Effect of the deposition temperature on the iridum film microstructure produced by metal-organic chemical vapour deposition: sample characterization using x-ray techniques

Abstract

The iridium films were prepared by metal-organic chemical vapour deposition (MOCVD) via the pyrolysis of iridium tris(acetylacetonate) on glass and quartz surfaces at atmospheric pressure with hydrogen as an additive in the deposition temperature range 370–550 °C. The phase composition and the microstructure of the films have been studied by means of the X-ray phase analysis and small-angle X-ray scattering techniques. Only the crystal phase of metal iridium has been found. The films consist of chaotically oriented close-spaced particles of different shapes and sizes. Iridium crystallites and other inhomogeneities of electron density in the films have a mean size in the range 100–400 Å. The analysis has made it possible to assume the presence of particles of two shapes in Ir films: “compact” (the axial ratio is no lower than 1:3) and “flattened-out” (disks, cracks, plates and shells) particles. For all the samples, the mean thicknesses r of “flattened-out” particles with spherical shells taken as models of their shapes have been estimated. The value of r increases with increasing substrate temperature from 370 to 470 °C. The maximum volume share of “flattened-out” particles is observed in the 420–470 °C deposition temperature range. An increase or a decrease in substrate temperature in MOCVD processes leads to almost complete disappearance of the particles of this shape. The average radii R g of gyration and the maximum distances L max in particles have been estimated. In addition, the specific surfaces S/V of film material and the functions of volumetric distribution D v( R) of compact particles in Ir films have been calculated depending on the deposition temperature.