P.K. Chaudhury

Improving the field emission of carbon nanotubes by lanthanum-hexaboride nano-particles decoration

Field emission of carbon nanotubes (CNTs) was remarkably improved by lanthanum-hexaboride (LaB6) nano-particles (NPs) decoration. CNTs were grown on the silicon substrate by chemical vapor deposition. Field emission of bare CNTs and LaB6-NPs decorated CNTs was carried out under same conditions. Physical, morphological, elemental, and graphitic nature changes were ascertained by scanning electron microscope, transmission electron microscope, energy dispersive x-ray spectroscopy, and Raman analysis. LaB6-NPs decorated CNTs show significant reduction of turn-on electric-field from 3.0 to 2.1 V/μm. A remarkable improvement of more than six-fold from 2.05 to 13.19 mA/cm2 at a field of 4.6 V/μm was also observed in the current-density.

Functionalization Of Carbon Nanotubes With Metal Phthalocyanine For SELECTIVE Gas Sensing Application

Composites of hydroxylated single-walled carbon nanotubes and copper phthalocyanine (CuPc) has been obtained. Phthalocyanines get noncovalently adsorbed onto CNTs surface by π–π stacking. Conversion of β-form of phthalocyanine to α-form gives clear evidence of composite formation. Only carboxyl and hydroxyl CNTs react with phthalocyanine while no reaction occurs for amided CNTs. High selectivity in the thin film resistors of SWNT–OH + CuPc composites toward NOx gases is observed. The response for NOx is 10 times and 100 times more then that of ammonia and Sox, respectively. This makes the SWNT–OH + CuPc composite a candidate for detection of NOx—a common pollutant.

Effect of purity, edge length, and growth area on field emission of multi-walled carbon nanotube emitter arrays

Present report aims to study the effect of purity, edge length, and growth area on field emission of patterned carbon nanotube (CNT) emitter arrays. For development of four CNT emitter arrays (CEAs), low resistively silicon substrates were coated with thin film of iron catalyst using photolithography, sputtering, and lift off process. Four CEAs were synthesized on these substrates using thermal chemical vapor deposition with minor changes in pretreatment duration. Out of these, two CEAs have 10 μm × 10 μm and 40 μm × 40 μm solid square dots of CNTs with constant 20 μm inter-dot separation. Other two CEAs have ring square bundles of CNTs and these CEAs are envisioned as 10 μm × 10 μm square dots with 4 μm × 4 μm scooped out area and 15 μm × 15 μm square dots with 5 μm × 5 μm lift out area with constant 20 μm inter-dot spacing. Solid square dot structures have exactly constant edge length per unit area with more than four-fold difference in CNT growth area however ring square dot patterns have minor differe...

Estimation and Reduction of Macroscopic Nonuniformity in CNT Thin Film Resistors

Carbon nanotube (CNT) thin film-based devices are expected to have better uniformity and reproducibility compared with single-tube devices due to statistical averaging. In this work, thin film resistors (TFR) were prepared from CNT dispersions and their nonuniformity estimated by multipoint, two-terminal resistance (TTR) measurements. I-V measurements were done for determining the nature of metal-CNT contact. For estimation of contact resistance, transmission line measurements (TLM) were carried out. Reduction of CNT-TFR nonuniformity was achieved using di-methyl formamide (DMF). Scanning electron microscopy and electrical measurements imply that DMF improves debundling of single-walled nanotubes, reduces the resistance and improves homogeneity of subsequently prepared thin films.