-
Monolayer transition metal dichalcogenides (TMDCs) exhibit exceptional properties including atomic-scale thickness, direct bandgap, and strong spin-orbit coupling, which make them have great potential applications in spintronics, optoelectronics, and other fields. Usually, materials contain various structural defects, which are either formed during preparation and growth or induced by subsequent treatments. These defects can significantly change their physicochemical properties. Consequently, controlling and comprehending defects is an important approach to adjusting the properties of these materials. Herein, we use Ar+ plasma to bombard monolayer WS2, which is exfoliated mechanically, thereby introducing defects whose density is controlled by changing the bombardment duration. The photoluminescence (PL) and Raman spectroscopic measurements at different temperatures and power values are utilized to investigate the optical properties of the defects. Furthermore, time-resolved photoluminescence is employed to unveil the dynamic behaviors of free and trapped excitons. The bombardment can introduce different types of defects into typical two-dimensional (2D) TMDCs such as MoS2 and WS2. Single sulfur vacancies are frequently generated, while other defects like double sulfur vacancies or metal atom vacancies can also occur. Exciton effects dominate the optical properties of monolayer TMDCs due to reduced screening and large effective mass. At low temperatures, bound exciton emissions arise from trapped states. Our measurements reveal two types of defect-bound excitons from the PL spectra at around 1.85 eV (XB1) and 1.55 eV (XB2). Meanwhile, the Raman peaks of the samples before and after treatment exhibit no obvious changes, indicating that the lattice structure remaines unchanged. After the Ar+ bombardment, the intensity of the free neutral exciton significantly decreases to 1/6 of untreated WS2, owing to the free exciton population and the increased non-radiative centers. The dynamic processes of these two bound excitons are considerably slower than the neutral exciton’s, showing the typical dynamic behavior of defect-bound excitons. Furthermore, comparison between the PL under vacuum condition and the PL under atmospheric condition shows that the intensities of the two bound excitons exhibit opposing behaviors. In an atmospheric environment, neutral excitons and bound exciton XB1 possess higher intensities. In the vacuum, the strength of neutral exciton and XB1 decrease quickly, while the intensity of deep-level bound exciton XB2 increases. In summary, we observe two bound exciton states arising from specific vacancy states in monolayer WS2 after Ar+ bombardment. Their energy values are 200 meV and 500 meV lower than those of the neutral exciton, with a splitting energy value being about 300 meV. The detailed evolution of the relative spectral weight with temperature and excitation power are presented. This work provides insights into the generation, control, and characteristic spectra of defects in 2D materials. -
Keywords:
- 2D semiconductor /
- WS2 /
- defect states /
- exciton
-
图 1 (a)经过20 s处理的单层WS2; (b)经过30 s处理的单层WS2, 插图为处理前的单层WS2; (c)室温下, 处理前后样品的PL谱; (d)室温下, 处理前后样品的Raman谱; (e)室温下, 处理前后样品的白光反射谱; (f)室温下, 处理前后样品的PL谱, 为图(c)淡蓝色区域位置的放大
Figure 1. (a) Monolayer WS2 after 20 s treatment; (b) monolayer WS2 after 30 s treatment, the insets are the monolayer WS2 before treatment; (c) PL spectra of the samples before and after treatment at room temperature; (d) Raman spectra of the samples before and after treatment at room temperature; (e) reflectivities of the samples before and after treatment at room temperature; (f) PL spectra of the sample before and after treatment at room temperature, zoom-in of the spectral range marked by the blue rectangle zone in panel (c).
图 2 温度依赖PL结果 (a) 77 K下未处理的单层和经过20 s, 30 s处理的单层WS2的PL谱; (b), (c)经过20 s, 30 s处理的单层WS2变温PL谱; (d)经过20 s, 30 s处理的样品XB1(XB2)发光峰强度和X0强度比值随温度的变化; (e), (f)经过20 s, 30 s处理的单层WS2的X0, XB1, XB2峰位随温度的变化
Figure 2. Temperature dependent PL results: (a) PL spectra of untreated monolayer WS2 and monolayers treated for 20 s and 30 s at 77 K; (b), (c) temperature dependent PL spectra of monolayer WS2 after 20 s and 30 s treatment; (d) temperature dependent PL intensity ratio of bound excitons XB1 and XB2 over X0 of monolayers treated for 20 s and 30 s; (e), (f) temperature dependent peak energies of X0, XB1, and XB2 of monolayers treated for 20 s and 30 s.
