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Using oxygen adsorption experiments on poly (dG)-poly (dC) DNA molecules, we found that their conductance can be easily controlled by several orders of magnitudes using oxygen hole doping, which is a characteristic behavior of a p-type semiconductor. It also suggests that the conductance of the DNA under doping results from charge carrier transport, not from an ionic conduction. On the other hand, we will also show that the poly (dA)-poly (dT) DNA molecules behave as an n-type semiconductor. This letter demonstrates that the concentration and the type of carriers in the DNA molecules could be controlled using proper doping methods.

A type of carbon nanotube transistors, which would be suitable for large-scale integration, has been fabricated from vertically aligned carbon nanotubes. We fabricated highly ordered carbon nanotubes, which are selectively grown on the patterned aluminum oxide nanotemplates. Each device element is formed on a vertical carbon nanotube attached to a bottom (source) and upper (drain) electrodes and a gate electrode, which is electrostatically switchable. The transistors can be integrated in large arrays with the potential for tera-level density (2×1011/cm2). The vertical carbon nanotube transistor shows ON/OFF switching operation at 30 K.

Electronic transport properties of a heterostructure junction made of two different multiwall carbon nanotubes are studied. Independent measurement of the current–voltage characteristics of each nanotube revealed that both of them were lightly p-doped semiconductors with energy gaps whose magnitudes are widely different from each other. The current–voltage characteristics measured across the heterojunction show reproducible rectifying diode behavior. The forward bias current across the heterojunction increases rapidly with the application of a positive gate bias voltage, implying an n-type gate response.

An in-plane single-electron memory cell operating at 77 K has been fabricated from a Si-doped thin GaAs film. This device utilizes an artificially fabricated floating node as a storage node and detects the charge stored on the floating node using a single-electron electrometer. Charging of the floating node is evidenced by a large peak in source–drain current as a function of control gate voltage, and is further confirmed by a discrete shift in the peak or threshold voltage.

We report a development of reduced graphene oxide (rGO)-based gas sensors with a practical recovery by facile functionalization with tin dioxide nanoclusters. Upon the introduction of UV illumination to this nanostructure, the reaction on surfaces of tin dioxide nanoclusters was activated and thereby the nanoscale heterojunction barriers between the rGO sheet and the nanoclusters were developed. This lowered the conductance to quickly recover, which was intensified as the cluster density has reached to the percolation threshold. However, after the formation of the cluster percolating network, the sensor response has totally changed into a deterioration of the sensitivity as well as the recovery.

We studied the effect of metal contact on the position of the Dirac point by means of transport measurements. To determine the sole effect of metal contact, we prepared more than 100 graphene devices following the same fabrication procedure and with a device layout that differed only in the type of metal electrode used. By measuring the peak position of the resistance, the Dirac points (VgDirac) were recorded in the gate response. The work function of metal-graphene complex was found to be a fair phenomenological indicator of the location of VgDirac in the transfer response.

We report air-stable n-type operations of the single-walled carbon nanotube field effect transistors (SWNT-FETs) fabricated with Gd electrodes. Unlike previously reported n-type SWNT-FETs, our devices maintained their n-type operation characteristics in ambient atmosphere for more than two months. The shallow Gd films with a thickness below 20 nm are corroded by environmental oxygen, whereas the well-contacted Gd-SWNT interfaces underneath the thick Gd layers are protected from contaminations by air molecules. Theoretical studies based on the first-principles electronic structure calculations confirm that Gd layers have an excellent binding affinity to the SWNTs.

We use an in situ Al decoration technique to control the transport characteristics of single-walled carbon nanotube field effect transistors (SWNT-FETs). Al nanoparticle decoration in a high vacuum caused the devices to change from p-type to n-type FETs, and subsequent exposure to the ambient atmosphere induced a gradual recovery of p-type character. In comparison with the bare SWNT-FETs under high vacuum, the channel-open devices with decorated Al particles exhibited reduced current under ambient conditions. However, selective Al decoration only at the contact resulted in an improved p-type current in ambient air.

The authors present a biosensor using pyrolyzed electron beam resist nanostructures as an active conducting channel. Versatile, arbitrarily shaped nanostructures such as nanowires, nanodots, and suspended nanobridges are fabricated by a facile electron beam resist thermal decomposition method. The nanostructures typically show 15–21nm thickness, 100–200nm width, 0.6nm roughness, and p-type majority conduction with tailored resistivity of 5.2–0.75Ωcm. Streptavidin-biotin binding and pH dependent conductance modulation are demonstrated using pyrolyzed resist based devices.

The authors report the construction of carbon nanotube Schottky diodes by covering a selectively exposed area of the electrode with self-assembling molecules. Two self-assembling molecules with different polarities, 2-aminoethanethiol and 3-mercaptopropionic acid, were used to modify the Fermi level lineup at the selected contact. The devices showed p-type behavior with symmetric I-V showing clear rectifying behavior after treatment of one contact with 2-aminoethanethiol. Their experiment, in conjunction with the results of ab initio electronic structure calculations, suggests that the diode action stems from the asymmetric Fermi level lineup between the bare and engineered contacts.

We investigated the effect of humidity on the electrical transport properties of single-walled carbon nanotube field effect transistors (SWNT-FETs). Water molecules are found to behave as electron donors to the nanotube: Current through the p-type carbon nanotube device is found to decrease under a modest humidity, and starts to increase as the humidity increases over 65%, which is believed to be due to the opening of electron channels. Through first principles calculations based on the density functional theory, we found that water molecules can donate electrons to the carbon nanotube. Moreover, a hydrogen-bonded water monolayer will be formed around the nanotube at fully covered conditions. We suggest that this result could provide a systematic understanding of the humidity effect on SWNT-FETs, which has been believed to be essential in the development of nanotube-based sensors.