In the present work, silicon nanowires were prepared by a thermal evaporation method. The evaporating source was a mixture of silicon and carbon nanopowders. Surface morphology, structural characteristics and emission properties of the silicon nanowires were investigated by several techniques. The results showed that the obtained products have the shape of nanowires with diameters ranging from 30 to 120 nm and lengths from 300 to 400 nm. The x-ray diffraction (XRD) patterns confirmed the presence of crystalline silicon. Transmission electron microscope (TEM) images revealed the core-shell structure of the wires. In the photoluminescence (PL) spectra recorded at room temperature, only a broad emission band peaking at about 650 nm was observed. In addition to the red emission, two other bands centered at around 455 nm and 510 nm appeared when measured at low temperatures. The origin and emission mechanism of these bands are discussed.
Silicon nanostructure-based light emitting devices (nc_SiLED) have been fabricated using conventional microelectronic technologies. The emissive layer composed of silicon and silicon dioxide was deposited by magnetron co-sputtering. Under forward bias, a broad electroluminescence (PL) spectrum in the range 450–900 nm was observed, peaking at around 705 nm. The effect of Si content in the active layer on the electrical and optical properties of these devices was measured and discussed.
Silicon nanowires were successfully synthesized by a thermal evaporation method. We have observed a strong and broad emission band centered at 670 nm, which is attributed to the quantum confinement effect related to Si nanostructures embedded in the complex SiO
x
matrix. By fitting an experimental Raman spectrum, we confirm that the as-received wires possess crystalline silicon cores whose sizes were around 5 nm. Furthermore, the abnormal dependence of integral photoluminescence intensity on measured temperature was investigated.
Many researchers over the world have pointed out the great economic and environmental benefits of using recycled aggregate from waste concrete to make concrete. In Vietnam, although the demand for concrete is increasing in both civil and infrastructure construction such as rural concrete roads, however, the use of waste concrete aggregate to make concrete still has not been adequately studied. With the experimental test, the authors have studied the change in the strength of concrete using large recycled aggregates, thereby clarifying the possibility of using this type of concrete in rural concrete road construction. The results show that, if the amount of recycled aggregate to replace natural aggregate is below 30%, the concrete strength achieved is slightly reduced compared to the control concrete. As the amount of recycled aggregate increases, the strength of the concrete decreases significantly but still can meet the strength requirement of concrete in rural roads.
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