Taehee Park

Improved field emission properties of CdS deposited single walled carbon nanotube emitter

The field emission (FE) properties of sigle-walled carbon nanotubes (SWNTs) are of great importance, especially in applications involving flat panel display devices such as field emission displays (FED) [1]. The electron emitters of the FED must be long-lived and stable, and possess a low turn-on threshold voltage and a high current density at a given external field. [2] In general, the emission source should have highly oriented and well-distributed tubes in order to utilize the characteristics of the nanotubes for FE. A notable method using plasma for the synthesis of the aligned CNTs was developed by Ren et al.[3] We report the modificated field emitter of CdS quantum-dot deposited on SWNTs (DcS/SWNTs). As a II–VI semiconductor compound, CdS has attracted considerable interest in optoelectronic application because of its relatively low electron affinity, high chemical inertness and sputter resistance.

Characteristic features of stone-wales defects in single-walled carbon nanotube; adsorption, dispersion, and field emission

Adsorption behaviors of dodecanethiol (C12H25SH) molecules are investigated on the surface of single-walled carbon nanotubes (SWCNTs) with vibrational and X-ray photoelectron spectrometers. The active adsorption sites are proved as Stone-Wales (SW) defects (5-7 ring defects). The SW defect-removed SWCNTs formed by reacting nanotubes with allyl acrylate molecules are compared with pristine SWCNTs in dispersion and field emission. The former shows higher dispersion and field emission than the latter.

The electric field enhancements by single-walled carbon nanotubes in In2S3/In2O3 photoelectrochemical solar cells

Using reverse-field emission (FE) current measurements, we demonstrate enhancement of the electric field by single-walled carbon nanotubes (SWNTs) in In2S3/In2O3 photoelectrochemical solar cells (PECs). In reverse-FE measurements, anode and cathode consists of In2S3/In2O3/(with or without) SWNTs on indium-doped tin oxide substrate and microtexturized tip silicon, respectively. The enhanced FE results for In2S3/In2O3/SWNTs show an electric field approximately two times more than In2S3/In2O3. The β value (i.e., electric field enhancement factor) of In2S3/In2O3 PECs with SWNT layers is 4950, which is ∼35.2% higher than that of In2S3/In2O3 PECs without SWNTs (3660). In PECs, the enhanced electric field intensifies the power of electron transfer, which accelerates the electron transfer rate in the cell.

Evaluation of a cesium iodide photocathode assisted with MgO-coated multiwall carbon nanotubes

This paper reports the enhanced photocurrent and relative quantum efficiency of cesium iodide (CsI) films on magnesium oxide (MgO)-coated multiwall carbon nanotubes (MWCNTs) on a silica substrate, i.e., CsI/MgO/MWCNTs/Si, when illuminating with 147 nm photons under an external electric field. The incorporation of MWCNTs resulted in significant enhancement of the photocurrent by several orders of magnitude compared to that of a conventional CsI. An analysis of the photoelectron energy spectrum attributed the phenomena to the creation of a very high electric field through the MgO/CsI film with the subsequent generation of avalanche secondary electrons.

Sensitive and Stable Gas Ionization Sensor Based on 3-D Single-Walled Carbon Nanotube Networks Suspended on ZnO Nanorods

We fabricated a gas ionization sensor based on 3-D single-walled carbon nanotube (SWNT) networks suspended between ZnO nanorods using a chemical vapor deposition method. ZnO nanorods were grown on the pyramid-like protrusions of a textured Si substrate. The breakdown voltages and stability of the 3-D SWNT networks were measured and compared with those of a SWNT film synthesized on Si substrate. Our results show that 3-D SWNT networks on ZnO nanorods enable ionization gas sensors to be sensitive, selective, and highly stable devices.

Improved field emission properties of CdSe deposited single-walled carbon nanotubes emitter

The field emission (FE) properties of sigle-walled carbon nanotubes (SWNTs) are of great importance, especially in applications involving flat panel display devices such as field emission displays (FED) [1]. The electron emitters of the FED must be long-lived and stable, and possess a low turn-on threshold voltage and a high current density at a given external field. [2] In general, the emission source should have highly oriented and well-distributed tubes in order to utilize the characteristics of the nanotubes for FE. A notable method using plasma for the synthesis of the aligned CNTs was developed by Ren et al.[3] We report the modificated field emitter of CdS quantum-dot deposited on SWNTs (DcS/SWNTs). As a II–VI semiconductor compound, CdS has attracted considerable interest in optoelectronic application because of its relatively low electron affinity, high chemical inertness and sputter resistance.

Improved field emission properties of GaAs/MgO-coated single-walled carbon nanotube

We measured the field emission (FE) properties and life time stability of single walled carbon nanotubes (SWNTs) after coating with wide-band-gap material (WBGM) and successive negative electron affinity (NEA) material, i.e., magnesium oxide and successive gallium arsenide. Their turn-on field and emission current densities were measured and compared with pristine SWNT film. The FE was increased successively after MgO coating and subsequent GaAs coating for SWNTs. A lifetime test revealed that GaAs/MgO/SWNTs protects SWNT film during FE under exposure to O2 gas. The field-enhancement factor, β, was calculated from the Fowler-Nordheim equation of FE results.

Field emission properties of a three-dimensional network of single-walled carbon nanotubes inside pores of porous silicon

This paper reports the characteristic field emission (FE) properties of single-walled carbon nanotubes (SWNTs) synthesized on the inside pores of a porous silicon (PS) substrate, as well as on the top surface of a PS substrate. Their turn-on fields and emission current densities are measured and compared with those of other types of SWNTs in similar environments. Investigation of field emission properties of single-walled carbon nanotubes (SWNTs) synthesized on the inside pores of a porous silicon (PS) substrate reveals a low turn-on field of about 2.25 V μm−1 at 10 μA/cm2 and a high field-enhancement factor (6182) compare with other samples. A life time stability test is performed by monitoring the current density change before and after repeated exposure to O 2 , suggesting that the pore channel can effectively prevent O 2 + ion etching from destroying the SWNTs within the pores of the PS layer.

P2–27: Enhanced field emission from hybrid CuO/ZnO nano-structure

The Field emission (FE) is one of the main applications of one-dimensional (1D) nanostructures with enhanced local electric field due to their sharp tips and high aspect ratio [1]. One of such 1D field emitters is CuO nanowires. CuO nanowires are capable of achieving a high field emission current density at relatively low field and exhibiting uniform field emission distributions [2]. An advantage of CuO nanowires is that they can be readily synthesized on a large scale from oxidizing Cu by a simple heating technique. Hybrid nano-structure combining the properties of two or more different types of nanostructures could further enhance the field emission. There has been no field emission study on hybrid nano-structure with CuO and ZnO reported. Hybrid CuO/ZnO nano-structure is synthesized by directly heating technique and magnetron sputtering. Field emission properties of the hybrids show the reduced emission turn-on field and enhanced current.

P2–13: Field emission characteristics of carbon nanotube forest on etched Si substrate

In this work, we investigatethe field emission characteristics of carbon nanotube forest on three types substrate: (1) mirror polished, (2) chemically etched (large pattern) and (3) chemically etched (small pattern) Si substrate. The surface morphology of CNTs forest was characterized by scanning electron microscopy (SEM), surface chemical state and electronic structure phase analyzed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.