新穎二維層狀材料被期待在未來能夠突破摩爾定律的限制與障礙，其中之一的過渡金屬二硫族化物(Transition-metal dichalcogenides, TMDCs)不但能在大氣下穩定存在，且具有合適的能隙大小，其擁有多元豐富的物理、化學特性都讓TMDCs在未來電子、光電元件等各方面的應用都極具發展潛力；因此本論文選用在TMDCs家族中具有穩定半導體特性的二硒化鎢(WSe2}和二硫化鎢(WS2)作為研究的主角，我們利用不鏽鋼遮罩熱蒸鍍形成圖紋化金屬氧化物後，再經過化學氣相沉積成長的方式，成功在氧化鋁基板上製備出我們想要的圖紋化WSe2和WS2及其垂直異質接面結構，並利用拉曼光譜、光致螢光光譜、X射線光電子能譜、穿透式電子顯微鏡來對我們所製備的材料進行品質檢測和分析，從檢測結果中，我們確定我們能利用上述方法得到高品質的圖紋化WSe2、WS2以及其異質接面結構，接下來我們分別將其成功製作成頂閘極場效電晶體與WSe2/WS2垂直異質接面p-n二極體，並在常溫常壓下對我們的WSe2和WS2場效電晶體進行電性量測，其分別展現出一p型和一n型的傳輸特性，其電流開關比也分別為水準之上的10^5和10^4，另外在WSe2/WS2垂直異質接面p-n二極體部分，其除了展現出傳統p-n二極體該有的整流特性外，還具有一定程度的光電特性與穩定的光反應性，更能利用外加閘極電場來增進其效能；本論文的研究成果可為後世想將TMDCs整合成各式數位邏輯元件與在光電元件上的應用發展跨出了良好的第一步。

Novel two-dimensional layered materials are expected to break through the limits and obstacles of Moore's law in the future, one of the transition-metal dichalcogenides (TMDCs) are not only stable in the atmosphere, but also have suitable bandgap size, TMDCs in the future of electronics, optoelectronics and other aspects of the application have great potential for development because they have wealth of rich physical and chemical properties. Therefore, we used WSe2 and WS2 with stable semiconductor properties in TMDCs family as the main characters of our study, we used a hollowed-pattern stainless steel hard mask to cover on our substrate for forming patterning metal oxide by thermal evaporation process, successfully we can get the patterning WSe2 and WS2 and their vertical heterojunction structure that we wanted on the sapphires by chemical vapor deposition chalcogenization growth process, and used Raman spectra, photoluminescence spectra, X-ray photoelectron spectroscopy, transmission electron microscopy to check quality and analysis of the materials we prepared, from our analyzed results, we confirmed that we can use the above method to get high-quality patterning WSe2, WS2 and their vertical heterojunction structure, then we successfully produced them as the top gate field-effect transistors and WSe2/WS2 vertical heterojunction p-n diodes. And then, we got the electrical information for the WSe2 and WS2 field-effect transistors by electrical measurement in the ambient environment, they showed a p-type and an n-type transport characteristics and their current on/off ratio were 10^5 and 10^4 above the average respectively. In addition, in the WSe2/WS2 vertical heterojunction p-n diodes part, which in addition to exhibiting the rectifying characteristics like as traditional p-n diode, but also had a certain degree of photoelectric properties and stable photoreactivity, more use of external gate electric field to improve its performances. Finally, our research results of this thesis can be used for future generations to integrate TMDCs into various types of digital logic elements and applications on optoelectronics.

