跳到主要內容

臺灣博碩士論文加值系統

(3.236.68.118) 您好!臺灣時間:2021/08/04 21:27
字體大小: 字級放大   字級縮小   預設字形  
回查詢結果 :::

詳目顯示

我願授權國圖
: 
twitterline
研究生:何安
研究生(外文):An Ho
論文名稱:以第一原理計算探討二氧化矽基材內的缺陷與摻雜以及高介電常數二氧化鉿絕緣層對二硫化鉬電子性質與其載子遷移率變化之影響
論文名稱(外文):First-Principles Study of the Doping Effect on MoS2 from the Impurities and Intrinsic Point Defects in the underlying SiO2 Substrate and the Origin of the Enhanced Carrier Mobility by the Top High-k HfO2 Layers
指導教授:郭錦龍
指導教授(外文):Chin-Lung Kuo
口試委員:林祥泰郭哲來蔡政達謝宗霖
口試委員(外文):Shiang-Tai LinJer-Lai KuoJeng-Da ChaiJay Shieh
口試日期:2015-07-24
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:材料科學與工程學研究所
學門:工程學門
學類:材料工程學類
論文種類:學術論文
論文出版年:2015
畢業學年度:103
語文別:英文
論文頁數:194
中文關鍵詞:二硫化鉬第一原理計算二氧化矽二氧化鉿蕭特基能障
外文關鍵詞:MoS2first-principles calculationSiO2HfO2Schottky barrier
相關次數:
  • 被引用被引用:0
  • 點閱點閱:94
  • 評分評分:
  • 下載下載:0
  • 收藏至我的研究室書目清單書目收藏:0
由於具有獨特且優異之物理性質,二硫化鉬在各種電子元件上的應用是極具發展潛力的二維奈米材料,而金氧半場效電晶體(MOSFET) 是其在眾多可能的應用中被認為最為可行的方向之一。這主要是因為二硫化鉬具有良好的載子遷移率與電流開關比,所以有機會取代矽作為新一代電晶體中的導電通道。然而,目前對於單層二硫化鉬的基本物理性質仍有許多不清楚和未解決的地方,特別是其與基材之間的相互作用如何導致二硫化鉬電子性質改變的物理機制仍不清楚。本論文的研究目標即是運用第一原理密度泛函計算來探討二氧化矽基材內部的缺陷與摻雜以及外加高介電常數二氧化鉿絕緣層對二硫化鉬電子性質與其載子遷移率變化產生之影響與其相關物理機制分析。
在第一部分研究中,我們主要探討了當二硫化鉬置於二氧化矽基材時其n型載子之來源以及硫空缺對其電子性質可能產生的影響。我們首先建構了數個含有固有點缺陷以及硼、鈉等常見雜質的二氧化矽基材結構模型,並依此個別分析其對單層二硫化鉬產生的影響。我們計算的結果顯示,二氧化矽基材中固有的點缺陷、與硼、鈉等雜質皆可能會對二硫化鉬產生n型摻雜的效果,而其中硼摻雜所引起的n型載子來源主要為硼雜質本身以及與其伴隨產生的二氧化矽本質結構缺陷。這些摻雜物以及伴隨而生的本質缺陷可能會在二氧化矽能隙中產生電子佔據或未佔據之缺陷能態,其中部分可能成為二硫化鉬之電子施體,因而造成二氧化矽基材中的缺陷電子移轉至二硫化鉬的現象。此外,二硫化鉬之硫空缺會在導帶下方產生兩個未佔據的缺陷能態,而此缺陷能態將有利於二氧化矽基材中缺陷電子的轉移,因而導致二硫化鉬中n型載子濃度的上升。在另一方面,計算的結果也顯示鈉原子對於二硫化鉬可以產生n型摻雜效果。然而,鈉元素在二氧化矽玻璃材料中主要是以鈉離子形態存在,不會對二硫化鉬產生任何摻雜的效果。因此,我們認為二氧化矽中的鈉雜質不會是二硫化鉬主要的n型載子來源。
接著我們也探討了含氮、磷、砷等摻雜之非晶二氧化矽基材對二硫化鉬電子性質之影響,我們希望瞭解是否能透過這些摻雜物來增加二硫化鉬中電洞載子的濃度,進而引導實驗達成p型場效電晶體之應用。計算結果顯示,氮和砷摻雜於二氧化矽基材中所產生的雜質缺陷以及其伴隨產生的二氧化矽本質結構缺陷對於二硫化鉬是有效的電子受體,可使二硫化鉬的價帶電子轉移至二氧化矽基材中而產生p型摻雜的效果。此外,由於原子半徑大小與電負度等基本性質的差異,磷和砷雖為同族的元素,它們在二氧化矽結構中會傾向形成不同的鍵結形式,因而使得磷在二氧化矽結構中無法有效對二硫化鉬產生p型摻雜的效果。
在第二部份的研究中,我們主要針對高介電常數二氧化鉿絕緣層對二硫化鉬中載子遷移率增強效應之物理原因進行探討。研究的動機主要在於實驗上觀察到當二硫化鉬導電通道上方披覆一層高介電常數二氧化鉿絕緣材料作為閘極氧化層時,二硫化鉬中的載子遷移率可獲得大幅的提升,但是目前實驗上對此現象並無法提供合理的物理解釋。我們計算的結果發現,無缺陷的二氧化鉿對於二硫化鉬之電子性質並無顯著影響;然而,當二氧化鉿中含有氧空缺時,其會對於二硫化鉬會產生顯著n型摻雜的效果。我們的結果也顯示此n型摻雜的效果可有效降低二硫化鉬和源極金屬間的蕭特基能障,因而使其接觸電阻下降,最終使得二硫化鉬電晶體之載子遷移率提升。此外,我們同時探討n型摻雜對於二硫化鉬介電性質之影響。計算的結果顯示,n型摻雜僅能些微提高二硫化鉬垂直平面方向之介電常數,對於介電屏蔽效應的增強效果十分有限。因此,我們認為二氧化鉿層對於二硫化鉬介電性質的影響並非是使其載子遷移率增加的主要原因,而主要的物理因素是其對二硫化鉬產生的n型摻雜能夠有效降低二硫化鉬與源極金屬間的蕭特基能障所致。

