Nanotechnology, Seebeck coefficient, figure of merit ZT

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1. Remove the plagiarism to below 15% without changing the science. You need a good knowledge of thermoelectric properties of a material. Do NOT use a software.

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Two-dimensional (2D) materials, such as graphene, hexagonal boron nitride (hBN), phosphorene, and transition metal dichalcogenides (TMDs) (e.g., MoS2,WS2, etc.), have attracted the attention of researchers in the last decades due to their extraordinary properties, and their various promising engineering applications. Graphene is well appreciated for its high electrical [1] and thermal conductivities[2] whereas hBN is an electrical insulator with to date an unmeasured thermal conductivity[3], [4]. The two-dimensional nanomaterials graphene and hexagonal boron nitride (h-BN) have good thermal properties. When the two are combined together to form a planar C-BN hybrid structure or a van der Waals heterostructure due to the differences in crystal lattice and the electronic structure between graphene and h-BN, the new material is formed with novel thermal characteristics. Recently, research groups worldwide have shown that by stacking two-dimensional(2D) crystals with different properties it is possible to create multi-layer materials, the Van der Waals Heterostructures (vdWHs), with highly-configurable electronic characteristics [5]. 2D heterostructures, for example, graphene/h-BN, graphene/MoS2, MoS2/MoSe2, and MoS2/h-BN, have emerged as a fascinating research topic. For instance, the applications of these 2D heterostructures in thermal management and thermoelectric energy generation are promising due to their attractive electrical and thermal transport properties. The technological potential of vdWHs is stimulating worldwide research including significant investment by industry, e.g., Samsung [6]. The application of vdWHs in thermo-electronics is still in research stage and more research is needed to understand and perfect their thermoelectric properties. Large-scale coplanar Graphene-hBN heterostructures have been successfully fabricated using chemical vapor deposition (CVD), enabling the possible control of periodic arrangements of domains whose sizes range from tens of nanometers to millimetres [7]–[10]. Their charge transport properties can be, however, quite surprising, such as the presence of a metal-insulator transition [11]–[13] and anomalous transport phenomena, that is not fully understood[14]. The unprecedented degree of tunability over the electronic properties of vdWHs suggests they are ideally placed to observe and exploit thermoelectric phenomena. Thermoelectric phenomena include the Peltier effect, where an electric potential difference can cause heating or cooling of material, and the Seebeck effect, where a temperature gradient can generate an electrical potential difference. These effects have been exploited in many technological applications: the Peltier effect is used to cool electronic devices from supercomputers to camping fridges and, due to the absence of moving parts, the Seebeck effect is exploited to scavenge heat in space technology applications and remote locations. Highly efficient thermoelectric devices can be created by utilizing quantum phenomena such as quantum tunnelling and charge coupling to the spin and lattice degrees of freedom [15]. Due to their reduced dimensionality and quantum confinement effects, 2D materials provide further enhancement of the Seebeck and Peltier coefficients. The graphene-hBN tunnel transistor comprises two graphene electrodes separated by an insulating hBN layer. Here, current flows by quantum tunnelling of electrons between the graphene electrodes through the hBN tunnel barrier. Their electronic properties can be tuned by controlling the relative