Precise Control of Carbon Nanotube Synthesis of a Single Chirality

2007 ◽  
Author(s):  
David R. Huitink ◽  
Debjyoti Banerjee ◽  
Saion K. Sinha
Keyword(s):  
Gas Flow ◽  
Chemical Vapor ◽  
Synthesis Conditions ◽  
Precise Control ◽  
Catalyst Composition ◽  
Cvd Synthesis ◽  
Before And After ◽  
Characterization Studies ◽  
Uniform Diameter ◽  
Carbon Nanotube Synthesis

This work demonstrates precise control over the synthesis conditions and location during CNT formation, such that single chirality tubes are obtainable. This technique obviates two significant hurdles that prevent the exploitation of CNTs in micro- and nano-devices. Microelectronic applications require precise location and chirality of synthesized CNTs. Conventional CVD synthesis techniques typically yield mixtures of CNTs (semi-conducting and metallic types) that grow at random locations. Dip Pen Nanolithography (DPN) techniques were used to deposit the catalysts at precisely defined locations and to pattern the catalysts on a substrate with specific sizes as well as to control the catalyst composition. After deposition of catalysts, a low temperature Chemical Vapor Deposition (CVD) process was used to synthesize CNT. Various known catalysts were deposited. Characterization studies before and after CVD synthesis of CNT showed that the CNT were of a single chirality as well as uniform diameter (with a very narrow range of variability). The results indicate that the chirality of the synthesized CNT can be controlled by changing the synthesis conditions (e.g., size of the catalyst patterns, composition of the catalysts, temperature of CVD, gas flow rates, etc.).

An Assessment of Chemical Vapor Deposition Synthesis of SnO2 Nanowires by Statistical Design

2016 ◽  
Vol 701 ◽  
pp. 52-56 ◽  
Author(s):  
Maisara Azad Mat Akhir ◽  
Khairudin Mohamed ◽  
Sheikh Abdul Rezan ◽  
Hooi Ling Lee ◽  
Siti Suhaila M. Izah
Keyword(s):  
Chemical Vapor Deposition ◽  
Flow Rate ◽  
Vapor Deposition ◽  
Deposition Time ◽  
Statistical Design ◽  
Chemical Vapor ◽  
Synthesis Conditions ◽  
Synthesis Parameters ◽  
Cvd Synthesis ◽  
Temperature Deposition

This paper studies the chemical vapor deposition (CVD) synthesis conditions for tin oxide (SnO2) nanowires (NWs) by using statistical design of experiment (DOE). The influences of synthesis parameters (growth temperature, deposition time and flow rate of argon) on SnO2 NWs diameter were studied. From perturbation analysis with DOE, it was found that temperature gave the most significant effect to the diameter of SnO2 NWs via CVD method followed by flowrate of argon and deposition time. Furthermore, based on the cube graph, the smallest SnO2 NWs (~18 nm) can be obtained at temperature of 850 °C with argon flow rate of 100 sccm using a deposition time of 60 min. On the other hand, the largest SnO2 NWs (~248 nm) can be produced at 900 °C.

Synthesis and Characterization of Single-Wall Carbon Nanotubes Grown by Chemical Deposition of Ethanol Vapor

2006 ◽  
Vol 48 ◽  
pp. 31-36 ◽  
Author(s):  
F.V. Golikov ◽  
A.S. Pozharov ◽  
E.D. Obraztsova ◽  
N.R. Arutyunyan ◽  
Serge V. Terekhov ◽  
...  
Keyword(s):  
Chemical Deposition ◽  
Chemical Vapor ◽  
Ethanol Vapor ◽  
Single Wall Carbon Nanotubes ◽  
Geometrical Parameters ◽  
Single Wall Carbon ◽  
Synthesis Conditions ◽  
Special Procedure ◽  
Carbon Nanotube Synthesis

In this work the method of single-wall carbon nanotube synthesis based on chemical vapor deposition from ethanol vapor has been developed. The films grown have been characterized in detail by the electron microscopy and the Raman scattering techniques. A typical split tangential mode (at 1592 cm-1) and a number of "breathing" modes (150-270 cm-1) have been revealed in the Raman spectra for a variety of synthesis regimes. It was possible to change the geometrical parameters of nanotubes by playing with the synthesis conditions. A key role of the catalyst (Co, Co:Mo) preparation has been revealed. A special procedure of the catalyst crystal growth has been developed.

