RHEED Pole Figure Measurements of Biaxial Thin Film Growth Front Evolution

Abstract

ABSTRACTThe most frequently used characterization technique for biaxial texture formation in thin films is x-ray pole figure analysis. However, x-rays interact weakly with matter and can penetrate a few microns deep into the film. The texture obtained by x-rays is therefore an average texture from the entire thickness of the film. As the texture of a film often changes during growth, information on the basic mechanisms that control the final texture is often lost. In contrast electrons interact strongly with matter and they have very limited penetration and escape depths of a few nm. In this paper we will show how we can use our newly developed reflection high energy electron diffraction (RHEED) surface pole figure technique to probe the surface texture evolution of the growth front from the initial stage (nm thick) to the later stage. The RHEED pole figure technique is a surface-sensitive technique that allows us to obtain information on the dynamic behavior of texture evolution of the growth front during film deposition. We shall explain the principle, measurement, and construction of such RHEED surface pole figures. An example of the biaxial texture evolution of CaF2 due to the atomic shadowing effect during oblique angle deposition is described.