alignment of the lattices of the two graphene electrodes and has promising properties for applications in high-frequency electronics and logic devices [16]. Thermoelectric effects often rely on strong asymmetry in the electronic density of states either side of a junction between two materials [17]. Electrostatic gating of graphene-hBN tunnel transistors allows precise control over the alignment of the density of states between the two graphene layers. Therefore, after the optimization of their layer and electrostatic configuration, we expect these devices to exhibit a tremendous and tuneable thermoelectric response. In this work we will study some important thermoelectric effects, such as Peltier effect, Seebeck effect, the coefficient of performance and figure-of-merit (ZT). Both the optimization of thermal and electrical transport properties are important in constructing an efficient direct energy conversion device. 1.1.1 Thermoelectric properties The thermal conductivity (TC), thermal resistance (TR), thermal rectification, and thermoelectric effects of nanomaterials affect the performance of microelectronic devices. Thermoelectrics is the field of study where a temperature gradient can be converted to electrical power and vice versa. In a typical thermoelectric device, a junction is formed between two different types of semiconducting materials, with one being p-type containing holes, while the other being n-type containing electrons as the major carrier. As shown in Fig. 1a, a temperature difference ∆𝑇 at the junction causes the carriers to flow away from the junction, leading to an open circuit voltage V and thus forming an electrical generator. This is called the Seebeck effect. 𝑆 = 𝑉 ∆𝑇 is defined as the Seebeck coefficient [18]. On the other side, when an electric current 𝐼 is passing through the junction, both electrons and holes move away from the junction and carry heat energy 𝑄 away, thus cooling the junction, which is called the Peltier effect. The ratio of 𝑄 to 𝐼 is defined as the Peltier coefficient. 𝑃𝑒𝑙𝑡𝑖𝑒𝑟 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 = 𝑄 𝐼 Figure 1. Schematic illustration of the thermoelectric effect. (a) thermoelectric generatoer (Seebeck effect). (b) thermoelectric cooler (Pertier effect)[19]. The quality factor (dimensionless figure of merit), 𝑇𝑍, is an important parameter to measure the performance of thermoelectric devices. It is expressed as:[18]–[20] 𝑆 2𝜎 𝑍𝑇 = 𝑇 𝑘 Where, 𝑆 is the Seebeck coefficient, 𝜎 is the electrical conductivity of the thermoelectric material, 𝑇 is the absolute temperature, and 𝑘 is the TC. Therefore, to improve the thermoelectric conversion efficiency of a thermoelectric device, a large Seebeck coefficient 𝑆, a high electrical conductivity 𝜎, and a low 𝑘 are required. Figure of merit is employed to evaluate the efficiency of thermal-to-electric energy conversion[18] of a material. For graphene, although a high Seebeck coefficient is observed,[21] its ultra-high thermal conductivity[22] offsets its advantage in the power factor and thus limits its application as an efficient thermoelectric material. In future thermal management and thermoelectric applications, it is expected that new 2D hybrid and novel van der waals heterostructures based on 2D materials with much large figure of merit will be discovered, leading to their values to be much higher than 3, and making heat-toelectricity energy generation commercially viable. To make this a reality, more systematic studies are needed to further understand the fascinating properties of this class of materials and to seek their novel thermoelectric applications. The electrical conductivity (σ) and electron thermal con- ductivity (ke) are proportional because of the Wiedemann-Franz law, which suggests optimization should be focused around increasing the Seebeck coefficient. the efficiency of the thermoelectric technology is still limited by currently available thermoelectric materials. The priority aim in thermoelectric industry is to achieve a higher ZT, the dimensionless thermoelectric figure of merit. There are key thermoelectric properties determining the efficiency ZT: Seebeck coefficient, electrical conductivity, and thermal conductivity. The efficiency of a thermoelectric system is measured through a dimensionless quantity referred to as the thermoelectric figure of merit 1.1.2 Graphene/h-BN van der Waals heterostructures Suspended graphene requires the aid of a substrate during its use and migration. Hexagonal boron nitride is the best substrate for graphene. The initial introduction of h-BN as a substrate is due to hBN and graphene having similar lattice structures [23]–[28], as the lattice mismatch between the two is only 1.7%. Different from substrates such as Si, SiC, or SiO2 [29]–[32] h-BN has the atomic level of a flat surface, very low roughness, almost no dangling bonds on the surface, and weaker van der Waals forces than graphene; there are smaller effects on the performance of graphene, and it provides outstanding performance [33], [34]. The different structure and combination of the two have special significance for controlling the electrical, magnetic, and thermal properties of composite materials[35]. This is a very important application value for the preparation of micro-nanoscale functional devices. The research on the double-layer graphene/h-BN heterostructure has become popular. 1.2 Challenge/problem Globally, there is a need for fast, efficient, and small electronics. Besides, Power dissipation in modern integrated circuits has become a big problem because it limits the performance of electronics. However, thermoelectric-energy-conversion techniques can be used to save this energy and improve the performance of devices. Two-dimensional (2D) materials show great promises for application in electronic devices and may solve these problems. My study which focus on 2D materials will contribute to this goal. [1] K. S. Novoselov et al., “Electric Field Effect in Atomically Thin Carbon Films,” vol. 306, no. September, pp. 666–670, 2004. [2] A. A. Balandin et al., “Superior Thermal Conductivity of Single-Layer Graphene 2008,” 2008. [3] I. Jo et al., “Thermal Conductivity and Phonon Transport in Suspended Few- Layer Hexagonal Boron Nitride,” 2013. [4] C. Wang, J. Guo, L. Dong, A. Aiyiti, X. Xu, and B. Li, “Superior thermal conductivity in suspended bilayer hexagonal boron nitride,” Nat. Publ. Gr., pp. 6–11, 2016. [5] R. Summary, “2D materials and van der Waals heterostructures.” [6] H. Lee, M. Kim, I. Kim, and H. Lee, “Flexible and Stretchable Optoelectronic Devices using Silver Nanowires and Graphene,” pp. 4541–4548, 2016. [7] M. P. Levendorf et al., “for atomically thin circuitry,” Nature, vol. 488, no. 7413, pp. 627– 632, 2012. [8] Z. Liu et al., “In-plane heterostructures of graphene and hexagonal boron nitride with controlled domain sizes,” Nat. Nanotechnol., vol. 8, no. 2, pp. 119–124, 2013. [9] C. Lee, N. J. Kybert, M. B. Lerner, G. H. Han, and J. A. Rodrı, “Continuous Growth of Hexagonal Graphene and Boron Nitride In-Plane Heterostructures by Atmospheric Pressure Chemical Vapor Deposition,” no. 11, pp. 10129–10138, 2013. [10] R. W. Ziolkowski et al., “Heteroepitaxial Growth of,” vol. 343, no. January, pp. 163–167, 2014. [11] Y. Gong et al., “Direct chemical conversion of graphene to boron- and nitrogen- and carboncontaining atomic layers,” Nat. Commun., vol. 5, pp. 1–8, 2014. [12] L. Matthes, P. Gori, O. Pulci, and F. Bechstedt, “Universal infrared absorbance of twodimensional honeycomb group-IV crystals,” vol. 035438, pp. 1–9, 2013. [13] R. Zhao, J. Wang, M. Yang, Z. Liu, and Z. Liu, “BN-Embedded Graphene with a Ubiquitous Gap Opening,” 2012. [14] L. Song et al., “Anomalous insulator-metal transition in boron nitride-graphene hybrid atomic layers,” vol. 075429, pp. 1–12, 2012. [15] M. Walter et al., “Seebeck effect in magnetic tunnel junctions,” Nat. Mater., vol. 10, no. 10, pp. 742–746, 2011. [16] A. Mishchenko et al., “Twist-controlled resonant tunnelling in graphene / boron nitride / graphene heterostructures,” no. September, pp. 1–6, 2014. [17] J. J. Van Den Berg, F. K. Dejene, and B. J. Van Wees, “Direct electronic measurement of Peltier cooling and heating in graphene,” Nat. Commun., vol. 7, no. May, pp. 1–6, 2016. [18] E. D. M. Rowe, D. Ph, D. Sc, and F. Group, HANDBOOK. 