Synthesis of Well-Aligned Multi-Walled Carbon Nanotubes by Floating Catalyst Chemical Vapor Deposition

2010 ◽  
Vol 123-125 ◽  
pp. 795-798
Author(s):  
Jin Cheng ◽  
Xiao Ping Zou ◽  
Gang Qiang Yang ◽  
Xue Ming Lü ◽  
Cui Liu Wei ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Gas Flow ◽  
Quartz Substrate ◽  
Chemical Vapor ◽  
Multi Walled Carbon Nanotubes ◽  
Uniform Diameter ◽  
High Degree ◽  
Walled Carbon Nanotubes ◽  
Catalyst Chemical Vapor Deposition

Well-aligned multi-walled carbon nanotube (MWNT) arrays were grown by floating catalyst chemical vapor deposition (CVD) on quartz substrate. The MWNTs in arrays had a uniform diameter of 30-50nm and high degree of graphitization. We find that catalyst nanoparticles with different sizes can be separated and deposit at different position by carrier gas flow under gravity effect in floating catalyst CVD. It is one of the main reasons that lead to the growth of well-aligned MWNTs.

The Influence of Temperature and Carrier Gas Flow in the Obtainment of Carbon Nanotubes by Chemical Vapor Deposition

2014 ◽  
Vol 976 ◽  
pp. 169-173
Author(s):  
Alejandro Gómez Sánchez ◽  
Lada Domratcheva Lvova ◽  
Victor López Garza ◽  
Leandro García González ◽  
Pedro González García ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Gas Flow ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
Carrier Gas ◽  
Synthesis Conditions ◽  
Xrd Diffraction ◽  
Carrier Gas Flow

The objective of this study was to evaluate the influence of the synthesis conditions on the characteristics of carbon nanotubes (CNTs), to optimize the process parameters in the growth of CNTs. The CNTs were obtained by Chemical Vapor Deposition (CVD) at 800, 850 and 900 °C and carrier gas flow of 50, 80 and 110 ml/min from ferrocene and benzene during 1 h. The CNTs obtained were analyzed with a field emission scanning electron microscope (FESEM) JSM-7600F. The degrees of crystallinity of the samples were obtained through X-ray diffraction (XRD). The lengths of the CNTs were 3-120 microns and average diameters were 29-72 nm. The highest yields of CNTs were obtained with a flow rate of 80 ml/min and temperature of 850 °C. The diagrams illustrate XRD diffraction peaks corresponding to crystalline phases of graphite, Fe α and cementite (Fe3C). The average CNTs walls were calculated with the Scherrer equation. The CNTs obtained with 50 ml/min carrier flow present an average of 40-42 walls, 80 ml/min-of 33-39 walls and 110 ml/min of 30-34 walls. These facts allow suppose that with a greater flow decreases the number of walls.

TEM evaluation of graded SixGe1-x heterolayers

1991 ◽  
Vol 49 ◽  
pp. 894-895
Author(s):  
N. David Theodore ◽  
Mamoru Tomozane ◽  
Ming Liaw
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
Gas Flow ◽  
Field Effect Transistors ◽  
Chemical Vapor ◽  
Dark Field ◽  
Bipolar Transistors ◽  
Structural Quality ◽  
Weak Beam ◽  
Transmission Electron ◽  
And Behavior