Abstract.................................................................................................................. I
論文摘要............................................................................................................. III
致謝...................................................................................................................... V
目錄..................................................................................................................... XI
第一章 緒論.......................................................................................................... 1
1.1 半導體科技演進與目前發展瓶頸. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2二維材料簡介. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.1 石墨烯. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.2 過渡金屬二硫族化物. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2.3 其他二維層狀材料. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.3 研究動機與目標. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
第二章 過渡金屬二硫族化物............................................................................ 19
2.1 二硒化鎢基本介紹. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1.1 二硒化鎢晶體結構. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1.2 二硒化鎢電子能帶. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.1.3 二硒化鎢聲子能帶. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.1.4 二硒化鎢之電子元件與其他應用. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2 二硫化鎢基本介紹. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.2.1 二硫化鎢晶體結構. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.2.2 二硫化鎢電子能帶. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.2.3 二硫化鎢聲子能帶. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.2.4 二硫化鎢之電子元件與其他應用. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.3 二硒化鎢與二硫化鎢之異質接面. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
第三章 檢測材料的工具.................................................................................... 45
3.1 拉曼光譜. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.2 光致螢光光譜. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.3 X射線光電子能譜. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.4 穿透式電子顯微鏡. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
第四章 材料檢測和分析.................................................................................... 53
4.1 圖紋化二硒化鎢與二硫化鎢及其異質接面的製備. . . . . . . . . . . . . . . . . . 53
4.2 圖紋化二硒化鎢與二硫化鎢之光學檢測分析. . . . . . . . . . . . . . . . . . . . . . 54
4.2.1 拉曼光譜. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.2.2 光致螢光光譜. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.3 圖紋化二硒化鎢與二硫化鎢之X射線光電子能譜分析. . . . . . . . . . . . . . 59
4.4 圖紋化二硒化鎢與二硫化鎢之掃描式穿透電子顯微鏡分析 . . . . . . . . . 60
4.5 二硒化鎢與二硫化鎢之異質接面材料檢測分析. . . . . . . . . . . . . . . . . . . . 62
第五章 元件製程與應用.................................................................................... 65
5.1 二硒化鎢與二硫化鎢場效電晶體. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.1.1 電子束微影技術. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.1.2 反應式離子蝕刻. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.1.3 金屬熱蒸鍍. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.1.4 頂閘極場效電晶體製作流程 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
5.2 異質接面p-n二極體 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
第六章 量測方法與結果分析............................................................................ 77
6.1 電晶體量測方法與量測系統. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
6.2 元件電性量測結果分析. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.2.1 場效電晶體. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.2.2 異質接面p-n二極體. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
第七章 結論與未來展望.................................................................................... 85
附錄..................................................................................................................... 87
參考文獻............................................................................................................. 91

[1] F. Braun, “Uber die stromleitung durch schwefelmetalle,” Ann. Phys. Chem.,
vol. 153, p. 556, 1874.
[2] J. Bardeen and W. H. Brattain, “The transistor, a semi-conductor triode,” Phys.
Rev., vol. 74, no. 2, pp. 230–231, 1948.
[3] D. Kahng and M. M. Atalla, “Silicon-silicon dioxide surface device,” in IRE Device Research Conference, (Pittsburgh), 1960.
[4] S. M. SZE and M. K. LEE, Semiconductor Devices Physics and Technology. John Wiley and Sons, INC., 3 ed., 2013.
[5] F. M. Wanlass and C. T. Sah, “Nanowatt logics using field-effect metal-oxide
semiconductor triodes,” Tech. Dig. IEEE Int. Solid-State Circuit Conf., p. 32, 1963.
[6] “The first integrated IC,” http://ds-wordpress.haverford.edu/bitbybit/bit-by-bitcontents/ chapter-eight/8-5-kilbys-integrated-circuit/.
[7] “The first silicon integrated circuit chip,” http://www.computerhistory.org/timeline/? category=cmpnt.
[8] “International technology roadmap for semiconductors (ITRS, 2012),” http://
electroiq.com/blog/2013/page/41/.
[9] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, and A. A. Firsov, “Electric field effect in atomically thin carbon films,” Science, vol. 306, no. 5696, pp. 666–669, 2004.
[10] K. I. Bolotin, K. J. Sikes, Z. Jiang, M. Klima, G. Fudenberg, J. Hone, P. Kim, and H. L. Stormer, “Ultrahigh electron mobility in suspended graphene,” Solid State Commun., vol. 146, no. 9, pp. 351–355, 2008.
[11] R. Murali, Y. X. Yang, K. Brenner, T. Beck, and J. D. Meindl, “Breakdown current density of graphene nanoribbons,” Appl. Phys. Lett., vol. 94, no. 24, p. 243114, 2009.
[12] T. Palacios, A. Hsu, and H. Wang, “Applications of graphene devices in RF communications,” IEEE Commun. Mag., vol. 48, no. 6, pp. 122–128, 2010.
[13] C. Lee, X. D. Wei, J. W. Kysar, and J. Hone, “Measurement of the elastic properties and intrinsic strength of monolayer graphene,” Science, vol. 321, no. 5887, pp. 385–388, 2008.
[14] R. R. Nair, P. Blake, A. N. Grigorenko, K. S. Novoselov, T. J. Booth, T. Stauber, N. M. R. Peres, and A. K. Geim, “Fine structure constant defines visual transparency of graphene,” Science, vol. 320, no. 5881, pp. 1308–1308, 2008.
[15] M. D. Stoller, S. Park, Y. Zhu, J. An, and R. S. Ruoff, “Graphene-based ultracapacitors,” Nano Lett., vol. 8, no. 10, pp. 3498–3502, 2008.
[16] K. S. Novoselov, V. I. Falko, L. Colombo, P. R. Gellert, M. G. Schwab, and
K. Kim, “A roadmap for graphene,” Nature, vol. 490, no. 7419, pp. 192–200, 2012.
[17] “Graphene structure,” http:// www.dignited.com/ 11593/ natural-resources-vstechnology/.
[18] A. H. Castro Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov, and A. K. Geim, “The electronic properties of graphene,” Rev. Mod. Phys., vol. 81, no. 1, pp. 109– 162, 2009.
