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Thickness-dependent electronic structure of the interface of 2,7-dioctyl[1]benzothieno[3,2-b][1] benzothiophene/Ni(100)

Zhang Hong Niu Dong-Mei Lü Lu Xie Hai-Peng Zhang Yu-He Liu Peng Huang Han Gao Yong-Li

Thickness-dependent electronic structure of the interface of 2,7-dioctyl[1]benzothieno[3,2-b][1] benzothiophene/Ni(100)

Zhang Hong, Niu Dong-Mei, Lü Lu, Xie Hai-Peng, Zhang Yu-He, Liu Peng, Huang Han, Gao Yong-Li
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  • Combining ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy and atomic force microscopy (AFM), we perform a systematic investigation on the correlation of energy level alignment, film growth and molecular orientation of 2, 7-dioctyl[1]benzothieno-[3, 2-b][1]benzothiophene (C8-BTBT) on Ni(100). The molecules lie down at the first layer and are partly devulcanized by the substrate. Chemical adsorption of reaction products of sulfur atoms on the Ni substrate and the evaporation of the hydrocarbon products into vacuum make the C/S ratio as low as 11.5 : 1 in the XPS of the initially deposited C8-BTBT film of 1-4 thickness, far less than the stoichiometric of 15 : 1. With the thickness increasing from 4 to 8 , there are sharp downward shifts of Evac, HOMO and core levels of C 1s, S 2p, and a sharp increase of C/S ratio, which can be ascribed to the change of molecular orientations from lying down at 4 to standing up at 8 . From 8 onward, the C/S ratio increases steadily till it reaches 15 : 1. The energy levels show relatively less changes when the thickness increases from 8 to 32 . When the thickness increases over 32 , the energy band starts bending downward apparently because of the charging effect during the photoelectron emission processes. The poor conductivity along the standing alkyl chain of C8-is the main cause for the charging. The standing up configurations of the C8-BTBT molecules are confirmed by the AFM investigation in which the heights of the upper layers of C8-BTBT are around 30 , close to the length of the long c-axis. AFM image also indicates that the molecules tend to grow into islands for larger thickness, which is consistent with the slower decrease of the (I/I0) of Ni 2p3/2 with the C8-BTBT film thickness. Our results suggest that a buffer layer be inserted between Ni and C8-BTBT and the thickness of the C8-BTBT film be controlled as thin as possible in related devices.
      Corresponding author: Niu Dong-Mei, mayee@csu.edu.cn
    • Funds: Project supported by the National Natural Science Foundation of China (Grant Nos. 51173205, 11334014) and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry.
    [1]

    Shi F F 1996 J. Macro. Sci. C 36 795

    [2]

    Zhou Y S, Peng J, Wang E B, Zhang L J 1998 Transition Metal Chemistry 23 125

    [3]

    Klauk H, Zschieschang U, Pflaum J, Halik M 2007 Nature 445 745

    [4]

    Sanvito S 2011 Chem. Soc. Rev 40 3336

    [5]

    Someya T, Pal B, Huang J, Katz H E 2008 Mrs Bull. 33 690

    [6]

    Burroughes J H, Bradley D D C, Brown A R, Maeks R N, Mackay K, Friend R H, Burns P L, Holmes A B 1990 Nature 347 539

    [7]

    Tang C W, Vanslyke S A 1987 Appl. Phys. Lett. 51 913

    [8]

    Yang F, Shtein M, Forrest S R 2005 Nat. Mater. 4 37

    [9]

    Facchetti A 2007 Mater. Today 10 28

    [10]

    Gelinck G H, Huitema H E A, van Veenendaal E, Cantatore E, Schrijnemakers L, van der Putten J B P H, Geuns T C T, Beenhakkers M, Giesbers J B, Huisman B H, Meijer E J, Benito E M, Touwslager F J, Marsman A W, van Rens B J E, De Leeuw D M 2004 Nat. Mater. 3 106

    [11]

    Baude P F, Ender D A, Haase M A, Kelley T W, Muyres D V, Theiss S D 2003 Appl. Phys. Lett. 82 3964

    [12]

    Someya T, Kato Y, Sekitani T, Iba S, Noguchi Y, Murase Y, Kawaguchi H, Sakurai T 2005 PNAS 102 12321

    [13]

    Kuribara K, Wang H, Uchiyama N, Fukuda K, Yokota T, Zschieschang U, Jaye C, Fischer D, Klauk H, Yamamoto T, Takimiya K, Ikeda M, Kuwabara H, Sekitani T, Loo Y L, Someya T 2012 Nat. Commun. 3 723

    [14]

    Berggren M, Dahlfors A R 2007 Adv. Mater. 19 3201

    [15]

