Photoelectron spectroscopy of metal oxides

The work described in the thesis divides essentially into two parts: (1) the experimental measurements of photoelectron spectra of a variety of solid metal oxides; and (2) the theoretical investigation of electronic structure problems concerning the final states of the photoionisation process (the states of the ionised system), much of which is directly relevant to the experimental studies. The spectroscopic investigation concentrates upon transition-metal oxides (for example, the rutile series MO2 various sesquioxides M2O3, and ternary systems such as ilmenites (MTiO3). Such materials are of considerable general interest by virtue of their diverse electronic properties, and their technological importance. Photoelectron spectra were measured from polycrystalline samples, using both UV (He I and He II) and X-ray (Mg Kα) excitation. The sequential measurement of UV- and X-ray photoelectron spectra is an important element of this work. From the technical point of view another important feature of the experimental work is the attention given to preparation of clean sample surfaces. The theoretical work concerns the 'fine structure' of photoelectron signals due to (1) electrostatic coupling effects and (2) electronic relaxation in the final state. The ionic approximation is invoked, all electronic structure calculations being performed on atomic species. Both core electrons in general, and the outer-shell electrons of heavy atoms, are highly relativistic in nature, their description demanding the use of Dirac-Fock theory rather than the simple Hartree-Fock model. A major feature of the theoretical work described is the use, where appropriate, of Dirac-Fock theory to obtain required atomic wavefunctions and state energies. The use of a relativistic model proves essential in many cases.