Technical Report:In-situStudies of Pulsed Laser Deposition Growth at CHESS

Abstract

Recent advances in thin-film growth using advanced in-situ monitoring techniques have enabled materials engineering with atomic precision via the carefully controlled deposition of sequences of single atomic layers [1][2][3][4]. Epitaxial oxide heterostructures are especially attractive due to the broad range of materials properties that are manifest with changes in stoichiometry, even within a single structure family. Researchers are beginning to search for new phenomena that occur when these dissimilar materials are joined at atomically smooth interfaces [5][6][7][8].By combining in-situ time-resolved studies of film growth with exsitu techniques such as atomic-scale electron energy loss spectroscopy, and theoretical approaches such as molecular dynamics simulations and multi-scale modeling, we seek to understand the mechanisms operating during nucleation and growth, and the pathways by which materials engineering at the atomic scale can be realized.Pulsed Laser Deposition (PLD) is a very attractive case to study for a number of reasons. Over the last two decades, PLD has been established as the research and development technique of choice for producing high quality, thin, epitaxial films of complex oxide materials. The strength of the Figure 1: A 100 MW/cm 2 , 248 nm, KrF excimer laser, 30 ns in duration, ablates material from a polycrystalline target, creating a hot plume of energetic neutrals, ions, and clusters. The plume expands, cools, and condenses on the opposing single crystal substrate, which is generally heated to temperatures between 500°C and 800°C. During growth, 10 KeV X-rays generated by the Cornell High Energy Synchrotron Source (CHESS) are directed at the single crystal substrate. The intensity of scattered X-rays is monitored as a function of time, yielding information about film thickness, surface roughness, and growth mode. Figure 2: A photograph of the in-situ PLD equipment. The growth chamber is an integral part of the diffractometer, yet can be easily removed to make room for studies of alternative growth techniques. The pulsed laser beam path is illustrated in purple, and the X-ray beam path in green.