[19] Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of
structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B: Condensed Matter, vol. 406, no. 11, pp. 2254 – 2260, 2011.
[20] M. Chhowalla, H. S. Shin, G. Eda, L.-J. Li, K. P. Loh, and H. Zhang, “The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets,”
Nat. Chem., vol. 5, no. 4, pp. 263–275, 2013.
[21] Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman, and M. S. Strano, “Electronics and optoelectronics of two-dimensional transition metal dichalcogenides,” Nat. Nanotechnol., vol. 7, no. 11, pp. 699–712, 2012.
[22] L. Mattheiss, “Energy bands for 2H-NbSe2 and 2H-MoS2,” Phys. Rev. Lett.,
vol. 30, no. 17, p. 784, 1973.
[23] X. Zhao, T. Wang, G. Wang, X. Dai, C. Xia, and L. Yang, “Electronic and magnetic properties of 1T-HfS2 by doping transition-metal atoms,” Appl. Surf. Sci., vol. 383, pp. 151–158, 2016.
[24] D. Jariwala, V. K. Sangwan, L. J. Lauhon, T. J. Marks, and M. C. Hersam,
“Emerging device applications for semiconducting two-dimensional transition
metal dichalcogenides,” ACS Nano, vol. 8, no. 2, pp. 1102–1120, 2014.
[25] Y. Wang, L. Li, W. Yao, S. Song, J. T. Sun, J. Pan, X. Ren, C. Li, E. Okunishi, Y.- Q. Wang, E. Wang, Y. Shao, Y. Y. Zhang, H.-t. Yang, E. F. Schwier, H. Iwasawa, K. Shimada, M. Taniguchi, Z. Cheng, S. Zhou, S. Du, S. J. Pennycook, S. T. Pantelides, and H.-J. Gao, “Monolayer PtSe2, a new semiconducting transitionmetal- dichalcogenide, epitaxially grown by direct selenization of Pt,” Nano Lett., vol. 15, no. 6, pp. 4013–4018, 2015.
[26] J. Wilson and A. Yoffe, “The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties,” Advances in Physics, vol. 18, no. 73, pp. 193–335, 1969.
[27] A. Kuc, N. Zibouche, and T. Heine, “Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2,” Phys. Rev. B, vol. 83,
no. 24, p. 245213, 2011.
[28] A. Klein, S. Tiefenbacher, V. Eyert, C. Pettenkofer, and W. Jaegermann, “Electronic band structure of single-crystal and single-layer WS2 : Influence of interlayer van der Waals interactions,” Phys. Rev. B, vol. 64, no. 20, p. 205416, 2001.
[29] S. Balendhran, S. Walia, H. Nili, S. Sriram, and M. Bhaskaran, “Graphene analogues: Elemental analogues of graphene: Silicene, germanene, stanene, and
phosphorene,” Small, vol. 11, no. 6, pp. 640–652, 2015.
[30] X. Zhang, H. Xie, M. Hu, H. Bao, S. Yue, G. Qin, and G. Su, “Thermal conductivity of silicene calculated using an optimized Stillinger-Weber potential,” Phys. Rev. B, vol. 89, no. 5, p. 054310, 2014.
[31] H. Liu, A. T. Neal, Z. Zhu, Z. Luo, X. Xu, D. Tománek, and P. D. Ye, “Phosphorene: An unexplored 2D semiconductor with a high hole mobility,” ACS Nano, vol. 8, no. 4, pp. 4033–4041, 2014.
[32] S. Das, W. Zhang, M. Demarteau, A. Hoffmann, M. Dubey, and A. Roelofs, “Tunable transport gap in phosphorene,” Nano Lett., vol. 14, no. 10, pp. 5733–5739, 2014.
[33] X. Peng, Q. Wei, and A. Copple, “Strain-engineered direct-indirect band gap transition and its mechanism in two-dimensional phosphorene,” Phys. Rev. B, vol. 90, no. 8, p. 085402, 2014.
[34] L. Li, Y. Yu, G. J. Ye, Q. Ge, X. Ou, H. Wu, D. Feng, X. H. Chen, and Y. Zhang, “Black phosphorus field-effect transistors,” Nat. Nanotechnol., vol. 9, no. 5, pp. 372–377, 2014.
[35] Y. Y. Illarionov, M. Waltl, G. Rzepa, J.-S. Kim, S. Kim, A. Dodabalapur, D. Akinwande, and T. Grasser, “Long-term stability and reliability of black phosphorus field-effect transistors,” ACS Nano, vol. 10, no. 10, pp. 9543–9549, 2016.
[36] W. Huang, L. Gan, H. Li, Y. Ma, and T. Zhai, “2D layered group IIIA metal
chalcogenides: synthesis, properties and applications in electronics and optoelectronics,” CrystEngComm, vol. 18, no. 22, pp. 3968–3984, 2016.
