簡易檢索 / 詳目顯示

研究生: 馬哈拉加
Nadar, Maharaja
論文名稱: 二維半導體之電晶體與光偵測器研究
2D layered semiconductors for transistor and photodetector applications
指導教授: 邱博文
Chiu, Po-Wen
口試委員: 連振炘
Lien, Chen-hsin
闕郁倫
Chueh, Yu-Lun
學位類別: 碩士
Master
系所名稱: 電機資訊學院 - 電子工程研究所
Institute of Electronics Engineering
論文出版年: 2019
畢業學年度: 107
語文別: 英文
論文頁數: 89
中文關鍵詞: 二维半导体
外文關鍵詞: 2D semiconductor
相關次數: 點閱:2下載:0
分享至:
查詢本校圖書館目錄 查詢臺灣博碩士論文知識加值系統 勘誤回報
  • 目前運算能力不斷提高以及降低處理器的功耗需求逐漸增加,互補式金屬氧化物半導體由於尺寸持續微縮導致下一代傳統矽電晶體嚴重限制了對摩爾定律發展。為了持續滿足摩爾定律的下一代電晶體性能,必須發展一個新的材料來解決此問題。
      過去十五年以來,二維半導體材料受到了很多關注,並且有希望取代傳統矽電晶體的通道材料,從而提高了計算能力。截至目前為止,雖然已經探索了許多不同的二維半導體材料,例如,石墨烯(graphene)是一種非常高遷移率的材料,但由於其能隙極小,我們不能將其用作於電晶體的通道材料;而二硫化鉬(MoS2)雖然具有非常好的電子和光電特性,但是二硫化鉬(MoS2)擁有較高的有效質量(m*= 0.45),這對於高速電晶體來說不太可能是一個最佳的選擇。
      在尋找具有高遷移率二維半導體材料時,我們發現硒化銦(InSe)具有非常高的本質遷移率,可當作良好的通道材料。只不過當我們施加背向閘極電壓時,硒化銦(InSe)表面顯現出不穩定的化學特性.為了能夠防止硒化銦(InSe)表面所生成之嚴重氧化問題,於實驗中使用乾氧化處理。另外,我們還探討當使用不同的金屬當作金屬-半導體接面的接觸時,硒化銦(InSe)電晶體光電特性之變化。結果顯示在的眾多金屬中,金屬銦(In)似乎很有前景,因為它能夠扮演硒化銦(InSe)通道中電子摻雜的豐富來源,進而減少金屬和半導體之間的蕭特基能障。
      此外,在論文中,我們也探討了量子點應用於光電探測器/光電晶體。其中,選擇二硫化鎢(WS2),因為它是一種良好的光子吸收材料。在二硫化鎢(WS2)成長幾天後,當暴露於大氣時,我們注意到二硫化鎢(WS2)表面被氧化並形成三角形空隙。我們將二硫化鎢(WS2)隨著時間的變化作拉曼和光致發光研究,其中拉曼和光致發光實驗的強度隨著天數的增加而持續減少。注意到二硫化鎢(WS2)的這種自然屬性後,我們決定於空隙中生長二硫化鉬(MoS2),使這個作為的二硫化鉬(MoS2)/二硫化鎢(WS2)的量子點異質結構。STEM圖像進一步顯示了鉬(Mo)原子取代了缺失的鎢(W)原子。我們的結果顯示通過微調量子點尺寸可以進一步提高檢測範圍和光響應特性


    There is an upsurge in the demand for increasing the computation capability and reducing
    the power consumption in a processor. The limitation in downscaling the limits of CMOS for
    next generation conventional silicon transistors pose a huge restriction to Moore’s law. In spite
    of the advances in technology, the next generation transistors would fail to follow Moore’s law.
    In order to meet Moore’s law for the next generation transistors, a new direction of thinking is
    necessary. Since a decade and a half, 2D semiconductor material has gained a lot of attention
    and promises to replace the channel material for conventional silicon transistors, thus boosting
    the computation capability.
    Even though a lot of different two dimensional semiconductor materials have been explored,
    a single best pick is still far from reality. Each material comes with its own set of advantages
    and disadvantages. For instance, graphene is a very high mobility material. But due to its
    non-bandgap, we cannot use this material as a channel material for transistor. Another example
    would be MoS2 which has very good electronic and optoelectronic properties. However,
    MoS2 has higher effective mass (m* = 0.45), which is not likely a good choice for high speed
    transistors.
