Supporting Information. Observation of Excitonic Fine Structure in a 2D Transition Metal. Dichalcogenide Semiconductor

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1 FWHM (ev) Normlized Intensity (. u.) Supporting Informtion Oservtion of Exitoni Fine Struture in 2D Trnsition Metl Dihlogenide Semiondutor Jingzhi Shng 1, Xionn Shen 1, Chunxio Cong 1, Nmphung Peimyoo 1, Binghen Co 1, Mustf Eginligil 1, Ting Yu 1,2,3* 1 Division of Physis nd pplied Physis, Shool of Physil nd Mthemtil Sienes, Nnyng Tehnologil University, Singpore Deprtment of Physis, Fulty of Siene, Ntionl University of Singpore, Singpore Grphene Reserh Centre, Ntionl University of Singpore, 2 Siene Drive 3, Singpore V -2 V V 2 V 4 V Gte Voltge (V) Figure S1 Exitoni emission from 1L WS 2 modulted y the eletril doping t room temperture., Widths (solid dots) of exiton ( ) nd negtive trion ( ) nds from the exfolited 1L WS 2 field-effet devie versus gte voltge, nd width (open irles) of the emission nd from the CVD-grown 1L WS 2 fieldeffet devie versus gte voltge. FWHM represents full width t hlf mximum., normlized PL spetr of the CVD-grown 1L WS 2 field-effet devie versus gte voltge. 1

Drin Current ( ) Drin Current ( ) Photon Energy of (ev) Integrted Intensity Rtio ( / ) 1.975 1.

, negtive trion ( ) energy versus exiton ( ) energy from the exfolited 1L WS 2 devie otined y eletril doping nd photoexittion.

6 4 Drk 65 W 49 W 6 W 3 K = 5V 2 e f g 4 3 2-4 -2 2 4 Bk-Gte Voltge (V) Drk 67 W 2113 W 483 W 3 K = 16 V 1-4 -2 2 4 Bk-Gte Voltge (V) Figure S3 Photoindued

2 Drin Current ( ) Drin Current ( ) Photon Energy of (ev) Integrted Intensity Rtio ( / ) Eletril doping Photoexittion 3 2 Eletril doping Photoexittion Photon Energy of (ev) Photon Energy of (ev) Figure S2 Comprison of photon energies nd integrted intensity rtio modulted y eletril doping nd photoexittion t room temperture., negtive trion ( ) energy versus exiton ( ) energy from the exfolited 1L WS 2 devie otined y eletril doping nd photoexittion., Integrted intensity rtio of negtive trion ( ) to exiton ( ) versus exiton ( ) energy from the exfolited 1L WS 2 devie. 6 4 Drk 65 W 49 W 6 W 3 K = 5V 2 e f g Bk-Gte Voltge (V) Drk 67 W 2113 W 483 W 3 K = 16 V Bk-Gte Voltge (V) Figure S3 Photoindued doping in 1L WS 2 t room temperture.,, Optil nd fluoresene imges of the exfolited 1L WS 2 field effet devie, respetively., Drin urrent versus k-gte voltge of the exfolited 1L WS 2 field effet devie under vrious exittion powers. e,f, Optil nd fluoresene imges of the CVD-grown 1L WS 2 field effet devie, respetively. g, Drin urrent versus k-gte voltge of the CVDgrown 1L WS 2 field effet devie under vrious exittion powers. represents the soure-drin voltge. 2

Drin Current ( ) Drin Current (n) Dissoition Energy (ev) Width Rtio FWHM (ev).1.8 LS.6.4.6 d.2. 1 1 1 2.5 Exittion Power ( W) 2. /.3 1.5 /. 1 1 1 Exittion Power ( W) 1.

, optil (upper) nd fluoresene (lower) imges of CVD-grown 1L WS 2., Widths of emission nds from exiton ( ), negtive trions ( ), iexitions ( ) nd lolized sttes (LS) s funtion of exittion power.

