In situ monitoring of the growth and characterization of (PrMnO3)n(SrMnO3)n superlattices

Superlattices having the general formula (PrMnO3)n(SrMnO3)n were grown from PrMnO3 and SrMnO3 ceramic targets by pulsed laser deposition (PLD) in low pressures (laser-MBE) and were compared to those grown in standard pressures (“classical”-PLD). For the laser-MBE grown films, the growth was monitored and the thickness of each deposited layer was controlled in situ at the level of one unit cell using reflection high energy electron diffraction. Perfectly ordered stacks of PrMnO3 and SrMnO3 layers were thusly grown. The transport and magnetic properties of the laser-MBE superlattices differ from similar superlattices grown in a “classical” PLD system. The different physical behaviors are explained by the combination of two factors, the roughness of the interfaces between the different layers and the oxygen deficiency, both of which are larger in the films grown using classical-PLD. X-ray and electron diffraction, as well as high-resolution electron microscopy, were used to characterize the structures of the laser-MBE superlattices. The valence of the manganese cations was probed by x-ray photoelectron spectroscopy and the results support the idea that the oxygen deficiency is larger in films grown in the classical-PLD system. This difference arises because pure molecular oxygen is used as the oxidizer in classical-PLD, whereas a mixture of molecular oxygen and ozone is used as the oxidizer in the laser-MBE system.