Characterization of Si nanocrystals into SiO2 matrix (original) (raw)
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Optoelectronics, Instrumentation and Data Processing, 2016
Experiments and simulations are performed to study the formation of silicon nanocrystals (Si-NCs) in multilayer structures with alternating ultrathin layers of SiO2 and amorphous hydrogenized silicon (α-Si:H) during high-temperature annealing. The effect of annealing on the transformation of the structure of the α-Si:H layers is studied by methods of high-resolution transmission electron microscopy, Raman spectroscopy, and photoluminescence spectroscopy. The conditions and kinetics of Si-NC formation are analyzed by the Monte Carlo technique. The type of the resultant crystalline silicon clusters is found to depend on the thickness and porosity of the original amorphous silicon layer located between SiO2 layers. It is shown that an increase in the thickness of the α-Si layer in the case of low porosity leads to the formation of a percolation silicon cluster instead of individual Si nanocrystals.
XPS and SIMS investigation on the role of nitrogen in Si nanocrystals formation
Surface Science, 2005
Since the demonstration of optical gain in silicon nanocrystals, in the last few years several papers appeared in the literature reporting gain measurements in silicon nanocrystals embedded in a silica matrix produced by different techniques. However, it is still unclear which are the structural, physical and chemical factors that contribute to enhance photoluminescence and gain in this type of samples. In particular, the presence and the role of nitrogen in the SiO 2 matrix are in fact supposed to be essential factors in understanding the gain mechanism.
Journal of Applied Physics, 2000
We have performed physical and optical characterization of Si nanocrystals grown by ion implantation of Si ϩ ions at multiple energies with varying doses into thermally grown SiO 2 films. The purpose of multiple implants was to achieve uniform composition of the added Si profile throughout the SiO 2 film to produce Si particles with a narrow size distribution upon annealing at 1000°C in a nitrogen atmosphere. The depth distribution of the composition and sizes of the Si particles in SiO 2 films before and after the anneal were determined using Rutherford backscattering ͑RBS͒, forward recoil spectroscopy, small-angle x-ray diffraction ͑SXRD͒, and high-resolution transmission electron microscopy ͑HRTEM͒. From RBS we concluded that the amount of free silicon was reduced by annealing, presumably due to oxidation in the annealing process. The mean cluster sizes of the annealed samples were determined by SXRD. HRTEM was also employed to determine the average size of Si particles. Photoluminescence spectra ͑PL͒ from these samples were broad and the peak positions of the PL spectra were blue-shifted with decreasing cluster size. The line shapes of the PL spectra were calculated with a quantum confinement model assuming a log-normal size distribution of Si nanoparticles and ͑1/D͒ 1.25 dependence of the band gap energy as a function of particle size D. The band gap energy and the average particle size obtained from the calculated line shape spectra agree well with the quantum confinement model.
Effect of rapid thermal annealing temperature on the dispersion of Si nanocrystals in SiO2 matrix
2015
Effect of rapid thermal annealing temperature on the dispersion of silicon nanocrystals (Si-NC's) embedded in SiO2 matrix grown by atom beam sputtering (ABS) method is reported. The dispersion of Si NCs in SiO 2 is an important issue to fabricate high efficiency devices based on Si-NC's. The transmission electron microscopy studies reveal that the precipitation of excess silicon is almost uniform and the particles grow in almost uniform size upto 850 C. The size distribution of the particles broadens and becomes bimodal as the temperature is increased to 950 C. This suggests that by controlling the annealing temperature, the dispersion of Si-NC's can be controlled. The results are supported by selected area diffraction (SAED) studies and micro photoluminescence (PL) spectroscopy. The discussion of effect of particle size distribution on PL spectrum is presented based on tight binding approximation (TBA) method using Gaussian and log-normal distribution of particles. The study suggests that the dispersion and consequently emission energy varies as a function of particle size distribution and that can be controlled by annealing parameters.
Journal of Applied Physics, 2017
Thin films consisting of silicon nanocrystals fabricated by high silicon content in silicon rich oxide show unique properties of decreasing resistivity and increasing light absorption while maintaining quantum confinement effects. With that said, the effect of the annealing temperature and doping element on the microscopic structure of silicon nanocrystals (Si NCs) and the film are still under research. In this study, individual intrinsic, boron-, and phosphorus-doped films are annealed at various temperatures, and their structural properties are analyzed via atom probe tomography together with glancing incidence x-ray diffraction, Raman spectroscopy (Raman), transmission electron microscopy (TEM), and energy filtered TEM. In addition, photoluminescence (PL) is performed and linked with their microstructural properties. The Si NC growth is confirmed at annealing temperatures of 1000 °C and 1100 °C. The microstructure of the Si NCs in the whole film is dramatically changed by increas...
