B.S. Satyanarayana

Determination of density-of-states of nanocluster carbon thin films mis structure using capacitance voltage technique

Nanocluster carbon thin films (NC) were deposited at room temperature by cathodic arc process. These films were clustered, amorphous and disordered in nature which is verified using Raman spectroscopy. Density of defect states (DOS), which influences electronic and optical properties, were determined from the capacitance–voltage (C–V) characteristic of Al/NC/c-Si metal–insulator–semiconductor (MIS) structure near the Fermi level of undoped samples. Dielectric constant of the films was also estimated using the same technique. The DOS were found to be varying from 5.68 × 1016 to 4.9 × 1019 cm-3. The dielectric constant varied between 2.76 to 11.8.

Quantitative and Indirect Qualitative Analysis Approach for Nanodiamond Using SEM Images and Raman Response

In the era of nanotechnology, one of the material which seems to be in the forefront, in terms of its application in medical domain is nanocarbon. Various forms of nanocarbon including, carbon nanotubes, nanostructured graphite, nanodiamond, nanowalls, nanocluster carbon, diamond like carbon (DLC) and tetrahedral amorphous carbon(taC) are being studied, for different biomedical applications includes Vacuum based X-ray source, Tribology coating for joints or surgical, Micro/Nano Elcecto Mechanical System (MEMS /NEMS) and Biosensor. Study of nanodiamond grown with Hot Filament Chemical Vapor Deposition(HFCVD) process with various CH4/H2 condition indicates various morphological and compositional properties. The surface based morphology are studied with SEM images provides visual information’s. Studied compositional variation using nondestructive and instantaneous approach using Raman response. Reported the mechanism of deposition and the influence of the deposition parameters in terms on the morphology and composition. Designed an insitu applicable software approach for SEM images analysis. The images are initially segmented for enhancing the cluster regions on the substrate and each individual clusters are labeled. Generated histogram using the area estimated for each cluster and analysed it quantitatively. The Raman and SEM based analysis evaluates cluster dimensions, distribution and provides quantitative and indirect qualitative information for evaluating the nanodiamond.

A comparison study of field assisted electron emission from nanocluster carbon films grown using a continuous and a pulsed cathodic arc process

Field emission from nanoclustered carbon films grown using pulsed cathodic arc process is presented and compared with carbon films grown using continuous cathodic arc process. The samples exhibit relatively low field electron emission. However, films grown using pulsed arc process show slightly higher emission threshold compared to those grown using continuous cathodic arc process. This may be attributed to the difference in the energy kinetics of the arc initiation process. Raman measurements also show that films grown using continuous arc have better clusters and less amorphous phase leading to relatively more distinct G and D peaks compared to the broader G peak and shoulder indicating the D peak observed for films grown using a trigger less pulsed arc.

Field emission from aligned carbon nanotubes grown on patterned oxide layers

A study on field emission from carbon nanotubes is reported. The CNTs are selectively grown on patterned silicon dioxide on silicon substrates using chemical vapour deposition. To understand the influence of the oxide layer thickness on the associated field emission characteristics, the oxide layer thickness is varied from 15 nm to 100 nm. Field emission measurements are carried out in a parallel plate configuration, with an anode-cathode spacing of 100 /spl mu/m, an anode of 1 mm diameter and a vacuum of the order of 10/sup -7/ Torr. Results show that carbon nanotubes grown on patterned silicon dioxide layer exhibit reasonable electron emission characteristics. The emission threshold field varies from 1.9 V//spl mu/m to 3.25 V//spl mu/m as the oxide thickness is increased. The emission behaviour seems to have a linear relation with the oxide thickness in the measured range of the samples. The influence of the oxide layer thickness is further discussed on the basis of Raman measurement.

Fourier‐Transform Infrared Absorption Study of the Nanocluster Carbon Thin Films Grown Using Cathodic Arc Process

Nanocluster carbon thin films are deposited on Silicon Substrate using Cathodic Arc process. These films are mixed phased materials containing both sp2 and sp3 bondings. The surface morphology is characterized by Fourier‐Transform Infrared Spectroscopy (FTIR) to find out different vibrational modes in these films. The various bendings modes with Olefinic and aromatic structures are associated with a broad absorption band between 1130 and 1550 cm−1. The peaks in and around 2900 cm−1 shows various stretching modes of C‐Hn (n = 1,2,3).