    In the search of high mobility 2D semiconductor material, we find InSe with a very high
    intrinsic mobility and therefore a very good channel material to be a suitable candidate. Its
    chemical instability presented a huge challenge though for we used back gate configuration.
    To prevent the severe oxidation problem on the InSe surface, we used dry oxygen treatment.
    We also explored different metal contacts to InSe transistor for improving the performance.
    Among the many metals that we explored, Indium seems promising as it acts as a rich source
    of electron doping into the InSe channel, thus reducing the schottky barrier between metal and semiconductor.

    Further into the thesis, we explored a quantum dot photodetector/phototransistor. We choose
    WS2 since it is a very good photon absorbing material. After a few days of WS2 growth, we noticed
    that the surface gets oxidized and forms triangular voids when exposed to atmosphere. We
    use a set of material characterization techniques such as time dependent Raman and photoluminence
    studies of WS2 material, where the intensity of Raman and photoluminence experiments
    keep decreasing as days pass on. After noticing this natural property of WS2, we decided to
    grow MoS2 in the voids and make this as a quantum dot heterostructure of MoS2/WS2. STEM
    images further reveals that Mo atom has taken the place of the missing W atom. Our results
    indicate that the detecting range and photoresponsivity can be increased further by fine tuning
    the quantum dot size.

    1 Introduction 1 1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Thesis organisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 I Field-effect transistor based on 2D semiconductors 5 2 Properties of InSe material and its material characterization 7 2.1 Introduction to 2D materials and 2D semiconductors materials . . . . . . . . . 7 2.2 Electrical properties of InSe material . . . . . . . . . . . . . . . . . . . . . . . 10 2.2.1 Raman analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2.2 Photoluminescence analysis . . . . . . . . . . . . . . . . . . . . . . . 16 2.2.3 TEM Analysis of InSe multilayer . . . . . . . . . . . . . . . . . . . . 17 2.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3 InSe Device fabrication and electrical measurements 21 3.1 Sample cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.2 Mechanical exfoliation from bulk to 270 nm SiO2/Si . . . . . . . . . . . . . . 21 3.3 Hard mask based metal contact pads for InSe backgate transistor . . . . . . . . 23 3.3.1 Electrical properties of surface unprotected InSe device . . . . . . . . . 25 3.4 Surface protected InSe device . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.4.1 Electrical properties of surface protected InSe device . . . . . . . . . . 27 3.5 Different work functions of metals for InSe devices . . . . . . . . . . . . . . . 28 3.5.1 Indium as electron dopant for InSe . . . . . . . . . . . . . . . . . . . . 29 3.5.2 Electrical properties of Au/In InSe transistor . . . . . . . . . . . . . . 29 3.5.3 Chromium as adhesion layer between gold and InSe . . . . . . . . . . 33 3.5.4 Electrical properties of Au/Cr InSe device . . . . . . . . . . . . . . . . 34 3.5.5 Titanium as adhesion layer for InSe device . . . . . . . . . . . . . . . 36 3.5.6 Electrical properties of Titanium based InSe transistor . . . . . . . . . 37 3.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 V Contents II Quantum dot phototransistor 41 4 Photon absorption theory and material characterisation of WS2 and MoS2/WS2 43 4.1 Introduction to phototransistor/photodetector . . . . . . . . . . . . . . . . . . 43 4.2 Photon detection Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.3 Photodetector figures of merit . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.4 Electronic and optical properties of transition metal dichalcogenides (TMD) . . 48 4.5 Quantum dot photodetector based on WS2/MoS2 heterostructure . . . . . . . . 50 4.6 Characterization of grown WS2 and MoS2/WS2 heterostructure: Raman and Photoluminescence studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 5 Quantum dot photodetector performance 63 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5.2 Device fabrication and experimental results . . . . . . . . . . . . . . . . . . . 63 5.2.1 Transferring material from sapphire to silicon substrate . . . . . . . . . 63 5.3 Source drain contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 5.4 Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 5.5 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 5.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 6 Conclusion and future work 75 Appendix A MoS2 Growth 77 Appendix B Spinning process to open the window for source/drain contact 79 Appendix C Resist etching by RIE 81 Bibliography 83

    [1] 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.