MoS2 is a promising candidate for the new nano-electronic devices primarily due to its outstanding physical and electronic properties. In practical applications, monolayer MoS2 has been successfully integrated into a MOS transistor showing a mobility of >200 cm2/V·s with an on/off current ratio >108. However, the MoS2-based transistors still have some disadvantages that require further improvements to uplift their performance. Therefore, it would be of great interest to develop detailed atomistic understanding of this material system in many fundamental aspects, particularly for the interactions between MoS2 and the insulating dielectric substrates.
In the first part of the thesis, we employed first-principles calculations to explore the origins of the n-type doping effect on MoS2 from the underlying SiO2 substrate. We first constructed various structure models of a-SiO2 containing boron, sodium and the relevant Si point defects in the substrates and then investigate the electronic structure changes of the MoS2/SiO2 hybrid system. Our calculated results show that B atoms can form various stable bonding configurations such as •BO-SiO3, •SiO2-BO2, SiO3-BO2 and B2O3 with the associated Si point defects like E’ and S centers in a-SiO2. Furthermore, those dopant configurations and the associated Si point defects can induce the formation of electronic defect states in the band gap of SiO2, some of which can be effective electron donors inducing electron transfer from a-SiO2 to monolayer MoS2. We also found that this n-type doping effect can be much enhanced by the appearance of S vacancies in MoS2 mainly attributed to the induced unoccupied defect states at ~0.7 eV below its conduction band minimum. On the other hand, Na atom in a-SiO2 was found to be an effective electron donor on MoS2 as well. Nevertheless, since Na generally appears as Na+ ions in a-SiO2 glasses, it is not expected to be the major source contributing to the n-type conducting behavior in MoS2 monolayer.
We next investigated the effects of the N-, P-, and As-doped SiO2 substrates on the electronic property changes of MoS2 monolayer. Our calculations unambiguously show that some of the bonding configurations of N and As atoms with the associated Si point defects in a-SiO2 can become effective electron acceptors for monolayer MoS2, providing one possible route to fabricate the MoS2-based p-MOSFET. Nevertheless, the P-doped SiO2 is not possible to induce any p-type doping on MoS2 monolayer though As and P are both the Group VA elements in the periodic table.
In the second part of the thesis, we intend to reveal the physical origin of the enhanced carrier mobility in MoS2 by the deposition of the top high-k HfO2 layers. We first investigated the influence of HfO2 layer on the electronic property of monolayer MoS2, and then probed for the effect of the induced electronic doping on the dielectric property changes of MoS2 as well as the contact resistance between the S/D metal and MoS2 layer. Our results show that perfect HfO2 layer has no significant effect on the electronic property change of MoS2, but as O vacancy is present in the high-k layer, it was found to induce significant amount of n-type doping on monolayer MoS2. Our calculations further show that the induced n-type doping from HfO2 can effectively reduce the Schottky barrier height between the S/D metal and monolayer MoS2, thereby largely enhancing the electron mobility in the MoS2-based MOS transistor. In addition, our calculations show that the dielectric screening along the z axis (zz) of MoS2 is nearly unchanged upon n-type doping. Therefore, the reduction of coulomb scattering arising from the charge traps in SiO2 cannot be used to account for the enhanced electron mobility in the MoS2 channel by the deposited HfO2 layer.


