Nanocluster Carbon Films Research Articles

Effect of electron irradiation on morphological, compositional and electrical properties of nanocluster carbon thin films grown using room temperature based cathodic arc process for large area microelectronics

The influence of 8MeV electron beam bombardment on room temperature grown nanocluster carbon using cathodic arc process has been studied here. Atomic force microscopy (AFM) study shows that surface roughness varies with varying electron doses. High doses of electrons could causes thermal induce graphitization and morphological changes in the films. Raman spectroscopy analysis reveals that G-peak vary from 1555cm−1 to 1570cm−1 and D-peak varying from 1361cm−1 to 1365cm−1 indicating the disorderness and presence of both graphitic and diamond-like phases. Room temperature conductivity changes by two to three orders in magnitude. The conductivity in the films could be due to conduction of charge carriers through neighboring islands of conductive chains. Defect states calculated using the differential technique varies from 8×1017cm−3eV−1 to 1.5×1019cm−3eV−1. Irradiation of nanocluster carbon thin films could be helpful to tune the electrical properties and defect densities of the nanocluster carbon films for various large area, flexible electronic and nano electronic applications.

Field emission from nano-cluster carbon films

Abstract Field emission has been reported to occur at much lower fields in carbon based thin film systems than from any other material systems. The emission has been shown to depend on the various material parameters, but whichever carbon based system is used, it is found that emission occurs at localised sites rather than uniformly over the entire surface. Carbon films with mixed sp 3 /sp 2 bonding, like nanocrystalline diamond and nanocluster graphitic films emit at lower fields with a higher emission site density than single-phase films. The sp 2 cluster size in any carbon film can be altered during deposition, but it is easier to control nanocluster size by post-deposition annealing. Annealing increases the sp 2 cluster size embedded in a sp 3 matrix until the sp 3 matrix disappears completely and the film transforms into nanocrystalline graphite. To distinguish the effects of the sp 2 cluster size from other material parameters, a series of different carbon films were annealed post-deposition and the sp 2 cluster size was measured using visible Raman. Field emission was then measured at a vacuum of 10 −8 mbar on all films using a parallel plate configuration. It was found that the field emission for all films tested depended upon the clustering of the sp 2 phase and this effect dominates the effects of the other parameters, such as chemical composition, surface termination, sp 3 content or conductivity. The optimum size of the sp 2 was of the order of 1 nm for all systems tested. We believe that field emission occurs form the localised conducting, predominantly sp 2 bonded regions, which provideds the large field enhancement required for effective emission.

Resonant Tunnelling Behaviour in Multilayered Cold Cathodes Made of Nanoseeded Diamond and Nanocluster Carbon

ABSTRACTMultilayered cold cathodes made of spin coated nanocrystalline diamond and cathodic arc process grown nanocluster carbon films, were studied. The nanocrystalline diamond was first coated on to the substrate. The nanocluster carbon films were then deposited on the seeded nanocrystalline diamond coated substrates using the cathodic arc process at room temperature. Theresultant hetrostructured microcathodes were observed to exhibit electron emission currents of 1μA/cm2 at fields as low as 1.2 V/μm. Further some of the samples seem to exhibit I-V characteristics witha negative differential resistance region at room temperature conditions. This negative differential resistance or the resonant tunneling behaviour was observed to be dependent on the nanoseeded diamond size and concentration for a given nanocluster carbon film.

Field Emission from Novel Room Temperature Grown Carbon Based Multilayered Cathodes

AbstractLow field electron emission from novel room temperature grown multilayered cold cathodes were studied. The cathodes consisted of a layer of nanocrystalline diamond and a layer of nanocluster carbon films. The nanocrystalline diamond was first coated on to the substrate. The nanocluster carbon films and the tetrahedral amorphous carbon films were then deposited on the nanocrystalline diamond coated substrates using the cathodic arc process at room temperature. The heterostructured microcathodes were observed to exhibit electron emission currents of 1µA/cm2 at fields as low as 1 V/µm. The effect of the nanoseeded diamond size and concentration and the properties of different nanocluster carbon films on emission characteristics is presented.

Electron emission from amorphous and nanocluster carbon films grown by the cathodic arc process

Carbon films with variable sp 3/sp 2 bonding ratio can be deposited on a variety of substrates at room temperature, using the cathodic vacuum arc deposition process. The variation in their surface morphology as a function of He and N 2 partial pressure during growth have been investigated and it has been shown that the morphology of the films can be varied from the mirror-like smooth tetrahedrally bonded amorphous carbon (ta-C) films through nanocluster to fibrous-type carbon. This paper reviews the work carried out on Field Emission from these various carbon films. Threshold fields as low as 1 V/μm for emission current densities of 1 μA/cm 2 and emission site densities of up to 10 4–10 5/cm 2 have been obtained.

Low field electron emission from nanoclustered carbon grown by cathodic arc

Abstract Nanocluster carbon films grown using a cathodic arc process at room temperature in the presence of background gases such as helium are found to be good electron emitters. The variation in the surface morphology and the corresponding emission characteristics of the films with change in helium partial pressure (5×10− 4 to 50 Torr) during film growth are reported. The effect of helium partial pressure on clustering was studied for films grown at nitrogen partial pressures of 10−4 and 10−3 Torr. The surface morphology of the films varied from smooth through clusters (with sizes 50–200 nm) to fibrous films. The threshold field varied from 1 to 10 V/μm for an emission current density 1 μA/cm 2.

Low threshold field emission from nanoclustered carbon grown by cathodic arc

Nanocluster carbon films grown using a cathodic arc process at room temperature in the presence of background gases such as He are found to be good electron emitters. The variation in the surface morphology and the corresponding emission characteristics of the films with change in helium partial pressure (5×10−4–50 Torr) during the film growth are reported. The effect of helium partial pressure on clustering was studied for films grown at nitrogen partial pressures of 10−4 and 10−3 Torr. The surface morphology of the films grown, varied from smooth through clusters (with sizes 50–200 nm), to fibrous films. The threshold field varied from 1 to 10 V/μm for an emission current density of 1 μA/cm2. These films exhibit an emission site density of ∼104–105/cm2 at an applied field of 5 V/μm.

Field emission from heterostructured nanoseeded diamond and nanocluster carbon cathodes

ABSTRACTNovel heterostructured cold cathodes made of nanoseeded diamond and cathodic arc process grown nanocluster carbon films, were studied. The nanocrystalline diamond with varying diamond concentration was first coated on to the substrate. The nanocluster carbon films were then deposited on the nanoseeded diamond coated substrates using the cathodic arc process at room temperature. The resultant heterostructured microcathodes were observed to exhibit electron emission currents of 1μA/cm2 at low fields of 1.2 - 5 V/μm. Further some of the samples seem to exhibit I-V characteristics with a negative differential resistance region at room temperature conditions. This negative differential resistance or the resonant tunneling behaviour was observed to be dependent on the nanoseeded diamond concentration.