[37] R. Addou and R. M. Wallace, “Surface analysis of WSe2 crystals: Spatial and
electronic variability,” ACS Applied Materials & Interfaces, vol. 8, no. 39, pp. 26400–26406, 2016.
[38] C. Ataca, H. Sahin, and S. Ciraci, “Stable, single-layer MX2 transition-metal oxides and dichalcogenides in a honeycomb-like structure,” The Journal of Physical Chemistry C, vol. 116, no. 16, pp. 8983–8999, 2012.
[39] “WSe2 crystal structure,” https:// en.wikipedia.org/ wiki/ Transition _metal_dichalcogenide_monolayers.
[40] H. Sahin, S. Tongay, S. Horzum, W. Fan, J. Zhou, J. Li, J. Wu, and F. M.
Peeters, “Anomalous Raman spectra and thickness-dependent electronic properties
of WSe2,” Phys. Rev. B, vol. 87, no. 16, p. 165409, 2013.
[41] G.-B. Liu, D. Xiao, Y. Yao, X. Xu, and W. Yao, “Electronic structures and theoretical modelling of two-dimensional group-VIB transition metal dichalcogenides,” Chem. Soc. Rev., vol. 44, no. 9, pp. 2643–2663, 2015.
[42] P.-C. Yeh, W. Jin, N. Zaki, D. Zhang, J. T. Liou, J. T. Sadowski, A. Al-Mahboob, J. I. Dadap, I. P. Herman, P. Sutter, and R. M. Osgood, “Layer-dependent electronic structure of an atomically heavy two-dimensional dichalcogenide,” Phys. Rev. B, vol. 91, no. 4, p. 041407, 2015.
[43] H. Liu, N. Han, and J. Zhao, “Atomistic insight into the oxidation of monolayer transition metal dichalcogenides: from structures to electronic properties,” RSC Adv., vol. 5, no. 23, pp. 17572–17581, 2015.
[44] W. S. Yun, S. W. Han, S. C. Hong, I. G. Kim, and J. D. Lee, “Thickness and
strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te),” Phys. Rev. B, vol. 85, no. 3, p. 033305, 2012.
[45] X. Zhang, X.-F. Qiao, W. Shi, J.-B. Wu, D.-S. Jiang, and P.-H. Tan, “Phonon
and Raman scattering of two-dimensional transition metal dichalcogenides from
monolayer, multilayer to bulk material,” Chem. Soc. Rev., vol. 44, no. 9, pp. 2757–
2785, 2015.
[46] V. Podzorov, M. E. Gershenson, C. Kloc, R. Zeis, and E. Bucher, “High-mobility field-effect transistors based on transition metal dichalcogenides,” Appl. Phys. Lett., vol. 84, no. 17, pp. 3301–3303, 2004.
[47] H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “Highperformance single layered WSe2 p-FETs with chemically doped contacts,” Nano Lett., vol. 12, no. 7, pp. 3788–3792, 2012.
[48] H. Fang, M. Tosun, G. Seol, T. C. Chang, K. Takei, J. Guo, and A. Javey, “Degenerate n-doping of few-layer transition metal dichalcogenides by potassium,” Nano Lett., vol. 13, no. 5, pp. 1991–1995, 2013.
[49] H. C. P. Movva, A. Rai, S. Kang, K. Kim, B. Fallahazad, T. Taniguchi, K. Watanabe, E. Tutuc, and S. K. Banerjee, “High-mobility holes in dual-gated WSe2 field-effect transistors,” ACS Nano, vol. 9, no. 10, pp. 10402–10410, 2015.
[50] M. Tosun, S. Chuang, H. Fang, A. B. Sachid, M. Hettick, Y. Lin, Y. Zeng, and
A. Javey, “High-gain inverters based on WSe2 complementary field-effect transistors,” ACS Nano, vol. 8, no. 5, pp. 4948–4953, 2014.
[51] S. Das, M. Dubey, and A. Roelofs, “High gain, low noise, fully complementary logic inverter based on bi-layer WSe2 field effect transistors,” Appl. Phys. Lett., vol. 105, no. 8, p. 083511, 2014.
[52] L. Yu, A. Zubair, E. J. G. Santos, X. Zhang, Y. Lin, Y. Zhang, and T. Palacios,
“High-performance WSe2 complementary metal oxide semiconductor technology
and integrated circuits,” Nano Lett., vol. 15, no. 8, pp. 4928–4934, 2015.
[53] A.-J. Cho, K. C. Park, and J.-Y. Kwon, “A high-performance complementary
inverter based on transition metal dichalcogenide field-effect transistors,” Nanoscale Research Letters, vol. 10, p. 115, 2015.