    [2] A. K. Geim and K. S. Novoselov, “The rise of graphene,” in Nanoscience and Technology:
    A Collection of Reviews from Nature Journals, pp. 11–19, World Scientific, 2010.
    [3] Y. Zhang, T.-T. Tang, C. Girit, Z. Hao, M. C. Martin, A. Zettl, M. F. Crommie, Y. R.
    Shen, and F. Wang, “Direct observation of a widely tunable bandgap in bilayer graphene,”
    Nature, vol. 459, no. 7248, p. 820, 2009.
    [4] X. Li, X. Wang, L. Zhang, S. Lee, and H. Dai, “Chemically derived, ultrasmooth graphene
    nanoribbon semiconductors,” science, vol. 319, no. 5867, pp. 1229–1232, 2008.
    [5] D. C. Elias, R. R. Nair, T. Mohiuddin, S. Morozov, P. Blake, M. Halsall, A. C. Ferrari,
    D. Boukhvalov, M. Katsnelson, A. Geim, et al., “Control of graphene’s properties by
    reversible hydrogenation: evidence for graphane,” Science, vol. 323, no. 5914, pp. 610–
    613, 2009.
    [6] J. B. Oostinga, H. B. Heersche, X. Liu, A. F. Morpurgo, and L. M. Vandersypen, “Gateinduced
    insulating state in bilayer graphene devices,” Nature materials, vol. 7, no. 2,
    p. 151, 2008.
    [7] K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin mos 2: a new
    direct-gap semiconductor,” Physical review letters, vol. 105, no. 13, p. 136805, 2010.
    [8] O. Lopez-Sanchez, D. Lembke, M. Kayci, A. Radenovic, and A. Kis, “Ultrasensitive photodetectors
    based on monolayer mos 2,” Nature nanotechnology, vol. 8, no. 7, p. 497,
    2013.
    [9] B. Radisavljevic, A. Radenovic, J. Brivio, i. V. Giacometti, and A. Kis, “Single-layer mos
    2 transistors,” Nature nanotechnology, vol. 6, no. 3, p. 147, 2011.
    [10] 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 letters,
    vol. 12, no. 7, pp. 3788–3792, 2012.
    [11] 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,” Nature nanotechnology, vol. 9, no. 5, p. 372, 2014.
    [12] 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.
    [13] Y. Huang, J. Qiao, K. He, S. Bliznakov, E. Sutter, X. Chen, D. Luo, F. Meng, D. Su,
    J. Decker, et al., “Interaction of black phosphorus with oxygen and water,” Chemistry of
    Materials, vol. 28, no. 22, pp. 8330–8339, 2016.
    83
    Bibliography
    [14] S. Sucharitakul, N. J. Goble, U. R. Kumar, R. Sankar, Z. A. Bogorad, F.-C. Chou, Y.-T.
    Chen, and X. P. Gao, “Intrinsic electron mobility exceeding 103 cm2/(v s) in multilayer
    inse fets,” Nano letters, vol. 15, no. 6, pp. 3815–3819, 2015.
    [15] D. A. Bandurin, A. V. Tyurnina, L. Y. Geliang, A. Mishchenko, V. Zólyomi, S. V. Morozov,
    R. K. Kumar, R. V. Gorbachev, Z. R. Kudrynskyi, S. Pezzini, et al., “High electron
    mobility, quantum hall effect and anomalous optical response in atomically thin inse,”
    Nature nanotechnology, vol. 12, no. 3, p. 223, 2017.
    [16] G. Fiori, F. Bonaccorso, G. Iannaccone, T. Palacios, D. Neumaier, A. Seabaugh, S. K.
    Banerjee, and L. Colombo, “Electronics based on two-dimensional materials,” Nature
    nanotechnology, vol. 9, no. 10, p. 768, 2014.
    [17] T. N. Theis and P. M. Solomon, “It’s time to reinvent the transistor!,” Science, vol. 327,
    no. 5973, pp. 1600–1601, 2010.
    [18] Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman, and M. S. Strano, “Electronics and
    optoelectronics of two-dimensional transition metal dichalcogenides,” Nature nanotechnology,
    vol. 7, no. 11, p. 699, 2012.
