Atomic force microscopy and Raman spectroscopy study of tantala films

[摘要] This thesis contains a report of two distinct areas of research into thin films of tantalum pentoxide (Ta2O5), also known as tantala. Firstly, the surfaces of the tantala films have been investigated with atomic force microscopy (AFM) and the results presented and analysed. Secondly, the same films have been investigated with Raman spectroscopy and conclusions have been drawn from the data. Thin films of tantala are used as mirror coatings in gravitational wave detectors. Theoretically predicted gravitational waves should induce a movement of 10-20 m Hz-1/2 in a gravitational wave detector. All sources of noise that could preclude the positive detection of a wave need to be minimised if not removed altogether. A mechanical dissipation within the tantala films is one such source of noise that limits the sensitivity of the detector. This mechanism is not altogether understood yet. In this work thin films of tantala (10-500nm) have been deposited by pulsed laser deposition (PLD), atomic layer deposition (ALD) and ion beam sputtering (IBS) on to silicon substrates. Studies by atomic force microscopy (AFM) have been made and show the influence of deposition conditions on the surface morphology of grown films. Films with low surface roughness will be good candidates for mirror coatings in order to minimise possible scattering of incident radiation. The same films have also been studied with Raman spectroscopy in an effort to characterise the vibrational energy of the films. Raman studies of glasses are relatively rare and this is a first study in the context of mirror coatings and doped tantala. An assessment is offered as to what films offer the best features for mirror coatings.

[发布机构] University:University of Glasgow;Department:School of Physics and Astronomy

[关键词] QC Physics