Silicon Nanocrystal Nucleation as a Function of the Annealing Temperature in SiOx Films
MRS Proceedings
Si nanocrystals (Si-nc) embedded in amorphous silica matrix have been obtained by thermal annealing of substoichiometric SiOx films, deposited by PECVD (plasma enhanced chemical vapour deposition) technique with different amount of Si concentrations (42 and 46 at.%). Both nucleation and evolution of Si-nc together with the changes of the amorphous matrix have been studied as a function of the annealing temperature. The comparison of x-ray absorption measurements in Total Electron Yield (TEY) mode at the Si k-edge with photoluminescence (PL), FTIR and Raman spectra, allowed clarifying the processes of Si-nc formation and structural evolution as a function of the annealing temperature and Si content.
Lamp annealing effects on the formation process of implanted silicon nanocrystals in SiO 2
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2007
Si ion implantation into SiO2 and subsequent high temperature anneals induce the formation of embedded luminescent Si nanocrystals. The potentialities of rapid thermal annealing to enhance the photoluminescence as well as those to induce low temperature formation of luminescent Si nanocrystals have been investigated. Si ion implantation was used to synthesize specimens of SiO2 containing supersaturated Si with different concentrations,
Bulletin of the Russian Academy of Sciences: Physics, 2011
The effect of annealing on the ion beam synthesis of silicon nanocrystals in Si layers was investi gated by low frequency Raman scattering (RS). The occurrence of crystal nuclei in a matrix of glass results in an additional contribution to density of the acoustic vibrational states associated with the surface vibra tional modes of nanocrytals. The low frequency RS caused by interaction of light with acoustic vibration modes of nanoparticles is an effective method of research. The low frequency Raman spectra show that the samples do not have a smooth distribution of nanoparticle size, but have two specific sizes of nanoparticles, 3 and 6 nm.
Journal of Applied Physics, 2006
The formation and subsequent growth of crystalline silicon nanoclusters ͑Si-ncs͒ in annealed silicon-rich silicon oxides ͑SRSOs͒ were studied by glancing angle x-ray diffraction. SRSO samples with Si concentrations ͑y͒ of 0.40, 0.42, and 0.45 were grown by inductively coupled plasma-enhanced chemical-vapor deposition ͑PECVD͒. Samples with y = 0.42 grown by electron-cyclotron-resonance PECVD were also studied. Annealing treatments were performed at temperatures ͑T͒ of 900, 1000, and 1100°C for times ͑t͒ between 0.5 and 3 h in flowing Ar. As-grown SRSO films did not present signs of Si clusters ͑amorphous or crystalline͒; however, ͑111͒, ͑220͒, and ͑311͒ Bragg peaks corresponding to c-Si were clearly seen after annealing at 900°C for the y = 0.45 sample, but only barely seen for the y = 0.42 and undetected for the y = 0.40 samples. For T = 1000°C, all studied SRSO samples clearly showed the c-Si diffraction peaks, which became narrower with increasing t and T. From the width of the Si ͑111͒ peaks, the mean size of Si-ncs and their dependence on T and t was determined. Activation energies were deduced from the T dependence by fitting the results to two growth models of Si precipitates in an a-SiO 2 matrix reported in the literature. The activation energies qualitatively agree with values deduced from transmission electron microscopy studies of annealed SRSO reported in the literature. However, they are significantly lower than Si diffusion activation energies available in the literature for SiO 2 with low excess Si. A broad feature is also observed in the x-ray diffractograms for as-grown samples with low y, which shifts to the peak position corresponding to a-SiO 2 with increasing T. This behavior is explained by the formation of a well-defined a-SiO 2 phase with increasing T, where mixed Si-O 4−n Si n ͑n = 1,2,3͒ tetrahedra in the as-grown alloy are gradually converted into Si-O 4 and Si-Si 4 as phase separation of Si and SiO 2 proceeds. From the measured Si ͑111͒ peak positions, small Si-ncs are found to be tensilely strained by as much as ϳ0.8%. This effect becomes insignificant as Si-ncs become larger with increasing y or T.