图 3 200 K温度下功率依赖PL结果 (a)—(c) 20 s处理样品的结果; (d)—(f) 30 s处理样品的结果; (a), (d)样品变功率PL光谱; (b), (d)样品XB1(XB2)发光峰强度和X0强度比值随功率的变化; (c), (f)样品X0, XB1, XB2发光峰强度积分随功率的变化
Figure 3. Power dependent PL results at 200 K: (a)–(c) Results of monolayer treated for 20 s; (d)–(f) results of monolayer treated for 30 s; (a), (d) power dependent PL spectra; (b), (e) power dependent PL intensity ratio of bound excitons XB1 and XB2 over X0; (c), (f) power dependent PL intensities of X0, XB1, XB2.
图 4 (a) 150 K下30 s处理的样品变功率的PL; (b) 30 s处理的样品中XB1变功率的PL; (c) 30 s处理的样品中X0变功率的PL
Figure 4. (a) Power dependent PL spectra of the sample treated for 30 s at 150 K; (b) power dependent PL spectra of XB1 in the sample treated for 30 s; (c) power dependent PL spectra of X0 in the sample treated for 30 s.
图 5 20 s和30 s处理样品的时间分辨光谱 (a) 77 K; (b) 300 K
Figure 5. Time-resolved PL of monolayer treated for 20 s and 30 s: (a) 77 K; (b) 300 K.
图 6 室温下, 大气环境和真空下单层WS2的PL (a)未处理的单层; (b) 20 s处理的单层; (c) 30 s处理的单层
Figure 6. PL of monolayer WS2 under atmosphere and vacuum conditions at room temperature: (a) Results of untreated monolayer WS2; (b) results of monolayer WS2 treated for 20 s; (c) results of monolayer WS2 treated for 30 s.
-
[1] Liang Q J, Zhang Q, Zhao X X, Liu M Z, Wee A T S 2021 ACS Nano 15 2165
Google Scholar
[2] Karaiskaj D, Thewalt M L, Ruf T, Cardona M, Pohl H J, Deviatych G G, Sennikov P G, Riemann H 2001 Phys. Rev. Lett. 86 6010
Google Scholar
[3] Skolnick M S, Tu C W, Harris T D 1986 Phys. Rev. B Condens. Matter 33 8468
Google Scholar
[4] Look D C, Farlow G C, Reunchan P, Limpijumnong S, Zhang S B, Nordlund K 2005 Phys. Rev. Lett. 95 225502
Google Scholar
[5] Wang G, Chernikov A, Glazov M M, Heinz T F, Marie X, Amand T, Urbaszek B 2018 Rev. Mod. Phys. 90 021001
Google Scholar
[6] Chernikov A, Berkelbach T C, Hill H M, Rigosi A, Li Y, Aslan B, Reichman D R, Hybertsen M S, Heinz T F 2014 Phys. Rev. Lett. 113 076802
Google Scholar
[7] Ferrari A C, Meyer J C, Scardaci V, Casiraghi C, Lazzeri M, Mauri F, Piscanec S, Jiang D, Novoselov K S, Roth S, Geim A K 2006 Phys. Rev. Lett. 97 187401
Google Scholar
[8] Shi W, Lin M L, Tan Q H, Qiao X F, Zhang J, Tan P H 2016 2D Mater. 3 2757
[9] Mounet N, Gibertini M, Schwaller P, Campi D, Merkys A, Marrazzo A, Sohier T, Castelli I E, Cepellotti A, Pizzi G, Marzari N 2018 Nat. Nanotechnol. 13 246
Google Scholar
[10] Tongay S, Suh J, Ataca C, Fan W, Luce A, Kang J S, Liu J, Ko C, Raghunathanan R, Zhou J, Ogletree F, Li J B, Grossman J C, Wu J Q 2013 Sci. Rep. 3 2657
Google Scholar
[11] Rhodes D, Chae S H, Ribeiro-Palau R, Hone J 2019 Nat. Mater. 18 541
