Semiconducting single-walled carbon nanotubes synthesized by S-doping

An approach was presented for synthesis of semiconducting single-walled carbon nanotubes(SWNTs) by sulfur(S) doping with the method of graphite arc discharge. Raman spectroscopy, UV-vis-NIR absorption spectroscopy and electronic properties measurements indicated the semconducting properties of the SWNTs samples. Simulant calculation indicated that S doping could induce convertion of metallic SWNTs into semiconducting ones. This strategy may pave a way for the direct synthesis of pure semiconducting SWNTs.

Combined Effect of Uniaxial Strain and Magnetic Field on the Exciton States in Semiconducting Single-Walled Carbon Nanotubes

The exciton states of semiconducting carbon nanotubes are calculated by a tight-binding model supplemented by Coulomb interactions under the combined effect of uniaxial strain and magnetic field. It is found that the excitation energies and absorption spectra of zigzag tubes（11,0） and（10,0） show opposite trends with the strain under the action of the magnetic field. For the（11,0） tube, the excitation energy decreases with the increasing uniaxial strain, with a splitting appearing in the absorption spectra. For the（10,0） tube, the variation trend firstly increases and then decreases, with a reversal point appearing in the absorption spectra. More interesting,at the reversal point the intensity of optical absorption is the largest because of the degeneracy of the two bands nearest to the Fermi Level, which is expected to be observed in the future experiment. The similar variation trend is also exhibited in the binding energy for the two kinds of semiconducting tubes.

Selective growth of semiconducting single-walled carbon nanotubes solely from carbon monoxide

The selective growth of semiconducting single-walled carbon nanotubes(s-SWCNTs)is of great importance in many high-end applications represented by nanoelectronics.Here,we developed a general approach to grow horizontally aligned s-SWCNT arrays on stable temperature(ST)-cut quartz with bimetallic catalysts using carbon monoxide(CO)as both catalyst reductant and single component carbon feedstock under atmospheric pressure.The disproportionation of CO produces not only carbon species for SWCNT growth but also CO_(2),which could act as an in-situ etchant to remove both amorphous carbon and metallic tubes.The employment of bimetallic catalyst and quartz substrate facilitates the selective etching by narrowing the diameter distribution of as-grown SWCNT arrays.At the optimized conditions,we realized the selective growth of horizontally aligned s-SWCNT arrays with the content above 97%using CoCu catalysts,confirmed by Raman characterization and electrical measurements of the fabricated field effect transistor devices.This CO-based process in selective growth of s-SWCNTs has demonstrated its feasibility and universality by the broad growth window and applicability for other bimetallic catalysts,such as FeCu and CoMn.It possesses a practical potential in obtaining semiconducting channel materials for the scalable fabrication of CNT-based devices.

Selective Suspension in Aqueous Sodium Dodecyl Sulfate According to Electronic Structure Type Allows Simple Separation of Metallic from Semiconducting Single-Walled Carbon Nanotubes

Both density gradient centrifugation and gel electrophoresis have been reported to allow high throughput separation of metallic from semiconducting single-walled carbon nanotubes(SWNTs)when using aqueous sodium dodecyl sulphate(SDS)suspensions.We show here that both methods rely on an initial dispersion-by-sonication step,which is already selective with respect to electronic structure type.The corresponding aqueous SDS“starting”suspensions obtained after sonication and purifi cation by simple centrifugation(70,000 g,1 h)contain semiconducting SWNTs primarily in the form of small bundles whereas metallic SWNTs are predominantly suspended as individual tubes.Density gradient centrifugation then separates the bundles from the individual tubes on the basis of differences in their overall buoyant densities.Gel electrophoresis separates the longer bundles from the shorter individual tubes on the basis of their different mobilities.We also demonstrate that such starting suspensions can be fractionated according to electronic structure type by even simpler techniques such as size exclusion chromatography or gel fi ltration,thus opening the way for simple scale-up.

