Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session Y23: Thermoelectrics, Low Dimensional MaterialsFocus

Hide Abstracts 
Sponsoring Units: DMP GERA FIAP Chair: Zhiting Tian, Virginia Tech Room: 322 
Friday, March 18, 2016 11:15AM  11:27AM 
Y23.00001: Optimizing Thermoelectric Properties in Composites Michael J. Adams, Hyungyu Jin, Joseph P. Heremans Here we consider semiconductor composites as a way to yield high thermoelectric figure of merit. Effective medium theory limits the figure of merit of a composite made from two noninteracting materials, A and B, to the larger of the two [1, 2]. In previous work, we describe a mechanism that can lift this limitation by treating charge and heat flux separately. Silica beads coated with a conducting shell are inserted into a thermoelectric host. Thermal conductivity decreases with insulating material added, but electrical conductivity is maintained via locally conducting surfaces. We apply the theory to ptype (Bi,Sb)2Te3 host material. Several permutations are possible: Tecoated beads in Sbrich material, or Sbcoated beads in Terich material. First, we review data for varying bead coatings and heat treatments, followed by varying stoichiometry in the host. New data considers an additional parameter of varying bead diameter, as well as optimizing these parameters simultaneously to enhance thermoelectric performance. References: [1] David J. Bergman and Ohad Levy, J. Appl. Phys. 70 6821 (1991) [2] David J. Bergman and Leonid G. Fel, J. Appl. Phys. 85 8205 (1999) [Preview Abstract] 
Friday, March 18, 2016 11:27AM  11:39AM 
Y23.00002: High thermoelectric figureofmerit in Sb$_{\mathrm{2}}$Te$_{\mathrm{3}}$/Ag$_{\mathrm{2}}$Te bulk composites as Pbfree $p$type thermoelectric materials MinHo Lee, JongSoo Rhyee, SuDong Park We investigated thermoelectric properties of the Sb$_{\mathrm{2}}$Te$_{\mathrm{3}}$/Ag$_{\mathrm{2}}$Te (ST/AT) composites with molar ratios of ST/AT $=$ 1/1, 2/1, 4/1, 8/1, 16/1, and 32/1. The extrinsic composites, synthesized by wet ball milling of two separate powders of Sb$_{\mathrm{2}}$Te$_{\mathrm{3}}$ and Ag$_{\mathrm{2}}$Te, are differentiated with intrinsic composites by high temperature phase separation in that it is low temperature synthesis process. The thermoelectric properties of the composites show systematic behaviour of decreased electrical and thermal conductivities with increasing Ag$_{\mathrm{2}}$Te dispersion concentration. The ST/AT $=$ 1/1 composite exhibits extremely low lattice thermal conductivity with high power factor over a wide temperature range, resulting in high \textit{ZT} value 1.5 at 700 K, which is the significantly enhanced value of \textit{ZT} compared with other Pbfree $p$type chalcogenide thermoelectric materials. [Preview Abstract] 
Friday, March 18, 2016 11:39AM  11:51AM 
Y23.00003: Coupled improvement between thermoelectric and piezoelectric materials David Montgomery, Corey Hewitt, Chaochao Dun, David Carroll A novel coupling effect in a thermoelectric and piezoelectric metastructure is discussed. Thermopiezoelectric generators (TPEGs) exhibit a synergistic effect that amplifies output voltage, and has been observed to increase piezoelectric voltages over 500{\%} of initial values a time dependent thermoelectric/pyroelectric effect. The resulting improvement in voltage has been observed in carbon nanotubes as well as inorganics such as twodimensional Bismuth Selenide platelets and Telluride nanorods thinfilm thermoelectrics. TPEGs are built by integrating insulating layers of polyvinylidene fluoride (PVDF) piezoelectric films between flexible thin film ptype and ntype thermoelectrics. The physical phenomena arising in the interaction between thermoelectric and piezoelectrics is discussed and a model is presented to quantify the expected coupling voltage as a function of stress, thermal gradient, and different thermoelectric materials. TPEG are ideal to capture waste heat and vibrational energy while creating larger voltages and minimizing space when compared with similar thermoelectric or piezoelectric generators. [Preview Abstract] 
Friday, March 18, 2016 11:51AM  12:03PM 