    Koezuka H, Tsumura A, Ando T 1987 Synthetic Metals 18 699

    [16]

    Takeya J, Yamagishi M, Tominari Y, Hirahara R, Nakazawa Y, Nishikawa T, Kawase T, Shimoda T, Ogawa S 2007 Appl. Phys. Lett. 90 102120

    [17]

    Yuan Y B, Giri G, Ayzner A L, Zoombelt A P, Mannsfeld S C B, Chen J H, Nordlund D, Toney M F, Huang J S, Bao Z N 2014 Nat. Commun. 5 3005

    [18]

    Sinha S, Wang C H, Mukherjee M, Yang Y W 2014 J. Phys. D 47 245103

    [19]

    Ding H J, Gao Y L 2008 Phys. Rev. B 78 075311

    [20]

    McCulloch L, Heeney M, Chabinyc M L, DeLongchamp D, Kline R J, Coelle M, Duffy W, Fischer D, Gundlach D, Hamadani B, Hamilton R, Richter L, Salleo A, Shkunov M, Sporrowe D, Tierney S, Zhong W 2009 Adv. Mater. 21 1091

    [21]

    Virkar A A, Mannsfeld S, Bao Z A, Stingelin N 2010 Adv. Mater. 22 3857

    [22]

    Chen W, Huang H, Chen S, Gao X Y, Wee A T S 2008 J. Phys. Chem. C 112 5036

    [23]

    Kobayashi H, Kobayashi N, Hosoi S, Koshitani N, Murakami D, Shirasawa R, Kudo Y, Hobara D, Tokita Y, Itabashi M 2013 J. Chem. Phys. 139 014707

    [24]

    Laquindanum J G, Katz H E, Lovinger A J, Dodabalapur A 1996 Chem. Mater. 8 2542

    [25]

    Resel R 2003 Thin Solid Films 433 1

    [26]

    Sirringhaus H, Brown P J, Friend R H, Nielsen M M, Bechgaard K, Langeveld-Voss B M W, Spiering A J H, Janssen R A J, Meijer E W, Herwig P, de Leeuw D M 1999 Nature 401 685

    [27]

    Sundar V C, Zaumseil J, Podzorov V, Menard E, Willett R L, Someya T, Gershenson M E, Rogers J A 2004 Science 303 1644

    [28]

    Tian X Y, Zhao S L, Xu Z, Yao J F, Zhang J F, Jia Q J, Chen Y, Fan X, Gong W 2011 Acta Phys. Sin. 60 027201 (in Chinese) [田雪雁, 赵谡玲, 徐征, 姚江峰, 张福俊, 贾全杰, 陈雨, 樊星, 龚伟 2011 物理学报 60 027201]

    [29]

    Yamane H, Yabuuchi Y, Fukagawa H, Kera S, Okudaira K K, Ueno N 2006 J. Appl. Phys. 99 093705

    [30]

    Cao N T, Zhang L, Lv L, Xie H P, Huang H, Niu D M, Gao Y L 2014 Acta Phys. Sin. 63 167903 (in Chinese) [曹宁通, 张雷, 吕路, 谢海鹏, 黄寒, 牛冬梅, 高永立 2014 物理学报 63 167903]

    [31]

    Richardson N V, Campuzano J C 1981 Vacuum 31 449

    [32]

    Schoofs G R, Preston R E, Benziger J B 1985 Langmuir 1 313

    [33]

    Huang H, Chen W, Chen S, Qi D C, Gao X Y 2009 Appl. Phys. Lett. 94 163304

    [34]

    Huntley D R, Mullins D R, Wingeier M P 1996 J. Phys. Chem. 100 19620

    [35]

    Xie F Z, Hu H R, Hua M Q, Yan S R, Fan K N, Lei H, Tan D L, Bao X H, Zong B N, Zhang X X 2006 Chem. J. Chinese Universities 27 1729 (in Chinese) [谢福中, 胡华荣, 华明桥, 闫世润, 范康年, 雷浩, 谭大力, 包信和, 宗保宁, 张晓昕 2006 高等学校化学学报 27 1729]

    [36]

    Chen W, Huang H, Chen S, Chen L, Zhang H L, Gao X Y, Wee A T S 2007 Appl. Phys. Lett. 91 114102

    [37]

    Wang C G, Turinske A J, Gao Y L 2013 Appl. Phys. B 113 361

    [38]

    Le Q T, Forsythe E W, Nuesch F, Rothberg L J, Yan L, Gao Y L 2000 Thin Solid Films 363 42

    [39]

    Razafitrimo H, Ettedgui E, Guo L H, McLendon G L, Gao Y L 1995 Appl. Phys. Lett. 67 2621