Google Scholar
[12] Dean C R, Young A F, Meric I, Lee C, Wang L, Sorgenfrei S, Watanabe K, Taniguchi T, Kim P, Shepard K L, Hone J 2010 Nat. Nanotechnol. 5 722
Google Scholar
[13] Pisoni R, Kormanyos A, Brooks M, Lei Z, Back P, Eich M, Overweg H, Lee Y, Rickhaus P, Watanabe K, Taniguchi T, Imamoglu A, Burkard G, Ihn T, Ensslin K 2018 Phys. Rev. Lett. 121 247701
Google Scholar
[14] Tanoh A O A, Alexander-Webber J, Xiao J, Delport G, Williams C A, Bretscher H, Gauriot N, Allardice J, Pandya R, Fan Y, Li Z, Vignolini S, Stranks S D, Hofmann S, Rao A 2019 Nano Lett. 19 6299
Google Scholar
[15] Kim H, Lien D H, Amani M, Ager J W, Javey A 2017 ACS Nano 11 5179
Google Scholar
[16] Chuang H J, Chamlagain B, Koehler M, Perera M M, Yan J, Mandrus D, Tomanek D, Zhou Z 2016 Nano Lett. 16 1896
Google Scholar
[17] Xie Y, Wu E X, Hu R X, Qian S B, Feng Z H, Chen X J, Zhang H, Xu L Y, Hu X D, Liu J, Zhang D H 2018 Nanoscale 10 12436
Google Scholar
[18] Tosun M, Chan L, Amani M, Roy T, Ahn G H, Taheri P, Carraro C, Ager J W, Maboudian R, Javey A 2016 ACS Nano 10 6853
Google Scholar
[19] Meng J L, Wei Z, Tang J, Zhao Y, Wang Q, Tian J, Yang R, Zhang G, Shi D 2020 Nanotechnology 31 235710
Google Scholar
[20] Shaik A B D, Palla P 2021 Sci. Rep. 11 12285
Google Scholar
[21] Palacios-Berraquero C, Barbone M, Kara D M, Chen X, Goykhman I, Yoon D, Ott A K, Beitner J, Watanabe K, Taniguchi T, Ferrari A C, Atature M 2016 Nat. Commun. 7 12978
Google Scholar
[22] Koperski M, Nogajewski K, Arora A, Cherkez V, Mallet P, Veuillen J Y, Marcus J, Kossacki P, Potemski M 2015 Nat. Nanotechnol. 10 503
Google Scholar
[23] Moody G, Tran K, Lu X, Autry T, Fraser J M, Mirin R P, Yang L, Li X, Silverman K L 2018 Phys. Rev. Lett. 121 057403
Google Scholar
[24] Refaely-Abramson S, Qiu D Y, Louie S G, Neaton J B 2018 Phys. Rev. Lett. 121 167402
Google Scholar
[25] Mujeeb F, Chakrabarti P, Mahamiya V, Shukla A, Dhar S 2023 Phys. Rev. B 107 115429
Google Scholar
[26] Manzeli S, Ovchinnikov D, Pasquier D, Yazyev O V, Kis A 2017 Nat. Rev. Mater. 2 17033
Google Scholar
[27] Butler S Z, Hollen S M, Cao L, Cui Y, Gupta J A, Gutiérrez H R, Heinz T F, Hong S S, Huang J, Ismach A F, Johnston-Halperin E, Kuno M, Plashnitsa V V, Robinson R D, Ruoff R S, Salahuddin S, Shan J, Shi L, Spencer M G, Terrones M, Windl W, Goldberger J E 2013 ACS Nano 7 2898
Google Scholar
[28] Zhou M F, Wang W H, Lu J P, Ni Z H 2021 Nano Res. 14 29
Google Scholar
[29] Vaquero D, Clericò V, Salvador-Sánchez J, Martín-Ramos A, Díaz E, Domínguez-Adame F, Meziani Y M, Diez E, Quereda J 2020 Commun. Phys. 3 194