    [19] M. Chhowalla, D. Jena, and H. Zhang, “Two-dimensional semiconductors for transistors,”
    Nature Reviews Materials, vol. 1, no. 11, p. 16052, 2016.
    [20] S. Manzeli, D. Ovchinnikov, D. Pasquier, O. V. Yazyev, and A. Kis, “2d transition metal
    dichalcogenides,” Nature Reviews Materials, vol. 2, no. 8, p. 17033, 2017.
    [21] A. S. Mayorov, R. V. Gorbachev, S. V. Morozov, L. Britnell, R. Jalil, L. A. Ponomarenko,
    P. Blake, K. S. Novoselov, K. Watanabe, T. Taniguchi, et al., “Micrometer-scale ballistic
    transport in encapsulated graphene at room temperature,” Nano letters, vol. 11, no. 6,
    pp. 2396–2399, 2011.
    [22] M. Y. Han, B. Özyilmaz, Y. Zhang, and P. Kim, “Energy band-gap engineering of graphene
    nanoribbons,” Physical review letters, vol. 98, no. 20, p. 206805, 2007.
    [23] R. Balog, B. Jørgensen, L. Nilsson, M. Andersen, E. Rienks, M. Bianchi, M. Fanetti,
    E. Lægsgaard, A. Baraldi, S. Lizzit, et al., “Bandgap opening in graphene induced by
    patterned hydrogen adsorption,” Nature materials, vol. 9, no. 4, p. 315, 2010.
    [24] J. A. 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.
    [25] A. Yoffe, “Layer compounds,” Annual Review of Materials Science, vol. 3, no. 1, pp. 147–
    170, 1973.
    [26] A. D. Yoffe, “Low-dimensional systems: quantum size effects and electronic properties
    of semiconductor microcrystallites (zero-dimensional systems) and some quasi-twodimensional
    systems,” Advances in Physics, vol. 42, no. 2, pp. 173–262, 1993.
    [27] 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, 2012.
    [28] S. Larentis, B. Fallahazad, and E. Tutuc, “Field-effect transistors and intrinsic mobility in
    ultra-thin mose2 layers,” Applied Physics Letters, vol. 101, no. 22, p. 223104, 2012.
    84
    Bibliography
    [29] A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C.-Y. Chim, G. Galli, and F. Wang,
    “Emerging photoluminescence in monolayer mos2,” Nano letters, vol. 10, no. 4, pp. 1271–
    1275, 2010.
    [30] R. F. Pierret and G. W. Neudeck, Advanced semiconductor fundamentals, vol. 6. Addison-
    Wesley Reading, MA, 1987.
    [31] J. Qiao, X. Kong, Z.-X. Hu, F. Yang, and W. Ji, “High-mobility transport anisotropy and
    linear dichroism in few-layer black phosphorus,” Nature communications, vol. 5, p. 4475,
    2014.
    [32] X. Liu, K.-W. Ang, W. Yu, J. He, X. Feng, Q. Liu, H. Jiang, D. Tang, J. Wen, Y. Lu, et al.,
    “Black phosphorus based field effect transistors with simultaneously achieved near ideal
    subthreshold swing and high hole mobility at room temperature,” Scientific reports, vol. 6,
    p. 24920, 2016.
    [33] A. Castellanos-Gomez, L. Vicarelli, E. Prada, J. O. Island, K. Narasimha-Acharya, S. I.
    Blanter, D. J. Groenendijk, M. Buscema, G. A. Steele, J. Alvarez, et al., “Isolation and
    characterization of few-layer black phosphorus,” 2D Materials, vol. 1, no. 2, p. 025001,
    2014.
    [34] J. O. Island, G. A. Steele, H. S. van der Zant, and A. Castellanos-Gomez, “Environmental
    instability of few-layer black phosphorus,” 2D Materials, vol. 2, no. 1, p. 011002, 2015.
    [35] S. Lei, L. Ge, S. Najmaei, A. George, R. Kappera, J. Lou, M. Chhowalla, H. Yamaguchi,
    G. Gupta, R. Vajtai, et al., “Evolution of the electronic band structure and efficient photodetection
    in atomic layers of inse,” ACS nano, vol. 8, no. 2, pp. 1263–1272, 2014.
