Causes of ferroelectricity in HfO-based thin films: an ab initio perspective.

We present a comprehensive first principles study of doped hafnia in order to understand the formation of ferroelectric orthorhombic[001] grains. Assuming that tetragonal grains are present during the early stages of growth, matching plane analysis shows that tetragonal[100] grains can transform into orthorhombic[001] during thermal annealing when they are laterally confined by other grains. We show that among 0%, 2% and 4% Si doping, 4% doping provides the best conditions for the tetragonal[100] → orthorhombic[001] transformation.

Black Phosphorus Mid-Infrared Photodetectors with High Gain.

Recently, black phosphorus (BP) has joined the two-dimensional material family as a promising candidate for photonic applications due to its moderate bandgap, high carrier mobility, and compatibility with a diverse range of substrates. Photodetectors are probably the most explored BP photonic devices, however, their unique potential compared with other layered materials in the mid-infrared wavelength range has not been revealed. Here, we demonstrate BP mid-infrared detectors at 3.