致謝 i
摘要 ii
Abstract iv
Contents vi
List of Figures viii
List of Tables xxv
Chapter 1. Introduction 1
Chapter 2. Theoretical Background 3
2.1 First principles calculation 3
2.2 Density functional theory (DFT) 3
2.2.1 Thomas-Fermi model 4
2.2.2 Hohenberg-Kohn theorem 4
2.2.3 Kohn-Sham equation 5
2.2.4 Exchange-correlation functional 7
2.2.5 Pseudopotential 7
2.3 Molecular dynamics 9
2.3.1 Verlet algorithm 9
2.3.2 Nosé-Hoover thermostat 10
2.4 Computational details 10
Chapter 3. The Doping Effects on MoS2 from Defects and Impurities in a-SiO2 11
3.1 Introduction 11
3.2 Electronic properties of MoS2 14
3.3 MoS2 on pure a-SiO2 18
3.3.1 Perfect a-SiO2 18
3.3.2 Defective a-SiO2 24
3.4 MoS2 on B, Na doped a-SiO2 55
3.4.1 Boron doped a-SiO2 substrate 55
3.4.2 Sodium doped a-SiO2 substrate 83
3.5 MoS2 on N, P, As doped a-SiO2 91
3.5.1 Nitrogen doped a-SiO2 substrate 91
3.5.2 Phosphorus doped a-SiO2 substrate 101
3.5.3 Arsenic doped a-SiO2 substrate 124
3.6 Summary 143
Chapter 4. The Origin of the Enhanced Carrier Mobility of MoS2 by HfO2 Layer 145
4.1 Introduction 145
4.2 Electronic properties of MoS2 on HfO2 147
4.2.1 Perfect HfO2 147
4.2.2 HfO2 with oxygen vacancy 150
4.3 Dielectric properties of n-type doped MoS2 161
4.4 The presence of HfO2 in metal/MoS2/HfO2 triple junction 165
4.4.1 Metal contact with MoS2 165
4.4.2 Metal/MoS2/HfO2 triple junction 177
4.5 Summary 184
Chapter 5. Conclusion 187
Reference 189