    [36] S. R. Tamalampudi, Y.-Y. Lu, R. Kumar U, R. Sankar, C.-D. Liao, K. Moorthy B, C.-H.
    Cheng, F. C. Chou, and Y.-T. Chen, “High performance and bendable few-layered inse
    photodetectors with broad spectral response,” Nano letters, vol. 14, no. 5, pp. 2800–2806,
    2014.
    [37] G. W. Mudd, S. A. Svatek, T. Ren, A. Patanè, O. Makarovsky, L. Eaves, P. H. Beton, Z. D.
    Kovalyuk, G. V. Lashkarev, Z. R. Kudrynskyi, et al., “Tuning the bandgap of exfoliated
    inse nanosheets by quantum confinement,” Advanced Materials, vol. 25, no. 40, pp. 5714–
    5718, 2013.
    [38] J. N. Coleman, M. Lotya, A. O’Neill, S. D. Bergin, P. J. King, U. Khan, K. Young,
    A. Gaucher, S. De, R. J. Smith, et al., “Two-dimensional nanosheets produced by liquid
    exfoliation of layered materials,” Science, vol. 331, no. 6017, pp. 568–571, 2011.
    [39] P.-H. Ho, Y.-R. Chang, Y.-C. Chu, M.-K. Li, C.-A. Tsai, W.-H. Wang, C.-H. Ho, C.-W.
    Chen, and P.-W. Chiu, “High-mobility inse transistors: the role of surface oxides,” Acs
    Nano, vol. 11, no. 7, pp. 7362–7370, 2017.
    [40] M. Li, C.-Y. Lin, S.-H. Yang, Y.-M. Chang, J.-K. Chang, F.-S. Yang, C. Zhong, W.-B. Jian,
    C.-H. Lien, C.-H. Ho, et al., “High mobilities in layered inse transistors with indiumencapsulation-
    induced surface charge doping,” Advanced Materials, vol. 30, no. 44,
    p. 1803690, 2018.
    [41] N. Kuroda and Y. Nishina, “Resonance raman scattering study on exciton and polaron
    anisotropies in inse,” Solid State Communications, vol. 34, no. 6, pp. 481–484, 1980.
    [42] E. Kress-Rogers, R. Nicholas, J. Portal, and A. Chevy, “Cyclotron resonance studies on
    bulk and two-dimensional conduction electrons in inse,” Solid State Communications,
    vol. 44, no. 3, pp. 379–383, 1982.
    85
    Bibliography
    [43] A. Segura, F. Pomer, A. Cantarero, W. Krause, and A. Chevy, “Electron scattering mechanisms
    in n-type indium selenide,” Physical Review B, vol. 29, no. 10, p. 5708, 1984.
    [44] X. Wei, C. Dong, A. Xu, X. Li, and D. D. Macdonald, “Oxygen-induced degradation of the
    electronic properties of thin-layer inse,” Physical Chemistry Chemical Physics, vol. 20,
    no. 4, pp. 2238–2250, 2018.
    [45] C. Carlone and S. Jandl, “Second order raman spectrum and phase transition in inse,” Solid
    State Communications, vol. 29, no. 1, pp. 31–33, 1979.
    [46] K. Kumazaki and K. Imai, “Far-infrared reflection and raman scattering spectra in
    -inse,”
    Physica Status Solidi B, vol. 149, no. 2, pp. K183–K186, 1988.
    [47] S. Jandl and C. Carlone, “Raman spectrum of crystalline inse,” Solid State Communications,
    vol. 25, no. 1, pp. 5–8, 1978.
    [48] R. Schwarcz, M. Kanehisa, M. Jouanne, J. Morhange, and M. Eddrief, “Evolution of raman
    spectra as a function of layer thickness in ultra-thin inse films,” Journal of Physics:
    Condensed Matter, vol. 14, no. 5, p. 967, 2002.
    [49] M. Brotons-Gisbert, J. Sánchez-Royo, and J. Martínez-Pastor, “Thickness identification of
    atomically thin inse nanoflakes on sio2/si substrates by optical contrast analysis,” Applied
    Surface Science, vol. 354, pp. 453–458, 2015.
