Time-resolved RHEED Studies of the Growth of Epitaxial ZnSe Films on GaAs by Pulsed Laser Deposition

Abstract

Film growth consists of two basic processes, deposition and surface relaxation, with opposing effects on the evolution of surface roughness. The pulsed-laser deposition (PLD) growth process has the unique feature of having periods of very high deposition rates on µs time scales followed by periods, on the order of seconds, with only surface relaxation. In this paper we report the first efforts towards exploiting this unique feature to study these two basic processes independently. Thin epitaxial films of ZnSe were grown using PLD on (001) GaAs and 2° miscut (001) GaAs substrates. For growth on both the singular and vicinal surfaces, RHEED patterns taken following growth showed clear, streaky first zone and sharp second zone spots, and well-defined Kikuchi lines; these features are indicative of a smooth growth surface and high quality film. No reconstruction of the growth surface was observed, in contrast to behavior observed in molecular beam epitaxy. Time-resolved RHEED measurements show that a single morphology developed during growth on singular (001) GaAs. However, during growth on miscut (001) GaAs, two morphologies developed, one transitory and one appearing to evolve towards steady state. When growth on the miscut substrate was stopped, recovery of the RHEED signal was observed. The rate of recovery could be attributed to two relaxation processes, as differentiated by their time constants. Potential origins of these observations are discussed.

Controlled piezotronic properties on recoverable energy storage density in rare-earth ions doped epitaxial PZT thin films

“…Figure 2 shows the backscatter Kikuchi patterns operating at 20 keV accelerating voltage of the substrate and the thin films. The images reveal that the (0 0 1) Kikuchi lines are well defined and sharp zone spots, which indicates the buffered conductive layer and thin films have a smooth surface and high quality thin film grown on the substrate [29]. The presence of a single sharp zone spot in the Kikuchi pattern (as shown in figure 2) indicates there is a single (0 0 1) orientation plane present in the SRO thin film and thin films on the substrate without any other orientation plane.…”