title: Large thermoelectric figure-of-merits from SiGe nanowires by simultaneously measuring electrical and thermal transport properties.
abstract: The strongly correlated thermoelectric properties have been a major hurdle for high-performance thermoelectric energy conversion. One possible approach to avoid such correlation is to suppress phonon transport by scattering at the surface of confined nanowire structures. However, phonon characteristic lengths are broad in crystalline solids, which makes nanowires insufficient to fully suppress heat transport. Here, we employed Si-Ge alloy as well as nanowire structures to maximize the depletion of heat-carrying phonons. This results in a thermal conductivity as low as ∼1.2 W/m-K at 450 K, showing a large thermoelectric figure-of-merit (ZT) of ∼0.46 compared with those of SiGe bulks and even ZT over 2 at 800 K theoretically. All thermoelectric properties were "simultaneously" measured from the same nanowires to facilitate accurate ZT measurements. The surface-boundary scattering is prominent when the nanowire diameter is over ∼100 nm, whereas alloying plays a more important role in suppressing phonon transport for smaller ones.
authors.affiliation: Frontier Research Laboratory, Samsung Advanced Institute of Technology, Samsung Electronics, Yongin, Kyunggi-do 446-712, South Korea.
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Lee
authors.forename: Liang
authors.initials: L
authors.lastname: Yin
authors.forename: Yongjin
authors.initials: Y
authors.lastname: Lee
authors.forename: Jong Woon
authors.initials: JW
authors.lastname: Lee
authors.forename: Sang Jin
authors.initials: SJ
authors.lastname: Lee
authors.forename: Junho
authors.initials: J
authors.lastname: Lee
authors.forename: Seung Nam
authors.initials: SN
authors.lastname: Cha
authors.forename: Dongmok
authors.initials: D
authors.lastname: Whang
authors.forename: Gyeong S
authors.initials: GS
authors.lastname: Hwang
authors.forename: Kedar
authors.initials: K
authors.lastname: Hippalgaonkar
authors.forename: Arun
authors.initials: A
authors.lastname: Majumdar
authors.forename: Choongho
authors.initials: C
authors.lastname: Yu
authors.forename: Byoung Lyong
authors.initials: BL
authors.lastname: Choi
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Kim
authors.forename: Kinam
authors.initials: K
authors.lastname: Kim
mesh_terms: D004579:Electron Transport; D004735:Energy Transfer; D005857:Germanium / Q000737:chemistry*; D006358:Hot Temperature; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties; D013814:Thermal Conductivity
chemical_list: D046911:Macromolecular Substances; D005857:Germanium; D012825:Silicon