    [50] A. Politano, G. Chiarello, R. Samnakay, G. Liu, B. Gürbulak, S. Duman, A. Balandin, and
    D. Boukhvalov, “The influence of chemical reactivity of surface defects on ambient-stable
    inse-based nanodevices,” Nanoscale, vol. 8, no. 16, pp. 8474–8479, 2016.
    [51] V. Katerynchuk and Z. Kovalyuk, “Surface morphology and electrical resistance of the
    oxide film on inse,” Inorganic Materials, vol. 47, no. 7, pp. 749–752, 2011.
    [52] Y.-R. Chang, P.-H. Ho, C.-Y. Wen, T.-P. Chen, S.-S. Li, J.-Y. Wang, M.-K. Li, C.-A. Tsai,
    R. Sankar, W.-H. Wang, et al., “Surface oxidation doping to enhance photogenerated carrier
    separation efficiency for ultrahigh gain indium selenide photodetector,” ACS Photonics,
    vol. 4, no. 11, pp. 2930–2936, 2017.
    [53] D. S. Schulman, A. J. Arnold, and S. Das, “Contact engineering for 2d materials and
    devices,” Chemical Society Reviews, vol. 47, no. 9, pp. 3037–3058, 2018.
    [54] W. Liu, J. Kang, D. Sarkar, Y. Khatami, D. Jena, and K. Banerjee, “Role of metal contacts
    in designing high-performance monolayer n-type wse2 field effect transistors,” Nano
    letters, vol. 13, no. 5, pp. 1983–1990, 2013.
    [55] W. Feng, X. Zhou, W. Q. Tian, W. Zheng, and P. Hu, “Performance improvement of
    multilayer inse transistors with optimized metal contacts,” Physical Chemistry Chemical
    Physics, vol. 17, no. 5, pp. 3653–3658, 2015.
    [56] S. Kim, A. Konar, W.-S. Hwang, J. H. Lee, J. Lee, J. Yang, C. Jung, H. Kim, J.-B. Yoo,
    J.-Y. Choi, et al., “High-mobility and low-power thin-film transistors based on multilayer
    mos 2 crystals,” Nature communications, vol. 3, p. 1011, 2012.
    [57] R. R. Nair, P. Blake, A. N. Grigorenko, K. S. Novoselov, T. J. Booth, T. Stauber, N. M.
    Peres, and A. K. Geim, “Fine structure constant defines visual transparency of graphene,”
    Science, vol. 320, no. 5881, pp. 1308–1308, 2008.
    86
    Bibliography
    [58] J. M. Dawlaty, S. Shivaraman, J. Strait, P. George, M. Chandrashekhar, F. Rana, M. G.
    Spencer, D. Veksler, and Y. Chen, “Measurement of the optical absorption spectra of
    epitaxial graphene from terahertz to visible,” Applied Physics Letters, vol. 93, no. 13,
    p. 131905, 2008.
    [59] A. Wright, J. Cao, and C. Zhang, “Enhanced optical conductivity of bilayer graphene
    nanoribbons in the terahertz regime,” Physical review letters, vol. 103, no. 20, p. 207401,
    2009.
    [60] Z. Sun, T. Hasan, F. Torrisi, D. Popa, G. Privitera, F. Wang, F. Bonaccorso, D. M.
    Basko, and A. C. Ferrari, “Graphene mode-locked ultrafast laser,” ACS nano, vol. 4, no. 2,
    pp. 803–810, 2010.
    [61] T. Mueller, F. Xia, and P. Avouris, “Graphene photodetectors for high-speed optical communications,”
    Nature photonics, vol. 4, no. 5, p. 297, 2010.
    [62] F. Bonaccorso, Z. Sun, T. Hasan, and A. Ferrari, “Graphene photonics and optoelectronics,”
    Nature photonics, vol. 4, no. 9, p. 611, 2010.
    [63] L. Vicarelli, M. Vitiello, D. Coquillat, A. Lombardo, A. C. Ferrari, W. Knap, M. Polini,
    V. Pellegrini, and A. Tredicucci, “Graphene field-effect transistors as room-temperature
    terahertz detectors,” Nature materials, vol. 11, no. 10, p. 865, 2012.
