Microwave Irradiation Assisted Synthesis of Gallium Aluminum Oxide Using Metal Acetylacetonate Precursors, Peculiar Observations and Safety Guidelines for Young Scientists

Abstract

Microwave-assisted nano-particle synthesis has seen a boom in recent decade. Different variants are being tested all over the world, be it microwave-irradiation-assisted solvothermal synthesis, thin-film deposition using microwave plasma-assisted CVD, microwave-assisted combustion synthesis, or mist CVD. This technology induces self-catalysis, faster reaction time, less energy and is considered safer from other purely chemical variants. Gallium-Aluminum Oxide is an oxide of vital importance. Gallium Oxide in its most stable form, β-Ga2O3, has a band-gap of ∼4.8 eV and cannot be used for deep ultra-violet (UV) applications (i.e., below 250 nm). Aluminum oxide is a wide band-gap material. The ionic radius of Aluminum ions is similar to that of Gallium ions. Therefore, according to Hume-Rothery rule, Aluminum ion can substitute Gallium in its lattice structure and vice-versa. This gives the possibility of band-gap engineering from 4.6 eV (band-gap, β-Gallium Oxide) to 8.8 eV (band-gap, α-Aluminum Oxide), extending the application of Gallium Oxide to deep UV applications. In present work, three different compositions of Gallium-Aluminum Oxide thin films (varied by mass) are deposited, using microwave-irradiation-assisted solvothermal thin-film deposition technique and metal acetylacetonate precursors. A stoichiometric ratio of ∼5:1 is obtained for 90:100 variation. For 50:50 and 10:90, the stoichiometric ratio remained close to 5:5 and 1:9, respectively, showing good agreement with the Gallium to Aluminum ratio in precursor solution. The investigation is done by using energy dispersive X-Ray analysis. A particle variation from 5 nm to 500 nm was obtained as calculated from Field Emission Scanning Electron Microscopy (FESEM) results. In second part of the work, the corresponding author wants to strongly argue that “Microwave in kitchen is not same as microwave in lab” and report some of the observations from lab to pave a way towards a truly Green or safer technology.