Monitoring oxide thin film growth with in-situ atomic force microscopy

Abstract

Format

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Abstract

Complex oxides exhibit various physical properties such as ferromagnetism, dielectricity, and superconductivity. The nature of these physical properties is determined by very small characteristic length scales. Future heteroepitaxial devices based on such oxides have great potential for applications provided that the growth can be controlled on an atomic level.Currently, in-situ growth morphology characterization is mostly performed by diffraction techniques such as Reflection High Energy Electron Diffraction (RHEED). We have now realized a system, in which Atomic Force Microscopy (AFM) can be performed during Pulsed Laser Deposition (PLD). Deposition and force microscopy are performed in one vacuum chamber and via a fast transfer (in the order of seconds) the surface of a sample can be scanned. In our system we take advantage of the pulsed deposition process, because microscopy measurements can be carried out between the pulses. This provides real-time morphology information on the microscopic scale during growth. The transfer mechanism allows switching between microscopy and deposition with a re-position accuracy of ±500 nm which gives new opportunities to study growth processes. This system is especially useful to study crystal growth, phase transitions, diffusion processes and nanoparticle formation. Furthermore, it will provide information if RHEED is not possible, for example during amorphous and polycrystalline growth. In this contribution, we will present the results obtained with a few model systems on oxide surfaces. We have used treated SrTiO3 (001) oxide substrates with 0.4 nm high substrate steps which are ideal for these experiments. Several materials are currently investigated, such as Au, SrRuO3, PbTiO3 and transparent conducting indium tin oxide. The in-situ AFM has been used to study the initial growth of these materials at various deposition conditions. The physical properties of these materials are correlated with the growth conditions, such as deposition pressure, fluency and substrate temperature. Besides showing the growth results obtained with the AFM, the latest equipment developments will be presented. To scan at elevated temperatures, small heaters have been developed. These small thermal mass heaters are designed in such a way to obtain stable monitoring settings at temperatures >973K in a high pressure environment or even ambient pressure. With high temperature microscopy, growth characterization at typical deposition conditions of complex oxides becomes feasible.