Abstract
We describe the next-generation system for in situ characterization of a complex oxide thin film and heterostructure growth by pulsed laser deposition (PLD) using synchrotron hard X-rays. The system consists of a PLD chamber mounted on a diffractometer allowing both real-time surface X-ray diffraction (SXRD) and in situ hard X-ray photoelectron spectroscopy (HAXPES). HAXPES is performed in the incident X-ray energy range from 4 to 12 keV using a Scienta EW4000 electron energy analyzer mounted on the PLD chamber fixed parallel with the surface normal. In addition to the standard application mode of HAXPES for disentangling surface from bulk properties, the increased penetration depth of high energy photoelectrons is used for investigation of the electronic structure changes through thin films grown deliberately as variable thickness capping layers. Such heterostructures represent model systems for investigating a variety of critical thickness and dead layer phenomena observed at complex oxide interfaces. In this new mode of operation, in situ HAXPES is used to determine the electronic structure associated with unique structural features identified by real-time SXRD during thin film growth. The system is configured for using both laboratory excitation sources off-line and on-line operation at beamline 33-ID-D at the Advanced Photon Source. We illustrate the performance of the system by preliminary scattering and spectroscopic data on oxygen vacancy ordering induced perovskite-to-brownmillerite reversible phase transformation in La2/3Sr1/3MnO3 films capped with oxygen deficient SrTiO3-δ (100) layers of varying thickness.
Highlights
The development of advanced thin film growth methods with submonolayer thickness control, such as molecular beam epitaxy (MBE) and pulsed laser deposition (PLD), enables the design and creation of interfaces with tunable properties for exploring condensed matter physics phenomena and developing novel technological applications.[1]
hard X-ray photoelectron spectroscopy (HAXPES) is performed in the incident X-ray energy range from 4 to 12 keV using a Scienta EW4000 electron energy analyzer mounted on the PLD chamber fixed parallel with the surface normal
We illustrate the performance of the system by preliminary scattering and spectroscopic data on oxygen vacancy ordering induced perovskiteto-brownmillerite reversible phase transformation in La2/3Sr1/3MnO3 films capped with oxygen deficient SrTiO3−δ (100) layers of varying thickness
Summary
The development of advanced thin film growth methods with submonolayer thickness control, such as molecular beam epitaxy (MBE) and pulsed laser deposition (PLD), enables the design and creation of interfaces with tunable properties for exploring condensed matter physics phenomena and developing novel technological applications.[1]. In addition to the standard HAXPES applications in widespread use for postgrowth characterization of the bulk and interface properties free of interference from surface contamination that are summarized in a number of recent reviews,[19,20] we implemented a special in situ mode of operation for spectroscopic characterization of materials during the actual thin film growth process This special mode is enabled by installation of HAXPES directly on a PLD growth chamber. The ordering is revealed by a dramatic increase in the SXRD intensity at the (0 0 0.5) anti-Bragg position resulting from the doubling of the PV unit cell in the buried layer when a BM phase forms This feature creates an extremely powerful combination of diffraction and spectroscopy enabled by the ability of HAXPES to penetrate the cap layer and characterize the electronic structure of the buried layer. The system is operational at beamline 33-ID-D at the Advanced Photon Source (APS)
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