  • [1]

    Shi F F 1996 J. Macro. Sci. C 36 795

    [2]

    Zhou Y S, Peng J, Wang E B, Zhang L J 1998 Transition Metal Chemistry 23 125

    [3]

    Klauk H, Zschieschang U, Pflaum J, Halik M 2007 Nature 445 745

    [4]

    Sanvito S 2011 Chem. Soc. Rev 40 3336

    [5]

    Someya T, Pal B, Huang J, Katz H E 2008 Mrs Bull. 33 690

    [6]

    Burroughes J H, Bradley D D C, Brown A R, Maeks R N, Mackay K, Friend R H, Burns P L, Holmes A B 1990 Nature 347 539

    [7]

    Tang C W, Vanslyke S A 1987 Appl. Phys. Lett. 51 913

    [8]

    Yang F, Shtein M, Forrest S R 2005 Nat. Mater. 4 37

    [9]

    Facchetti A 2007 Mater. Today 10 28

    [10]

    Gelinck G H, Huitema H E A, van Veenendaal E, Cantatore E, Schrijnemakers L, van der Putten J B P H, Geuns T C T, Beenhakkers M, Giesbers J B, Huisman B H, Meijer E J, Benito E M, Touwslager F J, Marsman A W, van Rens B J E, De Leeuw D M 2004 Nat. Mater. 3 106

    [11]

    Baude P F, Ender D A, Haase M A, Kelley T W, Muyres D V, Theiss S D 2003 Appl. Phys. Lett. 82 3964

    [12]

    Someya T, Kato Y, Sekitani T, Iba S, Noguchi Y, Murase Y, Kawaguchi H, Sakurai T 2005 PNAS 102 12321

    [13]

    Kuribara K, Wang H, Uchiyama N, Fukuda K, Yokota T, Zschieschang U, Jaye C, Fischer D, Klauk H, Yamamoto T, Takimiya K, Ikeda M, Kuwabara H, Sekitani T, Loo Y L, Someya T 2012 Nat. Commun. 3 723

    [14]

    Berggren M, Dahlfors A R 2007 Adv. Mater. 19 3201

    [15]

    Koezuka H, Tsumura A, Ando T 1987 Synthetic Metals 18 699

    [16]

    Takeya J, Yamagishi M, Tominari Y, Hirahara R, Nakazawa Y, Nishikawa T, Kawase T, Shimoda T, Ogawa S 2007 Appl. Phys. Lett. 90 102120

    [17]

    Yuan Y B, Giri G, Ayzner A L, Zoombelt A P, Mannsfeld S C B, Chen J H, Nordlund D, Toney M F, Huang J S, Bao Z N 2014 Nat. Commun. 5 3005

    [18]

    Sinha S, Wang C H, Mukherjee M, Yang Y W 2014 J. Phys. D 47 245103

    [19]

    Ding H J, Gao Y L 2008 Phys. Rev. B 78 075311

    [20]

    McCulloch L, Heeney M, Chabinyc M L, DeLongchamp D, Kline R J, Coelle M, Duffy W, Fischer D, Gundlach D, Hamadani B, Hamilton R, Richter L, Salleo A, Shkunov M, Sporrowe D, Tierney S, Zhong W 2009 Adv. Mater. 21 1091

    [21]

    Virkar A A, Mannsfeld S, Bao Z A, Stingelin N 2010 Adv. Mater. 22 3857

    [22]

    Chen W, Huang H, Chen S, Gao X Y, Wee A T S 2008 J. Phys. Chem. C 112 5036

    [23]

    Kobayashi H, Kobayashi N, Hosoi S, Koshitani N, Murakami D, Shirasawa R, Kudo Y, Hobara D, Tokita Y, Itabashi M 2013 J. Chem. Phys. 139 014707

    [24]

    Laquindanum J G, Katz H E, Lovinger A J, Dodabalapur A 1996 Chem. Mater. 8 2542

    [25]

    Resel R 2003 Thin Solid Films 433 1

    [26]

    Sirringhaus H, Brown P J, Friend R H, Nielsen M M, Bechgaard K, Langeveld-Voss B M W, Spiering A J H, Janssen R A J, Meijer E W, Herwig P, de Leeuw D M 1999 Nature 401 685

    [27]

    Sundar V C, Zaumseil J, Podzorov V, Menard E, Willett R L, Someya T, Gershenson M E, Rogers J A 2004 Science 303 1644

    [28]

