Application of carbon nanomaterials in the electronic industry

Nanomaterials have much improved properties compared to their bulk counterparts, which promotes them as ideal material for applications in various industries. Among the various nanomaterials, different nanoallotropes of carbon, namely fullerene, carbon nanotubes, and graphene, are the most important as indicated by the fact that their discoverers gained prestigious awards such as Nobel Prize or Kavli Prize. Carbon forms different nano-allotropes by varying the nature of orbital hybridization. Since all nanoallotropes of carbon possess exotic physical and chemical properties, they are extensively used in different applications, especially in the electronic industry.Comment: Carbon nanomaterialsfullerenecarbon nanotubegraphen

Effects of the Growth Time and the Thickness of the Buffer Layer on the Quality of the Carbon Nanotubes

Direct growth of carbon nanotubes (CNTs) array onto silicon substrate by the chemical vapor deposition (CVD) is reported. Experimental results show that the thickness of the buffer layer has a significant effect on the morphology and defects of the array, and when the buffer layer is about 15 nm, the best array on the silicon substrate can be obtained. Moreover, when the growth time is less than the threshold time (70 minutes), the array height will increase with the increase of the time. Importantly, when the growth time is higher than this threshold time, the growth of array will stop, but when the growth is continuing, the amorphous carbon and carbon can cluster, which will affect the structure of the array. These results provide a good material basis for the device, thermal, and conductivity technology

Charge Transport in and Luminescence from Covalently Functionalized Carbon Nanotube Networks

Their high ambipolar charge carrier mobilities and narrowband emission in the near-infrared make semiconducting single-walled carbon nanotubes (SWCNTs) a promising material for optoelectronic devices. The controlled low-level decoration of SWCNTs with covalently bound sp3 defects gives rise to red-shifted luminescence and single-photon emission, thus strongly expanding their application potential. While the spectroscopic properties of sp3-functionalized SWCNT dispersions under optical excitation are already well-understood, little research efforts have been directed at the impact of luminescent defects on charge transport as well as defect population and emission in thin films and under electrical excitation. A fundamental understanding of these aspects is a prerequisite for the realization of light-emitting devices based on functionalized SWCNTs. This thesis demonstrates high ambipolar charge carrier mobilities and red-shifted defect-state electroluminescence in light-emitting field-effect transistors with randomly oriented networks of functionalized SWCNTs as active layers. The results imply that luminescent defects act as shallow trapping potentials for charge carriers that still allow for fast detrapping at room temperature, thus explaining the moderate decrease in network mobilities upon functionalization. Time-resolved terahertz spectroscopy corroborates the impact of these defects on the intrinsic nanotube conductivity and provides further evidence that charge transport in semiconducting SWCNT networks, as opposed to the widespread belief, is not solely determined by the inter-nanotube junctions. To achieve better control over the spectroscopic properties of SWCNT thin films deposited on surfaces, substrate passivation with a cross-linked polymer is demonstrated to reduce peak broadening and suppress sideband emission that is assigned to the uncontrolled formation of lattice defects through nanotube–substrate interactions. The realization of pristine and sp3-functionalized SWCNT network transistors with near-intrinsic electroluminescence on passivated substrates showcases the compatibility of the developed method with standard semiconductor processing steps and device fabrication. Moreover, the selective introduction of luminescent defects with a larger spectral red-shift pushes the electroluminescence from SWCNT networks further towards telecommunication wavelengths and highlights their potential for optoelectronic applications such as electrically-pumped single-photon sources

X-ray generation using carbon nanotubes

Since the discovery of X-rays over a century ago the techniques applied to the engineering of X-ray sources have remained relatively unchanged. From the inception of thermionic electron sources, which, due to simplicity of fabrication, remain central to almost all X-ray applications, there have been few fundamental technological advances. However, with the emergence of ever more demanding medical and inspection techniques, including computed tomography and tomosynthesis, security inspection, high throughput manufacturing and radiotherapy, has resulted in a considerable level of interest in the development of new fabrication methods. The use of conventional thermionic sources is limited by their slow temporal response and large physical size. In response, field electron emission has emerged as a promising alternative means of deriving a highly controllable electron beam of a well-defined distribution. When coupled to the burgeoning field of nanomaterials, and in particular, carbon nanotubes, such systems present a unique technological opportunity. This review provides a summary of the current state-of-the-art in carbon nanotube-based field emission X-ray sources. We detail the various fabrication techniques and functional advantages associated with their use, including the ability to produce ever smaller electron beam assembles, shaped cathodes, enhanced temporal stability and emergent fast-switching pulsed sources. We conclude with an overview of some of the commercial progress made towards the realisation of an innovative and disruptive technology.Clare Collins is studying for the MRes in Ultra Precision, funded by the EPSRC, at the University of Cambridge.This is the final published version. It first appeared at http://www.nanoconvergencejournal.com/content/2/1/1

Effect of few-walled carbon nanotube crystallinity on electron field emission property

