Heat Transfer Across Metal-Dielectric Interfaces During Ultrafast-Laser Heating

2011 ◽  
Author(s):  
Liang Guo ◽  
Stephen L. Hodson ◽  
Timothy S. Fisher ◽  
Xianfan Xu
Keyword(s):  
Heat Transfer ◽  
Laser Heating ◽  
Ultrafast Laser ◽  
Direct Coupling ◽  
Phonon Coupling ◽  
Coupled Transport ◽  
Dielectric Interface ◽  
Electron Phonon Coupling ◽  
Measurement Results ◽  
Dielectric Interfaces

Heat transfer across a metal-dielectric interface involves coupled transport of electrons and phonons in metal and phonons in dielectric, which can be accomplished by coupling between phonons in metal and dielectric or direct coupling between electrons in metal and phonons in dielectric. Direct electron-phonon coupling across the metal-dielectric interface is neglected in some studies [1, 2] but considered in some others [3–5]. We investigate heat transfer across metal-dielectric interfaces during ultrafast-laser heating by employing transient thermo-reflectance (TTR) measurements on Au-Si samples. With ultrafast-laser heating that creates strong thermal non-equilibrium between electrons and phonons in metal, it is possible to isolate the effect of direct electron-phonon coupling across the interface. Simulation results based on the two-temperature model (TTM) are compared with the measurement results. The comparison shows a strong direct coupling between electrons in metal and phonons in dielectric.

Heat Transfer Across Metal-Dielectric Interfaces During Ultrafast-Laser Heating

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Liang Guo ◽  
Stephen L. Hodson ◽  
Timothy S. Fisher ◽  
Xianfan Xu
Keyword(s):  
Heat Transfer ◽  
Contact Resistance ◽  
Laser Heating ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Ultrafast Laser ◽  
Dielectric Substrates ◽  
Electron Phonon Coupling ◽  
Dielectric Interfaces ◽  
Investigate Heat Transfer

Heat transfer across metal-dielectric interfaces involves transport of electrons and phonons accomplished either by coupling between phonons in metal and dielectric or by coupling between electrons in metal and phonons in dielectric. In this work, we investigate heat transfer across metal-dielectric interfaces during ultrafast-laser heating of thin metal films coated on dielectric substrates. By employing ultrafast-laser heating that creates strong thermal nonequilibrium between electrons and phonons in metal, it is possible to isolate the effect of the direct electron–phonon coupling across the interface and thus facilitate its study. Transient thermo-reflectance measurements using femtosecond laser pulses are performed on Au–Si samples while the simulation results based on a two-temperature model are compared with the measured data. A contact resistance between electrons in Au and phonons in Si represents the coupling strength of the direct electron–phonon interactions at the interface. Our results reveal that this contact resistance can be sufficiently small to indicate strong direct coupling between electrons in metal and phonons in dielectric.

The role of electron–phonon coupling in ultrafast laser heating

2005 ◽  
Vol 17 (1) ◽  
pp. 63-68 ◽  
Author(s):  
J. K. Chen ◽  
W. P. Latham ◽  
J. E. Beraun
Keyword(s):  
Laser Heating ◽  
Ultrafast Laser ◽  
Phonon Coupling ◽  
Electron Phonon Coupling

scholarly journals Ultrafast Electron–Phonon Coupling at Metal-Dielectric Interface

2018 ◽  
Vol 40 (13-14) ◽  
pp. 1211-1219
Author(s):  
Qiaomu Yao ◽  
Liang Guo ◽  
Vasudevan Iyer ◽  
Xianfan Xu
Keyword(s):  
Phonon Coupling ◽  
Dielectric Interface ◽  
Electron Phonon Coupling

Two Carrier Heat Transfer Modeling for Heat Assisted Magnetic Recording

2013 ◽  
Author(s):  
Neil Zuckerman ◽  
Jin Fang
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Magnetic Recording ◽  
High Energy ◽  
Hot Electrons ◽  
Nanometer Scale ◽  
Phonon Coupling ◽  
Heat Assisted Magnetic Recording ◽  
Carrier Model ◽  
Electron Phonon Coupling

In this work we show the structure and application of a two carrier thermal model applied to a near field transducer, representative of that used in Heat Assisted Magnetic Recording (HAMR). As part of the HAMR device operation, high energy non-thermalized electrons are initially excited by laser incidence on a gold nanostructure. The high energy electrons can travel in a ballistic fashion over longer distances than the optical thickness of gold, resulting in a spreading of the local heat. During their travel the hot electrons collide with lower-energy electrons, thermalizing the hot electrons via inelastic scattering. The thermalized electrons then transfer energy to the lattice due to electron-phonon coupling, as captured in the two carrier model. Starting with an electromagnetic solution for local heating in a sub-micron-scale microfabricated gold structure, the chosen modeling technique applies physical effects of unique interest at the nanometer scale, including brief ballistic transport of hot electrons, experimentally-verified interface thermal resistance, and electron-phonon temperature mismatch. By design, the model is built to use far-field boundary conditions from conventional one-carrier FEMs as well as lubrication-flow computational fluid dynamics. The fundamental governing equations of the two carrier model are two versions of Poisson’s Equation for heat diffusion, coupled by empirically determined terms. These equations are combined with equations for interfacial discontinuities in the temperature fields, yielding a third degree of freedom. The continuous fields are discretized using the finite difference method, and solved using algorithms developed for linear algebra, such as Gaussian Elimination, or non-direct iterative methods. Through use of the model we explore effects of ballistic electron transport length, electron-phonon coupling, as well as interfacial thermal resistance between gold and neighboring ceramics. The model results show the relative impact of the nanoscale heat transfer phenomena in a nanometer scale metal-ceramic structure, allowing us to identify the relative importance of design features and compare candidate designs.

The Role of Thermal Excitation of D Band Electrons in Ultrafast Laser Interaction With Noble (Cu) and Transition (Pt) Metals

2007 ◽  
Author(s):  
Zhibin Lin ◽  
Leonid V. Zhigilei
Keyword(s):  
Heat Capacity ◽  
Coupling Factor ◽  
Ultrafast Laser ◽  
Thermal Excitation ◽  
Phonon Coupling ◽  
Laser Interaction ◽  
Electron Heat Capacity ◽  
Electron Heat ◽  
Electron Phonon Coupling ◽  
Temperature Dependences

The temperature dependences of the electron heat capacity and electron-phonon coupling factor for noble (Cu) and transition (Pt) metals are investigated based on the electron density of states (DOS) obtained from ab initio electronic structure calculations. For Cu, d band electrons could be thermally excited when the electron temperature exceeds ∼3000 K, leading to a significant increase, up to an order of magnitude, in the electron-phonon coupling factor and strong enhancement of the electron heat capacity away from the linear dependence on the electron temperature, which is commonly used in most of the current computational and theoretical investigations of ultrafast laser interactions with metals. Opposite to the case in Cu, the thermal excitation of d band electrons in Pt leads to a monotonic decrease of the electron-phonon coupling factor and contributes to significant negative deviations of the electron heat capacity from the linear dependence in the range of electron temperatures that are typically realized in ultrafast laser material processing applications. Strong and drastically different temperature dependences of the thermophysical properties predicted for Cu and Pt point to the importance of the electron DOS effects and the necessity of full consideration of thermal excitation of d band electrons for realistic modeling of short pulse laser interaction with noble and transition metals.

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