Time-of-flight pulsed ion beam surface analysis as a means of in situ, real-time characterization of the growth of ferroelectric and conductive oxide heterostructures

Pulsed beam Time-of-Flight Ion Scattering and Recoil Spectroscopy (TOF-ISARS) surface analysis methods have been developed which permit realtime, in situ characterization of the growth layer of multicomponent oxide thin films. Results are presented from a study of the deposition of Pb, Zr, Ti and Ru using a sequential layer-by-layer deposition method under ambient oxygen pressure conditions appropriate to the growth of PZT films, revealing layer-by-layer as well as 2D and 3D island growth processes during deposition. Thermodynamic stability conditions result in modification of the layered structure during deposition, in some cases altering the layer ordering of the growth region. Calculations using the Miedema model for surface segregation are in accord with experimental results that reveal an exchange between deposited Zr and Ti atoms and an underlying Pb layer. In addition, the room temperature studies revealed that Pb grows layer-by-layer, nucleating as 2D islands, while Zr tends to form three-dimensional islands. At room temperature, the Zr surface concentration is strongly enhanced by the presence of oxygen, but at high temperatures, surface Pb is found to be stabilized by the presence of an oxygen ambient, illustrating the importance of real-time, in situ analysis of the growth layer as opposed to more conventional surface analytical methods which require interruption of the deposition process in order to characterize the film surface.