9781420038903%2Ech14

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1、14SizeEffectsonThermalTransport14.1Introduction................................................................14-114.2PhononsandElectrons...............................................14-2ResistancetoFlow†RelaxationTimeApproximation†BoundariesinFilmsandGrains14.3ElectronsandPh

2、ononsinConfinedStructures.......14-4ElectronsinLowerDimensions†PhononConfinement†PhononDispersioninQuantumWellsandWires†QuantumWires14.4SuperlatticeStructures................................................14-8Introduction†QuantumWellSuperlattice†QuantumDotSuperlattice†Thermoelec

3、tricFigure-of-Merit14.5GraphiticMicrotubules..............................................14-10ChandraMohanBhandariIntroduction†ThermalTransportinNanotubes†UniversityofAllahabadOnsetofU-Processes14.1IntroductionRecentupsurgeofinterestinthermaltransportbehavioroflow-dimensionals

4、tructureshasbeenmotivatedbytwomainfactors.Thesecondhalfofthetwentiethcenturywitnessedanemphasisontheprocessofminiaturizationinmicroelectronicdevicesandcircuits.Theuseofthinsemiconductorchipswithever-increasingchipdensityhasledtoanincreaseinpowerdissipationperunitarea.Obviouslyt

5、heheatthusgeneratedhastobecarriedawaybyefficientthermalmanagement.Materialsthatcandothisjobwellwillbeofconsiderableinterestindevicedesign.Ontheotherhand,semiconductingmaterialswithlowthermalconductivityareofspecialinterestinthermoelectricdevices(generatorsand1–6refrigerators).Su

6、chmaterialshaveearlierbeenpreparedfromamongtheconventionalmaterialsseekingproperalloycombinations,dopingdensity,andgrainsizetoobtainahighelectrical-to-thermalconductivityratio.Duringthelasttwodecadesconsiderableeffortshavebeenmadetoengineermaterialparametersbasedonsizeeffects.A

7、reductioninsamplesizeopensupfascinatingandoftencomplexareasofquantumprocessesandeffects.Figure14.1displaysthelengthscalesofvariousobjectsalongwiththoseofparticularinterestinthermaltransport.Thesizerange50mmto1nmisofspecialinterestinthecontextofthermaltransport.Thischapterexamin

8、essomeoftheseaspectspertainingtolatticethermaltranspor