2006. [19] G. Zhang and Y. W. Zhang, “Thermoelectric properties of two-dimensional transition metal dichalcogenides,” J. Mater. Chem. C, vol. 5, no. 31, pp. 7684–7698, 2017. [20] A. J. Minnich, M. S. Dresselhaus, Z. F. Ren, and G. Chen, “Bulk nanostructured thermoelectric materials : current research and future prospects,” pp. 466–479, 2009. [21] F. Ghahari, H. Xie, T. Taniguchi, K. Watanabe, M. S. Foster, and P. Kim, “Enhanced Thermoelectric Power in Graphene : Violation of the Mott Relation by Inelastic Scattering,” vol. 136802, no. April, pp. 1–5, 2016. [22] A. A. Balandin, “nanostructured carbon materials,” Nat. Publ. Gr., vol. 10, no. 8, pp. 569– 581, 2011. [23] M. Wang, G. Zhang, H. Peng, and C. Yan, “Energetic and thermal properties of tilt grain boundaries in graphene/hexagonal boron nitride heterostructures,” Funct. Mater. Lett., vol. 8, no. 3, pp. 16–18, 2015. [24] K. Yang, Y. Chen, R. D’Agosta, Y. Xie, J. Zhong, and A. Rubio, “Enhanced thermoelectric properties in hybrid graphene/boron nitride nanoribbons,” Phys. Rev. B - Condens. Matter Mater. Phys., vol. 86, no. 4, pp. 1–8, 2012. [25] R. Drost, A. Uppstu, F. Schulz, and S. K. Ha, “Electronic States at the Graphene − Hexagonal Boron Nitride Zigzag Interface,” 2014. [26] P. Karamanis, N. Otero, and C. Pouchan, “Electric property variations in nanosized hexagonal boron nitride/graphene hybrids,” J. Phys. Chem. C, vol. 119, no. 21, pp. 11872–11885, 2015. [27] J. Jung, Z. Qiao, Q. Niu, and A. H. Macdonald, “Background Note : Portugal PROFILE,” pp. 1–7, 2004. [28] G. Gao et al., “Artificially stacked atomic layers: Toward new van der waals solids,” Nano Lett., vol. 12, no. 7, pp. 3518–3525, 2012. [29] W. L. Janes and D. M. Taylor, “Developments in the Practical Reconstruction of Blood Spatter Events,” Forensic Sci. Program, Dep. Chem., p. 159, 2001. [30] F. Hüser, T. Olsen, and K. S. Thygesen, “Quasiparticle GW calculations for solids, molecules, and two-dimensional materials,” Phys. Rev. B - Condens. Matter Mater. Phys., vol. 87, no. 23, pp. 1–14, 2013. [31] J. Xue et al., “Scanning tunnelling microscopy and spectroscopy of ultra-flat graphene on hexagonal boron nitride,” Nat. Mater., vol. 10, no. 4, pp. 282–285, 2011. [32] G. Argentero et al., “Unraveling the 3D Atomic Structure of a Suspended Graphene/hBN van der Waals Heterostructure,” Nano Lett., vol. 17, no. 3, pp. 1409–1416, 2017. [33] A. S. Mayorov et al., “Micrometer-scale ballistic transport in encapsulated graphene at room temperature,” Nano Lett., vol. 11, no. 6, pp. 2396–2399, 2011. [34] C. R. Dean et al., “Boron nitride substrates for high-quality graphene electronics,” Nat. Nanotechnol., vol. 5, no. 10, pp. 722–726, 2010. [35] J. Wang et al., “The thermal and thermoelectric properties of in-plane C-BN hybrid structures and graphene / h-BN van der Waals heterostructures,” Mater. Today Phys., vol. 5, pp. 29–57, 2018. Sue24 by Edward Ma Submission date: 03-Jan-2019 11:13PM (UT C-0700) Submission ID: 1061432688 File name: Background_inf o.docx (165.49K) Word count: 2210 Character count: 12613 Sue24 ORIGINALITY REPORT 66 % SIMILARIT Y INDEX 33% 62% 19% INT ERNET SOURCES PUBLICAT IONS ST UDENT PAPERS PRIMARY SOURCES 1 Jingang Wang, Xijiao Mu, Xinxin Wang, Nan Wang, Fengcai Ma, Wenjie Liang, Mengtao Sun. "The thermal and thermoelectric properties