Silicene

from Wikipedia, the free encyclopedia
Typical wave-like structure of a silicon layer.

Silicen ( English silicene ) is the name for a two-dimensional , allotropic modification of silicon with a hexagonal honeycomb structure , similar to that of graphene .

history

Although several theories have already speculated about the existence and material properties of silicene, silicon structures similar to silicene were observed in the form of one-dimensional wires in 2010 and as two-dimensional layers of silicon in 2012. By a combination of scanning tunneling microscopy , and other experimental procedures, it was possible the synthesis of silicene, so the deposition of silicene nanoribbons and Silicen- monolayers - in the experiment by the deposition of Ag (110) (111) surfaces and Ag of - silver crystals to study at the atomic level . The illustrations showed hexagons in a honeycomb structure that is similar to that of graphene. Density functional theory calculations showed that silicon atoms tend to form honeycomb shapes on silver, with a pronounced slight curvature. In the case of the one-dimensional silicene wires on Ag (110) surfaces, this interpretation was later questioned. In 2014, a team led by Deji Akinwande from the University of Texas succeeded for the first time in producing a field effect transistor based on silicene that works at room temperature .

properties

Curved structure of the hexagonal silicon ring.

In 2012, several independent research groups reported ordered phases on Ag (111) crystals. Investigations using angle-resolved photoelectron spectroscopy showed that silicene has a similar electronic configuration to graphene. Both form Dirac cones and have a linear dispersion around the K point of the crystal, but this interpretation was considered controversial. The existence of massless Dirac fermions (based on a model of the Dirac equation ) in silicene on Ag (111) crystals was later proven by scanning tunneling spectroscopy measurements.

Silicene is not perfectly planar, but has slight, regular curvatures within the rings of 0.44  Å (with a bond length of 2.28 Å), resulting in a regular waveform of the individual layers. Since the hydrogenation of the silicon to a silane is exothermic , it is assumed that this application can be used for hydrogen storage. The cause of the uneven structure of the silicene ring is stated to be the pseudo-Jahn-Teller effect (PJT effect). This is caused by a vibronic coupling of the unoccupied molecular orbitals (engl. Unoccupied molecular orbital , short UMO) (engl. With the occupied molecular orbitals occupied molecular orbital , short OMO). These orbitals have a similarly high energy level to cause the curvature of the otherwise highly symmetrical silicon ring. By adding lithium ions , the distance of the energy level between UMO and OMO can be increased, which results in a suppression of the PJT and thus in a flattening of the structure. In addition to the possible compatibility with existing semiconductor technologies, silicene has the advantage that the layer edges showed no reactivity with atmospheric oxygen .

In addition to silver, the development of silicon monolayers was also observed in other crystals such as zirconium diboride and iridium . Theoretical investigations showed that silicene forms a stable honeycomb layer on Al (111), as well as a so-called “polygonal silicene”, the structure of which consists of 3-, 4-, 5- and 6-atom rings.

Similarities and differences between silicene and graphene

Silicon and carbon atoms have a variety of similar properties. You are in the periodic table within the same main group (see: carbon group ) and form sp 2 - hybrid orbitals . The 2D structures of silicene and graphene also show a high number of similarities, but have significant distinguishing features. Both layers consist of hexagonal honeycomb structures, but the graphene layer is completely flat, while the silicon layer is slightly wavy and curved. This curvature gives silicene an adjustable band gap in the presence of an external electric field . In contrast to graphite, which consists of graphene layers that are connected by weak London forces , the binding forces within the monolayers in silicene are comparatively strong. However, since the silicon rings do not form π-π interactions , there is no graphite-like clumping of the rings to form fullerene- like structures in the case of silicene. Silicene and graphene have a similar electronic configuration . Both form Dirac cones and have a linear dispersion around the K point of the crystal. Both also have a quantum spin Hall effect .

Silicene layers with functional groups

In addition to the pure silicon structure, organo- modified monolayers with phenyl rings as functional groups on the free electrons have been successfully produced. This introduction of the functional groups enables, as an application, a dispersion of the layer in organic solvents .

