252:. Commonly used experimental techniques to investigate band-gap can be sensitive to many things such as the size of the band-gap, electronic structure features (direct versus indirect gap) and also the number of free charge carriers (which can frequently depend on synthesis conditions). Band-gap obtained from transport property modeling is essentially independent of such factors. Theoretical techniques to calculate the electronic structure on the other hand can often underestimate band-gap.
38:
206:, this is true at very low temperatures but at higher temperatures the carrier density increases with temperature giving rise to a semimetal-semiconductor transition. A semimetal also differs from an insulator or semiconductor in that a semimetal's conductivity is always non-zero, whereas a semiconductor has zero conductivity at zero temperature and insulators have zero conductivity even at ambient temperatures (due to a wider band gap).
261:
194:(as more electrons are shifted to the conduction band), before decreasing with intermediate temperatures and then, once again, increasing with still higher temperatures. The semimetallic state is similar to the metallic state but in semimetals both holes and electrons contribute to electrical conduction. With some semimetals, like
189:
and electrons), both the carrier mobilities and carrier concentrations will contribute to the conductivity and these have different temperature dependencies. Ultimately, it is observed that the conductivity of insulators and semiconductors increase with initial increases in temperature above
319:, semimetals have charge carriers of both types (holes and electrons), so that one could also argue that they should be called 'double-metals' rather than semimetals. However, the charge carriers typically occur in much smaller numbers than in a real metal. In this respect they resemble
247:
VAl for example, was historically thought of as a semi-metal (with a negative gap ~ -0.1 eV) for over two decades before it was actually shown to be a small-gap (~ 0.03 eV) semiconductor using self-consistent analysis of the transport properties, electrical resistivity and
343:. They also have small effective masses for both holes and electrons because the overlap in energy is usually the result of the fact that both energy bands are broad. In addition they typically show high
499:
Anand, Shashwat; Gurunathan, Ramya; Soldi, Thomas; Borgsmiller, Leah; Orenstein, Rachel; Snyder, Jeff (2020). "Thermoelectric transport of semiconductor full-Heusler VFe2Al".
243:
Classification of a material either as a semiconductor or a semimetal can become tricky when it has extremely small or slightly negative band-gaps. The well-known compound Fe
157:) than that of a semiconductor (e.g., < 4 eV). Because of the slight overlap between the conduction and valence bands, semimetals have no band gap and a small
612:
Reed, Evan J.; Manaa, M. Riad; Fried, Laurence E.; Glaesemann, Kurt R.; Joannopoulos, J. D. (2007). "A transient semimetallic layer in detonating nitromethane".
534:
Wang, Yang; N. Mansour; A. Salem; K.F. Brennan & P.P. Ruden (1992). "Theoretical study of a potential low-noise semimetal-based avalanche photodetector".
411:
are typically not considered metalloids. Transient semimetal states have been reported at extreme conditions. It has been recently shown that some
165:. A metal, by contrast, has an appreciable density of states at the Fermi level because the conduction band is partially filled.
308:
The figure is schematic, showing only the lowest-energy conduction band and the highest-energy valence band in one dimension of
225:
In a semimetal, the bottom of the conduction band is typically situated in a different part of momentum space (at a different
483:
181:. With a metal, the conductivity decreases with increases in temperature (due to increasing interaction of electrons with
713:
214:
To classify semiconductors and semimetals, the energies of their filled and empty bands must be plotted against the
106:
323:
more closely. This explains why the electrical properties of semimetals are partway between those of metals and
391:
but the terms semimetal and metalloid are not synonymous. Semimetals, in contrast to metalloids, can also be
149:. In insulators and semiconductors the filled valence band is separated from an empty conduction band by a
312:(or k-space). In typical solids, k-space is three-dimensional, and there are an infinite number of bands.
264:
This diagram illustrates a direct semiconductor (A), an indirect semiconductor (B), and a semimetal (C).
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222:
the conduction of electrons depends on the periodicity of the crystal lattice in different directions.
