ZrB2Y. Yamada-Takamura et al., PRL 95, 266105 (2005). Y. Yamada-Takamura et al., APL 97, 073109 (2010). A. Fleurence et al., PRL 108, 245501 (2012).Contents JAIST Chi-Cheng LeeHiroyuki Kawai Taisuke OzakiJAIST Antoine Fleurence Rainer Friedlein Yukiko Yamada-Takamura

C: GrapheneSi: SiliceneGe: GermaneneDirac cone

~0.1 eV~0.5 eV

CSiDiamond Graphene Si

S. Cahangirov et al., Phys. Rev. Lett. 102, 236804 (2009). Si, Ge :Low buckled (LB), High buckled (HB) LBDirac coneSiGe

ZrB2SiliceneSiZrB2GaNGaN(0001): a= 3.189ZrB2(0001): a= 3.187200GaNZrB2 on Si(111) ()ZrB2SiSiSiZrB2 ()STM imageA. Fleurence et al., PRL 108, 245501 (2012).A. Fleurence et al., Physica Status Solidi (c) 8, 779-783 (2011).

SiSi 2p3/2Si 2p1/2BCARelative binding energy (eV) Intensity (a.u.) 325%135%555%ABCSi 2p Si

A:B:C 2:3:1

ZrSiZrB2[1100]ZrB2[1120]--STMSTM(22)A:B:C = 2:3:1

SiA/BC/B[11-20]A/BSiASiB

ZrB2(0001)-(1x1)ZrB2(0001)-(2x2)silicene-(1x1)M(22)ZrB2Si-K(11)

OpenMXLCPAOGGA

STM Tersoff-Hamman

Si-2p Si-2p

:: NEB(a=3.187)(Zr: 7, B: 6)

ZrB2BulkSlabBlack: TotalRed: Zr-d

ZrB2 (0001) Si2.57 (Si height) 1.97 (Si height) 2.68 2.61 2.07 (Si height) Ebinding= 5.05 eVEbinding= 6.08 eVEbinding= 5.79 eVSiOn-top Hollow Bridge

CBBABABCBB 1Ebind=1.14 eV/ Si atom 2 Ebind=1.42 eV/Si atomNEB

12: Top view

Tersoff-HammanSTM1SiB(bridge) V=100mV2SiC(on-top) The calculations were performed by the Tersoff-Hamman approximation, and an isovalue of 8x10-7 e/bohr3 was used for generation of the height profile for both the cases.V=+300mVV=+300mV

Si-2p 1ABC 2ABC

Isovalue=0.01MKMThe wave functions just below Fermi level at ZrB2(2x2)--point(=Si(11)-K-point))are attributed to silicene.

PRL 108, 245501 (2012)Domain boundary might be the most important factorin revealing the realistic ground state by DFT calculation Domain boundary might be important?

Comparison between Expt. and TheoryModel 1 Model 2Relative energy(eV/(2x2) cell) 0 -1.589STM image Disagreement At least the position of the bright spot agreedChemical shift of Si-2pAgreement AgreementBand structure Large distortion of ZrB2 surface bandZrB2 surface band and X2 band reproducedRelative height of SiA and SiBAgreementSiA SiB