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- Institutt for fysikk 
The development of next-generation devices and technology requires micro- and nanoscale manipulation of complex functional material systems. The micro- to nanoscale experiments required to understand their function must be designed with flexibility to accommodate many different instrument considerations. For this task, the focused ion beam (FIB) platform is an optimal laboratory space, combining its own high-resolution characterization capabilities with the power to create or manipulate samples or arbitrary specimens for complementary study. This thesis represents the application of FIB to two promising functional material systems for next-generation devices and demonstrates some of the large untapped potential that can be accessed in this way. III-V semiconductor nanowires are a promising material system for optoelectronics, such as solar cells, light emitting diodes and lasers. Here FIB has been used to pattern the growth mask defining nanowire position-controlled growth, shortening and simplifying the fabrication process by leveraging the flexibility of FIB. To characterize the effect of FIB patterning parameters in a systematic way, techniques such as computer vision-based image analysis for scanning electron microscopy and efficient in-situ electrical probing have been developed. Ferroelectric domain walls in hexagonal manganites are sub-nanometer features that can exhibit varying degrees of conductivity. This makes them interesting as future circuit elements for nanoelectronics. Two important aspects of the hexagonal manganite ErMnO3 have been covered in this work: First, local field-induced conductivity enhancement has been characterized in 3D through use of FIB specimen preparation. Second, a workflow has been developed to prepare arbitrary domain wall specimens with sufficient surface quality for advanced scanning probe microscopy characterization while preserving the original domain structure. In both these example material systems it has been shown how FIB can be incorporated into their further development. The application of state-of-the-art FIB capabilities allows for the design of novel experiments, combining multiple characterization techniques and correlating results on the same volume to provide new insight in structure-property relationships for complex material systems.