    Tian X Y, Zhao S L, Xu Z, Yao J F, Zhang J F, Jia Q J, Chen Y, Fan X, Gong W 2011 Acta Phys. Sin. 60 027201 (in Chinese) [田雪雁, 赵谡玲, 徐征, 姚江峰, 张福俊, 贾全杰, 陈雨, 樊星, 龚伟 2011 物理学报 60 027201]

    [29]

    Yamane H, Yabuuchi Y, Fukagawa H, Kera S, Okudaira K K, Ueno N 2006 J. Appl. Phys. 99 093705

    [30]

    Cao N T, Zhang L, Lv L, Xie H P, Huang H, Niu D M, Gao Y L 2014 Acta Phys. Sin. 63 167903 (in Chinese) [曹宁通, 张雷, 吕路, 谢海鹏, 黄寒, 牛冬梅, 高永立 2014 物理学报 63 167903]

    [31]

    Richardson N V, Campuzano J C 1981 Vacuum 31 449

    [32]

    Schoofs G R, Preston R E, Benziger J B 1985 Langmuir 1 313

    [33]

    Huang H, Chen W, Chen S, Qi D C, Gao X Y 2009 Appl. Phys. Lett. 94 163304

    [34]

    Huntley D R, Mullins D R, Wingeier M P 1996 J. Phys. Chem. 100 19620

    [35]

    Xie F Z, Hu H R, Hua M Q, Yan S R, Fan K N, Lei H, Tan D L, Bao X H, Zong B N, Zhang X X 2006 Chem. J. Chinese Universities 27 1729 (in Chinese) [谢福中, 胡华荣, 华明桥, 闫世润, 范康年, 雷浩, 谭大力, 包信和, 宗保宁, 张晓昕 2006 高等学校化学学报 27 1729]

    [36]

    Chen W, Huang H, Chen S, Chen L, Zhang H L, Gao X Y, Wee A T S 2007 Appl. Phys. Lett. 91 114102

    [37]

    Wang C G, Turinske A J, Gao Y L 2013 Appl. Phys. B 113 361

    [38]

    Le Q T, Forsythe E W, Nuesch F, Rothberg L J, Yan L, Gao Y L 2000 Thin Solid Films 363 42

    [39]

    Razafitrimo H, Ettedgui E, Guo L H, McLendon G L, Gao Y L 1995 Appl. Phys. Lett. 67 2621

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  • Received Date:  22 October 2015
  • Accepted Date:  02 December 2015
  • Published Online:  05 February 2016

Thickness-dependent electronic structure of the interface of 2,7-dioctyl[1]benzothieno[3,2-b][1] benzothiophene/Ni(100)

    Corresponding author: Niu Dong-Mei, mayee@csu.edu.cn
  • 1. Institute of Super-Microstructure and Ultrafast Process in Advanced Materials, Central South University, Changsha 410083, China;
  • 2. Department of Physics and Astronomy, University of Rochester, Rochester 14627, USA
Fund Project:  Project supported by the National Natural Science Foundation of China (Grant Nos. 51173205, 11334014) and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry.

Abstract: Combining ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy and atomic force microscopy (AFM), we perform a systematic investigation on the correlation of energy level alignment, film growth and molecular orientation of 2, 7-dioctyl[1]benzothieno-[3, 2-b][1]benzothiophene (C8-BTBT) on Ni(100). The molecules lie down at the first layer and are partly devulcanized by the substrate. Chemical adsorption of reaction products of sulfur atoms on the Ni substrate and the evaporation of the hydrocarbon products into vacuum make the C/S ratio as low as 11.5 : 1 in the XPS of the initially deposited C8-BTBT film of 1-4 thickness, far less than the stoichiometric of 15 : 1. With the thickness increasing from 4 to 8 , there are sharp downward shifts of Evac, HOMO and core levels of C 1s, S 2p, and a sharp increase of C/S ratio, which can be ascribed to the change of molecular orientations from lying down at 4 to standing up at 8 . From 8 onward, the C/S ratio increases steadily till it reaches 15 : 1. The energy levels show relatively less changes when the thickness increases from 8 to 32 . When the thickness increases over 32 , the energy band starts bending downward apparently because of the charging effect during the photoelectron emission processes. The poor conductivity along the standing alkyl chain of C8-is the main cause for the charging. The standing up configurations of the C8-BTBT molecules are confirmed by the AFM investigation in which the heights of the upper layers of C8-BTBT are around 30 , close to the length of the long c-axis. AFM image also indicates that the molecules tend to grow into islands for larger thickness, which is consistent with the slower decrease of the (I/I0) of Ni 2p3/2 with the C8-BTBT film thickness. Our results suggest that a buffer layer be inserted between Ni and C8-BTBT and the thickness of the C8-BTBT film be controlled as thin as possible in related devices.

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