Pulsed injection MOCVD of functional electronic oxides

Abstract

A new source has been developed in LMGP and in Vilnius University for the generation of active gases for chemical vapour deposition of layers. The principle is a sequential injection of micro amounts (few milligrams) of a solution of organic precursors into an evaporator, where a flash volatilization occurs. The system is very different from the other liquid sources currently used for the MOCVD process, the main advantages are: For a fixed injection parameter, the thickness of the layer is only determined by the number of drops injected (‘digital growth’). The system uses a flash evaporation: only one source containing a solution of the different precursors in an organic solvent is required for the synthesis of complex compounds, but, of course, it is possible to use one source for each element. Multilayers or superlattices of complex compounds are obtained with several injection sources connected to the same reactor and working alternately. A wide variety of compounds and multilayers have already been grown using this new CVD source. In the field of high-temperature superconductors, high-quality YBa2Cu3O7 epitaxial layers have been recently obtained on 3 inch LaAlO3 single-crystal substrate (Tc=92.1 K, δTc=0.15 K, Jc(77K)=4–6 MA/cm2 over the whole surface). This demonstrates that the large amount of carbon existing in the gas phase does not affect the properties of the superconductor. Copyright © 2000 John Wiley & Sons, Ltd.