Deposition of Silver Nanoparticles on Indium Tin Oxide Substrates by Plasma-Assisted Hot-Filament Evaporation

Nanoparticles of noble metals have unique properties including large surface energies, surface plasmon excitation, quantum confinement effect, and high electron accumulation. Among these nanoparticles, silver (Ag) nanoparticles have strong responses in visible light region due to its high plasmon excitation. These unique properties depend on the size, shape, interparticle separation and surrounded medium of Ag nanoparticles. Indium tin oxide (ITO) is widely used as an electrode for flat panel devices in such as electronic, optoelectronic and sensing applications. Nowadays, Ag nanoparticles were deposited on ITO to improve their optical and electrical properties. Plasma-assisted hot-filament evaporation (PAHFE) technique produced high-density of crystalline Ag nanoparticles with controlling in the size and distribution on ITO surface. In this chapter, we will discuss about the PAHFE technique for the deposition of Ag nanoparticles on ITO and influences of the experimental parameters on the physical and optical properties, and electronic structure of the deposited Ag nanoparticles on ITO

A geant4 simulation on the application of multi-layer graphene as a detector material in high-energy physics

The excellent properties of graphene, such as its high thermal conductivity, high electrical conductivity, and high electron density, make it an ideal candidate as a detector material in high-energy physics applications. In this work, we demonstrate the feasibility of multi-layer graphene (MLG) as a detector material in a high-energy environment. The Geant4 software package was used to estimate the energy of the deposited electrons within various thicknesses of MLG, ranging from 3 to 20 nm. The efficiency of the MLG as a detector material was further analyzed from the scattering angle and the yield of the secondary particles produced from the electron interaction with the material. The incident electron’s kinetic energy used herein ranged between 30 keV and 1 GeV, at a particle fluence of 1×107 e/cm2 . The results show that the deposited energy was relatively low for the interaction with 1 MeV electrons, and dramatically increased as the thickness increases beyond 15 nm. This result was further supported by the highest yield of gamma radiation recorded by the interaction with a kinetic energy larger than 1 MeV, for thickness larger than 15 nm. The results suggest that the MLG works best as a charged particle detector in low energy ranges, while for high energy ranges, a thickness over 15 nm is suggested. The findings demonstrate that a MLG with a thickness larger than 15 nm could potentially be used as a detector material in high-energy conditions

Experimental investigation of energy storage properties and thermal conductivity of a novel organic phase change material/MXene as A new class of nanocomposites

Energy storage is a global critical issue and important area of research as most of the renewable sources of energy are intermittent. In this research work, recently emerged inorganic nanomaterial (MXene) is used for the first time with paraffin wax as a phase change material (PCM) to improve its thermo-physical properties. This paper focuses on preparation, characterization, thermal properties and thermal stability of new class of nanocomposites induced with MXene nanoparticles in three different concentrations. Acquired absorbance (UV-Vis) for nanocomposite with loading concentration of 0.3 wt.% of MXene achieved ~39% enhancement in comparison with the pure paraffin wax. Thermal conductivity measurement for nanocomposites in a solid state is performed using a KD2 PRO decagon. The specific heat capacity (cp) of PCM based MXene is improved by introducing MXene. The improvement of cp is found to be 43% with 0.3 wt.% of MXene loaded in PCM. The highest thermal conductivity increment is found to be 16% at 0.3 wt.% concentration of MXene in PCM. Decomposition temperature of this new class of nanocomposite with 0.3 wt.% mass fraction is increased by ~6%. This improvement is beneficial in thermal energy storage and heat transfer applications

Layer-by-layer plasma enhanced chemical vapour deposition of nanocrystalline silicon thin films / Goh Boon Tong

This work is focused on the study of hydrogenated silicon (Si:H) thin films and nanostructures grown by layer-by-layer (LBL) deposition technique using a home-built radio-frequency (rf) plasma enhanced chemical vapour deposition (PECVD) system. The initial phase of this work involved preparation and characterization of hydrogenated silicon (Si:H) thin films by continuous (CD) and LBL deposition techniques on crystal silicon (c-Si) and glass substrates at different rf powers, substrate temperatures and hydrogen to silane flow-rate ratios. The effects of the deposition conditions on the optical and structural properties of the films are studied by optical transmission spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-Ray diffraction (XRD). The influence of substrates on these properties is also investigated. The second phase is focused on the study of the morphology, crystallinity, crystallite size, siliconoxygen bonding and photoluminescence (PL) properties of the Si:H films grown on c-Si substrates by LBL deposition technique at the same deposition conditions in the first phase. These properties of the films are characterized by Micro-Raman scattering spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and Micro-photoluminescence spectroscopy including further analysis done on the characterization results obtained from XRD and FTIR measurements done in the first phase in this work. The results of this work demonstrated that rf power and substrate temperature produced significant changes to the optical and structural properties of the LBL films compared to the CD films. Increase in rf power increased the deposition rate of the LBL and vice-versa for the CD films. Also, increase in rf power increased the disorder of the CD films however suppressed the disorder in the LBL films. The preferred crystalline orientation was also changed from Si (311) to Si (111) plane with increase in rf power. Increase in substrate temperature increased the deposition rate, refractive index and structural order in the LBL films. The substrate temperature showed significant effects on optical band gap and hydrogen content in the LBL films. The LBL films deposited at substrate temperatures of 100 and 200°C showed large optical energy gaps suggesting that broadening of the band gap was due to quantum confinement effects. The LBL films deposited on c-Si substrates showed highly crystalline structure as compare to the other deposited films. The periodic hydrogen plasma treatment on the growth surface of the film during the LBL deposition processes showed effectively enhances the electrooptical properties of these LBL films. The LBL deposition produced silicon nanostructures with Si nano-crystallites embedded in either amorphous silicon (a-Si) or mixed phases of a-Si and amorphous silicon oxide (a-SiO) matrix for the films deposited on c-Si substrates. These nanostructures of nanocrystalline silicon (nc-Si) grains produced high intensity of PL emission due to enhancement of quantum confinement effects by the presence of high crystalline volume fraction (XC ~ 41-54 %) of Si nano-crystallites (~ 2 nm) in the matrix. The intensity of the PL emissions was strongly dependent on crystalline volume fraction, crystallite size and oxygen content in the a-SiO matrix. These parameters were significantly controlled by the rf power and substrate temperature. Based on these results, the growth kinetics and structural configuration of the LBL grown nc-Si grains were proposed. It was shown that high intensity of PL emission was emitted by these clusters of nc-Si grains

