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GROWTH OF CARBON NANOTUBES IN ETCHED ION TRACKS IN SILICON OXIDE ON SILICON
J. S. JUNG,L. T. CHADDERTON,A. S. BERDINSKY,P. S. ALEGAONKAR,H. C. LEE,J. H. HAN,J. B. YOO,D. FINK 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2007 NANO Vol.2 No.1
Carbon nanotubes (CNTs) were selectively grown in etched ion tracks in SiO2 layers on Si. For this sake, Ni-catalyst nanocrystals were initially deposited within the ion tracks by galvanic deposition. The characteristics of plasma-enhanced chemical vapor deposition (PECVD)- and thermal chemical vapor deposition (TCVD)-grown CNTs, such as structural details and length distribution, were investigated. In addition, field emission properties were studied. The analysis revealed that the emerging PECVD-grown CNTs were of cylindrical and/or conical shape and usually had diameters as large as the etched tracks. The exponential length distribution of these CNTs can be well understood by applying a simple defect-growth model. For contrast, many narrow and curled CNTs were found to cluster in spots well separated from each other, after applying TCVD instead of PECVD. The Raman investigations of PECVD-grown CNTs showed that Si–O–C and Si–C phases had formed during the growth of the CNTs. These ion-track-correlated PECVD-grown CNTs open the way for the production of novel 3D nanoelectronic devices based on the TEMPOS concept. These structures are also excellent candidates for experiments on channeling in CNTs. Application as field emitting devices, however, appears unfavorable due to poor mean-field enhancement factors and insufficient stability.
Patole, S.P.,Alegaonkar, P.S.,Lee, H.C.,Yoo, J.B. Pergamon Press ; Elsevier Science Ltd 2008 Carbon Vol.46 No.14
The optimization of water assisted chemical vapor deposition (WA-CVD) was carried out to synthesize ultra long, vertically aligned, densely packed carbon nanotube (CNT) forests. The effect of various WA-CVD parameters (viz. the flow rate of the reactant gas mixture and its injection temperature, growth kinetics, ramp rate and growth temperature) on the height of the CNTs was studied. A hypothesis for catalytic activity is proposed on the basis of the X-ray photoelectron spectroscopic analysis of the CNT grown substrates and further verified at the optimum condition. The effect of temperature on the growth of the CNTs is studied. The gas flow rate and injection temperature influence the onset of oxidation of the substrates, which in turn affects the CNT growth rate. A growth kinetics study is performed in order to monitor the growth temperature. The role of the onset of oxidation of the iron catalyst in the growth of the CNTs is studied by varying the ramp rate. The precise CNT growth temperature for WA-CVD is determined by growth temperature studies. The optimum condition allows ∼2.2+/-0.002mm long CNTs to be obtained.
Water-Assisted Synthesis of Long, Densely Packed and Patterned Carbon Nanotubes
Hyun Chul Lee,P. S. Alegaonkar,Do Yoon Kim,Jong Hak Lee,S. P. Patole,Ji Beom Yoo 대한금속재료학회(구 대한금속학회) 2007 ELECTRONIC MATERIALS LETTERS Vol.3 No.2
A systematic approach has been adopted to synthesize, long, densely packed, and patterned, multi wall carbon nanotubes (MWCNTs) using water assisted-chemical vapor deposition (WA-CVD) technique. Initially, the growth of MWCNTs has been carried out on Fe/Al/Si multi-layer samples, under the standard- and WA-CVD conditions. Under the WA-CVD conditions, the height of MWCNTs gradually increased form 2S±5 to 533±30μm with subsequent increase in the growth temperature from 650-900℃. Details of the growth conditioning have been discussed. Furthermore, the growth of MWCNTs has been investigated by varying the growth time from 10 to 60 min at two temperature regime 700℃ and 800℃. The growth rates have been estimated which shows gradual decrease in their magnitude with sequential increase in the growth time. The MWCNT patterning has been demonstrated. The results offers insight to use such MWCNTs for future device interconnects applications. The details of the analysis are presented.
