Tailoring of Epitaxial CoSi2/Si Nanostructures by Low Temperature Wet Oxidation

We have investigated a process for tailoring of epitaxial CoSi 2/Si nanostructures using low temperature wet oxidation. A separation between two CoSi2 layers on a Si substrate in the range of 60 nm is generated by a self-assembly process. During subsequent low temperature wet oxidation, SiO2 formation on top of the silicide layers pushes the latter into the substrate. At the edges of the gap, the silicide layers are shifted in both and directions, leading to an effective reduction of the separation width to dimensions below 20 nm and eventually to merging of the two layers. The significantly lower oxidation rate of the silicon in the initial gap compared with the CoSi2 provides the excess Si for the shift in the direction. The structures were investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM)

Broadband THz detection from 0.1 to 22 THz with large area field-effect transistors

We report on ultrafast detection of radiation between 100 GHz and 22 THz by field-effect transistors in a large area configuration. With the exception of the Reststrahlenband of GaAs, the spectral coverage of the GaAs-based detectors is more than two orders of magnitude, covering the entire THz range (100 GHz - 10 THz). The temporal resolution of the robust devices is yet limited by the 30 GHz oscilloscope used for read out. The responsivity roll-off towards higher frequencies is weaker than expected from an RC-roll-off model. Terahertz pulses with peak powers of up to 65kW have been recorded without damaging the devices