Web links

Individual evidence

  1. ↑ Kyozaburo Takeda, Kenji Shiraishi: Theoretical possibility of stage corrugation in Si and Ge analogs of graphite . In: Physical Review B . tape 50 , no. 20 , November 15, 1994, pp. 14916-14922 , doi : 10.1103 / PhysRevB.50.14916 .
  2. ^ Gian G. Guzmán-Verri, LC Lew Yan Voon: Electronic structure of silicon-based nanostructures . In: Physical Review B . tape 76 , no. 7 , August 30, 2007, pp. 075131 , doi : 10.1103 / PhysRevB.76.075131 .
  3. ↑ S. Cahangirov, M. Topsakal, E. Aktürk, H. Şahin, S. Ciraci: Two- and One-Dimensional Honeycomb Structures of Silicon and Germanium . In: Physical Review Letters . tape 102 , no. 23 , June 12, 2009, pp. 236804 , doi : 10.1103 / PhysRevLett.102.236804 .
  4. ↑ Bernard Aufray, Abdelkader Kara, Sébastien Vizzini, Hamid Oughaddou, Christel Léandri, Benedicte Ealet, Guy Le Lay: Graphene-like silicon nanoribbons on Ag (110): A possible formation of silicon . In: Applied Physics Letters . tape 96 , no. 18 , May 3, 2010, p. 183102 , doi : 10.1063 / 1.3419932 .
  5. ↑ a b c Patrick Vogt, Paola De Padova, Claudio Quaresima, Jose Avila, Emmanouil Frantzeskakis, Maria Carmen Asensio, Andrea Resta, Bénédicte Ealet, Guy Le Lay: Silicene: Compelling Experimental Evidence for Graphenelike Two-Dimensional Silicon . In: Physical Review Letters . tape 108 , no. 15 , April 12, 2012, p. 155501 , doi : 10.1103 / PhysRevLett.108.155501 .
  6. Jump up ↑ S. Colonna, G. Serrano, P. Gori, A. Cricenti, F. Ronci: Systematic STM and LEED investigation of the Si / Ag (110) surface . In: Journal of Physics: Condensed Matter . tape 25 , no. 31 , August 7, 2013, p. 315301 , doi : 10.1088 / 0953-8984 / 25/31/315301 .
  7. ↑ L. i. Tao, Eugenio Cinquanta, Daniele Chiappe, Carlo Grazianetti, Marco Fanciulli, Madan Dubey, Alessandro Molle, Deji Akinwande: Silicene field-effect transistors operating at room temperature. In: Nature Nanotechnology. 2015, doi: 10.1038 / nnano.2014.325 .
  8. ↑ Chun-Liang Lin, Ryuichi Arafune, Kazuaki Kawahara, Noriyuki Tsukahara, Emi Minamitani, Yousoo Kim, Noriaki Takagi, Maki Kawai: Structure of Silicene Grown on Ag (111) . In: Applied Physics Express . tape 5 , no. 4 , April 1, 2012, p. 045802 , doi : 10.1143 / APEX.5.045802 .
  9. ↑ Baojie Feng, Zijing Ding, Sheng Meng, Yugui Yao, Xiaoyue He, Peng Cheng, Lan Chen, Kehui Wu: Evidence of Silicene in Honeycomb Structures of Silicon on Ag (111) . In: Nano Letters . tape 12 , no. 7 , July 11, 2012, p. 3507-3511 , doi : 10.1021 / nl301047g .
  10. ↑ Zhi-Xin Guo, Shinnosuke Furuya, Jun-ichi Iwata, Atsushi Oshiyama: Absence of Dirac Electrons in Silicene on Ag (111) Surfaces . In: Journal of the Physical Society of Japan . tape 82 , no. 6 , May 29, 2013, p. 063714 , doi : 10.7566 / JPSJ.82.063714 .
  11. ↑ R. Arafune, C.-L. Lin, R. Nagao, M. Kawai, N. Takagi: Comment on "Evidence for Dirac Fermions in a Honeycomb Lattice Based on Silicon" . In: Physical Review Letters . tape 110 , no. May 22 , 2013, doi : 10.1103 / PhysRevLett.110.229701 .
