High-temperature Metal Organic Chemical Vapor Research Articles

Selective Synthesis of Hollow and Filled Fullerene-like (IF) WS2 Nanoparticles via Metal–Organic Chemical Vapor Deposition

The synthesis of WS2 onion-like nanoparticles by means of a high-temperature metal–organic chemical vapor deposition (MOCVD) process starting from W(CO)6 and elemental sulfur is reported. The reaction can be carried out as a single-step reaction or in a two-step process where the intermediate products, amorphous WS2 nanoparticles, formed through the high-temperature reaction of tungsten and sulfur in the initial phase of the reaction, are isolated and converted into onion-type WS2 nanoparticles in a separate annealing step. Analysis of the reaction product using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) combined with energy dispersive X-ray spectroscopy (EDX) allowed to optimize the reaction in such a way that filled onion-like structures are formed in a one-step reaction, whereas hollow onion-like structures are obtained by the two-step procedure. A model could be devised that allows us to rationalize the different outcome of the reactions. The MOCVD approach therefore allows a selective synthesis of open and filled fullerene-like chalcogenide nanoparticles.

Synthesis of ZnO nanorods by a hot-wall high-temperature metalorganic chemical vapor deposition process

ZnO nanorods with diameter of 30–200 nm were synthesized by a metalorganic chemical vapor deposition process in a hot-wall type chamber at elevated temperatures above 700 °C. At temperatures between 400 and 500 °C, ZnO thin films and wrinkles were synthesized. Above 500 °C, vertically aligned ZnO nanorods were grown on a Si and sapphire substrate without any catalysts. The range of diameter was 30–200 nm. When Au catalysts were deposited on the substrate prior to the deposition, nanocombs and nanosheets as well as nanorods were synthesized. In particylar, ZnO could be grown selectively along the pattern of the Au catalyst with the aid of a Au–Zn alloy.

Fabrication of Highly Dense Ru Thin Films by High-Temperature Metal-Organic Chemical Vapor Deposition with NH3 Gas as Ru Oxidation Suppressing Agent

We attempted to fabricate highly dense Ru thin films by metal-organic chemical vapor deposition at an elevated temperature of 400°C, employing NH3 gas to suppress Ru oxidation. A solution of 0.2 mol/L tris(2,4-octanedionato)ruthenium [Ru(od)3, Ru(C8H13O2)3] dissolved in n-butylacetate was used as a Ru source and O2 as a reactant gas. It was revealed that NH3 gas effectively eliminated residual oxygen from the Ru films. However, at higher feeding rates of a metal-organic source, Ru films showed poor densities and high electrical resistivities mainly due to significant carbon incorporation. By optimizing Ru(od)3 flow rate to less than 0.3 g/min to reduce contaminating carbon supply, we successfully produced highly dense and conductive Ru films. The best Ru film had a density of 12.2 g/cm3 and a resistivity of 12.0 µΩ·cm, which were excellent values close to the bulk ones.

Growth of crack-free hexagonal GaN films on Si(100)

Hexagonal GaN films have been grown on Si(100) substrates by employing a sputtered AlN buffer layer followed by another high-temperature metalorganic chemical vapor deposition (MOCVD) grown AlN buffer layer. The highly oriented structure of sputtered AlN provides a hexagonal template for subsequent AlN and GaN growth. The GaN films are evaluated by transmission electron microscopy, selected area electron diffraction, x-ray diffraction, and photoluminescence and exhibit a purely hexagonal columnar structure. The orientation of the GaN columns depends on the thickness of both the sputtered AlN buffer layer and the MOCVD grown AlN buffer layer. The surface of GaN films is shiny and crack free up to a thickness of 2 μm studied in this work.