Applied Physics A

, Volume 103, Issue 1, pp 113–121

Superheating in liquid and solid phases during femtosecond-laser pulse interaction with thin metal film

Article

DOI: 10.1007/s00339-010-6175-1

Cite this article as:
Huang, J., Zhang, Y. & Chen, J.K. Appl. Phys. A (2011) 103: 113. doi:10.1007/s00339-010-6175-1

Abstract

Superheating of the liquid phase caused by non-equilibrium evaporation during femtosecond-laser processing of a thin metal film is investigated by adopting the wave hypothesis along with the two-temperature model. The simulation results show that the superheating in the liquid occurs shortly after the evaporation. For a 100-fs laser pulse of 0.7 J/cm2, the maximum degree of superheating in liquid can reach 600 K. The superheating in solid can also be captured in the current model, which can be as high as 300 K. The effects of laser fluence, pulse duration and film thickness on the degree of superheating were studied. A higher laser fluence will increase the degree of superheating in liquid significantly but has little effect for the solid part. In the range adopted in the current work, the pulse duration has little effect on the degree of superheating in both liquid and solid phases.

Nomenclature

Be

coefficient for electron heat capacity (J/m3 K2)

C

heat capacity (J/m3 K)

c

speed of sound (m/s)

cp

specific heat (J/kg K)

G

electron-lattice coupling coefficient (W/m3 K)

h

latent heat of phase change (J/kg)

J

heat source fluence (J/m2)

k

thermal conductivity (W/m K)

L

thickness of the metal film (m)

M

molar mass (kg/kmol)

p

pressure (Pa)

q

heat flux (W/m2)

R

reflectivity

Rg

specific gas constant (J/kg K)

Ru

universal gas constant (J/kmol K)

s

interfacial location (m)

S

intensity of the internal heat source (W/m3)

t

time (s)

tp

pulse width (s)

T

temperature (K)

TF

Fermi temperature (K)

Tm

melting point (K)

u

interfacial velocity (m/s)

V0

interfacial velocity factor (m/s)

x

coordinate (m)

Greek Symbols

δ

optical penetration depth (m)

δb

ballistic range (m)

ε

total emissivity

ρ

density (kg/m3)

σ

Stefan-Boltzmann constant (W/m2 K4)

τ

variable of integration that denotes temperature (K)

Superscripts

0

last time step

Subscripts

e

electron

eq

thermal equilibrium state

i

initial condition

l

lattice

liquid

ℓv

liquid–vapor interface

R

thermal radiation

s

solid

sℓ

solid–liquid interface

sur

surface

ambient environment

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Department of Mechanical and Aerospace EngineeringUniversity of MissouriColumbiaUSA