Nguyen Van Quy

A high-performance triode-type carbon nanotube field emitter for mass production

A triode-type field emission device based on carbon nanotubes (CNTs) synthesized on an anodic aluminum oxide (AAO) template was fabricated. For the improvement of device performance, in addition to the basic advantages of using AAO to obtain uniform CNTs with strong adhesion, several considerations were taken into account, including highly crystalline CNTs synthesized through thermal chemical vapor deposition (CVD) at 1200 °C, lowering the contact resistance with a Ti buffer layer and reducing the pixel size and gate-to-emitter distance. The triode-type field emitter showed a high current density of 20 mA cm−2 and a low turn-on voltage of 16 V. The very high field enhancement factor of 1.6 × 106 cm−1 confirmed the high efficiency of the triode structure in electron extraction.

The use of anodic aluminium oxide templates for triode-type carbon nanotube field emission structures toward mass-production technology

A new triode-type field emitter structure using carbon nanotubes synthesized on an anodic aluminium oxide template is demonstrated. The emitter structure is characterized by uniform diameters and heights, as well as by high mechanical stability. The structure is proven to be advantageous in mass production. In the structure, the leakage current to the gate can be reduced to near zero by coating the insulator on the gate. Through this, a very high current density of 5xa0mAxa0cm−2 is achieved. The very high field enhancement factor of 1.5 × 106xa0cm−1 illustrates the high performance of the triode structure, which is realized by freely using well developed semiconductor processing technologies.

Synthesis of a long strand of single-wall carbon nanotubes

Carbon nanotubes (CNTs) can be usefully applied to composites for extremely high strength, and thermal and electrical conductivity. Longer CNTs are better fitted for the implementation, and the syntheses have been reported. However, a detailed synthesis process has not yet been discovered to optimize the CNT quality and production yield. In this report, the synthesis temperature, composition of the source solution, source feed rate, etc, have been examined for production of high quality long strands of single-wall CNTs using scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and thermo-gravimetric analysis. It has been revealed that the higher synthesis temperature can produce higher quality CNTs, but only when the process parameters are optimized. Therefore, different optimum conditions exist at different synthesis temperatures. The best quality CNTs were obtained at 1100u2009°C, the highest temperature among the conditions tested.

A comparative study on the NH3 gas-sensing properties of ZnO, SnO2, and WO3 nanowires

In this work, a large quantity of ZnO, SnO2 and WO3 nanowires (NWs) was successfully synthesised by simple and efficient methods. Their morphology and microstructure were characterised by FE-SEM, TEM, XRD, PL, and Raman. The NH3 gas-sensing properties of these NWs were investigated and compared. It was found that the responses and response-recovery time of SnO2 and WO3 NWs sensors to NH3 gas are relatively comparable, and they have a better NH3 gas-sensing performance than that of ZnO NWs sensor. In addition, the SnO2 NWs sensor has the lowest operating temperature.

Transparent Field Emission Device from a Spray Coating of Single-Wall Carbon Nanotubes

A transparent field emission device made from spray coating a single-wall carbon nanotube SWNT in N,N-dimethylformamide DMF was developed. Highly crystalline SWNTs were successfully synthesized using a vapor phase method. Amorphous carbon and catalyst metal particles that remained in the SWNTs were removed using a purification process. The purified SWNTs were diluted and dispersed in DMF using an ultrasonic bath and a magnetic stirrer. The residue was removed by centrifugation of the SWNT DMF solution. The solution was then spray-coated to fabricate the emitter devices. The SWNT emitter has a transparency of more than 60% and a resistance of 200 /. The transparent field emission device shows a maximum current density of 0.9 mA cm x7f1 , a low turn-on field of 1.1 V m x7f1

Carbon Nanotube Gas Sensor Fabricated on Anodic Aluminum Oxide

A new type of gas sensor was realized by directly depositing carbon nanotube on nano channels of the anodic alumina oxide (AAO) fabricated on p-type silicon substrate. The carbon nanotubes were synthesized by thermal chemical vapor deposition at a very high temperature of 1200 oC to improve the crystallinity. The device fabrication process was also developed. The contact of carbon nanotubes and p-type Si substrate showed a Schottky behavior, and the Schottky barrier height increased with exposure to gases while the overall conductivity decreased. The sensors showed fast response and recovery to ammonia gas upon the filling (400 mTorr) and evacuation.