The response of carbon-nanotube (CNT) transistors to large tensile strains has not been studied because of lack of stretchable devices. In this letter, we fabricate extremely stretchable single-wall CNT (SWCNT) conductive coatings on flexible and transparent elastomer substrates. We then measure the mechanical and electrical properties of the coatings and found excellent stretchability (Poisson ratio ≈ 0.31). The sheet resistances of the coatings remain largely unchanged under a large tensile strain. We then construct an active transistor on SWCNT thin films, which serve as active channel and electrodes, with polydimethylsiloxane thin film as the gate dielectric layer. The transistor exhibits excellent mechanical stability, showing no noticeable change (less than 5%) in electrical performance up to a large strain of 22.5%. The stretchable SWCNT thin-film transistor exhibits a current on–off ratio of ∼50 and field-effect mobility of ∼24 cm2 V−1 s−1, with 75% transmissivity in visible wavelength. We also found that on–off ratio increases with increased stretch strain, while mobility initially increases and then decreases with increased stretch strain.

In this work, we synthesized high-quality InAs nanowires by a convenient chemical vapor deposition method, and developed a simple laser heating method to measure the thermal conductivity of a single InAs nanowire in air. During the measurement, a focused laser was used to heat one end of a freely suspended nanowire, with its other end embedded into a carbon conductive adhesive. In order to obtain the thermal conductivity of InAs nanowires, the heat loss in the heat transfer process was estimated, which includes the heat loss through air conduction, the heat convection, and the radiation loss. The absorption ratio of the laser power in the InAs nanowire was calculated. The result shows that the thermal conductivity of InAs nanowires monotonically increases from 6.4 W m -1 K -1 to 10.5 W m -1 K -1 with diameters increasing from 100 nm to 190 nm, which is ascribed to the enhanced phonon-boundary scattering.

The electrical and thermal conductivities are measured for individual zinc oxide (ZnO) nanowires with and without gallium ion (Ga+) implantation at room temperature. Our results show that Ga+ implantation enhances electrical conductivity by one order of magnitude from 1.01 × 103 Ω−1m−1 to 1.46 × 104 Ω−1m−1 and reduces its thermal conductivity by one order of magnitude from 12.7 Wm−1K−1 to 1.22 Wm−1K−1 for ZnO nanowires of 100 nm in diameter. The measured thermal conductivities are in good agreement with those in theoretical simulation. The increase of electrical conductivity origins in electron donor doping by Ga+ implantation and the decrease of thermal conductivity is due to the longitudinal and transverse acoustic phonons scattering by Ga+ point scattering. For pristine ZnO nanowires, the thermal conductivity decreases only two times when its diameter reduces from 100 nm to 46 nm. Therefore, Ga+-implantation may be a more effective method than diameter reduction in improving thermoelectric performance.

No abstract

The characterization of junctions in nanowires by high-resolution transmission electron microscopy with spherical aberration correction is tricky and tedious. Many disadvantages also exist, including rigorous sample preparation and structural damage inflicted by high-energy electrons. In this work, we present a simple, low-cost, and non-destructive Raman spectroscopy method of characterizing anomalous junctions in nanowires with axially degraded components. The Raman spectra of SixGe1−x nanowires with axially degraded components are studied in detail using a confocal micro-Raman spectrometer. Three Raman peaks (νSi–Si = 490 cm−1, νSi–Ge = 400 cm−1, and νGe–Ge = 284 cm−1) up-shift with increased Si content. This up-shift originates in the bond compression induced by a confined effect on the radial direction of nanowire. The anomalous junctions in SixGe1−x nanowires with axially degraded components are then observed by Raman spectroscopy and verified by transmission electron microscopy energy-dispersive X-ray spectroscopy. The anomalous junctions of SixGe1−x nanowires with axially degraded components are due to the vortex flow of inlet SiH4 and GeH4 gas in their synthesis. The anomalous junctions can be used as raw materials for fabricating devices with special functions.