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    Nanoscale Heat Transfer at Contact Between a Hot Tip

    and a Substrate

    Stphane Lefvre

    Laboratoire dEtude Thermiques, UMR CNRS !"

    E#o$e Nationa$e Suprieure de M#anique et d%rote#hnique, "&!

    'uturos#ope Cede(

    Sebastian )o$* and +ierre-$ivier Chapuis

    Laboratoire dEner.tique Mo$#u$aire et Ma#ros#opique, Combustion, U+R

    CNRS /""

    E#o$e Centra$e +aris, &//&0 Ch1tena2Ma$abr2

    Corresponding Author 3

    Sebastian )o$*, +h454

    EM/CEC+, &//&0 Ch1tena2 Ma$abr2, 'ran#e

    T 3 66787767!8& ' 3 66789!/"!60, vo$*:em/#4e#p4fr

    Abstract

    ;ot tips are used either for #hara#teri*in. nanostru#tures b2 usin.

    S#annin. Therma$ Mi#ros#opes or for $o#a$ heatin. to assist data

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    Nomenclature3

    %3 a##ommodation #oe>#ient

    a3 therma$ di?usivit2 @m/4s7A

    b3 #onta#t radius @mA

    Cv,p3 heat #apa#ities @B4.74D7A

    E3 oun.Fs modu$us3 @+aA

    e3 G$m thi#ness @mA

    '3 for#e bet#ient @=4m/4D7A

    I3 e$e#tri#a$ #urrent @%A

    L3 ha$f $en.th of the rhodiump$atinum

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    *!3 #oordinate on the +tRh #ient @D7A

    : temperature amplitude(K)

    3 heat #apa#ities ratio

    : thermal conductivity (W.m-1.K-1)

    3 e$e#tri#a$ resistivit2 @4mA

    Subscripts3

    %3 air

    C3 tota$ #onta#t #ondu#tan#e probe #urvature radius

    Eq3 #onta#t and samp$e #ondu#tan#es in series

    +3 probe

    S3 so$idso$id #onta#t

    =3

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    Thermoe$e#tri# ener.2 #onversion

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    measurements are not dependent on the temperature distribution on the

    samp$e surfa#e4

    Homes et a$ K su..ested that the

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    properties Jma.neti#, e$e#tri#, e$asti#, O4 %nd in 7&", D4 =i#ramasin.he

    K7! proposed to mount a thermo#oup$e tip in a #onventiona$ %'M4 =hi$e

    the temperature

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    90mi#rons and shaped as a tip4 The si$ver #oatin. is removed at the tip

    samp$e #onta#t to un#over the p$atinumrhodium

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    the tip and the ambient4 ppand apare the probe perimeter and therma$

    di?usivit24

    #! The solid$solid and water meniscus contact conductances

    The #onta#t bet

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    bet

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    estimated to !4/07nm from this si.na$4 !4/0nm is the

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    %!Conduction through air

    =e

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    h x0y

    0( )=C

    vv.z

    0 3

    z0

    1+ 2(2A) A +1( )$r , @7A

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    transfer #oe>#ient h bet

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    enhan#ement of heat u( in the ba$$isti# area be#ause the 'EM predi#tions

    sho< that the heat transfer in the ba$$isti# area is mu#h $ess than the tota$

    heat transfer4 The tip is assimi$ated to an e$$ipsoid

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    #ondu#tan#e is hi.her than the ba$$isti# one

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    the heat u( #rossin. the samp$e surfa#e b2 usin. our 'EM4 The tip hei.ht

    is /!nm so that no so$idso$id heat #ondu#tion is invo$ved4 'i.ure " reports

    a s$i.ht di?eren#e in the u( distributions

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    and

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    '()('(NC(S

    [1] R. Venkatasubramanian, E. Siivola, T. Colpitts and B. OQuinn, Thin-film thermoelectric

    devices with high-room temperature figures of merit, Nature, 413, (2001), 597.

    [2] P. Vettiger et al., The Millipedenanotechnology entering data storage, IEEE

    Transaction on Nanotechnology, 1, (2002), 39.

    [3] C.L. Tien and G. Chen, Challenges in microscale conductive and radiative heat transfer,

    ASME J. Heat Transfer, 116, (1994), 799.

    [4] D.G. Cahill et al., Nanoscale thermal transport, Journal of Applied Physics, 93, (2003),

    793-818.

    + . %hi and . 4a5umdar 'hermal transport mechanisms at nanoscale point contact

    6ournal of 7eat 'ransfer 12! (2002) 328.

    [6] S. Gomes, Contribution thorique et exprimentale la microscopie thermique sonde

    locale: calibration dune pointe thermorsistive, analyse des divers couplages thermiques,

    Ph.D. Report, Reims University, France (1999).

    %. ef9vre et al. 'hermal conductivity cali"ration for hot wire "ased dc scannin# thermal

    microscope :eview of %cientific ;nstruments ! (2003) 2!1

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    [12] O. Kwon, L. Shi and A. Majumdar, Scanning thermal wave microscopy, Journal of Heat

    Transfer, 125, (2003), 156.

    [13] D.G. Cahill and R. Pohl, Thermal conductivity of amorphous solids above the plateau,

    Physical Review B, 35, (1987), 1259-1266.

    [14] M.M. Yovanovitch, General expressions for circular constrictions resistances for

    arbitrary flux distribution, Progress in Astronautics and Aeronautics: Radiative transfer and

    thermal control, 49, (1976), 381-396.

    [15] W.M. Rohsenow and H. Choi, Heat, Mass and Momentum Transfer, chapter 11,

    Prentice-Hall ed, 1961.

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    CAPTIONS

    Table 1: Contact radius bW corresponding to heat conduction in the water meniscus for

    different water film thickness.

    Table 2: Thermal conductances and radii for the four heat transfer modes involved in the tip-

    sample heat transfer.

    Figure 1: Schematic of the probe-sample interaction including conduction through air,

    through the water meniscus and through the solid-solid contact.

    Figure 2: Scanning Electronic Microscope image of the thermal probe. The Wollaston wire is

    a silver coating 75 microns in diameter and a Pt-Rh core 5 microns in diameter. The mirror

    ensures the laser reflection to control the tip deflection.

    Figure 3: Thermal conductances of the contact and the sample versus the force applied by the

    tip on the sample.

    Figure 4: Thermal contact conductance through the water meniscus versus the meniscus

    thickness.

    Figures 5(a) and 5(b): Thermal resistance of the contact and the sample versus the tip

    altitude. Figure 5(a) reveals a convective regime when z>20m and a linear regime

    corresponding to conduction in air when z

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    Figure 8: Flux versus radius (small ellipse axis direction) when the tip is in contact and for

    different values of sample thermal conductivities. The insert reveals that the contact radius

    due to air conduction may vary with the sample thermal conductivity by a factor of 2.

    .

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    Table 1:

    Table 2:

    Heat Transfer Mode Conductance (W.K-1) Contact Radius b (nm)

    Radiation

    Solid-solid

    Conduction through air

    Water Meniscus

    1-!

    " 1.#

    $.%

    % - !

    -

    $

    1 " !

    1 - $

    Fig 1:

    Fig 2:

    &ilm Thic'ness W(nm) bW(nm)

    0.25

    0.5

    1

    100

    140

    200

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    Fig 3:

    Fig 4:

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    Fig 5:

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    Fig 6:

    Fig 7:

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    Fig 8: