Growth and in situ high-pressure reflection high energy electron diffraction monitoring of oxide thin films

Interface and surface physics is an important sub-discipline within condensed matter physics in recent decades. Novel concepts like oxide-electronic device are prompted, and their performance and lifetime are highly dependent on the flatness and abruptness of the layer surfaces and interfaces. Reflection high-energy electron diffraction (RHEED), which is extremely sensitive to surface morphology, has proven to be a versatile technique for the growth study of oxide thin films. A differential pumping unit enables an implementation of RHEED to pulsed laser deposition (PLD) systems, ensuring an in situ monitoring of the film growth process in a conventional PLD working oxygen pressure up to 30 Pa. By optimizing the deposition conditions and analyzing the RHEED intensity oscillations, layer-by-layer growth mode can be attained. Thus atomic control of the film surface and unit-cell control of the film thickness become reality. This may lead to an advanced miniaturization in the oxide electronics, and more importantly the discovery of a range of emergent physical properties at the interfaces. Herein we will briefly introduce the principle of high-pressure RHEED and summarize our main results relevant to the effort toward this objective, including the growth and characterization of twinned La_2/3Ca_1/3MnO₃ thin films and ReTiO_3+δ/2 (Re = La, Nd; δ = 0 ～ 1) A _n B _n O_3n+2 structures, on YSZ-buffered ‘Silicon on Insulator’ and LaAlO₃ substrates, respectively, as well as the study of the initial structure and growth dynamics of YBa₂Cu₃O_7?δ thin films on SrTiO₃ substrate. Presently we have realized in situ monitoring and growth mode control during oxide thin film deposition process.