Y23.00004: Thermomagnetic transport properties of ferromagnetic MnBi Stephen Boona, Joseph Heremans Spindependent transport phenomena such as the spin Seebeck effect and magnon drag offer intriguing new possibilities for tuning the thermoelectric properties of magnetically ordered materials. One particularly interesting approach is to examine magnetic materials that are expected to display large intrinsic spin orbit coupling, such as MnBi. In spite of this material's popularity as a candidate for rareearth free permanent magnets, no studies have been published so far concerning its Seebeck or Nernst coefficients. This talk will discuss our recent measurements of the thermomagnetic properties of high purity polycrystalline MnBi between 2K and 385K and in magnetic fields up to 7T. Our measurements reveal the existence of a substantial anomalous Nernst effect (ANE) from 382K down to the spin reorientation temperature of 90K, while the other transport phenomena show relatively weak magnetic field dependence at all temperatures. We also observe that the Seebeck and ANE coefficients display strikingly similar temperature dependence, with the former peaking at approximately 10 $\mu $V/K and the latter at approximately 2.5 $\mu $V/K/T, hinting at the important role of spindependent processes in determining the transport properties of this material. [Preview Abstract] 
Friday, March 18, 2016 12:03PM  12:15PM 
Y23.00005: Integration of 2Dimensional Materials for Thermoelectric Power Generation Fadhel Alsaffar, Abdulrahman Al Hussain, Moh. R. Amer Recent developments in nanomaterial research have significantly progressed the performance of thermoelectric devices. Theoretical investigations of the thermoelectic properties of 2Dimentional monolayers demonstrate a high figure of merit (ZT) .[1, 2]. Here, we investigate the integration of these 2Dimensional materials for power generation applications using solar heat. We show that using black phosphorus monolayer (phosphorene) as the $p$type material, and Molybdenum disulfide (MoS$_{\mathrm{2}})$ monolayers as the $n$type material, we get an effective figure of merit (ZT) at least (1.5) with a conversion efficiency of 13{\%} at 280$^{\mathrm{o}}$C. Our results suggest that the integration of various 2Dimensional materials is a promising approach for commercial thermoelectric power generation applications. \textbf{References:} .[1] W. Huang, X. Luo, C. K. Gan, S. Y. Quek, and G. Liang, "Theoretical study of thermoelectric properties of fewlayer MoS 2 and WSe 2," \textit{Physical Chemistry Chemical Physics, }vol. 16, pp. 1086610874, 2014. [2] R. Fei, A. Faghaninia, R. Soklaski, J.A. Yan, C. Lo, and L. Yang, "Enhanced thermoelectric efficiency via orthogonal electrical and thermal conductances in phosphorene," \textit{Nano Letters, }vol. 14, pp. 63936399, 2014. [Preview Abstract] 
Friday, March 18, 2016 12:15PM  12:27PM 
Y23.00006: FirstPrinciples Study on Thermoelectric Performance of Phosphorene and Phosphorene Oxide Seungjun Lee, Jejune Park, SeoungHun Kang, YoungKyun Kwon Using firstprinciples density functional theory, we studied thermoelectric properties of phosphorene and its oxidized structure called phosphorene oxide (PO). Using the identified stable configurations and electronic structrues of phosphorene and PO, we solved the Boltzmann transport equation to evaluate their electrical conductivity, Seebeck coefficient, and thermal conductivity contributed from both electrons and phonons. In order to correctly estimate the thermoelectric figure of merit or ZT values, it is indispensable to determine the relaxation time, which can be estimated by applying the deformation potential theory. We observe that the electrical conductivity of phosphorene is higher along the armchair direction than along the zigzag direction, while the thermal conductivity shows an opposite behavior. Because of such an orthogonal relation between the electrical and thermal conductivities, phosphorene exhibits quite a large ZT value along the armchair direction. It is, on the other hand, calculated that PO has electrical conductivity similar to phosphorene, however its thermal conductivity is significantly smaller than phosphorene, resulting in larger ZT values. we expect that PO can be utilized for a high performance thermoelectric application. [Preview Abstract] 
Friday, March 18, 2016 12:27PM  1:03PM 
