Thin films of LiMn204 and LiCo02 have been prepared by pulsed laser deposition on heated stainless steel substrates. These films have thicknesses from 0.2 to 1.5 p.m and are crystalline without postdeposition annealing. The films' electrochemical properties were studied with cyclic voltammetry current pulse measurements, and galvanostatic charge/discharge techniques. Film capacity densities as high as 56 and 62 p.Ah/cm2-p.m were measured for Li.Mn204 and LiCo02, respectively. Chemical diffusivities on the order of 2.5 x 10 -11 and 1 x 10-10 were measured for LiMn204 and LiCo02, respectively. Some of the films were cycled electrochemically for up to 300 cycles against lithium metal in 1 M LiC1O4/propylene carbonate electrolyte, demonstrating the promise of pulsed laser deposition for the production of cathode films for rechargeable lithium microbatteries.

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Laser ablation of copper with a 4ns laser pulse at 1064nm was studied with a series of synchronized shadowgraph (100fs laser pulses at 400nm) and emission images (spectral line at 515nm). Data were obtained at two laser pulse energies (10 and 30mJ) and in three background gases (He, Ne, and Ar) at atmospheric pressure. The laser energy conversion ratio and the amount of sample vaporized for ablation in each condition were obtained by the theoretical analysis reported in paper I from trajectories of the external shock wave, internal shock wave, and contact surface between the Cu vapor and the background gas. All three quantities were measured from shadowgraph and emission images. The results showed that E, the amount of energy that is absorbed by the copper vapor, decreases as the atomic mass of the background gas increases; and M, the mass of the sample converted into vapor, is almost independent of the background gas [Horn et al., Appl. Surf. Sci. 182, 91 (2001)]. A physical interpretation is given based on the phenomena observed in shadowgraph and emission images during the first tens of nanoseconds after the beginning of the laser pulse for ablation in different background gases. In addition, an internal shock wave was observed in the emission images during the first tens of nanoseconds after the laser pulse, which strikes the surface and should be one of the mechanisms inducing the liquid sample ejection. Also, a significant vortex ring near the target was observed in emission images at longer times after the laser pulse (>100ns) which distorts the otherwise hemispherical expansion of the vapor plume.

Electrochemical properties of thin films of LiMn2O4 spinel prepared by pulsed laser deposition were studied using constant current cycling and cyclic voltammetry. Films have been cycled more than 220 times with no significant capacity fading. The shape of the cyclic voltammogram is very sensitive to the composition and morphology of the film. The diffusion process for the LirMn2O4 thin films with an excess of lithium (x> 1) appears to be slower than for lithium-deficient films. Films were subjected to overcharge (5 V vs. Li/Lit) and overdischarge (2 V vs. Li/Lit). Overcharge does not significantly affect the structure of the film. Overdischarge leads to changes in the shape of the cyclic voltammogram: (i) loss of resolution of the two oxidation peaks at 4.1 and 4.2 V which are the signatures of the spinel structure, and (ii) loss of capacity. These changes in the electrochemical behavior may be correlated to the structural disorder associated with the phase transition when more than one lithium is intercalated in LiMn2O4. It is a reversible phenomenon.

A study of the gas dynamics of the vapor plume generated during laser ablation was conducted including a counterpropagating internal shock wave. The density, pressure, and temperature distributions between the external shock wave front and the sample surface were determined by solving the integrated conservation equations of mass, momentum, and energy. The positions of the shock waves and the contact surface (boundary that separates the compressed ambient gas and the vapor plume) were obtained when the incident laser energy that is transferred to the vapor plume and to the background gas, E, and the vaporized sample mass, M, are specified. The values for E and M were obtained from a comparison of the calculated trajectories of the external shock wave and the contact surface with experimental results for a copper sample under different laser fluences. Thus E and M, which are the two dominant parameters for laser ablation and which cannot be measured directly, can be determined. In addition, the internal shock wave propagation within the vapor plume was determined; the interaction of the internal shock wave with the sample may be one of the mechanisms inducing liquid sample ejection during laser ablation.

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Pulsed laser ablation (266nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150 fs) and nanosecond (4 ns) laser pulses with identical fluences of 50 J cm -2 . Characterization of particles and correlation with InductivelyCoupled Plasma Mass Spectrometer (ICP-MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without internal voids). Particles produced by femtosecond laser ablation consisted of spherical primary particles and soft agglomerates formed from numerous small particles. Examination of the craters by white light interferometric microscopy showed that there is a rim of material surrounding the craters formed after nanosecond laser ablation. The determination of the crater volume by white light interferometric microscopy, considering the rim of material surrounding ablation craters, revealed that the volume ratio (fs/ns) of the craters on the selected samples was approximately 9 (Zn), 7 (NIST627 alloy) and 5 (NIST1711 alloy) times more ablated mass with femtosecond pulsed ablation compared to nanosecond pulsed ablation. In addition, an increase of Al concentration from 0 to 5% in Zn base alloys caused a large increase in the diameter of the particles, up to 65% while using nanosecond laser pulses.When the ablated particles were carried in argon into an ICP-MS, the Zn and Al signals intensities were greater by factors of ~ 50 and ~ 12 for fs vs. ns ablation. Femtosecond 2 pulsed ablation also reduced temporal fluctuations in the 66 Zn transient signal by a factor of ten compared to nanosecond laser pulses.

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