The possibility of using methylamines instead of ammonia as a nitrogen precursor for the CVD of nitrides is studied using quantum chemical computations of reaction energies: reaction electronic energy (ฮ๐๐ธ๐๐๐๐) reaction enthalpy (ฮ๐๐ป) and reaction free energy (ฮ๐๐บ). The reaction energies were calculated for three types of reactions: Uni- and bimolecular decomposition to more reactive nitrogen species, adduct forming with trimethylgallium (TMG) and trimethylaluminum (TMA) followed by a release of methane or ethane and surface adsorption to gallium nitride for both the unreacted ammonia or methylamines or the decomposition products. The calculations for the reaction entropy and free energy were made at both STP and CVD conditions (300ยฐC-1300ยฐC and 50 mbar). The ab inito Gaussian 4 (G4) theory were used for the calculations of the decomposition and adduct reactions while the surface adsorptions were calculated using the Density Functional Theory method B3LYP. From the reactions energies it can be concluded that the decomposition was facilitated by the increasing number of methyl groups on the nitrogen. The adducts with mono- and dimethylamine were more favorable than ammonia and trimethylamine. ๐๐ป2 was found to be most readily to adsorb to ๐บ๐๐ while the undecomposed ammonia and methylamines was not willingly to adsorb.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:liu-132812 |
| Date | January 2015 |
| Creators | Rรถnnby, Karl |
| Publisher | Linkรถpings universitet, Kemi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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