    [64] X. Gan, R.-J. Shiue, Y. Gao, I. Meric, T. F. Heinz, K. Shepard, J. Hone, S. Assefa, and
    D. Englund, “Chip-integrated ultrafast graphene photodetector with high responsivity,”
    Nature Photonics, vol. 7, no. 11, p. 883, 2013.
    [65] C.-H. Liu, Y.-C. Chang, T. B. Norris, and Z. Zhong, “Graphene photodetectors with ultrabroadband
    and high responsivity at room temperature,” Nature nanotechnology, vol. 9,
    no. 4, p. 273, 2014.
    [66] B. E. Saleh and M. C. Teich, “Fundamentals of photonics. 2007,” John Wiey & Sons, Inc,
    pp. 260–269.
    [67] G. Konstantatos and E. H. Sargent, “Solution-processed quantum dot photodetectors,”
    Proceedings of the IEEE, vol. 97, no. 10, pp. 1666–1683, 2009.
    [68] E. L. Dereniak and G. D. Boreman, Infrared detectors and systems, vol. 306. Wiley New
    York, 1996.
    [69] R. C. Jones, “A method of describing the detectivity of photoconductive cells,” Review of
    Scientific Instruments, vol. 24, no. 11, pp. 1035–1040, 1953.
    [70] C.-H. Yeh, H.-C. Chen, H.-C. Lin, Y.-C. Lin, Z.-Y. Liang, M.-Y. Chou, K. Suenaga, and P.-
    W. Chiu, “Ultrafast monolayer in/gr-ws2-gr hybrid photodetectors with high gain,” ACS
    nano, 2019.
    [71] A. Kuc, N. Zibouche, and T. Heine, “Influence of quantum confinement on the electronic
    structure of the transition metal sulfide t s 2,” Physical Review B, vol. 83, no. 24, p. 245213,
    2011.
    [72] F. Xia, H. Wang, D. Xiao, M. Dubey, and A. Ramasubramaniam, “Two-dimensional material
    nanophotonics,” Nature Photonics, vol. 8, no. 12, p. 899, 2014.
    [73] C. R. Dean, A. F. Young, I. Meric, C. Lee, L. Wang, S. Sorgenfrei, K. Watanabe,
    T. Taniguchi, P. Kim, K. L. Shepard, et al., “Boron nitride substrates for high-quality
    graphene electronics,” Nature nanotechnology, vol. 5, no. 10, p. 722, 2010.
    87
    Bibliography
    [74] S. Lebegue and O. Eriksson, “Electronic structure of two-dimensional crystals from ab
    initio theory,” Physical Review B, vol. 79, no. 11, p. 115409, 2009.
    [75] 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 ws 2 nanoflakes,” Scientific reports, vol. 4,
    p. 5209, 2014.
    [76] M. Bernardi, M. Palummo, and J. C. Grossman, “Extraordinary sunlight absorption and
    one nanometer thick photovoltaics using two-dimensional monolayer materials,” Nano
    letters, vol. 13, no. 8, pp. 3664–3670, 2013.
    [77] T. Li and G. Galli, “Electronic properties of mos2 nanoparticles,” The Journal of Physical
    Chemistry C, vol. 111, no. 44, pp. 16192–16196, 2007.
    [78] G. Frey, R. Tenne, M. Matthews, M. Dresselhaus, and G. Dresselhaus, “Optical properties
    of ms 2 (m= mo, w) inorganic fullerenelike and nanotube material optical absorption and
    resonance raman measurements,” Journal of materials research, vol. 13, no. 9, pp. 2412–
    2417, 1998.
    [79] C. Ballif, M. Regula, P. Schmid, M. Remškar, R. Sanjinés, and F. Lévy, “Preparation and
    characterization of highly oriented, photoconducting ws 2 thin films,” Applied Physics A,
    vol. 62, no. 6, pp. 543–546, 1996.
    [80] Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties
    of perfect, vacancy-doped, and nonmetal adsorbed mose 2, mote 2 and ws 2 monolayers,”
    Physical Chemistry Chemical Physics, vol. 13, no. 34, pp. 15546–15553, 2011.
    [81] 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 letters, vol. 13, no. 8, pp. 3447–
    3454, 2012.
    [82] G. Konstantatos, I. Howard, A. Fischer, S. Hoogland, J. Clifford, E. Klem, L. Levina, and
    E. H. Sargent, “Ultrasensitive solution-cast quantum dot photodetectors,” Nature, vol. 442,
    no. 7099, p. 180, 2006.
