Unexpected size effect in the thermopower of thin-film stripes

For low-dimensional materials, size effect of a physical property is usually expected to occur when one (or more) of the dimension sizes decreases to that comparable to or smaller than one of the intrinsic characteristic lengths, e.g., the mean free path. We report here an unexpected size effect, that in centimeter-long stripes of 100-nm-thick metallic thin films, a reduction of the absolute value of thermopower occurs when the stripe width is in the order of 30-50 μm, which is 100–1000 times larger than the intrinsic mean free path of the material. When the stripe width is reduced to 1.5 μm, a relative reduction of thermopower up to 35% is measured in some metals. We suggest that the sidewall scattering due to rough edges of these stripes may be the origin of this unexpected phenomenon. The results may be applied to construct novel thermoelectric devices, such as thermocouples made from a single metal film.

[1]  Stephen B. Soffer,et al.  Statistical Model for the Size Effect in Electrical Conduction , 1967 .

[2]  G. J. Snyder,et al.  Complex thermoelectric materials. , 2008, Nature materials.

[3]  H. Yin,et al.  Energy Conversion Efficiency of a Novel Hybrid Solar System for Photovoltaic, Thermoelectric, and Heat Utilization , 2011, IEEE Transactions on Energy Conversion.

[4]  C. R. Tellier,et al.  A theoretical description of grain boundary electron scattering by an effective mean free path , 1978 .

[5]  J. Gasser.  Understanding the resistivity and absolute thermoelectric power of disordered metals and alloys , 2008, Journal of physics. Condensed matter : an Institute of Physics journal.

[6]  X. Zhao,et al.  Preparation and thermoelectric properties of bulk in situ nanocomposites with amorphous/nanocrystal hybrid structure , 2007 .

[7]  P. Chaikin,et al.  Thermoelectric power of two-dimensional Pd and Pd-Au films , 1983 .

[8]  S. M. Shivaprasad,et al.  Thermoelectric power measurements in thin palladium films , 1982 .

[9]  SIZE EFFECTS ON THERMAL PROPERTIES OF THIN METAL FILMS WITH ROUGH SURFACES , 1990 .

[10]  Philip Kim,et al.  Diameter dependence of the transport properties of antimony telluride nanowires. , 2010, Nano letters.

[11]  C. Tellier,et al.  An extension of the Cottey conduction model , 1978 .

[12]  S. Chaudhuri,et al.  Thermoelectric power of aluminum films , 1983 .

[13]  L. Bell.  Cooling, Heating, Generating Power, and Recovering Waste Heat with Thermoelectric Systems , 2008, Science.

[14]  M. Dresselhaus,et al.  Thermoelectric figure of merit of a one-dimensional conductor. , 1993, Physical review. B, Condensed matter.

[15]  F. Disalvo,et al.  Thermoelectric cooling and power generation , 1999, Science.

[16]  Gang Zhang,et al.  Size dependent thermoelectric properties of silicon nanowires , 2009 .

[17]  R. Boughton.  The effect of boundary scattering on the diffusion thermopower , 1979 .

[18]  Ho-Yuan Yu,et al.  Thermoelectric power of thin copper films , 1973 .

[19]  Das,et al.  Size and temperature effects on the Seebeck coefficient of thin bismuth films. , 1987, Physical review. B, Condensed matter.

[20]  C. Tellier,et al.  Thermoelectric power due to thickness-dependent scattering in metal films , 1981 .

[21]  K. Schröder,et al.  Thermopower of thin iron films , 1992 .

[22]  M A Angadi,et al.  Thermoelectric power measurements in thin tin films , 1981 .

[23]  M. Kanatzidis.  Nanostructured Thermoelectrics: The New Paradigm?† , 2010 .

[24]  D. Greig,et al.  Thermoelectric Power of Metals , 1976 .

[25]  W. F. Leonard,et al.  Thermoelectric Power of Thin Gold Films , 1971 .

[26]  M. Angadi,et al.  Thermopower measurements in chromium films , 1982 .

[27]  M A Angadi,et al.  Thermoelectric effect in ytterbium and samarium films , 1981 .

[28]  C. Boutrit,et al.  The Mayadas-Shatzkes conduction model treated as a Fuchs-Sondheimer model , 1977 .

[29]  Gang Chen,et al.  High-performance flat-panel solar thermoelectric generators with high thermal concentration. , 2011, Nature materials.

[30]  A. J. Tosser,et al.  Thermoelectric power of thin polycrystalline metal films in an effective mean free path model , 1980 .

[31]  Saffa Riffat,et al.  Thermoelectrics: a review of present and potential applications , 2003 .

[32]  Klaus Fuchs,et al.  The conductivity of thin metallic films according to the electron theory of metals , 1938, Mathematical Proceedings of the Cambridge Philosophical Society.

[33]  Qing Chen,et al.  Thin-Film Thermocouple Array for Time-Resolved Local Temperature Mapping , 2011, IEEE Electron Device Letters.

[34]  C. Pichard,et al.  Thermoelectric power of supported thin polycrystalline films , 1982 .

[35]  M. Kanatzidis,et al.  New and old concepts in thermoelectric materials. , 2009, Angewandte Chemie.

[36]  M. Shatzkes,et al.  Electrical-Resistivity Model for Polycrystalline Films: the Case of Arbitrary Reflection at External Surfaces , 1970 .

[37]  A. Majumdar,et al.  Enhanced thermoelectric performance of rough silicon nanowires , 2008, Nature.

[38]  Thermoelectric power of metallic films in the Mayadas-Shatzkes model , 1977 .

[39]  E. H. Sondheimer,et al.  The mean free path of electrons in metals , 1952 .

[40]  Mildred S. Dresselhaus,et al.  Effect of quantum-well structures on the thermoelectric figure of merit. , 1993, Physical review. B, Condensed matter.

[41]  J. Ziman,et al.  In: Electrons and Phonons , 1961 .

[42]  A. Nikolaeva,et al.  Diameter-dependent thermopower of bismuth nanowires , 2008 .

[43]  Jacob,et al.  Surface-roughness contributions to the electrical resistivity of polycrystalline metal films. , 1990, Physical review. B, Condensed matter.