  12. ↑ Chun-Liang Lin, Ryuichi Arafune, Kazuaki Kawahara, Mao Kanno, Noriyuki Tsukahara, Emi Minamitani, Yousoo Kim, Maki Kawai, Noriaki Takagi: Substrate-Induced Symmetry Breaking in Silicene . In: Physical Review Letters . tape 110 , no. 7 , February 11, 2013, p. 076801 , doi : 10.1103 / PhysRevLett.110.076801 .
  13. ↑ Paola Gori, Olivia Pulci, Fabio Ronci, Stefano Colonna, Friedhelm Bechstedt: Origin of Dirac-cone-like features in silicon structures on Ag (111) and Ag (110) . In: Journal of Applied Physics . tape 114 , no. 11 , September 21, 2013, p. 113710 , doi : 10.1063 / 1.4821339 .
  14. ↑ Lan Chen, Cheng-Cheng Liu, Baojie Feng, Xiaoyue He, Peng Cheng, Zijing Ding, Sheng Meng, Yugui Yao, Kehui Wu: Evidence for Dirac Fermions in a Honeycomb Lattice Based on Silicon . In: Physical Review Letters . tape 109 , no. 5 , August 3, 2012, p. 056804 , doi : 10.1103 / PhysRevLett.109.056804 .
  15. ^ Emilio Scalise, Michel Houssa, Geoffrey Pourtois, B. van den Broek, Valery Afanas'ev, André Stesmans: Vibrational properties of silicene and germanene . In: Nano Research . tape 6 , no. 1 , 2013, p. 19-28 , doi : 10.1007 / s12274-012-0277-3 .
  16. ^ A b c Deepthi Jose, Ayan Datta: Structures and Chemical Properties of Silicene: Unlike Graphene . In: Accounts of Chemical Research . tape 47 , no. 2 , February 18, 2014, p. 593-602 , doi : 10.1021 / ar400180e .
  17. ↑ Paola De Padova, Christel Leandri, Sebastien Vizzini, Claudio Quaresima, Paolo Perfetti, Bruno Olivieri, Hamid Oughaddou, Bernard Aufray, Guy Le Lay: Burning Match Oxidation Process of Silicon Nanowires Screened at the Atomic Scale . In: Nano Letters . tape 8 , no. 8 , 2008, p. 2299-2304 , doi : 10.1021 / nl800994s .
  18. ↑ Antoine Fleurence, Rainer Friedlein, Taisuke Ozaki, Hiroyuki Kawai, Ying Wang, Yukiko Yamada-Takamura: Experimental Evidence for Epitaxial Silicene on Diboride Thin Films . In: Physical Review Letters . tape 108 , no. 24 , June 11, 2012, p. 245501 , doi : 10.1103 / PhysRevLett.108.245501 .
  19. ↑ Lei Meng u. a .: Buckled Silicene Formation on Ir (111) . In: Nano Letters . tape 13 , no. 2 , February 13, 2013, p. 685-690 , doi : 10.1021 / nl304347w .
  20. ↑ Tetsuya Morishita, Michelle JS Spencer, Shuhei Kawamoto, Ian K. Snook: A New Surface and Structure for Silicene: Polygonal Silicene Formation on the Al (111) Surface . In: Journal of Physical Chemistry C . tape 117 , no. 42 , October 24, 2013, p. 22142-22148 , doi : 10.1021 / jp4080898 .
  21. ↑ Yusuke Sugiyama, Hirotaka Okamoto, Takuya Mitsuoka, Takeshi Morikawa, Koji Nakanishi, Toshiaki Ohta, Hideyuki Nakano: Synthesis and Optical Properties of Monolayer Organosilicon Nanosheets . In: Journal of the American Chemical Society . tape 132 , no. 17 , May 5, 2010, pp. 5946–5947 , doi : 10.1021 / ja100919d .