[1]K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, and A. A. Firsov, Science 306, 666 (2004).
[2]A. K. Geim and I. V. Grigorieva, Nature 499, 419 (2013).
[3]B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, Nature nanotechnology 6, 147 (2011).
[4]K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, Physical Review Letters 105, 136805 (2010).
[5]Y. H. Lee et al., Advanced materials 24, 2320 (2012).
[6]Y. Guo, X. Wei, J. Shu, B. Liu, J. Yin, C. Guan, Y. Han, S. Gao, and Q. Chen, Applied Physics Letters 106, 103109 (2015).
[7]C. P. Lu, G. Li, J. Mao, L. M. Wang, and E. Y. Andrei, Nano letters 14, 4628 (2014).
[8]L. H. Thomas, Mathematical Proceedings of the Cambridge Philosophical Society 23, 542 (2008).
[9]P. Hohenberg and W. Kohn, Physical Review 136, B864 (1964).
[10]W. Kohn and L. J. Sham, Physical Review 140, A1133 (1965).
[11]P. A. M. Dirac, Mathematical Proceedings of the Cambridge Philosophical Society 26, 376 (2008).
[12]S. H. Vosko, L. Wilk, and M. Nusair, Canadian Journal of Physics 58, 1200 (1980).
[13]J. P. Perdew, J. A. Chevary, S. H. Vosko, K. A. Jackson, M. R. Pederson, D. J. Singh, and C. Fiolhais, Physical Review B 46, 6671 (1992).
[14]D. M. Ceperley and B. J. Alder, Physical Review Letters 45, 566 (1980).
[15]J. P. Perdew and A. Zunger, Physical Review B 23, 5048 (1981).
[16]Y. Wang and J. P. Perdew, Physical Review B 43, 8911 (1991).
[17]J. P. Perdew, K. Burke, and M. Ernzerhof, Physical Review Letters 77, 3865 (1996).
[18]B. J. Alder and T. E. Wainwright, The Journal of Chemical Physics 31, 459 (1959).
[19]L. Verlet, Physical Review 159, 98 (1967).
[20]D. J. Evans and B. L. Holian, The Journal of Chemical Physics 83, 4069 (1985).
[21]G. Kresse and J. Furthmuller, Comp Mater Sci 6, 15 (1996).
[22]G. Kresse and J. Furthmuller, Physical Review B 54, 11169 (1996).
[23]G. Kresse and J. Hafner, Physical Review B 49, 14251 (1994).
[24]G. Kresse and J. Hafner, Physical Review B 47, 558 (1993).
[25]G. Kresse and D. Joubert, Physical Review B 59, 1758 (1999).
[26]A. Kumar and P. K. Ahluwalia, The European Physical Journal B 85, 186 (2012).
[27]H. Y. Chang, S. Yang, J. Lee, L. Tao, W. S. Hwang, D. Jena, N. Lu, and D. Akinwande, ACS nano 7, 5446 (2013).
[28]T. Stephenson, Z. Li, B. Olsen, and D. Mitlin, Energy Environ. Sci. 7, 209 (2014).
[29]D. Sarkar, W. Liu, X. Xie, A. C. Anselmo, S. Mitragotri, and K. Banerjee, ACS nano 8, 3992 (2014).
[30]S. Bertolazzi, D. Krasnozhon, and A. Kis, ACS nano 7, 3246 (2013).
[31]D. Le, T. B. Rawal, and T. S. Rahman, The Journal of Physical Chemistry C 118, 5346 (2014).
[32]M. A. Lukowski, A. S. Daniel, F. Meng, A. Forticaux, L. Li, and S. Jin, Journal of the American Chemical Society 135, 10274 (2013).
[33]D. Jariwala, V. K. Sangwan, L. J. Lauhon, T. J. Marks, and M. C. Hersam, ACS nano 8, 1102 (2014).
[34]J. Kang, W. Liu, D. Sarkar, D. Jena, and K. Banerjee, Physical Review X 4, 031005 (2014).
[35]Z. Yin et al., ACS nano 6, 74 (2012).
[36]A. Carvalho and A. H. C. Neto, Physical Review B 89, 081406(R) (2014).
[37]J.-Y. P. Noh, M.; Kim, Y.-S.; Kim, H. , arXiv: 1307.3813 (2013).
[38]K. Dolui, I. Rungger, and S. Sanvito, Physical Review B 87, 165402 (2013).
[39]K. Dolui, I. Rungger, C. Das Pemmaraju, and S. Sanvito, Physical Review B 88, 075420 (2013).
[40]R. Gillen, J. Robertson, and J. Maultzsch, physica status solidi (b) 251, 2620 (2014).
[41]R. Gillen, J. Robertson, and J. Maultzsch, Physical Review B 90, 075437 (2014).
[42]H.-J. Sung, D.-H. Choe, and K. J. Chang, New Journal of Physics 16, 113055 (2014).
[43]M. R. Laskar et al., Applied Physics Letters 104, 092104 (2014).
[44]S. Lebègue and O. Eriksson, Physical Review B 79, 115409 (2009).
[45]C. Ataca and S. Ciraci, The Journal of Physical Chemistry C 115, 13303 (2011).
[46]C. Ataca, H. Şahin, E. Aktürk, and S. Ciraci, The Journal of Physical Chemistry C 115, 3934 (2011).
[47]A. R. Botello-Mendez, F. Lopez-Urias, M. Terrones, and H. Terrones, Nanotechnology 20, 325703 (2009).
[48]A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, Nano letters 10, 1271 (2010).
[49]R. O. Lussow, Journal of The Electrochemical Society 115, 660 (1968).
[50]L. T. Zhuravlev, Colloid Surface A 173, 1 (2000).