of in-plane C-BN hybrid structures and graphene/h-BN van der Waals heterostructures", Materials Today Physics, 2018 15% Publicat ion 2 Gang Zhang, Yong-Wei Zhang. "Strain effects on thermoelectric properties of twodimensional materials", Mechanics of Materials, 2015 12% Publicat ion 3 José Eduardo Barrios-Vargas, Bohayra Mortazavi, Aron W. Cummings, Rafael Martinez-Gordillo et al. "Electrical and Thermal Transport in Coplanar Polycrystalline Graphene–hBN Heterostructures", Nano Letters, 2017 Publicat ion www.ideals.illinois.edu 4% 4 5 6 7 Int ernet Source 3% Submitted to University of Nottingham 2% St udent Paper tesisenxarxa.net Int ernet Source Logoteta, D., G. Fiori, and G. Iannaccone. "Optimization and benchmarking of graphenebased heterostructure FETs", 2014 International Workshop on Computational Electronics (IWCE), 2014. 2% 1% Publicat ion 8 Kexiu Dong, Dunjun Chen, Yujie Wang, Yonghua Shi, Wenjuan Yu, Jianping Shi. "AlGaN Solar-Blind Avalanche Photodiodes With p-Type Hexagonal Boron Nitride", IEEE Photonics Technology Letters, 2018 1% Publicat ion 9 10 epub.uni-regensburg.de Int ernet Source Wang, Han, Thiti Taychatanapat, Allen Hsu, Kenji Watanabe, Takashi Taniguchi, Pablo Jarillo-Herrero, and Tomas Palacios. "BN/Graphene/BN Transistors for RF Applications", IEEE Electron Device Letters, 2011. 1% 1% Publicat ion 11 12 13 tud.qucosa.de Int ernet Source Submitted to University of Southampton St udent Paper Rakesh D. Mahyavanshi, Golap Kalita, Ajinkya Ranade, Pradeep Desai, Masaharu Kondo, Takehisa Dewa, Masaki Tanemura. "Photovoltaic Action With Broadband Photoresponsivity in Germanium-MoS₂ Ultrathin Heterojunction", IEEE Transactions on Electron Devices, 2018 1% 1% 1% Publicat ion 14 Xu, Yin, Yun Ji Kim, Yonghun Kim, Young Gon Lee, and Byoung Hun Lee. "Extraction of the Interface State Density of Top-Gate Graphene Field-Effect Transistors", IEEE Electron Device Letters, 2015. 1% Publicat ion 15 Itai Leven, Tal Maaravi, Ido Azuri, Leeor Kronik, Oded Hod. " Interlayer Potential for Graphene/ -BN Heterostructures ", Journal of Chemical Theory and Computation, 2016 1% Publicat ion 16 Gibertini, Marco, Giovanni Pizzi, and Nicola Marzari. "Engineering polar discontinuities in 1% honeycomb lattices", Nature Communications, 2014. Publicat ion 17 18 thesis.library.caltech.edu Int ernet Source Mina Park, Aram Lee, Ho Kyun Rho, Seoung-Ki Lee et al. "Large area thermal light emission from autonomously formed suspended graphene arrays", Carbon, 2018 1% 1% Publicat ion 19 20 hal.archives-ouvertes.fr Int ernet Source Yazdanpanah Goharrizi, Arash, Milad Zoghi, and Mehdi Saremi. "Armchair Graphene Nanoribbon Resonant Tunneling Diodes Using Antidote and BN Doping", IEEE Transactions on Electron Devices, 2016. 1% 1% Publicat ion 21 22 Submitted to University of Warwick St udent Paper Ken-ichi Uchida, Hiroto Adachi, Takashi Kikkawa, Akihiro Kirihara et al. "Thermoelectric Generation Based on Spin Seebeck Effects", Proceedings of the IEEE, 2016 Publicat ion 23 Yu, Zhi Gen, and Yong-Wei Zhang. "Band gap 1% 1% engineering of graphene with inter-layer embedded BN: From first principles calculations", Diamond and Related Materials, 2015. 1% Publicat ion 24 Ye, Tao, Li Jun, Li Kun, Wang Hu, Chen Ping, Duan Ya-Hui, Chen Zheng, Liu Yun-Fei, Wang Hao-Ran, and Duan Yu. "Inkjet-printed Ag grid combined with Ag nanowires to form a transparent hybrid electrode for organic electronics", Organic Electronics, 2016. 