There is extensive interest in SiGe for use in heterojunction bipolar transistors. SiGe/Si superlattices are also of interest because of their potential for use in infrared detectors and field-effect transistors. The processing required for these materials is quite compatible with existing silicon technology. However, before SiGe can be used extensively for devices, there is a need to understand and then control the origin and behavior of defects in the materials. The present study was aimed at investigating the structural quality of, and the behavior of defects in, graded SiGe layers grown by chemical vapor deposition (CVD).The structures investigated in this study consisted of Si1-xGex[x=0.16]/Si1-xGex[x= 0.14, 0.13, 0.12, 0.10, 0.09, 0.07, 0.05, 0.04, 0.005, 0]/epi-Si/substrate heterolayers grown by CVD. The Si1-xGex layers were isochronally grown [t = 0.4 minutes per layer], with gas-flow rates being adjusted to control composition. Cross-section TEM specimens were prepared in the 110 geometry. These were then analyzed using two-beam bright-field, dark-field and weak-beam images. A JEOL JEM 200CX transmission electron microscope was used, operating at 200 kV.

scholarly journals Deposition of Boron-Doped Thin CVD Diamond Films from Methane-Triethyl Borate-Hydrogen Gas Mixture

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 666 ◽  
Author(s):  
Nikolay Ivanovich Polushin ◽  
Alexander Ivanovich Laptev ◽  
Boris Vladimirovich Spitsyn ◽  
Alexander Evgenievich Alexenko ◽  
Alexander Mihailovich Polyansky ◽  
...  
Keyword(s):  
Film Growth ◽  
Chemical Vapor ◽  
Hydrogen Gas ◽  
Diamond Growth ◽  
Structural Defects ◽  
Boron Doped Diamond ◽  
Diamond Deposition ◽  
Synthesis Conditions ◽  
Surface Etching ◽  
Boron Doped

Boron-doped diamond is a promising semiconductor material that can be used as a sensor and in power electronics. Currently, researchers have obtained thin boron-doped diamond layers due to low film growth rates (2–10 μm/h), with polycrystalline diamond growth on the front and edge planes of thicker crystals, inhomogeneous properties in the growing crystal’s volume, and the presence of different structural defects. One way to reduce structural imperfection is the specification of optimal synthesis conditions, as well as surface etching, to remove diamond polycrystals. Etching can be carried out using various gas compositions, but this operation is conducted with the interruption of the diamond deposition process; therefore, inhomogeneity in the diamond structure appears. The solution to this problem is etching in the process of diamond deposition. To realize this in the present work, we used triethyl borate as a boron-containing substance in the process of boron-doped diamond chemical vapor deposition. Due to the oxygen atoms in the triethyl borate molecule, it became possible to carry out an experiment on simultaneous boron-doped diamond deposition and growing surface etching without the requirement of process interruption for other operations. As a result of the experiments, we obtain highly boron-doped monocrystalline diamond layers with a thickness of about 8 μm and a boron content of 2.9%. Defects in the form of diamond polycrystals were not detected on the surface and around the periphery of the plate.

scholarly journals Improving the W Coating Uniformity by a COMSOL Model-Based CVD Parameter Study for Denser Wf/W Composites

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1089
Author(s):  
Leonard Raumann ◽  
Jan Willem Coenen ◽  
Johann Riesch ◽  
Yiran Mao ◽  
Daniel Schwalenberg ◽  
...  
Keyword(s):  
Relative Density ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Process Time ◽  
Parameter Study ◽  
Reactor Model ◽  
Production Route ◽  
Coating Uniformity ◽  
Hydrogen Retention ◽  
Return Lead

