and epitaxial ErAs have electron and hole concentrations of order 1020 cm−3, characteristic of a compensated semimetal.
Magnetic properties
[edit]The localized Er 4f electrons give ErAs a substantial magnetic moment. At low temperature, bulk ErAs orders antiferromagnetically, with a Néel temperature of approximately 4 K.
The magnetic structure has commonly been described as alternating erbium moments along a ⟨111⟩ direction, requiring a doubling of the crystallographic unit cell in the magnetically ordered state.
Epitaxy and nanostructures
[edit]The lattice parameter of ErAs, approximately 5.74 Å, is close to that of GaAs, 5.653 Å, giving a lattice mismatch of about 1.5%. This allows high-quality epitaxial ErAs/GaAs heterostructures to be grown.[4]
Because erbium has very low equilibrium solubility in GaAs, ErAs readily forms self-organized nanoparticles when erbium is codeposited during GaAs growth.[3]
Embedded ErAs nanoparticles and nanorods retain semimetallic electronic behaviour.[7]
ErAs inclusions have also been incorporated into GaAs/AlAs superlattices, where they scatter and localize phonons and can strongly reduce thermal transport.[8]
Applications
[edit]ErAs/GaAs nanocomposites and heterostructures have been investigated for ultrafast optoelectronics, Schottky contacts and terahertz photoconductive devices.
Carrier lifetimes in GaAs containing embedded ErAs inclusions can be reduced to the sub-picosecond range; decay times as short as approximately 200 fs have been reported.[9]
ErAs nanoparticles have also been studied for plasmonic enhancement of infrared absorption and for modifying the electrical and thermal properties of III–V semiconductors.
References
[edit]- 1 2 Delaney, Kris T.; Spaldin, Nicola A.; Van de Walle, Chris G. (2008). "Theoretical study of the structural and electronic properties of strained ErAs". Physical Review B. 77 235117. doi:10.1103/PhysRevB.77.235117.
- 1 2 Komesu, Takashi; Jeong, Hae-Kyung; Choi, Jaewu; Borca, C. N.; Dowben, P. A.; Petukhov, A. G.; Schultz, B. D.; Palmstrøm, C. J. (2003). "Electronic structure of ErAs(100)". Physical Review B. 67 035104. doi:10.1103/PhysRevB.67.035104.
- 1 2 Allen, J. W. (1992). "Growth and structural characterization of molecular beam epitaxial erbium-doped GaAs". Journal of Crystal Growth. 121 (1–2): 121–131. doi:10.1016/0022-0248(92)90181-H.
- 1 2 Klenov, Dmitri O.; Zide, Joshua M.; Zimmerman, Jeramy D.; Gossard, Arthur C.; Stemmer, Susanne (2005). "Interface atomic structure of epitaxial ErAs layers on (001) In0.53Ga0.47As and GaAs". Applied Physics Letters. 86 241901.
- 1 2 Brixner, Lothar H. (1960). "Preparation and crystallographic study of some new rare earth compounds". Journal of Inorganic and Nuclear Chemistry. 15 (3): 352–355. doi:10.1016/0022-1902(60)80064-4.
- ↑ Petukhov, A. G.; Lambrecht, W. R. L.; Segall, B. (1996). "Electronic structure of rare-earth pnictides". Physical Review B. 53: 4324–4333. doi:10.1103/PhysRevB.53.4324.
- ↑ Kawasaki, Jason K.; Timm, Rainer; Buehl, Trevor E.; Lundgren, Edvin; Mikkelsen, Anders; Gossard, Arthur C.; Palmstrøm, Chris J. (2011). "Cross-sectional scanning tunneling microscopy and spectroscopy of semimetallic ErAs nanostructures embedded in GaAs". Journal of Vacuum Science & Technology B. 29 03C104. arXiv:1204.2643. doi:10.1116/1.3547713.
- ↑ "Phonon localization in heat conduction". Science Advances. 4 (12) eaat9460. 2018. doi:10.1126/sciadv.aat9460. PMC 6303120.
- ↑ Kadow, C.; Ibbetson, J. P.; Fleischer, S. B.; Gossard, A. C.; Bowers, J. E. (1999). "Ultrafast response of ErAs islands in GaAs". Ultrafast Electronics and Optoelectronics. doi:10.1364/UEO.1999.UFB6.
