Narrow Results

Amorphous carbon nitride films (a-CN_x) were deposited by pulsed laser deposition of camphoric carbon target at different substrate temperatures (ST). The influence of ST on the bonding properties of a-CN_x films was investigated. The nitrogen to carbon (N/C) atomic ratio and oxygen to carbon (O/C) atomic ratio, bonding state and microstructure of the deposited a-CN_x films were characterized by X-ray photoelectron spectroscopy and confirmed by other standard measurement techniques. The bonding states between the C and N, and C and O in the deposited films are found significantly influenced by the ST during deposition process. The N/C and O/C atomic ratio of the a-CN_x films reached the maximum value at 400°C. The ST of 400°C was proposed to promote the desired sp³-hybridized C and the C₃N₄ phase. The C–N bonding of C–N, C=N and C–N were observed in the deposited a-CN_x films.

Raman scattering analysis revealed that the structure of carbon films prepared by pulsed laser deposition (PLD) at room temperature is predominantly amorphous and the structure of amorphous carbon nitride (a-CN_x) thin films can be changed with varying substrate temperatures (ST) from 20°C to 500°C. The deposited a-CN_x films are composed of C–N, C≡N and C–O bonded materials and the C–N and C≡N bonds are increased with ST. We have found that no other obvious peaks can be distinguished in the range 900–2300 cm^-1 in which several peaks always appear in a-CN_x films. The spectra were deconvoluted into Raman D and G peaks and the structural parameters are determined. The upward shifts of the Raman G peak towards 1592 cm^-1 shows the evidence of a progressive formation of crystallites in a-CN_x films upon increase of ST. While the upward shifts of the Raman D peak towards 1397 cm^-1 have been related to the decrease of bond-angle disorder and sp³ tetrahedral bonding in its structure. Raman FWHM and I_D/I_G also indicate that N incorporation with increase of ST caused an increase in the number and/or size of graphitic domains in the a-CN_x films.

The effects of annealing temperature on the optical properties of nitrogenated amorphous carbon (a-C:N) films grown on quartz substrates by a novel surface wave microwave plasma chemical vapor deposition (SWMP-CVD) method are reported. The thickness, optical, structural and bonding properties of the as-grown and anneal-treated a-C:N films were measured and compared. The film thickness decreased rapidly with increasing annealing temperature above 350°C. A wide range of optical absorption characteristics is observed, depending on the annealing temperature. The optical band gap of as-grown a-C:N films is approximately 2.8 eV, gradually decreasing to 2.5 eV for the films anneal-treated at 300°C, and beyond that decreasing rapidly down to 0.9 eV at 500°C. The Raman and FTIR spectroscopy measurements have shown that the structural and composition of the films can be tuned by optimizing the annealing temperature. The change of optical, structural and bonding properties of SWMP-CVD-grown a-C:N films with higher annealing temperature was attributed to the fundamental changes in the bonding and band structures of the films.

Hydrogenated amorphous carbon films (a-C:H) were deposited on p-type silicon (a-C:H/p-Si) and quartz substrates by excimer laser at room temperature using mixture ratios 1 to 9 and 3 to 7 of camphor to graphite by weight percentages. The presence of hydrogen in the a-C:H films has been confirmed by Fourier transform infrared spectroscopy (FTIR) measurements. The structure and optical properties of a-C:H films were respectively investigated by Raman scattering and UV-visible spectroscopy. The increase of sp³ sites in the a-C:H films has also been confirmed by the Raman spectra spectroscopy analysis. The increase of the optical band gap with higher camphor percentage in the target was believed to be due to the increase of the sp³ hybrid forms of carbon arising from camphor incorporation. The formation of a heterojunction between the a-C:H film and Si substrate was confirmed by current–voltage (I–V) measurement. The structure of a-C:H/p-Si cells deposited using mixture ratios 1 to 9 of camphor to graphite by weight percentages showed better photovoltaic characteristics with an open-circuit voltage of 400 mV and short-circuit current density of about 15 mA/cm² under AM 1.5 (100 mW/cm² at room temperature) illumination. The energy conversion efficiency and fill factor were found to be approximately 2.1% and 0.38, respectively. The carbon layer contributed to the energy conversion efficiency in the lower wavelength region has been proved by the quantum efficiency measurement.