Tungsten (W) has the unique combination of excellent thermal properties, low sputter yield, low hydrogen retention, and acceptable activation. Therefore, W is presently the main candidate for the first wall and armor material for future fusion devices. However, its intrinsic brittleness and its embrittlement during operation bears the risk of a sudden and catastrophic component failure. As a countermeasure, tungsten fiber-reinforced tungsten (Wf/W) composites exhibiting extrinsic toughening are being developed. A possible Wf/W production route is chemical vapor deposition (CVD) by reducing WF6 with H2 on heated W fabrics. The challenge here is that the growing CVD-W can seal gaseous domains leading to strength reducing pores. In previous work, CVD models for Wf/W synthesis were developed with COMSOL Multiphysics and validated experimentally. In the present article, these models were applied to conduct a parameter study to optimize the coating uniformity, the relative density, the WF6 demand, and the process time. A low temperature and a low total pressure increase the process time, but in return lead to very uniform W layers at the micro and macro scales and thus to an optimized relative density of the Wf/W composite. High H2 and low WF6 gas flow rates lead to a slightly shorter process time and an improved coating uniformity as long as WF6 is not depleted, which can be avoided by applying the presented reactor model.

Effect of Temperature and Gas Flow on Bi2Se3 Nanoplates Grown by Chemical Vapor Deposition

2018 ◽  
Vol 18 (11) ◽  
pp. 7590-7594 ◽  
Author(s):  
Peng Gu ◽  
Jinling Yu ◽  
Xiaolin Zeng ◽  
Shuying Cheng ◽  
Yunfeng Lai ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Effect Of Temperature

Hydrogen Concentration Analysis in Pecvd and Rtcvd Silicon Nitride Thin Films and It's Impact on Device Performance

2001 ◽  
Vol 664 ◽  
Author(s):  
C. Y. Wang ◽  
E. H. Lim ◽  
H. Liu ◽  
J. L. Sudijono ◽  
T. C. Ang ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Threshold Voltage ◽  
Vapor Deposition ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Gate Oxide ◽  
Nitride Film ◽  
Device Performance ◽  
Gas Flow Ratio ◽  
The Impact

ABSTRACTIn this paper the impact of the ESL (Etch Stop layer) nitride on the device performance especially the threshold voltage (Vt) has been studied. From SIMS analysis, it is found that different nitride gives different H concentration, [H] in the Gate oxide area, the higher [H] in the nitride film, the higher H in the Gate Oxide area and the lower the threshold voltage. It is also found that using TiSi instead of CoSi can help to stop the H from diffusing into Gate Oxide/channel area, resulting in a smaller threshold voltage drift for the device employed TiSi. Study to control the [H] in the nitride film is also carried out. In this paper, RBS, HFS and FTIR are used to analyze the composition changes of the SiN films prepared using Plasma enhanced Chemical Vapor deposition (PECVD), Rapid Thermal Chemical Vapor Deposition (RTCVD) with different process parameters. Gas flow ratio, RF power and temperature are found to be the key factors that affect the composition and the H concentration in the film. It is found that the nearer the SiN composition to stoichiometric Si3N4, the lower the [H] in SiN film because there is no excess silicon or nitrogen to be bonded with H. However the lowest [H] in the SiN film is limited by temperature. The higher the process temperature the lower the [H] can be obtained in the SiN film and the nearer the composition to stoichiometric Si3N4.

The SiNx films process research by plasma-enhanced chemical vapor deposition in crystalline silicon solar cells

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744101 ◽  
Author(s):  
Bitao Chen ◽  
Yingke Zhang ◽  
Qiuping Ouyang ◽  
Fei Chen ◽  
Xinghua Zhan ◽  
...  
Keyword(s):  
Thin Film ◽  
Chemical Vapor Deposition ◽  
Solar Cell ◽  
Vapor Deposition ◽  
Gas Flow ◽  
Silicon Solar Cell ◽  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Double Layers ◽  
Crystalline Silicon Solar Cell

SiNx thin film has been widely used in crystalline silicon solar cell production because of the good anti-reflection and passivation effect. We can effectively optimize the cells performance by plasma-enhanced chemical vapor deposition (PECVD) method to change deposition conditions such as temperature, gas flow ratio, etc. In this paper, we deposit a new layer of SiNx thin film on the basis of double-layers process. By changing the process parameters, the compactness of thin films is improved effectively. The NH3passivation technology is augmented in a creative way, which improves the minority carrier lifetime. In sight of this, a significant increase is generated in the photoelectric performance of crystalline silicon solar cell.

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