Nature and Application of Particulate Matter Produced by Pulsed Laser Ablation

Abstract

ABSTRACTParticulates produced by 248 nm KrF excimer laser ablation were investigated in two systems: Nb-Al and Cr-Nb. Both systems contain intermetallics which are potentially useful high temperature materials. While the melting temperature of Nb is three times higher than that of Al, the melting temperature difference between Nb and Cr is less substantial. This work focuses on the effects of melting temperature difference between the terminal elements in binary alloy systems on the nature of the particulate matter formed by laser ablation.Transmission (TEM) and scanning electron microscopy (SEM), energy dispersive X-rayanalysis (EDX), and optical image analysis were used to characterize the products. The particulate generation rate and the size distribution depend on various growth parameters. In both Nb-Al and Cr-Nb systems, the particulates are all enriched in Nb, with the smallest particulates richest in Nb. Single phase particulates containing barely detectable Al were found in Nb-Al system. In the Cr-Nb system, electron diffraction patterns indicate two types of particulates: one exhibiting a new metastable diamond cubic structure and the other being a two phase mixture of bcc Cr and bcc Nb. A plausible mechanism whereby the lower melting temperature element is depleted as well as the correlation of the particulate size and the overall composition of individual particulate will be discussed. Stoichiometric studies of the particulatesgenerated in the Nb-Al and Cr-Nb systems using the pulsed laser deposition (PLD) technique help illustrate the merits and limitations of the same. One example of the potential applications of the particulate-containing films will be demonstrated.