Y23.00007: Understanding phonon transport in thermoelectric materials using \textit{ab initio} approaches Invited Speaker: David Broido Good thermoelectric materials have low phonon thermal conductivity, k$_{ph}$ [1]. Accurate theories to describe k$_{ph}$ are important components in developing predictive models of thermoelectric efficiency that can help guide synthesis and measurement efforts. We have developed \textit{ab initio} approaches to calculate k$_{ph}$, in which phonon modes and phonon scattering rates are computed using interatomic force constants determined from density functional theory, and a full solution of the Boltzmann transport equation for phonons is implemented [25]. A recent approach to calculate interatomic force constants using \textit{ab initio} molecular dynamics [6] has yielded a good description of the thermal properties of Bi$_{2}$Te$_{3}$. But, the complexity of new promising candidate thermoelectric materials introduces computational challenges in assessing their thermal properties. An example is germanane, a germanium based hydrogenterminated layered semiconductor [7], which we will discuss in this talk. [1] H. J. Goldsmid, Thermoelectric Refrigeration (Plenum, New York, 1964); [2] D. A. Broido et al, Appl. Phys. Lett., 91, 231922 (2007); [3] A. Kundu et al, Phys. Rev. B, 84, 125426 (2011); [4] W. Li et al, Phys. Rev. B 86, 174307 (2012); [5] Olle Hellman and I. A. Abrikosov, Phys. Rev. B 88, 144301 (2013); [6] O. Hellman and D. A. Broido, Phys. Rev. B 90, 134309 (2014); [7] E. Bianco, et al., ACS Nano 7, 4414 (2013). [Preview Abstract] 
Friday, March 18, 2016 1:03PM  1:15PM 
Y23.00008: Ab initio theory of thermal properties of germanane Matthew Heine, Lucas Lindsay, Jes\'{u}s Carrete, Natalio Mingo, Olle Hellman, David Broido Germanane(GeH) is a germanium based hydrogenterminated multilayered graphane analogue semiconductor, which may be a promising thermoelectric due to its high electron mobility and the capability to tune its transport properties [1]. We have performed first principles calculations of the thermal properties of germanane. Harmonic and anharmonic interatomic force constants are calculated within the framework of density functional theory, from which phonon dispersions, specific heat, thermal expansion are obtained. The phonon Boltzmann equation is solved to obtain the lattice thermal conductivity. The disparity in constituent masses in GeH gives phonon modes that are distinctly Ge or H in character and causes the specific heat not to saturate until much higher temperatures than in bulk Ge. Weak interlayer bonding and strong phononphonon scattering result in highly anisotropic and quite low intrinsic lattice thermal conductivity compared to Ge. \newline [1] E. Bianco et. al., ACS Nano 7, 44144421 (2013). [Preview Abstract] 
Friday, March 18, 2016 1:15PM  1:27PM 
Y23.00009: Thermal Conductance at the 2D MoS$_{\mathrm{2}}$hexagonal Boron Nitride Interface Yi Liu, Kedar HIPPALGAONKAR, Zhun Yong Ong, John TL Thong, Chengwei Qiu In recent years, a number of 2D heterostructure devices have emerged, including graphene/hexagonal boron nitride ($h$BN), graphene/MoS$_{\mathrm{2}}$ and MoS$_{\mathrm{2}}$/$h$BN. Among them, MoS$_{\mathrm{2}}$/$h$BN fieldeffect transistors with MoS$_{\mathrm{2}}$~channels and~$h$BN dielectric have been reported to have higher carrier mobility and reduced hysteresis compared to MoS$_{\mathrm{2}}$~on SiO$_{\mathrm{2}}$. Despite relatively high inplane thermal conductivity of MoS$_{\mathrm{2}}$~and~$h$BN, heat dissipation from these 2D devices is mainly limited by heat transfer in the vertical direction. Consequently, their operating temperatures are strongly influenced by the interface thermal conductance. In this work, we demonstrate the measurement of interface thermal conductance between MoS$_{\mathrm{2}}$~and~$h$BN. This is realized by electrically heating MoS$_{\mathrm{2}}$~and monitoring their temperatures through Raman spectroscopy. The obtained interface thermal conductance between MoS$_{\mathrm{2}}$~and~$h$BN is 1.77 MW/m$^{\mathrm{2}}$K, smaller than the reported value for the graphene/$h$BN interface, due to the weak coupling of phonon modes between MoS$_{\mathrm{2}}$~and~$h$BN based on our NEGF calculation. The low interface thermal conductance value suggests this interface is not favorable for heat dissipation, and should be considered carefully for the design of electronic and optoelectronic devices based on MoS$_{\mathrm{2}}$/$h$BN heterostructures. [Preview Abstract] 
Friday, March 18, 2016 1:27PM  1:39PM 
