Precursor routes to selected metal and semiconductor nanomaterials

Nano-scale materials have stimulated great interest due to their importance in basic scientific research and potential technological applications. A selection of very different nano-scale materials such as indium nitride nanowhiskers, gallium nitride, cadmium selenide nanocrystals within the mesopores of silica templates (MCM-41, SBA-15) and ligand stabilised gold and titanium dioxide colloidal nanocrystals were synthesised and characterised by different characterisation techniques and summarised in different chapters of the thesis. In the last part of the thesis, the growth and characterisation of nano-porous epitaxial GaN films by a simple chemical solution deposition technique using molecular precursors is discussed

Tailoring iron(III) oxide nanomorphology by chemical vapor deposition: growth and characterization

Iron(III) oxide nanosystems are actually the focus of an intensive attention due to their low cost, non-toxicity, ample abundance and attractive chemico-physical properties. In this work, iron(III) oxide nanomaterials were deposited by chemical vapor deposition (CVD) under O2 atmospheres in the temperature range 500-800\ub0C, starting from the scarcely investigated tris(tert-butyl acetoacetato)iron(III) precursor. All nanodeposits were found to consist of the alpha-Fe2O3 (hematite) polymorph. Surface and in-depth analyses demonstrated the presence of high purity Fe2O3, indicating the occurrence of a clean precursor decomposition under the adopted conditions. Interestingly, the system morphology could be controlled by varying the deposition temperature and ranged from the circular assembly of ordered nanosheets, to rough vortices, up to dense deposits characterized by the copresence of nanosheets and nanocolumns. The unique surface features offer great properties for advanced applications in various technological fields, such as catalysis and photocatalysis, solid state gas sensing and magnetic recording media

Rare-earth substituted HfO2 thin films grown by metalorganic chemical vapor deposition.

Thin films of HfGdOx and HfDyOx were deposited by metalorganic chemical vapor deposition (MOCVD) utilizing guanidinate precursors for Hf, Gd and Dy. The close match in the thermal properties of the precursors enabled the MOCVD of rare-earth (RE) substituted HfO2 over a wide temperature window. Film deposition was carried out in the temperature range 300–700 °C in the presence of oxygen on Si(100) substrates. HfGdOx films were analyzed in detail for their structure, composition and morphology using X-ray diffraction, Rutherford backscattering spectrometry, proton induced X-ray emission, X-ray photoelectron spectroscopy and scanning electron microscopy. The electrical properties of HfGdOx in terms of capacitance–voltage and current–voltage characteristics of metal-insulator-semiconductor device structures were evaluated

Rare-Earth based Oxide and Nitride thin films employing volatile homoleptic guanidinate precursors.

The application of the metalorganic compound tris(N,N'-diisopropyl-2-dimethlyamidoguanidinato)gadolinium(III) (1) as a precursor for MOCVD of Gd2O3 is discussed. Depositions were carried out in the presence of oxygen at reduced pressure and varying the substrate temperature in the range 300 - 700{degree sign}C. Employing a multi-technique approach (XRD, SEM, AFM, EDX, RBS, SNMS, SE, C-V), variations of the growth characteristics and film properties with deposition temperature are studied in terms of crystallinity, structure, surface roughness, composition, optical and electrical properties. In addition, the use of 1 as single source precursor for the MOCVD of GdN thin films is also demonstrated

Lanthanide oxide thin films by metalorganic chemical vapor deposition employing volatile guanidinate precursors.

The application of two novel metalorganic complexes, namely the isostructural tris(N,N'diisopropyl-2-dimethlyamido-guanidinato)gadolinium(III) (1) and tris(N,N'-diisopropyl-2-dimethlyamido-guanidinato)dysprosium(III) (2) as precursors for metalorganic chemical vapor deposition (MOCVD) of Gd 2O3 and Dy2O3 is discussed. On the basis of the detailed thermal gravimetric analysis (TGA) and isothermal TGA studies, both the precursors are very volatile and able to deliver continuous mass transport into the gas phase. The extraordinary thermal stability of the precursors was revealed by nulcear magnetic resonance (NMR) decomposition studies. Depositions were carried out in the presence of oxygen at reduced pressure and varying the substrate temperature in the range 300-700 °C. Uniform films with reproducible quality were deposited on Si(100) and Al 2O3(000l) substrates over the entire temperature range. Employing a multitechnique approach (XRD, SEM, AFM, EDX, XPS, RBS, SNMS, C- V), variations of the growth characteristics and film properties with deposition temperature are studied in terms of crystallinity, structure, surface roughness, composition, and electrical properties