Tunable and sizable band gap in silicene by surface adsorption

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1 Supplementry mteril Tunle nd sizle nd p in silicene y surfce dsorption Rue Quhe,, Ruixin Fei, Qihn Liu, Jixin Zhen,, Hon Li, Chenyon Xu, Zeyun Ni, Ynyn Wn, Dpen Yu, Zhenxin Go, nd Jin Lu,* Stte Key Lortory of Mesoscopic Physics nd Deprtment of Physics, Pekin University, Beijin 87, P. R. Chin Acdemy for Advnced Interdisciplinry Studies, Pekin University, Beijin 87, P. R. Chin *Correspondin uthor: jinlu@pku.edu.cn Methods The spin-oritl couplin (SOC) effects re investited y usin the plne wve (PW) sis set nd the projector-umented wve (PAW) pseudopotentil implemented in the ASP pcke. Generlized rdient pproximtion (GGA) of the Perdew-Burke- Ernzerhof (PBE) form is employed for the exchne-correltion functionl. A PW enery cutoff of 5 e nd Monkhorst-Pck k-mesh 3 re used to enerte the chre densities. The qusiprticle clcultions re crried out usin the ABINIT pcke. 4 First, we compute the wve functions usin DFT. The locl density pproximtion (LDA) of the Ceperley-Alder form is employed for the exchne-correltion functionl. 5 A PW enery cutoff of 5 e is used, toether with the norm-conservin pseudopotentils, 6 nd the Brillouin zone is smpled with n 8 8 Monkhorst-Pck rid. 3 Second, the qusiprticle eneries E nk re clculted usin the followin qusiprticle Schrödiner eqution, which uses the self-enery cquired from the GW pproximtion. 7 [ ( ) () Therein, the Green function nd the Coulom screenin re constructed from the LDA results in the first step, nd the plsmon pole model is used for the screenin computtion. We perform the GW clcultion in nonself-consistent wy. S

2 d (Å) d (Å) () Most stle stte () Su-stle Metstle stte d d Fiure S: Possile confiurtions of AMSi 8 monolyer. The AM tom is ove the hexon center in the most stle stte of AMSi 8 monolyer nd ove one of the lower Si tom in the metstle stte..8.6 Li N K R Cs N (%) Fiure S: Dependences of the silicene ucklin d nd the distnce etween the AM tom nd silicene d on the AM covere. d of the pure silicene is 6 Å. S

3 E (e) E (e) - without SOC with SOC - Fiure S3: Bnd structures of NSi 8 monolyer with nd without the inclusion of the SOC effects. In order to keep consistency nd otin relile compred result, ll the ove nd structures re clculted y usin the PW sis set implemented in the ASP pcke. The nd p of NSi 8 monolyer with the inclusion of the SOC effects is. e, which is only. me lrer thn the one without the inclusion of the SOC effects. LDA GW Fiure S4: Bnd structures of NSi monolyer t the LDA nd GW levels. For the ske of comprison, oth the nd structures re clculted y usin the PW sis set implemented in the ABINIT pcke. S3

4 Trnsmission Trnsmission Trnsmission SZ SZP =, = NSi. - - Fiure S5: Trnsmission spectrum of the N-covered silicene FET with N = 5%. The chnnel is 3.8 Å lon. A smller trnsport p is otined in the trnsmission spectrum y usin the SZP sis set compred with the SZ sis set. Both nd re set to zero. =, =. = -, =. =, =. KSi LiSi E -E f (e) - - E -E f (e) Fiure S6: Trnsmission spectr of the AM-covered silicene FET. The chnnel is composed of () K-covered or () Li-covered silicene with N = 5.%. The chnnel is 3.8 Å lon. The SZ sis set is used. The verticl dshed-line indictes the is window. S4

5 References. Kresse, G. & Jouert, D. From ultrsoft pseudopotentils to the projector umentedwve method. Phys. Rev. B 59, (999).. Perdew, J. P., Burke, K. & Ernzerhof, M. Generlized rdient pproximtion mde simple. Phys. Rev. Lett. 77, (996). 3. Monkhorst, H. J. & Pck, J. D. Specil points for rillouin-zone intertions. Phys. Rev. B 3, (976). 4. Brunevl, F. & Gonze, X. Accurte GW self-eneries in plne-wve sis usin only few empty sttes: Towrds lre systems. Phys. Rev. B 78, 855 (8). 5. Ceperley, D. M. & Alder, B. J. Ground stte of the electron s y stochstic method. Phys. Rev. Lett. 45, (98). 6. Hmnn, D. R., Schlüter, M. & Chin, C. Norm-conservin pseudopotentils. Phys. Rev. Lett. 43, (979). 7. Onid, G., Reinin, L. & Ruio, A. Electronic excittions: Density-functionl versus mny-ody Green's-function pproches. Rev. Mod. Phys. 74, (). S5