Direct etching at the nanoscale through nanoparticle-directed capillary condensation.

We report a method to locally deliver a chemical etchant at the nanoscale in the vapor phase by capillary condensation forming a meniscus at the nanoparticle/substrate interface. The process is simple, scalable and does not require functionalization of the nanoparticles. Furthermore, it does not rely on any specific chemical properties of the materials other than the solution being aqueous and the wettability properties of the surfaces involved, which should enable its application to other material and chemical combinations. In particular, in this work we demonstrate the proposed process by periodically pattering a SiO2 layer using a self-assembled monolayer of polystyrene particles exposed to HF vapors. The patterned SiO2 layer is then used as a mask to etch a pattern of inverted nanopyramids on Si. The silicon nanopatterning has been demonstrated for particles sizes ranging from 800 nm down to 100 nm, providing pyramids with a size down to 50 nm for 100 nm nanoparticles.

Natural occurrence of the diamond hexagonal structure in silicon nanowires grown by a plasma-assisted vapour-liquid-solid method.

Silicon nanowires have been grown by a plasma-assisted vapour-liquid-solid method using tin as the catalyst. Transmission electron microscopy in the [12[combining macron]10] zone axis shows that the diamond hexagonal (P63/mmc) crystal structure is present in several nanowires. This is the first unambiguous proof of the natural occurrence of this metastable phase to our knowledge.

Radio frequency current-voltage probe for impedance and power measurements in multi-frequency unmatched loads.

A broad-band, inline current-voltage probe, with a characteristic impedance of 50 Ω, is presented for the measurement of voltage and current waveforms, impedance, and power in rf systems. The probe, which uses capacitive and inductive sensors to determine the voltage and current, respectively, can be used for the measurement of single or multi-frequency signals into both matched and unmatched loads, over a frequency range of about 1-100 MHz. The probe calibration and impedance/power measurement technique are described in detail, and the calibrated probe results are compared with those obtained from a vector network analyzer and other commercial power meters. Use of the probe is demonstrated with the measurement of power into an unmatched capacitively coupled plasma excited by multi-frequency tailored voltage waveforms.