Y23.00010: Maximizing the thermoelectric performance of topological insulator Bi$_{\mathrm{2}}$Te$_{\mathrm{3}}$ films in the fewquintuple layer regime Huijun Liu, Jinghua Liang, Long Cheng, Jie Zhang, Zhenyu Zhang Using firstprinciples calculations and Boltzmann theory, we explore the feasibility to maximize the thermoelectric figure of merit (\textit{ZT}) of topological insulator Bi$_{\mathrm{2}}$Te$_{\mathrm{3}}$ films in the fewquintuple layer regime. We discover that the delicate competitions between the surface and bulk contributions, coupled with the overall quantum size effects, lead to a novel and generic nonmonotonous dependence of \textit{ZT} on the film thickness. In particular, when the system crosses into the topologically nontrivial regime upon increasing the film thickness, the much longer surface relaxation time associated with the robust nature of the topological surface states results in a maximal \textit{ZT} value, which can be further optimized to \textasciitilde 2.0 under physically realistic conditions. We also reveal the appealing potential of bridging the longstanding \textit{ZT} asymmetry of $p$ and $n$type Bi$_{\mathrm{2}}$Te$_{\mathrm{3}}$ systems. These findings help to establish intricate connections between the thermoelectric materials and topological insulators. [Preview Abstract] 
Friday, March 18, 2016 1:39PM  1:51PM 
Y23.00011: Temperature sensing and realtime twodimensional mapping at the microscale Xiaoye Huo, Gang Li, Zhenhai Wang, Xinyu Mao, Shengyong Xu To sense temperature at micro/nano scales and obtain its detailed distribution in space and in time remains a technical challenge in many cases. We observed an unexpected thermoelectric size effect, where the absolute Seebeck coefficient of metallic thin film stripes (e.g. Ni, Cr, Pd, W, Bi, Sc, etc.) decreased with the stripe width from 100$\mu $m down to 100nm. This phenomenon was utilized in micro/nanostripebased thin film temperature sensors. By using an array of such sensors, twodimensional temperature distribution at the microscale could be precisely mapped. Small temperature sensors with a total width less than 1$\mu $m and a sensitivity of 0.52.2$\mu $V/K were fabricated, showing a potential for monitoring temperatures at submicroscales. By using a special multiplexer and software, nearly realtime 2D temperature mapping was performed, demonstrating 2D thermal history of target surface with a delay of less than one minute. These thin film sensors were also fabricated on flexible ParyleneC substrates for application in flexible electronic devices, temperature monitoring of cell culturing, and heat transfer between Au nanoparticles and metallic stripes due to plasmonic excitation under laser radiation. [Preview Abstract] 
Friday, March 18, 2016 1:51PM  2:03PM 
Y23.00012: Engineering GroupIV Monochalcogenides by Doping and Alloying Hansika Sirikumara, Trevor Fitzpatrick, Thushari Jayasekera GroupIV monochalcogenides, MX (M=Sn,Ge and X=S,Se) have shown to be promising materials for thermoelectric and photovoltaic applications. These properties can be further engineered by substitutional doping and alloying. Using the results from ab initio Density Functional Theory calculations, we identified a series of new class of monochalcogenide alloys in the form Ge(1x)SnxS, Ge(1x)SnxSe, GeSxSe(1 x), SnSxSe(1x). Stability of their twodimensional counterparts will also be discussed in this presentation. [Preview Abstract] 
Friday, March 18, 2016 2:03PM  2:15PM 
Y23.00013: Thermal conductivity behavior of superatom molecular crystals weeliat ong, Evan O’Brien, Patrick Dougherty, Jillian Epstein, C. Fred Higgs, Alan McGaughey, Xavier Roy, Jonathan Malen The room temperature thermal conductivity of several superatom molecular crystals (SMCs) are measured and found to be below 0.3 W/mK. The trend of room temperature thermal conductivity of the different crystals agree well with their sound speeds obtained independently using nanoindentation. These crystals, however, can exhibit noncrystalline thermal conductivity behavior depending on their constituent elements. A superatom is a cluster of atoms that acts as a stable entity [e.g., fullerenes (C60)]. By careful mixing and assembling these nanosized superatoms, the resulting superatomassembled materials hold promises for improving various technological devices. Organicinorganic superatoms can assemble into unary SMCs or cocrystallized with C60 superatoms into binary SMCs. Thermal transport is of considerable interest with possible new physics in these hierarchically atomic precise crystals in the low temperature regime. The thermal conductivity of the SMCs are measured using the frequency domain thermoreflectance setup. Unary SMCs exhibit an almost invariant thermal conductivity down to a temperature of 150 K. Binary SMCs, however, can either show a crystallinelike increase or an amorphouslike decrease with decreasing temperature. [Preview Abstract] 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2022 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700