Electron Microscopy of Multi-walled Carbon Nanotubesfor Display Devices Application

The opportunity of creating and tailoring unprecedented and beautifully symmetric 3-D structures haspropelled the science of carbon nanotubes to become one of the highly promising areas in the field ofnanotechnology. The unique properties of carbon nanotubes have promoted research in the fabrication ofdevices composed of carbon nanotubes and in other applications. Characterisation tools are crucial in the studyof these emerging materials to evaluate their full potential in applications and to comprehend their basicproperties. The aim of this study was electron microscopy characterisation of the carbon nanotubes synthesisedto fabricate display devices. Both thermal chemical vapour deposition (CVD) and plasma enhanced chemicalvapour deposition routes were used to synthesise patterned and aligned carbon nanotubes. Several batchesof CNTs were produced by varying the process parameters such as growth temperature, gas ratio, durationof growth, catalyst condition, etc. Characterisation of these CNTs have been done using scanning electronmicroscope, transmission electron microscope, high resolution transmission electron microscope, and electronenergy loss spectrum. Structure, uniformity, chemistry, diameter, length, number of walls of the multi-wallednanotubes were characterised using various electron microscopes, which finally lead to the production of thedisplay devices using CNTs.Defence Science Journal, 2008, 58(5), pp.655-663, DOI:http://dx.doi.org/10.14429/dsj.58.168

Carbon Nanotube-based Cold Cathode for High Power MicrowaveVacuum Electronic Devices: A Potential Field Emitter

Carbon nanotubes (CNTs) can be grown in the form of small, sharp spikes capable of carrying very highcurrent densities which suggest great potential application of CNTs as cold cathode in high power microwavevacuum device applications. These cold cathode vacuum microwave devices are expected to be ideally suitedfor air-borne and space applications. This paper  reports the initial efforts made in the development of coldcathode using PECVD grown vertically-aligned matrix of CNTs with uniform height and optimum tip densityon silicon substrate. The high aspect ratio (of the order of 10,000) and novel electrical, mechanical, and thermalproperties of the CNT are found to be very attractive characteristics for emission of large and stable currentdensities at reasonably low field. The field emission current voltage characteristics of a typical cathode gaveemission current density in excess of 35 mA/cm2 at reasonably low field. The emission current in most of thesamples is found to be stable over long period of time but is greatly effected by the vacuum condition duringmeasurement. The initial measured data suggests great promise for achieving high current densities at practicalelectric fields.Defence Science Journal, 2008, 58(5), pp.650-654, DOI:http://dx.doi.org/10.14429/dsj.58.168

Highly Sensitive NO2 Detection and DMP Sensing at Room Temperature using Flexible SWNT Thick Film Sensor

  Low cost; easy to fabricate and flexible single wall carbon nanotubes thick film resistor (SWNT-TFR) for detailed study of NO2 detection is reported. SWNT-TFR was fabricated by vacuum filtration technique on flexible polycarbonate membrane. SWNT-TFR sensor shows selective response to NO2. The response increases from 1.47 per cent to 17.34 per cent with increasing the NO2 concentration from 0.2 ppm to 10 ppm, respectively. Different energy sources, IR, thermal and UV were explored for achieving fast recovery of the SWNT-TFR sensor. The results showed that the gas sensor gives immediate and fast recovery in the presence of UVC light. The calculated detection limit is less than 764 ppt for NO2. We are also presenting sensing of dimethyl methylphosphonate (DMMP) as a simulant of sarin. SWNT-TFR gives repeatable response of ~2.7 per cent for 500 ppm of DMMP. This work suggests the possibility to utilise SWNTs-TFR as NO2 sensors for air-quality monitoring.