Generalized thermo-elastodynamics for semiconductor material subject to ultrafast laser heating. Part I: Model description and validation

• Published in: International journal of heat and mass transfer Vol. 53; no. 1; pp. 41 - 47
• Main Authors: Qi, Xuele, Suh, C. Steve
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.01.2010; Elsevier
• Subjects: Axisymmetric model; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Generalized thermoelasticity; Physics; Silicon wafer; Staggered finite difference; Thermal expansion; thermomechanical effects and density; Thermal properties of condensed matter; Thermal properties of crystalline solids; Ultrafast laser pulse; Staggered finite difference; Axisymmetric model; Ultrafast laser pulse; Silicon wafer; Generalized thermoelasticity; Near field; Transport equation; Boltzmann equation; Laser-radiation heating; Thermomechanical properties; Relaxation time; Equation system; Free carrier; Lattice dynamics; Temperature effects; Multi-phonon processes; Thermoelasticity; Impact ionization; Silicon; Damage; Carrier density; Finite difference method; Ultrafast process
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2009.10.010

A generalized thermo-elastodynamic formulation applicable to the investigation of coupled thermomechanical responses of a silicon thin structure excited by ultrafast laser pulses is presented. Hyperbolic energy transport equations with two relaxation times is incorporated along with the relaxation-time approximation of the Boltzmann equation and a set of balance equations that consider temperature-dependent multi-phonons, free-carrier absorptions, and the recombination and impact ionization processes. A staggered-grid finite difference scheme allows the coupled equations system that govern the transport dynamics in silicon wafer to be solved without having to be concerned with non-physical numerical oscillations. The time evolution of carrier density and the non-thermal melting fluence level at which damages are inflicted in response to a given pulse duration are examined and compared favorably with experimental data. The feasibility of using the model formulation in describing near-field, short time scale thermal–mechanical responses induced by ultrafast laser pulses is thus validated.