Crystallographic structures, optoelectronic properties, and nanoscale surface morphologies of ex situ phosphorus-doped polycrystalline silicon (poly-Si)/SiO x passivating contacts, formed by different deposition methods (sputtering, plasmaenhanced chemical vapour deposition [PECVD], and low-pressure chemical vapour deposition [LPCVD]), are investigated and compared. Across all these deposition technologies, we noted the same trend: higher diffusion temperatures yield films that are more crystalline but that have rougher surface morphologies due to bigger surface crystal grains. Also, the recrystallization process of the as-deposited Si films starts from the SiO x interface, rather than from the film surface and bulk. However, there are some distinct differences among these technologies. First, the LPCVD method yields the lowest deposition rate, roughest surfaces, and smallest degree of crystallinity on finished poly-Si films. In contrast, the PECVD method has the highest deposition rate and smoothest surfaces for both as-deposited Si and annealed poly-Si films. Second, as-deposited sputtered and PECVD Si films contain only an amorphous phase, whereas as-deposited LPCVD films already has some crystalline phase. Third, the LPCVD phosphorus in-diffusion into the substrate depends strongly on the initial film thickness, whereas for the other two methods, it is weakly dependent on thickness. Finally, the passivation quality of every poly-Si film type has different responses to the film thickness and diffusion temperature, suggesting that the ex situ doping optimization should be performed independently.

Functionality of domain walls and other topological defects in ferroelectrics is being widely investigated for applications in electronic devices. While the intrinsic electronic properties of a wall have been considered, its inherent mechanical properties remain explored very little, despite the fact that coupling between strain and polarization is prevalent in many of these materials. Herein, an in-depth study of variations in nanomechanical properties at 90 o domain walls and their adjacent domains in single-crystalline lead titanate (PbTiO 3 ) is presented as a prototypical ferroelectric material using a combination of various atomic force microscopy (AFM)-based methods. Considerable variations of elastic moduli are found at 90 o domain walls extending up to ~100 nm into the domain areas. AFM nanoindentation also allows to extract local domain wall hardness and plastic and elastic deformation energies. These findings have implications for the design of ferroelectric domain wall functionality that incorporates the intrinsic elastic compliance of a domain wall.