[54] P. J. Jeon, J. S. Kim, J. Y. Lim, Y. Cho, A. Pezeshki, H. S. Lee, S. Yu, S.-W. Min, and S. Im, “Low power consumption complementary inverters with n-MoS2 and p-WSe2 dichalcogenide nanosheets on glass for logic and light-emitting diode
circuits,” ACS Applied Materials & Interfaces, vol. 7, no. 40, pp. 22333–22340,
2015.
[55] H. Du, X. Lin, Z. Xu, and D. Chu, “Electric double-layer transistors: a review of recent progress,” J. Mater. Sci., vol. 50, no. 17, pp. 5641–5673, 2015.
[56] J.-K. Huang, J. Pu, C.-L. Hsu, M.-H. Chiu, Z.-Y. Juang, Y.-H. Chang, W.-H.
Chang, Y. Iwasa, T. Takenobu, and L.-J. Li, “Large-area synthesis of highly
crystalline WSe2 monolayers and device applications,” ACS Nano, vol. 8, no. 1,
pp. 923–930, 2014.
[57] A. Allain and A. Kis, “Electron and hole mobilities in single-layer WSe2,” ACS Nano, vol. 8, no. 7, pp. 7180–7185, 2014.
[58] H.-J. Chuang, X. Tan, N. J. Ghimire, M. M. Perera, B. Chamlagain, M. M.-C.
Cheng, J. Yan, D. Mandrus, D. Tománek, and Z. Zhou, “High mobility WSe2 p-and n-type field-effect transistors contacted by highly doped graphene for low-resistance contacts,” Nano Lett., vol. 14, no. 6, pp. 3594–3601, 2014.
[59] J. S. Ross, P. Klement, A. M. Jones, N. J. Ghimire, J. Yan, D. G. Mandrus,
T. Taniguchi, K. Watanabe, K. Kitamura, W. Yao, D. H. Cobden, and X. Xu,
“Electrically tunable excitonic light-emitting diodes based on monolayer WSe2
p-n junctions,” Nat. Nanotechnol., vol. 9, no. 4, pp. 268–272, 2014.
[60] A. Pospischil, M. M. Furchi, and T. Mueller, “Solar-energy conversion and light emission in an atomic monolayer p-n diode,” Nat. Nanotechnol., vol. 9, no. 4,
pp. 257–261, 2014.
[61] B. W. H. Baugher, H. O. H. Churchill, Y. Yang, and P. Jarillo-Herrero, “Optoelectronic devices based on electrically tunable p-n diodes in a monolayer dichalcogenide,” Nat. Nanotechnol., vol. 9, no. 4, pp. 262–267, 2014.
[62] W. Zhang, M.-H. Chiu, C.-H. Chen, W. Chen, L.-J. Li, and A. T. S. Wee, “Role of metal contacts in high-performance phototransistors based on WSe2 monolayers,” ACS Nano, vol. 8, no. 8, pp. 8653–8661, 2014.
[63] S. Das, R. Gulotty, A. V. Sumant, and A. Roelofs, “All two-dimensional, flexible, transparent, and thinnest thin film transistor,” Nano Lett., vol. 14, no. 5, pp. 2861– 2866, 2014.
[64] S. B. Desai, G. Seol, J. S. Kang, H. Fang, C. Battaglia, R. Kapadia, J. W. Ager, J. Guo, and A. Javey, “Strain-induced indirect to direct bandgap transition in multilayer WSe2,” Nano Lett., vol. 14, no. 8, pp. 4592–4597, 2014.
[65] B. Cho, A. R. Kim, D. J. Kim, H.-S. Chung, S. Y. Choi, J.-D. Kwon, S. W.
Park, Y. Kim, B. H. Lee, K. H. Lee, D.-H. Kim, J. Nam, and M. G. Hahm,
“Two-dimensional atomic-layered alloy junctions for high-performance wearable
chemical sensor,” ACS Applied Materials & Interfaces, vol. 8, no. 30, pp. 19635–
19642, 2016.
[66] H. R. Gutiérrez, N. Perea-López, A. L. Elías, A. Berkdemir, B. Wang, R. Lv,
F. López-Urías, V. H. Crespi, H. Terrones, and M. Terrones, “Extraordinary room-temperature photoluminescence in triangular WS2 monolayers,” Nano Lett., vol. 13, no. 8, pp. 3447–3454, 2013.
[67] A. L. Elías, N. Perea-López, A. Castro-Beltrán, A. Berkdemir, R. Lv, S. Feng,
A. D. Long, T. Hayashi, Y. A. Kim, M. Endo, H. R. Gutiérrez, N. R. Pradhan,
L. Balicas, T. E. Mallouk, F. López-Urías, H. Terrones, and M. Terrones, “Controlled synthesis and transfer of large-area WS2 sheets: From single layer to few layers,” ACS Nano, vol. 7, no. 6, pp. 5235–5242, 2013.