Optical constants and electronic transition in hydrogenated silicon (Si:H) thin films deposited by layer-by-layer (LBL) deposition technique

Optical constants derived from optical transmission (T) and reflectance (R) spectra in the wavelength range of 220 to 2200 nm are presented in this paper for hydrogenated silicon (Si:H) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) using the layer-by-layer (LBL) deposition technique. The films were deposited on quartz substrate by decomposition of SiH4 and H2 gases at flow-rate of 5 sccm and 20 sccm, respectively. The substrate temperature, deposition pressure and deposition rate are 100°C, 0.8 mbar and 2.8 nm/s, respectively. The as-prepared films were annealed in nitrogen for one hour at annealing temperatures of 400°C, 600°C, 800°C and 1000°C. The as-prepared film thickness of 301 nm decreased to 260 nm when samples were annealed at 1000°C. The refractive indices (~ 3.0 to 3.4) of annealed films were determined from the interference fringes of transmission spectrum following Manifacier and Davies methods. The electronic transition from valence band to conduction band in these films are characterized from the optical energy gap; EG (~1.64 to 2.41 eV), the dispersion energy; Ed (~26.4 to 34.0 eV) and the oscillator strength; Eo (~2.8 to 3.2 eV). It is interesting to note that EG is lowest for the films annealed at temperature of 600°C which has the lowest hydrogen content, CH in the film. Evidence of the presence of nanocrystallites formed in amorphous matrix is also observed for the films annealed at temperatures above 600°C

Effects of rf power on structural properties of Nc-Si:H thin films deposited by layer-by-layer (LbL) deposition technique

The effects of rf power on the structural properties of hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited using layer-by-layer (LbL) deposition technique in a home-built plasma enhanced chemical vapor deposition (PECVD) system were investigated. The properties of the films were characterized by X-ray diffraction (XRD), micro-Raman scattering spectroscopy, high resolution transmission electron microscope (HRTEM) and Fourier transform infrared (FTIR) spectroscopy. The results showed that the films consisted of different size of Si crystallites embedded within an amorphous matrix and the growth of these crystallites was suppressed at higher rf powers. The crystalline volume fraction of the films was optimum at the rf power of 60 W and contained both small and big crystallites with diameters of 3.7 nm and 120 nm, respectively. The hydrogen content increased with increasing rf power and enhanced the structural disorder of the amorphous matrix thus decreasing the crystalline volume fraction of the films. Correlation of crystalline volume fraction, hydrogen content and structure disorder of the films under the effect of rf power is discussed

Optical properties of annealed Si:H thin film prepared by layer-by-layer (LBL) deposition technique

Optical studies were performed on annealed hydrogenated silicon (Si:H) thin films deposited by plasma-enhanced chemical vapor deposition (PECVD) using the layer-by-layer (LBL) deposition technique. The films were annealed for 1 h at temperatures of 400, 600, 800 and 1000 degrees C in ambient nitrogen. The effects of annealing temperatures on the optical properties, such as the optical-energy gap, Urbach energy, refractive index, dispersion energy and single oscillator strength, were studied. These parameters were determined from optical transmission and reflection spectroscopy. X-ray diffraction (XRD) and optical reflectance measurements were performed on the samples, showing the onset of transformation from an amorphous to a crystalline phase in the film structure when annealed at a temperature of 800 degrees C. The films were of mixed phase, with nanocrystalline grains embedded in the amorphous matrix. (C) 2010 Elsevier B.V. All rights reserved

Au/nc-Si:H core–shell nanostructures prepared by hot wire assisted plasma enhanced chemical vapor deposition technique

In this study, Au film was embedded in Si:H film on quartz substrate with and without an SiOx layer by using the hot wire assisted plasma enhanced chemical vapor deposition (HW-PECVD) technique. The as-prepared Au/Si:H films were post-thermally annealed at 800 °C in nitrogen ambient in order to initiate the growth of Au NPs. The annealed Au/a-Si:H film deposited on quartz substrate without an SiOx layer showed the formation of well-distributed and spherical Au NPs. Formations of Au/nc-Si:H core shell nanostructures were observed on annealed film deposited on quartz substrate with an SiOx layer. XRD and micro-Raman scattering spectra revealed that the degree of crystallinity of nc-Si:H was dependent on the annealing temperature and interaction between a-Si:H film and SiOx layer. Optical spectra showed that the Au NPs on annealed films deposited on quartz substrate without an SiOx layer exhibited prominent SPR peak while annealed Au/nc-Si:H core shell nanostructures showed increased reflectance of light in the visible region