Growth of carbon nanotubes: effect of Fe diffusion and oxidation
Lee, H. C.,Alegaonkar, P. S.,Kim, D. Y.,Lee, J. H.,Yoo, J. B. Taylor and Francis 2007 Philosophical magazine letters Vol.87 No.10
<P> The diffusion and surface oxidation rates of Fe deposited on Si and barrier layers of Al/SiO2 and Al2O3/SiO2 have been comparatively studied and correlated with the growth of carbon nanotubes (CNTs). Initially, Fe/Si, Fe/Al/SiO2/Si and Fe/Al2O3/SiO2/Si samples were subjected to thermal chemical vapour deposition (CVD) at ∼650°C for ∼30 min to grow the CNTs. Scanning electron microscopy analysis showed that the height of the CNTs on the Fe/Al2O3/SiO2/Si samples was relatively high (∼9.5-11 µm), as compared with the other samples. To investigate this, a few as-prepared samples were thermally annealed at ∼650°C for ∼30 min and characterized by dynamic secondary ion mass spectroscopy (D-SIMS) and X-ray photoelectron spectroscopy (XPS). The D-SIMS results showed that the diffusion depth, xFe, and magnitude of the diffusivity, DFe, of the Fe atoms are highest for the Fe/Si sample. This is attributed to vacancy-mediated migration, which leads to the formation of unstable, non-stoichiometric Fe-Si and Fe-O-Si phases. However, for the Fe/Al2O3/SiO2/Si samples, the magnitudes of xFe and DFe are found to be the lowest, which indicates steric hindrance to Fe by the Al2O3 layers. The XPS analysis revealed that the surface metallic state, after annealing, is almost unaffected for the Fe/Al2O3/SiO2/Si samples, whereas the majority of the Fe precipitate was observed to be oxidized in the case of the other samples.</P>
( A. S. Berdinsky ),( D. Fink ),( Hui Gon Chun ),( Yong Zoo Yoo ),( Ji Beom Yoo ),( A. V. Petrov ),( P. S. Alegaonkar ) 한국센서학회 2004 센서학회지 Vol.13 No.5
It is known that the conductivity of fullerite depends on the applied pressure. In this paper we compare the variation of conductivity of three different fullerite structure with pressure. We examined C_(60) powder, filled into thin glass capillaries and also studied fullerite nanotubules produced within etched swift heavy ion tracks in polymer foils. These investigations are compared with the results of planar Si-C_(60)-Au structures.
( Jae Hee Han ),( Jae Hong Park ),( A. S. Berdinsky ),( P. S. Alegaonkar ),( Ji Beom Yoo ),( Hae Jin Kim ),( Jin Joo Choi ),( Joong Woo Nam ),( Chun Kyu Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 ELECTRONIC MATERIALS LETTERS Vol.2 No.2
The field emission (FE) properties of carbon nanotube (CNT) paste on a cathode with a curved surface are reported in terms of its application in a traveling wave tube-microwave power amplifier (TWT-MPA). Initially, a stable and uniform emission current from the activated CNT paste emitter was obtained, during multiple trial of FE cycling (>80 mA/㎠ at 3.5 V/㎛). In addition, the effective electrical aging conditions (aging time and current) were investigated in an attempt to improve the emission reliability of the CNT emitters. After electrical aging, a gridded CNT cathode structure was fabricated, and the diode FE characteristics with the common ground configurations in anode and gate were investigated.
A New Method of Carbon-Nanotube Patterning Using Reduction Potentials
Lee, Jong Hak,Shin, Jun Ho,Kim, Yu Hee,Park, Sung Min,Alegaonkar, P. S.,Yoo, Ji-Beom WILEY-VCH Verlag 2009 Advanced Materials Vol.21 No.12
<B>Graphic Abstract</B> <P>Noble metals promote the oxidation of carbon nanotubes (CNTs) at the relatively low temperature of 350 °C. The reduction potential of multiwalled CNTs is located between those of W and Ni, while that of single-walled CNTs is between those of Ni and In. Nanometer-sized patterns on CNT films were successfully fabricated using differences in reduction potential between the CNTs and noble metals. <img src='wiley_img/09359648-2009-21-12-ADMA200802507-content.gif' alt='wiley_img/09359648-2009-21-12-ADMA200802507-content'> </P>