The implementation of graphene in different applications will only be possible if the large-area and high-quality production of this material becomes a reality. The ideal synthesis method would allow for precisely controlled formation of graphene layers directly on the insulating substrate of choice. In that context, molecular beam epitaxy (MBE) appears as a promising method. The growth by this technique does not involve catalytic processes and could in principle be extended to different substrates. One of the main advantages of MBE is that it offers the benefit of exact deposition rates and sub-monolayer thickness precision. This is especially attractive regarding the preparation of graphene with a specific number of atomic layers.
So far, the use of Si as n-type dopant for GaAs nanowires has been hampered by its amphoteric behavior that leads to heavy charge-carrier compensation. We demonstrate how the doping amphotericity of Si is related to the growth mode and the growth kinetics, and how it can be controlled in favor of donor-like behavior by employing a shell-doping scheme under certain growth conditions.
With the ability to synthesize semiconductors in high crystal quality on foreign substrates, nanowires (NWs) offer new and promising possibilities for the future miniaturization of optoelectronic devices and their integration with Si technology. The bottom-up fabrication of NW-based light emitting diodes (LEDs) on Si represents an example of this integration.
GaN nanowires (NWs) have attracted great interest for the fabrication of nanoscale devices such as light emitting diodes, bio-sensors, and photovoltaic cells because they exhibit a high crystal quality independent of the substrate used for growth. However, despite the potential of these nanostructures, and the fact that they have been grown by plasma-assisted molecular beam epitaxy (PA-MBE) since the late nineties, the physical mechanisms underlying the formation of GaN NWs are not well understood.