Soo-Hwan Jeong

Fabrication of carbon nanotube emitters in an anodic aluminium oxide nanotemplate on a Si wafer by multi-step anodization

AAO template technology was combined with silicon technology to be directly applied to electronic device fabrication. Thin film anodic aluminium oxide (AAO) templates were fabricated on a silicon wafer by multiple anodizations. No electropolishing was used after the deposition of the aluminium layer on Si wafers. The ordering of the pore arrangement was improved by repeated anodizations, and highly ordered AAO templates could be obtained on Si wafers. CNT field emitter arrays were made with the AAO templates on Si wafers. Field emission measurement revealed that the emission current density increased with the synthesis temperature of CNTs. The large field enhancement factor in the range of 2440–4000 indicates the potential of the CNT field emitter array based on the AAO template on a Si wafer.

Stretchable carbon nanotube conductors and their applications

Stretchable electronics has evolved rapidly in the past decade because of its promising applications, as electronic devices undergo large mechanical deformation (e.g., bending, folding, twisting, and stretching). Stretchable conductors are particularly crucial for the realization of stretchable electronic devices. Therefore, tremendous efforts have been dedicated toward developing stretchable conductors, with a focus on conductive material/polymer composites. This review summarizes the recent progress in stretchable conductors and related stretchable devices based on carbon nanotubes (CNTs), which was enabled by their outstanding electrical and mechanical properties. Various strategies for developing highly stretchable conductors that can deform into nonplanar shapes without significant degradation in their electronic performance are described in terms of preparation processes. Finally, challenges and perspectives for further advances in CNT-based stretchable conductors are discussed.

Facile route to multi-walled carbon nanotubes under ambient conditions

A facile and practical route is demonstrated to prepare multi-walled carbon nanotubes (MWCNTs) by a sonochemical method. By applying ultrasonic irradiation to the mixture of ferrocene and xylene with small amount of water, crystalline MWCNTs were selectively synthesized under ambient conditions, allowing MWCNTs with diameter of 25-40 nm to be obtained. A control experiment revealed that a small amount of water was essential for producing MWCNTs. The analysis of Raman spectra of MWCNTs showed that the intensity of the D-band relative to the G-band was 0.98, indicating relatively good crystallinity of these MWCNTs. This result was consistent with that of TEM observation.

Field emission of ZnO nanorods synthesized by sonication

Vertically aligned ZnO nanorods were grown on the substrate by sonication. Transmission electron microscopy, photoluminescence, and X-ray diffraction were performed for nanorods synthesized by sonication, which leads to formation of ZnO crystals. For field emission measurements, ZnO nanorods were used as cathode and a green phosphor coated ITO glass was used as anode, where cathode and anode plates were separated by a spacer of 270 mum. Therefore, due to the easy fabrication process and good field emission characteristics, these sonochemically synthesized ZnO nanorods can be regarded as one of key potential field emitters.

NO sensing characteristics of ZnO nanorod prepared by ultrasound radiation method

ZnO sensors were fabricated from ZnO nanorods prepared by ultrasound radiation method and their gas sensing properties were investigated for NO, (CH3)3N, H2S, CO and CH3SH. In a procedure, zinc nitrate hydrate [Zn(No3)2ldr6H2O] and hexamethyleneteramine [C6H12N4,] were dissolved in deionized water and then the solution was irradiated with high intensity ultrasound radiation for lh by employing a direct immersion titanium horn. The lengths of ZnO nanorod were from 250 nm to 500 nm and the diameters were from 40 nm to 80 nm. The size of ZnO nanorod can be controlled by concentration of solution. The sensing characteristics of these nanostructures were investigated for three kinds of sensor fabricated by different concentrations (0.01, 0.005 and 0.001 M) of solution. We observed that the property of sensors was influenced by the morphology. Crystal structure and ceramic microstructure of ZnO nanorod were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Sulfurization-induced growth of single-crystalline high-mobility β-In2S3 films on InP

Metalorganic chemical vapor deposition was used to grow single-crystalline tetragonal β-In2S3 films on InP to afford covalently bonded In2S3/InP heterostructures, with the crystal structure of these films identified by high-resolution scanning transmission electron microscopy, X-ray diffraction, and Raman spectroscopy analyses, and the corresponding bandgap energies determined by photoluminescence measurements at room (300 K) and low temperatures (40 K). RT-PL measurements reveal the three peaks spectral emission at 464.3, 574.7, and 648.5 nm associated with luminescence from band-edge and two above conduction band-edge, respectively, although the LT-PL (40K) measurements of β-In2S3 film found two dominant peaks. Moreover, the above films exhibited n-type conductivity, with background electron concentration = 4.9 × 1015 cm–3, electron mobility = 1810.9 cm2 V–1 s–1, and resistivity = 0.704 Ω cm. Thus, single-crystalline β-In2S3 films deposited on InP are promising constituents of high-performance next-gene...

Flexible Field Emitters Based on Carbon Nanotubes and Other Materials

Publisher Summary This chapter provides a representative overview of the present status of flexible field emitters based on carbon nanotubes (CNTs), with a special emphasis on recent development. This development has been considered in the context of preparation methods of flexible emitters and their electron emission properties, with the focus on CNT-based emitters. The brief description of the basic and general principle of field emission is given and field emission properties of CNTs are outlined. A lot of effort and progress has been made during the past decade in the preparation and characterization of the flexible field emitter arrays (FEAs) based on CNTs and other materials. In addition, the flexible field emitters, especially CNT-based emitters, have developed into a new research field. Several strategies, such as attachment, composite/matrix and direct growth methods, have been successfully developed for CNT flexible emitters and have exhibited considerable electron emission properties.