[68] W. Zhao, Z. Ghorannevis, L. Chu, M. Toh, C. Kloc, P.-H. Tan, and G. Eda, “Evolution of electronic structure in atomically thin sheets of WS2 and WSe2,” ACS Nano, vol. 7, no. 1, pp. 791–797, 2013.
[69] H. Yuan, Z. Liu, G. Xu, B. Zhou, S. Wu, D. Dumcenco, K. Yan, Y. Zhang, S.-
K. Mo, P. Dudin, V. Kandyba, M. Yablonskikh, A. Barinov, Z. Shen, S. Zhang,
Y. Huang, X. Xu, Z. Hussain, H. Y. Hwang, Y. Cui, and Y. Chen, “Evolution of the
valley position in bulk transition-metal chalcogenides and their monolayer limit,”
Nano Lett., vol. 16, no. 8, pp. 4738–4745, 2016.
[70] A. Molina-Sánchez and L. Wirtz, “Phonons in single-layer and few-layer MoS2 and WS2,” Phys. Rev. B, vol. 84, no. 15, p. 155413, 2011.
[71] W. S. Hwang, M. Remskar, R. Yan, V. Protasenko, K. Tahy, S. D. Chae, P. Zhao, A. Konar, H. G. Xing, A. Seabaugh, and D. Jena, “Transistors with chemically synthesized layered semiconductor WS2 exhibiting 105 room temperature modulation and ambipolar behavior,” Appl. Phys. Lett., vol. 101, no. 1, p. 013107, 2012.
[72] X. Liu, J. Hu, C. Yue, N. Della Fera, Y. Ling, Z. Mao, and J. Wei, “High performance field-effect transistor based on multilayer tungsten disulfide,” ACS Nano, vol. 8, no. 10, pp. 10396–10402, 2014.
[73] M. W. Iqbal, M. Z. Iqbal, M. F. Khan, M. A. Shehzad, Y. Seo, J. H. Park,
C. Hwang, and J. Eom, “High-mobility and air-stable single-layer WS2 field-effect
transistors sandwiched between chemical vapor deposition-grown hexagonal
BN films,” Scientific Reports, vol. 5, p. 10699, 2015.
[74] L. Yang, K. Majumdar, H. Liu, Y. Du, H. Wu, M. Hatzistergos, P. Y. Hung,
R. Tieckelmann, W. Tsai, C. Hobbs, and P. D. Ye, “Chloride molecular doping
technique on 2D materials: WS2 and MoS2,” Nano Lett., vol. 14, no. 11, pp. 6275– 6280, 2014.
[75] H. M. W. Khalil, M. F. Khan, J. Eom, and H. Noh, “Highly stable and tunable
chemical doping of multilayer WS2 field effect transistor: Reduction in contact
resistance,” ACS Applied Materials & Interfaces, vol. 7, no. 42, pp. 23589–23596,
2015.
[76] M. W. Iqbal, M. Z. Iqbal, M. F. Khan, M. A. Kamran, A. Majid, T. Alharbi, and J. Eom, “Tailoring the electrical and photo-electrical properties of a WS2 field
effect transistor by selective n-type chemical doping,” RSC Adv., vol. 6, no. 29,
pp. 24675–24682, 2016.
[77] D. Braga, I. Gutiérrez Lezama, H. Berger, and A. F. Morpurgo, “Quantitative determination of the band gap of WS2 with ambipolar ionic liquid-gated transistors,” Nano Lett., vol. 12, no. 10, pp. 5218–5223, 2012.
[78] N. Ubrig, S. Jo, H. Berger, A. F. Morpurgo, and A. B. Kuzmenko, “Scanning
photocurrent microscopy reveals electron-hole asymmetry in ionic liquid-gated
WS2 transistors,” Appl. Phys. Lett., vol. 104, no. 17, p. 171112, 2014.
[79] S. Jo, N. Ubrig, H. Berger, A. B. Kuzmenko, and A. F. Morpurgo, “Mono- and
bilayer WS2 light-emitting transistors,” Nano Lett., vol. 14, no. 4, pp. 2019–2025,
2014.
[80] N. Perea-López, A. L. Elías, A. Berkdemir, A. Castro-Beltran, H. R. Gutiérrez, S. Feng, R. Lv, T. Hayashi, F. López-Urías, S. Ghosh, B. Muchharla, S. Talapatra, H. Terrones, and M. Terrones, “Photosensor device based on few-layered WS2 films,” Adv. Funct. Mater., vol. 23, no. 44, pp. 5511–5517, 2013.
[81] S. H. Lee, D. Lee, W. S. Hwang, E. Hwang, D. Jena, and W. J. Yoo, “High-performance photocurrent generation from two-dimensional WS2 field-effect
transistors,” Appl. Phys. Lett., vol. 104, no. 19, p. 193113, 2014.
[82] H. Tan, Y. Fan, Y. Zhou, Q. Chen, W. Xu, and J. H. Warner, “Ultrathin 2D photodetectors utilizing chemical vapor deposition grown WS2 with graphene electrodes,” ACS Nano, vol. 10, no. 8, pp. 7866–7873, 2016.