1% Publicat ion 25 26 tplab.vuse.vanderbilt.edu Int ernet Source Minglei Sun, Jyh-Pin Chou, Lihong Shi, Junfeng Gao, Alice Hu, Wencheng Tang, Gang Zhang. " Few-Layer PdSe Sheets: Promising Thermoelectric Materials Driven by High Valley Convergence ", ACS Omega, 2018 1% 1% Publicat ion 27 28 Submitted to Chungnam National University St udent Paper Jing Wu, Yabin Chen, Junqiao Wu, Kedar Hippalgaonkar. "Perspectives on Thermoelectricity in Layered and 2D Materials", Advanced Electronic Materials, 2018 Publicat ion 1% 1% 29 30 31 32 33 science.sciencemag.org Int ernet Source www.etsf.eu Int ernet Source Submitted to University of Technology, Sydney St udent Paper Submitted to University College London St udent Paper Gang Zhang, Yong-Wei Zhang. "Thermal properties of two-dimensional materials", Chinese Physics B, 2017 1% 1% 1% 1% 1% Publicat ion 34 35 Submitted to Associatie K.U.Leuven St udent Paper Bianchi, Catarina, Joana Loureiro, Paulo Duarte, Jose Marques, Joana Figueira, Ines Ropio, and Isabel Ferreira. "V2 O5 Thin Films for Flexible and High Sensitivity Transparent Temperature Sensor", Advanced Materials Technologies, 2016.
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Materials that are configured in two-dimension (2D), such as hexagonal boron nitride ( hBN ) ,
graphene, phosphorene, and transition metal dichalcogenides (TMDs) (for example, WS2,MoS2,
etc.), have the attention of researchers in the last number of years. This to credit goes to their
extraordinary properties, and their various promising engineering applications. Graphene is known
for being a superb electrical conductor [1] including its high thermal conductivity [2] while hBN is a
poor conductor of electricity as well as an infinite thermal conductor[3], [4].
Nanomaterials graphene with two-dimensional configuration together with hexagonal boron nitride

( hBN )

have good heat transfer properties. Combining the dual due to the differences structure of the

electrons and crystal lattice, the new material formed has a van der Waals heterostructure or a planar
C-BN hybrid structure with novel thermal characteristics.
Recently, research groups worldwide have shown that by stacking crystals of two-dimensional(2D)
configurations with different properties, multi-layer materials can be created, the Van der Waals
Heterostructures ( vdWHs ) , characterised with electronic properties that are highly configurable [5].
2D materials with heterostructures, e.g., graphene/h-BN, MoS2/MoSe2, graphene/MoS2, and
MoS2/h-BN, is an interesting emerging topic of research. For instance, 2D heterostructures’
applications in management of thermal properties and generation of thermoelectric energy are
assuring. This is because of their attractive electrical and thermal transport characteristics. The
technological potential of vdWHs is stimulating worldwide research including significant investment
by industry, e.g., Samsung [6].
The application of vdWHs in thermo-electronics is still in research stage and more research is needed
to understand and perfect their thermoelectric properties. The fabrication of coplanar Graphene-hBN
heterostructures on large scale have been a success by the help of chemical vapor deposition ( CVD ) .
This has enabled the control of domains periodic arrangements with sizes of a range of tens of
nanometers to millimetres [7]–[10]. These large scale coplanar Graphene-hBN heterostructures
charge transport characteristics can be, however, utterly astonishing, like the having a metal
insulator transition [11]–[13] and phenomena of anomalous transport, that is not wholly
comprehended [14].
The unprecedented degree of tunability over the electronic properties of vdWHs suggests they are
ideally placed to observe and exploit thermoelectric phenomena. Thermoelectric phenomena include
the Peltier effect, where an electric potential difference can cause heating or cooling of material, and
the Seebeck effect, where a temperature gradient can generate an electrical potential difference.
These effects have been exploited in many technological applications: the Peltier effect is used to
cool electronic devices from supercomputers to camping fridges and, due to the absence of moving
parts, the Seebeck effect is exp...


Anonymous
Just what I needed…Fantastic!

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