| || Electron Microscopy of Multi-walled Carbon Nanotubes for Display Devices Application
Author : Ghosal, P.;Harsh;Rawat, J.S.B.S.;Chaturvedi, P.;Muraleedharan, K. ;Sarkar, R.
Source : Defence Science Journal ; Vol:58(5) ; 2008 ; pp 655-663
Keywords : PECVD;Plasma-enhanced chemical vapour deposition;Thermal chemical vapour deposition;EELS;Electron energy loss spectrum;HRTEM;Carbon nanotubes
Abstract : The opportunity of creating and tailoring unprecedented and beautifully symmetric 3-D structures has propelled the science of carbon nanotubes to become one of the highly promising areas in the field of nanotechnology. The unique properties of carbon nanotubes have promoted research in the fabrication of devices composed of carbon nanotubes and in other applications. Characterisation tools are crucial in the study of these emerging materials to evaluate their full potential in applications and to comprehend their basic properties. The aim of this study was electron microscopy characterisation of the carbon nanotubes synthesized to fabricate display devices. Both thermal chemical vapour deposition (CVD) and plasma enhanced chemical vapour deposition routes were used to synthesise patterned and aligned carbon nanotubes. Several batches of CNTs were produced by varying the process parameters such as growth temperature, gas ratio, duration of growth, catalyst condition, etc. Characterisation of these CNTs have been done using scanning electron microscope, transmission electron microscope, high resolution transmission electron microscope, and electron energy loss spectrum. Structure, uniformity, chemistry, diameter, length, number of walls of the multi-walled nanotubes were characterised using various electron microscopes, which finally lead to the production of the display devices using CNTs.
| || Carbon Nanotube-based Cold Cathode for High Power Microwave Vacuum Electronic Devices: A Potential Field Emitter
Author : Verma, P.;Gautam, S.;Pal, S.;Kumar, P.;Chaturvedi, P.;Rawat, J.S.B.S.;Chaudhary, P.K.;Harsh;Basu, P.K.;Bhatanagar, P.K.
Source : Defence Science Journal ; Vol:58(5) ; 2008 ; pp 650-654
Keywords : Carbon nanotubes;Microwwave vacuum electronic devices;Cold cathode;Field emission
Abstract : Carbon nanotubes (CNTs) can be grown in the form of small, sharp spikes capable of carrying very high current densities which suggest great potential application of CNTs as cold cathode in high power microwave vacuum device applications. These cold cathode vacuum microwave devices are expected to be ideally suited for air-borne and space applications. This paper reports the initial efforts made in the development of cold cathode using PECVD grown vertically-aligned matrix of CNTs with uniform height and optimum tip density on silicon substrate. The high aspect ratio (of the order of 10,000) and novel electrical, mechanical, and thermal properties of the CNT are found to be very attractive characteristics for emission of large and stable current densities at reasonably low field. The field emission current voltage characteristics of a typical cathode gave emission current density in excess of 35 mA/cm2 at reasonably low field. The emission current in most of the samples is found to be stable over long period of time but is greatly effected by the vacuum condition during measurement. The initial measured data suggests great promise for achieving high current densities at practical electric fields.