3 Drin Current ( ) Drin Current (n) Dissoition Energy (ev) Width Rtio FWHM (ev).1.8 LS d Exittion Power ( W) 2. / / Exittion Power ( W) Exittion Power ( W) Figure S4 Optil imges nd widths of the emission omponents from CVD-grown 1L WS 2 s funtion of exittion power t 4.2 K., optil (upper) nd fluoresene (lower) imges of CVD-grown 1L WS 2., Widths of emission nds from exiton ( ), negtive trions ( ), iexitions ( ) nd lolized sttes (LS) s funtion of exittion power., Dissoition energies of negtive trions ( ) nd iexitions ( ) in the CVD-grown 1L WS 2 s funtion of exittion power. d, Width rtios of the emission nds of to exiton emission nd. The sle rs in re 15 μm. nd 6 4 Drk 491 W 6 W 75 5 Drk 2113 W 483 W Exfolited 1L WS 2 CVD-grown 1L WS K = 5V K =16 V Bk-Gte Voltge (V) Bk-Gte Voltge (V) Figure S5 Photoindued doping in 1L WS 2 t 4.2 K., Drin urrent versus k-gte voltge of the exfolited 1L WS 2 field effet devie t 4.2 K under vrious exittion powers., Drin urrent versus kgte voltge of the CVD-grown 1L WS 2 field effet devie t 4.2 K under vrious exittion powers. represents the soure-drin voltge. 3

4 Figure S6 Linerly polrized photoluminesene of CVD-grown 1L WS 2 t 4.2 K. -, Polriztiondependent photon energies of, nd s funtions of the detetion polriztion ngle t exittion powers of 97, 175 nd 292 μw, respetively. The exittion polriztion is fixed nd the detetion polriztion ngle is tuned y use of liner polrizer. The periodi ehviour is fitted with sinusoidl urve s shown y the solid urve. Suh ehviours hve often een oserved in quntum dot systems nd used s the ritil fingerprint for the ssignment of 1-6, whih is strongly orrelted to the fine-struture splitting. The typil resons for suh splitting inlude struturl symmetries, strin, nd interfil effets in s-prepred low-dimensionl mterils 4, 7. In our se, the opposite polriztion ehviours for the photon energies of nd re proly due to the ntive (unintentionl) splitting of the exiton level, i.e. exiton fine struture splitting (ΔE, ~.5 mev), in 1L WS 2. Further systemti investigtion is needed to lrify the preise origin for suh the unintentionl reking of the exiton-energy degenery. 4

1 X -6 V 2 X -3 V 3 X X V 4 3 V 4 X 6 V 2. 2.5 2.1 2-5V X 2 X -4V X 2 X -2V 3 X -1V 3 X X V 2. 2.5 2.1 1k -6 V 1k -3 V 1k V 1k 3 V 1k 6 V 2. 2.5 2.1 Figure S7 Enlrged PL spetr from the CVD-grown 1L WS 2 devie t vrious k-gte voltges nd 4.

5 1 X -6 V 2 X -3 V 3 X X V 4 3 V 4 X 6 V V X 2 X -4V X 2 X -2V 3 X -1V 3 X X V k -6 V 1k -3 V 1k V 1k 3 V 1k 6 V Figure S7 Enlrged PL spetr from the CVD-grown 1L WS 2 devie t vrious k-gte voltges nd 4.2 K., Enlrged spetrl fetures of PL spetr s funtion of gte voltge shown in Figure 4., PL spetr t other negtive gte voltges from the CVD-grown 1L WS 2 devies mesured t the exittion power of 65 µw., PL spetr versus gte voltge mesured t the exittion power of 157 µw, orresponding to Figure LS 4.2 K 65 W 5 5k 157 W 25k 6 W LS 185 W X X k 957 W Figure S8 Optil imges nd photoluminesene spetr t 4.2 K from exfolited 1L WS 2 t vrious exittion powers., optil (upper) nd fluoresene (lower) imges of exfolited 1L WS 2., Photoluminesene spetrum t the exittion power of 65 µw., Photoluminesene spetr t the high exittion powers. s shown in Fig. S6, the shpe of the photoluminesene spetrum t 4.2 K shows multiomponent hrter. The emission omponents from exiton nd trion sttes re well distinguished. The dissoition energy of the negtive trion is ~3 mev. Different from the emission fetures t room temperture (Fig. 1), the new emission speies with shrp spikes pper t lower energies thn tht of the trion nd, whih re ssigned to the lolized sttes (LS). The speifi origin of LS nd the identifition of eh spike require further investigtion, where the ound exiton omplexes proly ply importnt roles. Note tht, in our se, the PL spetr of exfolited WS 2 1Ls vry from smple to smple, eing similr to other studies on 1Ls of WS 2 8 nd MoS 2 9, whih proly results from the smple inhomogeneity nd/or the oupling vrition with sustrtes. With the inrese in the exittion power, the overll pek shpe hnges from the strutured spetr to predominnt single pek, i.e. the LS emission eomes dominnt. The sle rs in re 15 μm. 5