The effect of boron weight percentage in the camphoric carbon target of pulsed laser deposition on the preparation of boron-doped amorphous carbon (a-C:B) films has been studied using standard measurement techniques. XPS results showed the a-C:B films bonding properties almost unchanged at lower Bwt% up to 10 Bwt%, after which it changes with the increase of Bwt%, indicating increasing doping concentration with increase of Bwt% in the target. This phenomenon is further supported by FTIR and Visible-Raman spectroscopy analyses. The variation of bonding and structural properties are also correlated with the optical gap (E_g) and electrical resistivity (ρ) characteristics which are related to successful doping of B for low content of B in the amorphous carbon (a-C) films as the bonding, structural and E_g remain almost unchanged, and the ρ decreased untill the film deposited at 10 Bwt%. Since both the E_g and ρ decrease sharply with higher Bwt%, this phenomenon can be related to the graphitization.

Amorphous carbon nitride (a-CN_x) films have been deposited by pulsed laser deposition at 0.8 Torr nitrogen gas ambient with varying substrate temperature from 20 to 500°C. The effects of the substrate temperature and ambient nitrogen gas pressure on the surface morphology, composition, nitrogen content, structure, and electrical properties of the a-CN_x thin films have been investigated. The deposited a-CN_x films were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-Visible transmittance, and four-probe resistance measurement. It is found that the amorphous structure of a-CN_x films can be changed by the substrate temperature (ST) and the a-CN_x films with high nitrogen content have relatively high electrical resistivity. Also, graphitization is found to cause the reduction of nitrogen content and changes in the bonding structure of nitrogen atoms in the films.

The synchronized self-motion of three camphor boats was investigated on a circular water route as a simple example of mode-emergence. When three camphor boats were floated on the surface of water in a circular route in the same direction, various kinds of synchronization could be produced by changing the inherent velocities of the boats. The essential features of synchronization were reproduced by a numerical calculation regarding the distances among three camphor boats, which changed the driving forces of the individual boats. We believe that the present results may be useful for developing novel experiments with vector processes and mode-switching.

Naturally occurring molecules offer intricate structures and functionality that are the basis of modern medicinal chemistry, but are under-represented in materials science. Herein, we review recent literature describing the use of abundant and relatively inexpensive, natural products for the synthesis of ligands for luminescent organometallic complexes used for organic light emitting diodes (OLEDs) and related technologies. These ligands are prepared from the renewable starting materials caffeine, camphor, pinene and cinchonine and, with the exception of caffeine, impart performance improvements to the emissive metal complexes and resulting OLED devices, with emission wavelengths that span the visible spectrum from blue to red. The advantages of these biologically-derived molecules include improved solution processibility and phase homogeneity, brighter luminescence, higher quantum efficiencies and lower turn-on voltages. While nature has evolved these carbon-skeletons for specific purposes, they also offer some intriguing benefits in materials science and technology.

Potato brown rot; known as bacterial wilt disease, is a serious disease causing problems in the warm regions of the tropics and subtropics. It has been reported also in cool climates of North Western Europe. Primary infection by Ralstonia solanacearum bacteria occurs through roots or the stolons as soil born disease. This study carried out to study the effect of organic matters and mineral fertilizers as soil amendments on bacterium population of Ralstonia solanacearum and disease severity (virulent and avirulent forms), under artificial inoculation condition. Result indicated that bacterium population and disease severity were significantly reduced when treated with the soil amendments "Garlic" and "Potassium Sulfate" after 90 days in comparison to the control treatment. Additionally, it was clear from the experiment that organic matters were more successful in the virulent forms reduction.