Sorting Semiconducting Single-Walled Carbon Nanotubes by Water-Soluble Polyfluorene Assisted Electrophoresis and Its Application in Field-effect Transistors

We report a considerably promising method based on agarose gel electrophoresis （AGE） to separate single-walled carbon nanotubes by adding a water-soluble polyfluorene （w-PFO） as surfactant into the agarose gel. In this effective method, the AGE/w-PFO gel network will trap more semiconducting single-walled carbon nanotubes （SWNTs） with the assistance ofw-PFO, for the strong interaction between w-PFO and semiconducting species. The optical absorbance, photoluminescence emission and resonant Raman scattering characterization were used to ver- ify the separation effect. The purity of separated semiconducting species is as high as （98±1）%. The demonstrated field effect transistors give the on/off ratio and mobility about 27000 and 10.2 cm^2·V^-1·s^-1, respectively.

The importance of H_(2) in the controlled growth of semiconducting single-wall carbon nanotubes

H_(2) is considered an indispensable component of the atmosphere for the growth of high-quality singlewall carbon nanotubes(SWCNTs)by chemical vapor deposition.However,details of the roles H_(2) playing are still unclear due to the complex conditions of SWCNT growth.In this study,we elucidate the functions of H_(2) in the selective growth of semiconducting SWCNTs(s-SWCNTs)by using monodispersed uniform Fe nanoparticles as a catalyst.High-quality s-SWCNTs were synthesized by finely tuning the concentration of H_(2) and the other growth parameters.Experimental data combined with atomistic simulations indicate that H_(2) not only adjusts the concentration of the carbon source,but also serves as a mild etchant that selectively removes small carbon caps grown by a perpendicular mode from the Fe nanoparticles.These results provide useful hints for the controlled growth of SWCNTs with a semiconducting or metallic conductivity,and even a specific chirality.

Recent progress of photodetector based on carbon nanotube film and application in optoelectronic integration

Due to its remarkable electrical and optical capabilities,optoelectronic devices based on the semiconducting single-walled carbon nanotube(s-SWCNT)have been studied extensively in the last two decades.First,s-SWCNT is a direct bandgap semiconductor with a high infrared absorption coefficient and high electron/hole mobility.In addition,as a typical one-dimensional material,there is no lattice mismatch between s-SWCNT and any substrates.Another advantage is that the optoelectronic devices of s-SWCNT can be processed at low temperatures.s-SWCNT has intriguing potential and applications in solar cells,light-emitting diodes(LEDs),photodetectors,and three-dimensional(3D)optoelectronic integration.In recent years,along with the advancement of solution purification technology,the high-purity s-SWCNTs film has laid the foundation for constructing large-area,homogenous,and high-performance optoelectronic devices.In this review,optoelectronic devices based on s-SWCNTs film and related topics are reviewed,including the preparation of high purity s-SWCNTs film,the progress of photodetectors based on the s-SWCNTs film,and challenges of s-SWCNTs film photodetectors.

Air-stable synaptic devices based on bismuth triiodide and carbon nanotubes

Artificial synaptic devices with the functions of emulating important biological synaptic behaviors are playing an increasingly important role in the development of neuromorphic computing systems.Single-walled carbon nanotubes(SWCNTs)with excellent electrical properties and high stability have been studied as active materials for synaptic devices.However,the performance of optical synaptic devices(OSDs)based on pure SWCNTs is limited by the weak light absorption property.Herein,bismuth triiodide(BiI_(3)),an environmentally stable and friendly optoelectronic material,is firstly combined with SWCNTs to fabricate OSDs with decent properties of perceiving and memorizing optical information.The OSDs can exhibit typical synaptic behaviors including excitatory postsynaptic current,paired-pulse facilitation,and short/long-term memory.Distinctively,the photoresponse of the OSD is independent of pulse light wavelength in the range of 365 to 650 nm,different from most of the previously reported OSDs,which usually have wavelength-dependent photo-response.Temperature-dependent photo-response behaviors of the devices are investigated.Importantly,the OSD without encapsulation holds good excitatory post-synaptic current(EPSC)behavior after being stored in the ambient environment for 170 days,indicating reliable environmental stability.Furthermore,an OSD array with nine synaptic devices is employed to mimic the human visual perception and memory functions.These results suggest the feasibility of BiI3/SWCNTs-based OSDs for the simulation of human visual memory.