Google Scholar
[30] Ross J S, Wu S F, Yu H Y, Ghimire N J, Jones A M, Aivazian G, Yan J Q, Mandrus D G, Xiao D, Yao W, Xu X D 2013 Nat. Commun. 4 1474
Google Scholar
[31] Zhang X X, You Y, Zhao S Y, Heinz T F 2015 Phys. Rev. Lett. 115 257403
Google Scholar
[32] Tang Y H, Mak K F, Shan J 2019 Nat. Commun. 10 4047
Google Scholar
[33] You Y, Zhang X X, Berkelbach T C, Hybertsen M S, Reichman D R, Heinz T F 2015 Nat. Phys. 11 477
Google Scholar
[34] Ye Z, Waldecker L, Ma E Y, Rhodes D, Antony A, Kim B, Zhang X X, Deng M, Jiang Y, Lu Z, Smirnov D, Watanabe K, Taniguchi T, Hone J, Heinz T F 2018 Nat. Commun. 9 3718
Google Scholar
[35] Zhang X X, Cao T, Lu Z, Lin Y C, Zhang F, Wang Y, Li Z, Hone J C, Robinson J A, Smirnov D, Louie S G, Heinz T F 2017 Nat. Nanotechnol. 12 883
Google Scholar
[36] Li Y, Ludwig J, Low T, Chernikov A, Cui X, Arefe G, Kim Y D, van der Zande A M, Rigosi A, Hill H M, Kim S H, Hone J, Li Z, Smirnov D, Heinz T F 2014 Phys. Rev. Lett. 113 266804
Google Scholar
[37] Zhou W, Zou X L, Najmaei S, Liu Z, Shi Y M, Kong J, Lou J, Ajayan P M, Yakobson B I, Idrobo J C 2013 Nano Lett. 13 2615
Google Scholar
[38] Amani M, Taheri P, Addou R, Ahn G H, Kiriya D, Lien D H, Ager J W, 3rd, Wallace R M, Javey A 2016 Nano Lett. 16 2786
Google Scholar
[39] Komsa H P, Kotakoski J, Kurasch S, Lehtinen O, Kaiser U, Krasheninnikov A V 2012 Phys. Rev. Lett. 109 035503
Google Scholar
[40] Zhao G Y, Deng H, Tyree N, Guy M, Lisfi A, Peng Q, Yan J A, Wang C, Lan Y 2019 Appl. Sci. 9 678
Google Scholar
[41] Chee S S, Lee W J, Jo Y R, Cho M K, Chun D, Baik H, Kim B J, Yoon M H, Lee K, Ham M H 2020 Adv. Funct. Mater. 30 1908147
Google Scholar
[42] Li Y L, Liu W, Wang Y K, Xue Z H, Leng Y C, Hu A Q, Yang H, Tan P H, Liu Y Q, Misawa H, Sun Q, Gao Y N, Hu X Y, Gong Q H 2020 Nano Lett. 20 3747
Google Scholar
[43] Wu Z T, Zhao W W, Jiang J, Zheng T, You Y M, Lu J P, Ni Z H 2017 J. Phys. Chem. C 121 12294
Google Scholar
[44] Zheng Y J, Chen Y, Huang Y L, Gogoi P K, Li M Y, Li L J, Trevisanutto P E, Wang Q, Pennycook S J, Wee A T S, Quek S Y 2019 ACS Nano 13 6050
Google Scholar
[45] Schuler B, Qiu D Y, Refaely-Abramson S, Kastl C, Chen C T, Barja S, Koch R J, Ogletree D F, Aloni S, Schwartzberg A M, Neaton J B, Louie S G, Weber-Bargioni A 2019 Phys. Rev. Lett. 123 076801
Google Scholar
[46] Carozo V, Wang Y, Fujisawa K, Carvalho B R, McCreary A, Feng S, Lin Z, Zhou C, Perea-López N, Elías A L, Kabius B, Crespi V H, Terrones M Sci. Adv. 3 e1602813
[47] Liu H, Wang C, Liu D M, Luo J B 2019 Nanoscale 11 7913
Google Scholar