92:
50:
17:
202:, there is a temperature-independent carrier density below room temperature (as in metals) while, in
185:(lattice vibrations)). With an insulator or semiconductor (which have two types of charge carriers –
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The insulating/semiconducting states differ from the semimetallic/metallic states in the
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153:. For insulators, the magnitude of the band gap is larger (e.g., > 4
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As semimetals have fewer charge carriers than metals, they typically have lower
91:; however, in semiconductors the bands are near enough to the Fermi level to be
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is a material with a small energy overlap between the bottom of the
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for a certain energy in the material listed. The shade follows the
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Filling of the electronic states in various types of materials at
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569:
Wallace, P.R. (1947). "The Band Theory of
Graphite".
240:, although they are seldom described in those terms.
647:Bubnova, Olga; Zia, Ullah Khan; Wang, Hui (2014).
700:
646:
387:. The first two (As, Sb) are also considered
27:Metal with a small negative indirect band-gap
45:. Here, height is energy while width is the
284:a semiconductor with an indirect gap (like
218:of conduction electrons. According to the
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478:. Academic Press, Inc. pp. 339–40.
273:a semiconductor with a direct gap (e.g.
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36:
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359:The classic semimetallic elements are
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473:
354:
536:IEEE Journal of Quantum Electronics
79:lies inside at least one band. In
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347:susceptibilities and high lattice
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730:
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501:Journal of Materials Chemistry C
268:Schematically, the figure shows
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137:, solids can be classified as
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129:, but they do not overlap in
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87:the Fermi level is inside a
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47:density of available states
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425:Charge-transfer insulators
415:can behave as semimetals.
29:
321:degenerate semiconductors
714:Condensed matter physics
649:"Semi-Metallic Polymers"
101:intrinsic semiconductors
51:Fermi–Dirac distribution
30:Not to be confused with
179:electrical conductivity
99:. "intrin." indicates
61:: no state filled). In
591:10.1103/PhysRev.71.622
474:Burns, Gerald (1985).
341:thermal conductivities
275:copper indium selenide
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169:Temperature dependency
135:electronic band theory
111:
57:: all states filled,
301:alkaline earth metals
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40:
349:dielectric constants
177:dependency of their
665:2014NatMa..13..190B
626:2008NatPh...4...72R
583:1947PhRv...71..622W
548:1992IJQE...28..507W
507:(30): 10174–10184.
476:Solid State Physics
455:Solid-state physics
413:conductive polymers
331:Physical properties
250:Seebeck coefficient
125:and the top of the
93:thermally populated
513:10.1039/D0TC02659J
393:chemical compounds
355:Classic semimetals
291:a semimetal (like
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112:
95:with electrons or
485:978-0-12-146070-9
397:mercury telluride
315:Unlike a regular
159:density of states
145:, semimetals, or
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16:(Redirected from
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577:(9): 622–634.
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345:diamagnetic
175:temperature
163:Fermi level
71:Fermi level
43:equilibrium
703:Categories
461:References
430:Half-metal
395:, such as
389:metalloids
337:electrical
139:insulators
120:conduction
81:insulators
67:semimetals
32:Half-metal
18:Semi-metal
709:Materials
689:205409397
521:225448662
381:allotrope
256:Schematic
116:semimetal
681:24317188
599:53633968
450:Nonmetal
419:See also
409:graphite
377:graphite
365:antimony
299:and the
297:graphite
295:(Sn) or
200:antimony
151:band gap
89:band gap
661:Bibcode
622:Bibcode
579:Bibcode
544:Bibcode
405:bismuth
369:bismuth
361:arsenic
286:silicon
277:(CuInSe
230:-vector
204:bismuth
196:arsenic
183:phonons
161:at the
719:Metals
687:
679:
597:
519:
482:
407:, and
385:carbon
147:metals
63:metals
685:S2CID
595:S2CID
517:S2CID
440:Metal
379:, an
317:metal
288:(Si))
187:holes
97:holes
59:white
55:black
677:PMID
480:ISBN
371:, α-
339:and
198:and
123:band
107:edit
83:and
69:the
65:and
669:doi
630:doi
587:doi
552:doi
509:doi
401:tin
383:of
373:tin
293:tin
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