We measured field emission from a silicon nanopillar mechanically oscillating between two electrodes. The pillar has a height of about 200 nm and a diameter of 50 nm, allowing resonant mechanical excitations at radio frequencies. The tunneling barriers for field emission are mechanically modulated via displacement of the gold island on top of the pillar. We present a rich frequency-dependent response of the emission current in the frequency range of 300 ~ 400 MHz at room temperature. Modified Fowler-Nordheim field emission is observed and attributed to the mechanical oscillations of the nanopillar.
Inorganic semiconductor nanocrystals, also known as quantum dots (QDs), are interesting as as fluorescent labels in biological studies. We have found that introduction of CdSe QDs to the vicinity of black lipid membranes (BLMs) results in current bursts through the membranes with bias voltage. These current bursts resemble those of the peptaibol class of antibiotics such as alamethicin and trichorzins, and are dependent both on voltage level and on concentration of the QDs applied to the membrane. Our data suggest that QDs with dipole moments similar to alamethicin are influenced by an external electric field, which creates a torque promoting insertion into the BLM, and a simple model predicts that at least three QDs can aggregate to form a pore leading to a macroscopic conductance.
KEYWORDS: Quantum dots, Photon transport, Superconductors, Microwave radiation, Extremely high frequency, Bridges, Near field, Aluminum, Atomic force microscopy, Electron transport
A new technique is presented enabling the combination of highly transparent superconducting weak links with mesoscopic devices. These can serve as on-chip millimeter wave sources working at frequencies in the range of 10-100 GHz suitable for photon-assisted transport experiments. We use a modified FM tip to plough grooves into superconducting material, thus defining Josephson junctions. The weak links are easily integrated within mesoscopic structures such as quantum point contacts or quantum dots with high accuracy in alignment. In combination with a quantum point contact we observe photoconductance signal. Embedding these versatile millimeter wave sources in single and multiple quantum dot structures enables us to investigate photon-assisted transport phenomena and their modifications due to near- field effects.
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