[83] Y. Gong, V. Carozo, H. Li, M. Terrones, and T. N. Jackson, “High flex cycle
testing of CVD monolayer WS2 TFTs on thin flexible polyimide,” 2D Materials,
vol. 3, no. 2, p. 021008, 2016.
[84] Y. Wang, C. Cong, W. Yang, J. Shang, N. Peimyoo, Y. Chen, J. Kang, J. Wang, W. Huang, and T. Yu, “Strain-induced direct–indirect bandgap transition and phonon modulation in monolayer WS2,” Nano Research, vol. 8, no. 8, pp. 2562– 2572, 2015.
[85] W. Fang, A. K. Ian, W. Daniel, T. Reshef, Z. Alla, O. Eoghan, B. Ursel, and
J. Y. Robert, “Strain-induced phonon shifts in tungsten disulfide nanoplatelets
and nanotubes,” 2D Materials, vol. 4, no. 1, p. 015007, 2016.
[86] X. He, H. Li, Z. Zhu, Z. Dai, Y. Yang, P. Yang, Q. Zhang, P. Li, U. Schwingenschlogl, and X. Zhang, “Strain engineering in monolayer WS2, MoS2, and the WS2/MoS2 heterostructure,” Appl. Phys. Lett., vol. 109, no. 17, p. 173105, 2016.
[87] N. Huo, S. Yang, Z. Wei, S.-S. Li, J.-B. Xia, and J. Li, “Photoresponsive and gas sensing field-effect transistors based on multilayer WS2 nanoflakes,” Scientific
Reports, vol. 4, p. 5209, 2014.
[88] K. Y. Ko, J.-G. Song, Y. Kim, T. Choi, S. Shin, C. W. Lee, K. Lee, J. Koo, H. Lee, J. Kim, T. Lee, J. Park, and H. Kim, “Improvement of gas-sensing performance of large-area tungsten disulfide nanosheets by surface functionalization,” ACS Nano, vol. 10, no. 10, pp. 9287–9296, 2016.
[89] Y. Xue, Y. Zhang, Y. Liu, H. Liu, J. Song, J. Sophia, J. Liu, Z. Xu, Q. Xu,
Z. Wang, J. Zheng, Y. Liu, S. Li, and Q. Bao, “Scalable production of a few-layer
MoS2/WS2 vertical heterojunction array and its application for photodetectors,”
ACS Nano, vol. 10, no. 1, pp. 573–580, 2016.
[90] N. Huo, J. Kang, Z. Wei, S.-S. Li, J. Li, and S.-H. Wei, “Novel and enhanced optoelectronic performances of multilayer MoS2-WS2 heterostructure transistors,”
Adv. Funct. Mater., vol. 24, no. 44, pp. 7025–7031, 2014.
[91] X. Hong, J. Kim, S.-F. Shi, Y. Zhang, C. Jin, Y. Sun, S. Tongay, J. Wu, Y. Zhang, and F. Wang, “Ultrafast charge transfer in atomically thin MoS2/WS2 heterostructures,” Nat. Nanotechnol., vol. 9, no. 9, pp. 682–686, 2014.
[92] Y. Gong, J. Lin, X. Wang, G. Shi, S. Lei, Z. Lin, X. Zou, G. Ye, R. Vajtai,
B. I. Yakobson, H. Terrones, M. Terrones, B. Tay, J. Lou, S. T. Pantelides,
Z. Liu, W. Zhou, and P. M. Ajayan, “Vertical and in-plane heterostructures from
WS2/MoS2 monolayers,” Nat. Mater., vol. 13, no. 12, pp. 1135–1142, 2014.
[93] J. H. Yu, H. R. Lee, S. S. Hong, D. Kong, H.-W. Lee, H. Wang, F. Xiong, S. Wang, and Y. Cui, “Vertical heterostructure of two-dimensional MoS2 and WSe2 with vertically aligned layers,” Nano Lett., vol. 15, no. 2, pp. 1031–1035, 2015.
[94] R. Cheng, D. Li, H. Zhou, C. Wang, A. Yin, S. Jiang, Y. Liu, Y. Chen, Y. Huang, and X. Duan, “Electroluminescence and photocurrent generation from atomically sharp WSe2/MoS2 heterojunction p-n diodes,” Nano Lett., vol. 14, no. 10, pp. 5590–5597, 2014.
[95] A. Nourbakhsh, A. Zubair, M. S. Dresselhaus, and T. Palacios, “Transport properties of a MoS2/WSe2 heterojunction transistor and its potential for application,” Nano Lett., vol. 16, no. 2, pp. 1359–1366, 2016.
