Discrete model for laser driven etching and microstructuring of metallic surfaces

We present a unidimensional discrete solid-on-solid model evolving in time using a kinetic Monte Carlo method to simulate micro-structuring of kerfs on metallic surfaces by means of laser-induced jet-chemical etching. The precise control of the passivation layer achieved by this technique is responsible for the high resolution of the structures. However, within a certain range of experimental parameters, the microstructuring of kerfs on stainless steel surfaces with a solution of $\mathrm{H}_3\mathrm{PO}_4$ shows periodic ripples, which are considered to originate from an intrinsic dynamics. The model mimics a few of the various physical and chemical processes involved and within certain parameter ranges reproduces some morphological aspects of the structures, in particular ripple regimes. We analyze the range of values of laser beam power for the appearance of ripples in both experimental and simulated kerfs. The discrete model is an extension of one that has been used previously in the context of ion sputtering and is related to a noisy version of the Kuramoto-Sivashinsky equation used extensively in the field of pattern formation.Comment: Revised version. Etching probability distribution and new simulations adde

GENERAL INTRODUCTORY SESSIONTECHNIQUES AND RESULTS OF HEAT PULSE EXPERIMENTS

A general review of experimental heat pulse techniques with interpretations of some typical data is given. Several heat pulse generators are described including thin films utilizing pulsed currents, tunnel junctions and superconducting films in which the down-conversion of high frequency phonons occurs. The black body radiation model will be reviewed and related to the temperature of the pulsed current generator and the resulting phonon propagation. A brief review of heat pulse detectors will be given in order to characterize their properties as a function of temperature and magnetic field. Results of heat pulse experiments will be presented by interpreting several portions of some detected heat pulse signals including [1] the ballistic region and the relation between the energy and phase velocities [2], the second sound regime (if any) and its relation to normal and umklapp scattering rates [3], the scattered or diffusive portions and their relation to crystal defects and phonon polarization. Of the specific examples of scattering to be discussed, emphasis will be on phonon scattering in Ge due to donor impurities

Thermoelastic Structures for High Density Ultrasonic Energy

The use of lasers to generate thermoelastic waves has received considerable attention since the publication of the theoretical work of White.1 The author derives equations for the propagation of longitudinal elastic waves produced by surface heating of a semi-infinite medium with harmonic thermal (laser) excitation. The importance of the boundary conditions in determining the magnitude of the resulting elastic waves is described. Two conditions are imposed and the resulting amplitudes derived: (1) Laser absorption at x = 0 with elastic amplitude u=0 at x = 0 for all times t ≥ 0 (perfectly clamped or constrained surface) and (2) for the stress σ = 0 at x = 0 for t ≥ 0 (free surface). Propagation of the elastic wave is in the x direction.</p

STUDIES OF SAPPHIRE PHOTOABLATION BY LASER-INDUCED FLUORESCENCE AND PHOTOTHERMAL DEFORMATION MEASUREMENTS

Crystalline sapphire displays a low, 0.6 J/CM2, threshold for etching with 193 nm excimer pulses. Understanding this low-threshold etching involves knowledge of the pathways by which laser energy gives rise to material removal. An accurate knowledge of surface temperature during irradiation appears sufficient to differentiate between classical thermal vaporization and electronic, I.E. photochemical mechanisms for etching