    [83] G. Konstantatos, J. Clifford, L. Levina, and E. H. Sargent, “Sensitive solution-processed
    visible-wavelength photodetectors,” Nature photonics, vol. 1, no. 9, p. 531, 2007.
    [84] V. Sukhovatkin, S. Hinds, L. Brzozowski, and E. H. Sargent, “Colloidal quantum-dot photodetectors
    exploiting multiexciton generation,” Science, vol. 324, no. 5934, pp. 1542–
    1544, 2009.
    [85] S. Keuleyan, E. Lhuillier, V. Brajuskovic, and P. Guyot-Sionnest, “Mid-infrared hgte colloidal
    quantum dot photodetectors,” Nature Photonics, vol. 5, no. 8, p. 489, 2011.
    [86] G. Konstantatos, M. Badioli, L. Gaudreau, J. Osmond, M. Bernechea, F. P. G. De Arquer,
    F. Gatti, and F. H. Koppens, “Hybrid graphene–quantum dot phototransistors with
    ultrahigh gain,” Nature nanotechnology, vol. 7, no. 6, p. 363, 2012.
    [87] N. Huo, S. Gupta, and G. Konstantatos, “Mos2–hgte quantum dot hybrid photodetectors
    beyond 2 m,” Advanced materials, vol. 29, no. 17, p. 1606576, 2017.
    [88] Y.-C. Lin, C.-H. Yeh, H.-C. Lin, M.-D. Siao, Z. Liu, H. Nakajima, T. Okazaki, M.-Y. Chou,
    K. Suenaga, and P.-W. Chiu, “Stable 1t tungsten disulfide monolayer and its junctions:
    Growth and atomic structures,” ACS nano, vol. 12, no. 12, pp. 12080–12088, 2018.
    88
    Bibliography
    [89] K. Kang, K. Godin, Y. D. Kim, S. Fu, W. Cha, J. Hone, and E.-H. Yang, “Grapheneassisted
    antioxidation of tungsten disulfide monolayers: Substrate and electric-field effect,”
    Advanced Materials, vol. 29, no. 18, p. 1603898, 2017.
    [90] J. Gao, B. Li, J. Tan, P. Chow, T.-M. Lu, and N. Koratkar, “Aging of transition metal
    dichalcogenide monolayers,” ACS nano, vol. 10, no. 2, pp. 2628–2635, 2016.
    [91] A. Berkdemir, H. R. Gutiérrez, A. R. Botello-Méndez, N. Perea-López, A. L. Elías, C.-
    I. Chia, B. Wang, V. H. Crespi, F. López-Urías, J.-C. Charlier, et al., “Identification of
    individual and few layers of ws 2 using raman spectroscopy,” Scientific reports, vol. 3,
    p. 1755, 2013.
    [92] C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations
    of single-and few-layer mos2,” ACS nano, vol. 4, no. 5, pp. 2695–2700, 2010.
    [93] W. Choi, M. Y. Cho, A. Konar, J. H. Lee, G.-B. Cha, S. C. Hong, S. Kim, J. Kim, D. Jena,
    J. Joo, et al., “High-detectivity multilayer mos2 phototransistors with spectral response
    from ultraviolet to infrared,” Advanced materials, vol. 24, no. 43, pp. 5832–5836, 2012.
    [94] L. Zeng, L. Tao, C. Tang, B. Zhou, H. Long, Y. Chai, S. P. Lau, and Y. H. Tsang, “Highresponsivity
    uv-vis photodetector based on transferable ws 2 film deposited by magnetron
    sputtering,” Scientific reports, vol. 6, p. 20343, 2016.
    [95] Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang,
    “Single-layer mos2 phototransistors,” ACS nano, vol. 6, no. 1, pp. 74–80, 2011.
    [96] E. Liu, M. Long, J. Zeng, W. Luo, Y. Wang, Y. Pan, W. Zhou, B. Wang, W. Hu, Z. Ni, et al.,
    “High responsivity phototransistors based on few-layer res2 for weak signal detection,”
    Advanced Functional Materials, vol. 26, no. 12, pp. 1938–1944, 2016.

    QR CODE