6 Referenes 1. Ghli, M.; Ohtni, K.; Ohno, Y.; Ohno, H. Genertion nd Control of Polriztion-Entngled Photons from Gs Islnd Quntum Dots y n Eletri Field. Nt. Commun. 212, 3, rhi, M.; Mstrndre, C..; Kurod, T.; Mno, T.; Skod, K.; Koguhi, N.; Snguinetti, S.; Vinttieri,.; Gurioli, M. Exiton Fine Struture in Strin-Free Gs/l.3 G.7 s Quntum Dots: Extrinsi effets. Phys. Rev. B 28, 78, kopin, N.; Lindner, N. H.; Poem, E.; Berltzky, Y.; vron, J.; Gershoni, D.; Gerrdot, B. D.; Petroff, P. M. Entngled Photon Pirs from Semiondutor Quntum Dots. Phys. Rev. Lett. 26, 96, Seguin, R.; Shliw,.; Rodt, S.; Potshke, K.; Pohl, U. W.; Bimerg, D. Size-Dependent Fine- Struture Splitting in Self-Orgnized Ins/Gs Quntum Dots. Phys. Rev. Lett. 25, 95, Trott, R.; Wildmnn, J. S.; Zllo, E.; Shmidt, O. G.; Rstelli,. Highly Entngled Photons from Hyrid Piezoeletri-Semiondutor Quntum Dot Devies. Nno Lett. 214, 14, rhi, M.; Troini, F.; Mstrndre, C.; Goldoni, G.; Kurod, T.; Mno, T.; Skod, K.; Koguhi, N.; Snguinetti, S.; Vinttieri,.; et l. Spetrl Diffusion nd Line Brodening in Single Self- ssemled Gs/lGs Quntum Dot Photoluminesene. ppl. Phys. Lett. 28, 93, Stevenson, R. M.; Young, R. J.; tkinson, P.; Cooper, K.; Rithie, D..; Shields,. J. Semiondutor Soure of Triggered Entngled Photon Pirs. Nture 26, 439, Mitioglu,..; Plohok, P.; Jdzk, J. N.; Esoffier, W.; Rikken, G. L. J..; Kulyuk, L.; Mude, D. K. Optil Mnipultion of the Exiton Chrge Stte in Single-Lyer Tungsten Disulfide. Phys. Rev. B 213, 88, Serome, D.; Shwrz, S.; Del Pozo-Zmudio, O.; Liu, F.; Roinson, B. J.; Chekhovih, E..; Trtkovskii, I. I.; Kolosov, O.; Trtkovskii,. I. Optil Investigtion of the Nturl Eletron Doping in Thin MoS 2 Films Deposited on Dieletri Sustrtes. Si. Rep. 213, 3,

Supporting Information

Supporting Information tom-thik Interlyer Mde of VD-Grown Grphene Film on Seprtor for dvned thium-sulfur tteries Zhenzhen Du 1, hengkun Guo 2, njun Wng 3, jun Hu 1, Song Jin 1, Timing Zhng 1, Honghng Jin 1, Zhiki Qi 1, Sen Xin