Surface Dynamics of GaAs Thin Film Formation by Pulsed Laser Deposition Investigated Using RHEED
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Surface Dynamics of GaAs Thin Film Formation by Pulsed Laser Deposition Investigated Using RHEED A. Pun1, S.M. Durbin2, J. Kennedy3, A. Markwitz3, R. Reeves4, and J.P. Zheng1 1 Department of Electrical and Computer Engineering, Florida A&M University and Florida State University, Tallahassee, FL, USA 2 Department of Electrical and Computer Engineering, University of Canterbury, Christchurch, NEW ZEALAND 3 Institute of Geological & Nuclear Sciences, Lower Hutt, NEW ZEALAND 4 Department of Physics & Astronomy, University of Canterbury, NEW ZEALAND ABSTRACT Post-growth surface dynamics of epitaxial GaAs (100) thin films grown by pulsed laser deposition (PLD) have been studied using dynamic reflection high-energy electron diffraction (RHEED) in an effort to better understand the growth mechanisms present in pulsed laser deposition. Results have indicated, as expected, that processes occurring at reduced substrate temperatures manifest themselves more slowly than at elevated temperatures. This has been shown through the analysis of static RHEED images and dynamic specular beam intensity as well as profile scans. INTRODUCTION Pulsed laser deposition is a deposition technique that has recently gained more attention in the fabrication of high-quality single crystal films. In this technique, a pulsed high-energy laser is used to ablate a target material resulting in a plume of highly energetic species. This deposition technique differs significantly from other material growth techniques in that it involves periods of high growth rates (~100µs) followed by comparatively long periods of interrupted growth and the opportunity for surface relaxation [1]. During the growth period, highly energetic (1-100eV) atoms and ions arrive at the surface of the film in large quantities [2, 3]. Because of these properties, the physics of film formation and dynamics are expected to vary from other techniques such as molecular beam epitaxy (MBE). The mechanisms present in PLD growth are still not fully understood and are of considerable interest. In this study, we aim to perform time-resolved RHEED analysis techniques to observe surface dynamics during the PLD process. EXPERIMENT A series of experiments were performed in which we studied the homoepitaxial growth of GaAs(100) by PLD over the substrate temperature range of 350°C to 550°C. For the purpose of in-situ analysis, a 12 kV reflection high-energy electron diffraction (RHEED) was performed at an incidence angle of 1.7°. All films were grown at a base pressure of approximately 10-7 Torr employing a KrF excimer laser producing a fluence of 3 J/cm2 with a target-to-substrate separation of 6cm. Prior to growth, each substrate was degreased, etched, and loaded into the chamber for subsequent heating to 550°. Each film was grown for 30 minutes. Following
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growth the RHEED pattern is recorded for ten minutes in the form of a digital movie with a frame rate of 3 frames/second. RESULTS AND DISCUSSION RHEED Images The RHEED patterns presented in figure 1 show the results of fi
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