[51]R. Mueller, H. K. Kammler, K. Wegner, and S. E. Pratsinis, Langmuir 19, 160 (2003).
[52]D. Ceresoli, M. Bernasconi, S. Iarlori, M. Parrinello, and E. Tosatti, Phys Rev Lett 84, 3887 (2000).
[53]F. Mazen, T. Baron, G. Brémond, N. Buffet, N. Rochat, P. Mur, and M. N. Séméria, Journal of The Electrochemical Society 150, G203 (2003).
[54]A. Stesmans, B. Nouwen, D. Pierreux, and V. V. Afanas''ev, Applied Physics Letters 80, 4753 (2002).
[55]S. T. Pantelides, Z. Y. Lu, C. Nicklaw, T. Bakos, S. N. Rashkeev, D. M. Fleetwood, and R. D. Schrimpf, Journal of Non-Crystalline Solids 354, 217 (2008).
[56]T. Suzuki, L. Skuja, K. Kajihara, M. Hirano, T. Kamiya, and H. Hosono, Phys Rev Lett 90, 186404 (2003).
[57]G. Lucovsky, Philosophical Magazine Part B 39, 531 (1979).
[58]M. Kastner, D. Adler, and H. Fritzsche, Physical Review Letters 37, 1504 (1976).
[59]G. N. Greaves, Philosophical Magazine Part B 37, 447 (1978).
[60]G. N. Greaves, Journal of Non-Crystalline Solids 32, 295 (1979).
[61]G. Lucovsky, Philosophical Magazine Part B 39, 513 (1979).
[62]G. Lucovsky, Journal of Non-Crystalline Solids 35–36, Part 2, 825 (1980).
[63]K. Hubner, Journal of Physics C: Solid State Physics 17, 6553 (1984).
[64]J. Robertson, Journal of Physics C: Solid State Physics 17, L221 (1984).
[65]J. Robertson, Philosophical Magazine Part B 52, 371 (1985).
[66]L. P. Ginzburg, Journal of Non-Crystalline Solids 171, 164 (1994).
[67]L. Martin-Samos, Y. Limoge, J. P. Crocombette, G. Roma, N. Richard, E. Anglada, and E. Artacho, Physical Review B 71, 014116 (2005).
[68]L. Martin-Samos, Y. Limoge, and G. Roma, Physical Review B 76, 104203 (2007).
[69]M. Otani, K. Shiraishi, and A. Oshiyama, Physical Review Letters 90 (2003).
[70]M. Otani, K. Shiraishi, and A. Oshiyama, Physical Review B 68, 184112 (2003).
[71]C.-L. Kuo and G. S. Hwang, Physical Review B 79, 165201 (2009).
[72]E.-C. Lee and K. J. Chang, Physica B: Condensed Matter 340-342, 974 (2003).
[73]W. Orellana, Applied Physics Letters 84, 933 (2004).
[74]D. L. Griscom, Journal of Non-Crystalline Solids 357, 1945 (2011).
[75]J. Lægsgaard and K. Stokbro, Physical Review B 61, 12590 (2000).
[76]Y. Y. Huang, Master thesis of Y. Y. Huang (2013).
[77]N. R. Pradhan, D. Rhodes, Q. Zhang, S. Talapatra, M. Terrones, P. M. Ajayan, and L. Balicas, Applied Physics Letters 102, 123105 (2013).
[78]R. Y. e. al., arXiv: 1211.4136 (2013).
[79]H. Fang, M. Tosun, G. Seol, T. C. Chang, K. Takei, J. Guo, and A. Javey, Nano letters 13, 1991 (2013).
[80]S. Das, H. Y. Chen, A. V. Penumatcha, and J. Appenzeller, Nano letters 13, 100 (2013).
[81]S. McDonnell, R. Addou, C. Buie, R. M. Wallace, and C. L. Hinkle, ACS nano 8, 2880 (2014).
[82]N. Kaushik, A. Nipane, F. Basheer, S. Dubey, S. Grover, M. M. Deshmukh, and S. Lodha, Applied Physics Letters 105, 113505 (2014).
[83]S. Walia et al., Applied Physics Letters 103, 232105 (2013).
[84]Y. Du, H. Liu, A. T. Neal, M. Si, and P. D. Ye, IEEE Electron Device Letters 34, 1328 (2013).
[85]C. Gong, L. Colombo, R. M. Wallace, and K. Cho, Nano letters 14, 1714 (2014).
[86]L. P. Feng, J. Su, D. P. Li, and Z. T. Liu, Physical chemistry chemical physics : PCCP 17, 6700 (2015).
[87]I. Popov, G. Seifert, and D. Tománek, Physical Review Letters 108, 156802 (2012).
[88]L.-p. Feng, J. Su, and Z.-t. Liu, RSC Adv. 5, 20538 (2015).
[89]W. Chen, E. J. Santos, W. Zhu, E. Kaxiras, and Z. Zhang, Nano letters 13, 509 (2013).
[90]H. B. Michaelson, Journal of Applied Physics 48, 4729 (1977).
[91]W. Liu, J. Kang, D. Sarkar, Y. Khatami, D. Jena, and K. Banerjee, Nano letters 13, 1983 (2013).
[92]T. C. Leung, C. L. Kao, W. S. Su, Y. J. Feng, and C. T. Chan, Physical Review B 68, 195408 (2003).
[93]K. T. Chan, J. B. Neaton, and M. L. Cohen, Physical Review B 77, 235430 (2008).

QRCODE
 
 
 
 
 
                                                                                                                                                                                                                                                                                                                                                                                                               
第一頁 上一頁 下一頁 最後一頁 top
無相關點閱論文