[48] Liu H, Wang C, Zuo Z, Liu D M, Luo J B 2020 Adv. Mater. 32 e1906540
Google Scholar
[49] Greben K, Arora S, Harats M G, Bolotin K I 2020 Nano Lett. 20 2544
Google Scholar
[50] Zhang S, Wang C G, Li M Y, Huang D, Li L J, Ji W, Wu S 2017 Phys. Rev. Lett. 119 046101
Google Scholar
[51] Gutierrez H R, Perea-Lopez N, Elias A L, Berkdemir A, Wang B, Lv R, Lopez-Urias F, Crespi V H, Terrones H, Terrones M 2013 Nano Lett. 13 3447
Google Scholar
[52] Tang Y, Mak K F, Shan J 2019 Nat. Commun. 10 4047
Google Scholar
[53] Tsai C, Li H, Park S, Park J, Han H S, Norskov J K, Zheng X, Abild-Pedersen F 2017 Nat. Commun. 8 15113
Google Scholar
[54] Godde T, Schmidt D, Schmutzler J, Aßmann M, Debus J, Withers F, Alexeev E M, Del Pozo-Zamudio O, Skrypka O V, Novoselov K S, Bayer M, Tartakovskii A I 2016 Phys. Rev. B 94 165301
Google Scholar
[55] McCreary A, Berkdemir A, Wang J, Nguyen M A, Elías A L, Perea-López N, Fujisawa K, Kabius B, Carozo V, Cullen D A, Mallouk T E, Zhu J, Terrones M 2016 J. Mater. Res. 31 931
Google Scholar
[56] Kim M S, Yun S J, Lee Y, Seo C, Han G H, Kim K K, Lee Y H, Kim J 2016 ACS Nano 10 2399
Google Scholar
[57] Feng J Y, Li Y Z, Li J X, Feng Q S, Xin W, Liu W Z, Xu H Y, Liu Y C 2022 Nano Lett. 22 3699
Google Scholar
[58] Xin M, Lan W Z, Wang G, Zhou Q, Gu C Z, Liu B L 2021 Appl. Phys. Lett. 119 153101
Google Scholar
[59] Liu H L, Yang T, Tatsumi Y, Zhang Y, Dong B J, Guo H H, Zhang Z D, Kumamoto Y, Li M Y, Li L J, Saito R, Kawata S 2018 Sci. Rep. 8 11398
Google Scholar
[60] Chow P K, Jacobs-Gedrim R B, Gao J, Lu T M, Yu B, Terrones H, Koratkar N 2015 ACS Nano 9 1520
Google Scholar
[61] Goodman A J, Willard A P, Tisdale W A 2017 Phys. Rev. B 96 121404
Google Scholar
[62] Berkdemir A, Gutiérrez H R, Botello-Méndez A R, Perea-López N, Elías A L, Chia C I, Wang B, Crespi V H, López-Urías F, Charlier J C, Terrones H, Terrones M 2013 Sci. Rep. 3 1755
Google Scholar
[63] Shang J Z, Shen X N, Cong C X, Peimyoo N, Cao B C, Eginligil M, Yu T 2015 ACS Nano 9 647
Google Scholar
[64] Wang G, Bouet L, Lagarde D, Vidal M, Balocchi A, Amand T, Marie X, Urbaszek B 2014 Phys. Rev. B 90 097403
[65] Jadczak J, Kutrowska-Girzycka J, Kapuscinski P, Huang Y S, Wojs A, Bryja L 2017 Nanotechnology 28 395702
Google Scholar
[66] Singh A, Singh A K 2021 Phys. Rev. Mater. 5 084001
Google Scholar
[67] Carozo V, Wang Y, Fujisawa K, Carvalho B R, McCreary A, Feng S, Lin Z, Zhou C, Perea-López N, Elías A L, Kabius B, Crespi V H, Terrones M 2017 Sci. Adv. 3 e1602813
Google Scholar
DownLoad:
Metrics
- Abstract views: 234
- PDF Downloads: 14
- Cited By: 0