Nanocluster carbon thin film as a semiconducting layer and feasibility for device application

Nanocluster Carbon thin films have been seen as an alternative semiconducting layer to a-Si:H. Amorphous and polycrystalline hydrogenated silicon are used as an active channel layer for the thin film transistors (TFTs) for long time. But these materials are fabricated at high temperatures. In this paper, we describe nanocluster carbon thin films as alternative materials for the TFT device application. We present numerical simulations of the TFT, using the semiconductor device simulator ATLAS from silvaco. We study the ON/OFF ratio of the nanocluster carbon thin film based TFT.

A Study on the Correlation between Raman Response and Field Emission Characteristics in Case of Various Low Field Emitting Nano Carbons

Summary form only given. Various forms of carbon including nanodiamond, nanotubes, nanohorns, nanofibers, nanocluster or nanostructured carbon are being studied as materials for diverse applications including energy storage, nanoelectronics and vacuum nanoelectronics. Many of these materials have been shown to be very low field electron emitters. The change in the sp3 and sp2 bonding ratio in these materials defines the material. Presented in this paper is a comparative study of low field electron emission from nanocarbons including nanodiamond, nanotubes, nanowalls and nano cluster carbon films grown using diverse processes, such as the thermal CVD, hot filament CVD, DC plasma CVD, pulsed laser assisted cluster beam assembly and cathodic arc. Most of these films exhibit low field electron emission of around 1 V/mum for an emission current density of around 1 muA /cm2, when measuring using samples of emission area around 1 cm2. Discussed further in this paper is the correlation between the field emission properties and the Raman response characteristics of the material. This is to see if an indication of an empherical relation between Raman response (a non invasive, instantaneous measuring tool for nanostructured materials characterization) and field emission can be established

Resonant Tunneling Behaviour in the I-V Response of Multilayered Nanocarbon Based Field Assisted Electron Emitters

Summary form only given. There is an increasing interest in carbon based nanostructured materials like the nanodiamond, nanotubes, nanocluster and nanowall carbon. The interest stems from the diverse fields of application envisaged for these materials which include, vacuum microelectronics, energy storage systems, MEMS, electronics, nanotechnology and sensors. Recently, these materials including nanocrystalline diamond, nanotubes and nanocluster carbon have all been widely reported as low field electron emitters. Most of these nanocarbons have been grown using high temperature process such as hot filament CVD, thermal CVD, microwave plasma CVD and Plasma CVD. In an effort to develop a low temperature grown carbon based field assisted electron emitters. We observe that under optimum conditions nanodiamond and nanocluster carbon based multilayered films exhibit relatively low field electron emission of 1 V/mum. 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 type behaviour was observed to be dependent on the nanoseeded diamond size and concentration for a given nanocluster carbon film. Further we observe similar behaviour in the case of thin silicon dioxide layer and carbon nanotube based multilayered electron emitters. Presented is a possible mechanism for such behaviour in these nanomaterial based multilayered devices

Field Assisted Electron Emission from Novel Self Aligned Multilayered Nanocarbons Grwon at Flexible Substrates

Summary form only given. Field assisted electron emission from nanostructured carbon materials is becoming increasingly attractive. The interest stems from the feasibility of diverse applications, which include field emission displays, electron-beam lithography, electron and ion guns, multitude of sensors, electron microscopes and microprobes, low & medium power microwave sources and lamps. Based on the present understanding of the carbon based field emitters, we may broadly define the requirements for field emission or the main factors influencing emission as a) field enhancement factor, b) highly conducting sp2 bonded (pi bond) nanostructured carbon, in its various manifestations c) the presence of sp3 bonded (sigma bond) material in the sp2 matrix and d) optimum emission site density distribution, taking into consideration factors such as shielding or overlapping of field, which could inhibit or limit emission. Taking into consideration the above, proposed is a novel, room temperature grown, self aligned carbon based multilayered electron emitter, suitable for most vacuum microelectronic applications. Discussed in this paper is a possible emission mechanism for such an electron emitter. Also presented is some of the experimental results of field assisted electron emission from such an electron emitter deposited on flexible substrates like polyamide. These emitters exhibit emission threshold fields, as low as 5-10 V/mum for a current density of 1 muA/cm2

Emission mechanism for field assisted electron emission from a novel multilayered nanocarbon based electron emitter

In an effort to develop a relatively low cost-low temperature process based technology compatible with semiconductor technology, a low field electron emission from a nanocarbon based multilayered electron emitter was studied. Some of the results are presented in this paper as well as a possible mechanism of emission from such multilayered electron emitter.