[96] X. Duan, C. Wang, J. C. Shaw, R. Cheng, Y. Chen, H. Li, X. Wu, Y. Tang,
Q. Zhang, A. Pan, J. Jiang, R. Yu, Y. Huang, and X. Duan, “Lateral epitaxial
growth of two-dimensional layered semiconductor heterojunctions,” Nat. Nanotechnol., vol. 9, no. 12, pp. 1024–1030, 2014.
[97] N. Huo, J. Yang, L. Huang, Z. Wei, S.-S. Li, S.-H. Wei, and J. Li, “Tunable polarity behavior and self-driven photoswitching in p-WSe2/n-WS2 heterojunctions,” Small, vol. 11, no. 40, pp. 5430–5438, 2015.
[98] J. Chen, W. Zhou, W. Tang, B. Tian, X. Zhao, H. Xu, Y. Liu, D. Geng, S. J. R. Tan, W. Fu, and K. P. Loh, “Lateral epitaxy of atomically sharp WSe2/WS2 heterojunctions on silicon dioxide substrates,” Chem. Mater., vol. 28, no. 20, pp. 7194–7197, 2016.
[99] H. Li, P. Li, J.-K. Huang, M.-Y. Li, C.-W. Yang, Y. Shi, X.-X. Zhang, and L.-J. Li, “Laterally stitched heterostructures of transition metal dichalcogenide: Chemical vapor deposition growth on lithographically patterned area,” ACS Nano, vol. 10, no. 11, pp. 10516–10523, 2016.
[100] X. Luo, Y. Zhao, J. Zhang, M. Toh, C. Kloc, Q. Xiong, and S. Y. Quek, “Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2,” Phys. Rev. B, vol. 88, no. 19, p. 195313, 2013.
[101] W. Zhao, Z. Ghorannevis, K. K. Amara, J. R. Pang, M. Toh, X. Zhang, C. Kloc, P. H. Tan, and G. Eda, “Lattice dynamics in mono- and few-layer sheets of WS2 and WSe2,” Nanoscale, vol. 5, no. 20, pp. 9677–9683, 2013.
[102] P. Tonndorf, R. Schmidt, P. Böttger, X. Zhang, J. Börner, A. Liebig, M. Albrecht, C. Kloc, O. Gordan, D. R. T. Zahn, S. M. de Vasconcellos, and R. Bratschitsch, “Photoluminescence emission and Raman response of monolayer MoS2, MoSe2, and WSe2,” Opt. Express, vol. 21, no. 4, pp. 4908–4916, 2013.
[103] Y. Zhang, Y. Zhang, Q. Ji, J. Ju, H. Yuan, J. Shi, T. Gao, D. Ma, M. Liu, Y. Chen, X. Song, H. Y. Hwang, Y. Cui, and Z. Liu, “Controlled growth of high-quality monolayer WS2 layers on sapphire and imaging its grain boundary,” ACS Nano, vol. 7, no. 10, pp. 8963–8971, 2013.
[104] S. Zhang, N. Dong, N. McEvoy, M. O′Brien, S. Winters, N. C. Berner, C. Yim, Y. Li, X. Zhang, Z. Chen, L. Zhang, G. S. Duesberg, and J. Wang, “Direct observation of degenerate two-photon absorption and its saturation in WS2 and MoS2 monolayer and few-layer films,” ACS Nano, vol. 9, no. 7, pp. 7142–7150, 2015.
[105] H. Wang, D. Kong, P. Johanes, J. J. Cha, G. Zheng, K. Yan, N. Liu, and Y. Cui, “MoSe2 and WSe2 nanofilms with vertically aligned molecular layers on curved and rough surfaces,” Nano Lett., vol. 13, no. 7, pp. 3426–3433, 2013.
[106] X. Mao, Y. Xu, Q. Xue, W. Wang, and D. Gao, “Ferromagnetism in exfoliated tungsten disulfide nanosheets,” Nanoscale Research Letters, vol. 8, no. 1, p. 430, 2013.
[107] Y. Yan, B. Xia, N. Li, Z. Xu, A. Fisher, and X. Wang, “Vertically oriented
MoS2 and WS2 nanosheets directly grown on carbon cloth as efficient and stable
3-dimensional hydrogen-evolving cathodes,” J. Mater. Chem. A, vol. 3, no. 1, pp. 131–135, 2015.
[108] S. Tongay, W. Fan, J. Kang, J. Park, U. Koldemir, J. Suh, D. S. Narang, K. Liu, J. Ji, J. Li, R. Sinclair, and J. Wu, “Tuning interlayer coupling in large-area heterostructures with CVD-grown MoS2 and WS2 monolayers,” Nano Lett., vol. 14, no. 6, pp. 3185–3190, 2014.
[109] K. Gloos, P. J. Koppinen, and J. P. Pekola, “Properties of native ultrathin aluminium oxide tunnel barriers,” J. Phys. Condens. Mat., vol. 15, no. 10, pp. 1733– 1746, 2003.