Online proceedings - EDA Publishing Association

24-26 September 2008, Rome, ItalyEXTENDED SUMMARY: Nanoscale management of electron-phonon energy transferVladimir Mitin and Andrei SergeevUnderstanding of nanoscale energy transfer and transformations is of fundamental importance toa variety of technologies, such as chip packaging and energy conversion. Nanostructuredmaterials provide scientists and engineers with many possibilities to manipulate energy transferand its conversion into various forms. Currently, nanoscale management of energy-relatedtransport and kinetics is mainly associated with engineering of phonons, because these energycarriers have characteristic wavelengths in the nanoscale range.By engineering phonon states in nanostructures and nanostructured materials, one alsoinevitably changes scattering processes [1,2]. Modification of electron-phonon (e-ph) processescould be critical for nanoscale management of energy-related problems. Vibrating interfaces andboundaries generate a new important channel for the electron-phonon (e-ph) interaction, whichprovides energy transfer from electrons to phonons and vice versa [3]. Moreover, in the case ofinelastic electron-boundary scattering the energy can be transferred directly between electronsand external phonons without the participation of internal phonons in the nanoconductor [4].Nanostructuring in semiconductor and hybrid devices is often reached by selective doping. In thiscase, vibrating dopants also result in energy transfer between electrons and phonons. Besides this,interfaces and nano-blocks, such as quantum wells and dots, accumulate some electric charge,which modifies screening and scattering processes. Local charges form potential barriers, whichcan substantially redirect thermal and charge transport [5]. Thus, interfaces and dopants play animportant role in the energy exchange and transformations and, at the same time, they provide apowerful tool for effective management of energy-related transport and kinetics. As an example,Fig. 1 shows the energy transformations from energy of electromagnetic radiation absorbed byelectron subsystem in a nano-block, e.g. in a quantum dot, to the electric energy and to the heat.ElectromagneticenergyInternal electronse-ph scatteringInternalphononsOpticalAcousticTunnelingThermo-excitationOut-diffusionImpurities& DopantsInelastic e-boundary scatteringKapitzaconductanceInterface: Barrier & Vibrating BoundaryBack scatteringConversionto electricenergyExternal electronsImpurities& Dopantse-ph scatteringThermal conductivityHeatExternal phononsFig. 1. Energy transfer between a nano-block and its surroundings. Kinetics of electrons andphonons includes electron-phonon scattering, inelastic electron scattering from interfaces anddopants, phonon scattering and transfer through the interface (Kapitza conductance), andelectron processes of tunneling and thermo-excitation. Interfaces and potential barriers play amajor role in nanostructures and nanostructured materials.©EDA Publishing/THERMINIC 2008 168ISBN: 978-2-35500-008-9