We discuss the influence of few-walled carbon nanotubes (FWCNTs) treated with nitric acid and/or sulfuric acid on field emission characteristics. FWCNTs/tetraethyl orthosilicate (TEOS) thin film field emitters were fabricated by a spray method using FWCNTs/TEOS sol one-component solution onto indium tin oxide (ITO) glass. After thermal curing, they were found tightly adhered to the ITO glass, and after an activation process by a taping method, numerous FWCNTs were aligned preferentially in the vertical direction. Pristine FWCNT/ TEOS-based field emitters revealed higher current density, lower turn-on field, and a higher field enhancement factor than the oxidized FWCNTs-based field emitters. However, the unstable dispersion of pristine FWCNT in TEOS/N,N-dimethylformamide solution was not applicable to the field emitter fabrication using a spray method. Although the field emitter of nitric acid-treated FWCNT showed slightly lower field emission characteristics, this could be improved by the introduction of metal nanoparticles or resistive layer coating. Thus, we can conclude that our spray method using nitric acid-treated FWCNT could be useful for fabricating a field emitter and offers several advantages compared to previously reported techniques such as chemical vapor deposition and screen printing.ope

Copper-nanoparticle decorated graphene thin films: applications in metal-assisted etching and synthesis of next-generation graphene-based nanomaterials

Since 2006, the experimental discovery of graphene, a single-layer of carbon atoms, has spurred tremendous efforts towards new graphene-based materials. In graphene research, there is a recent trend towards next-generation materials in which graphene layers are locally modified in a controlled fashion at the nanoscale and tailored for specific applications. Examples include nanoparticle-decorated graphene thin films with surface potential tailored for nanoelectronics or advanced catalysis, graphene nanoribbons, graphene quantum dots, and the scalable fabrication of tiny pores in graphene, which are suitable to applications requiring ultrathin molecular sieving membranes. This research is focused on the development of new applications of copper-nanoparticle (Cu-np) decorated graphene thin films, towards the metal-assisted etching of graphene and the synthesis of next-generation graphene-based materials. Two different methods were utilized for Cu-np deposition: thermal evaporation – a technique operating under thermodynamic equilibrium, and DC-biased radio-frequency sputtering – a plasma-based quasi-equilibrium technique. Both methods are capable of producing ultrathin Cu layers on graphene, which can be subsequently annealed to nucleate Cu-np’s of tuneable diameter depending on the Cu layer thickness. Both techniques are suitable to be used in conjunction with large-area graphene thin films prepared by solution processing. In this thesis, three examples are presented involving the use of Cu-np’s to process graphene. In the first example, both etching and synthesis are involved: It was found that the simultaneous removal of Cu-np’s and the underlying graphene has led to the formation of graphene ribbons from corrugated graphene layers, in which nanoparticles do not deposit on ridges and wrinkles. In a second example, it was demonstrated that Cu-np-assisted etching may lead to the formation of nanoporous graphene-based membranes that are finding interesting applications as water nanofilters for the removal of impurities (e.g. Fe3+ and Mn2+) from water. In a third example, plasma-assisted synthesis of carbon on Cu-np’s was shown to lead to the growth of curved graphene quantum dots, with resistive memory effects that can find applications in data storage. These examples well represent the versatility of the Cu-np assisted processing methodology of graphene thin films, towards a large variety of next-generation carbon-based nanomaterials

Luminescence studies : Part I. Lanthanide nanoGUMBOS Part II. Near infrared photothermal nanoGUMBOS

Group of Uniform Materials Based on Organic Salts (GUMBOS) are a class of molten salts that have been focused to be specifically tailored towards applications. Primitively, from Davy to Walden molten salts were desirable for organic synthesis due to the properties. GUMBOS have been synthesized into nanoparticles (nanoGUMBOS) by various methods to be used for lanthanide luminescence and hyperthermal cancer therapeutics. Lanthanide photochemistry has been frequently studied for its high luminescence intensity, narrow emission band, and stable luminescent lifetime decay. Aerosol-derived europium nanoGUMBOS were characterized using electron microscopy (39.5 ± 8.4 nm), XPS, and spectroscopic techniques. Spectroscopic measurements indicated intense and steady luminescence, which suggests a multitude of possible applications for lanthanide-based GUMBOS, especially in sensory and photovoltaic devices. Several near infrared (NIR) nanoparticles of GUMBOS composed of cationic dyes coupled with biocompatible anions were investigated for their photothermal properties. These nanoparticles were synthesized using a reprecipitation method performed at increasing pH values. The cations for the nanoGUMBOS, [1048] and [1061], have absorbance maxima at wavelengths overlapping with human soft tissue absorbance minima. NIR nanoGUMBOS excited with a 1064 nm continuous laser led to heat generation (20.4 ± 2.7 °C) after five minutes. While the [1061][Deoxycholate] nanoGUMBOS generated the highest temperature increase (23.7 ± 2.4 °C), it was the least photothermally efficient compound (13.0%) due to its relatively large energy band gap of 0.892 eV. The energy band gap is a measurement of the HOMO and LUMO distance, and predictor of photothermal efficiency. The more photothermally efficient compound, [1048][Ascorbate] (64.4%), had a smaller energy band gap of 0.861 eV provided an average photothermal temperature increase of 21.0 ± 2.1 °C. Hyperthermal therapeutics originating from hot pokers has evolved into facilitation of NIR nanomaterials photothermal response. NanoGUMBOS can employ a variety of curative techniques by pairing fluorescent and biocompatible ions. NanoGUMBOS, [1048][Folate] and [1061][Folate], were evaluated using electron microscopy, spectroscopic, thermal imaging, and fluorescent assays. In order to generate highly responsive nanomaterials for NIR-laser-triggered hyperthermia, optimization of nanoparticle size, shape, and uniformity were investigated