Crystallization of amorphous Si films by pulsed laser annealing and their structural characteristics

Peng, Ying; Fu, Guangsheng; Yu, Wei; Li, S Q; Wang, Y L

doi:10.1088/0268-1242/19/6/018

Cited by 20 publications

(10 citation statements)

References 11 publications

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“…One can observe that the c-Si peak remained whatever the power density suggesting that the structure of the SiN x thin layer was definitively modified. This is then explained by the formation of small crystalline Si-np in the spot of the focused laser as observed elsewhere [45,50,51]. Moreover, one can notice that, for the same excitation densities, all baselines levels significantly dropped after the local formation of small Si nanocrystals.…”

Section: Resultssupporting

confidence: 71%

Structural and optical characterization of pure Si-rich nitride thin films

et al. 2013

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The specific dependence of the Si content on the structural and optical properties of O- and H-free Si-rich nitride (SiNx>1.33) thin films deposited by magnetron sputtering is investigated. A semiempirical relation between the composition and the refractive index was found. In the absence of Si-H, N-H, and Si-O vibration modes in the FTIR spectra, the transverse and longitudinal optical (TO-LO) Si-N stretching pair modes could be unambiguously identified using the Berreman effect. With increasing Si content, the LO and the TO bands shifted to lower wavenumbers, and the LO band intensity dropped suggesting that the films became more disordered. Besides, the LO and the TO bands shifted to higher wavenumbers with increasing annealing temperature which may result from the phase separation between Si nanoparticles (Si-np) and the host medium. Indeed, XRD and Raman measurements showed that crystalline Si-np formed upon 1100°C annealing but only for SiNx<0.8. Besides, quantum confinement effects on the Raman peaks of crystalline Si-np, which were observed by HRTEM, were evidenced for Si-np average sizes between 3 and 6 nm. A contrario, visible photoluminescence (PL) was only observed for SiNx>0.9, demonstrating that this PL is not originating from confined states in crystalline Si-np. As an additional proof, the PL was quenched while crystalline Si-np could be formed by laser annealing. Besides, the PL cannot be explained neither by defect states in the bandgap nor by tail to tail recombination. The PL properties of SiNx>0.9 could be then due to a size effect of Si-np but having an amorphous phase.

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Section: Resultssupporting

confidence: 71%

Structural and optical characterization of pure Si-rich nitride thin films

et al. 2013

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“…Such an evolvement of an effectively two‐dimensional meander network and the growth of the structures with increasing laser fluence is also found for laser‐sintered films of Si nanoparticles, for SiGe alloy nanoparticles and for composite powders of Si and Ge nanoparticles. Very similar structures have been reported in the literature for other materials, many of them in the context of (pulsed) laser‐sintering . The formation of these particular structures is caused by surface tension effects.…”

Section: Processing To Nanocrystalline Bulk and Laser‐sintered Thin Fsupporting

confidence: 77%

Silicon‐based nanocomposites for thermoelectric application

Schierning

Stoetzel

Chavez

et al. 2016

Physica Status Solidi (a)

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Here we present the realization of efficient and sustainable silicon‐based thermoelectric materials from nanoparticles. We employ a gas phase synthesis for the nanoparticles which is capable of producing doped silicon (Si) nanoparticles, doped alloy nanoparticles of silicon and germanium (Ge), SixGe1–x, and doped composites of Si nanoparticles with embedded metal silicide precipitation phases. Hence, the so‐called “nanoparticle in alloy” approach, theoretically proposed in the literature, forms a guideline for the material development. For bulk samples, a current‐activated pressure‐assisted densification process of the nanoparticles was optimized in order to obtain the desired microstructure. For thin films, a laser annealing process was developed. Thermoelectric transport properties were characterized on nanocrystalline bulk samples and laser‐sintered‐thin films. Devices were produced from nanocrystalline bulk silicon in the form of p–n junction thermoelectric generators, and their electrical output data were measured up to hot side temperatures of 750 °C. In order to get a deeper insight into thermoelectric properties and structure forming processes, a 3D‐Onsager network model was developed. This model was extended further to study the p–n junction thermoelectric generator and understand the fundamental working principle of this novel device architecture. Gas phase synthesis of composite nanoparticles; nanocrystalline bulk with optimized composite microstructure; laser‐annealed thin film.

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“…Laser annealing has been widely used to rapidly induce crystal nucleation in amorphous silicon films. [28][29][30] In the case of organic materials, there are few reports of successfully annealing crystal imperfections by inducing preferred molecular arrangements. [31][32][33] In this study on cryomilled Griseofulvin sample 1 using focused 632.8 nm laser irradiation, the most pronounced annealing occurred after only 30 min of exposure, as is evident from Fig.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic and X-Ray Diffraction Study of Structural Disorder in Cryomilled and Amorphous Griseofulvin

et al. 2011

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Structural disorder induced by cryogenic milling and by heating to the amorphous phase in the active pharmaceutical ingredient Griseofulvin has been studied using Raman spectroscopy, X-ray powder diffraction (XRPD), and fluorescence spectroscopy. A broad, exciting-frequency-independent scattering background in the Raman spectra and changes in intensities and splitting of some of the Raman lines due to lattice and molecular modes have been observed. In the cryomilled samples this strong background is deconvoluted into two components: one due to lattice disorder induced by cryomilling and the other due to Mie scattering from nanosized crystallites. A single-component background scattering attributed to lattice disorder is seen in the Raman spectrum of the amorphous sample. Fluorescence measurements showed an intrinsic fluorescence signal in as-received Griseofulvin that does not correspond to the inelastic background in the Raman spectra and, moreover, decreases in intensity upon cryomilling, thus excluding an assignment of the Raman background intensity to impurity- or molecular-defect-induced fluorescence. Wide-angle XRPD measurements on cryomilled Griseofulvin shows a broad two-component background consistent with the background-scattering component in the Raman data associated with lattice disorder, but at longer correlation lengths. Persistence of this disorder to even longer lengths is evident in small-angle synchrotron XRPD data on micronized Griseofulvin taken as a function of temperature from the crystalline to the amorphous phase.

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Crystallization of amorphous Si films by pulsed laser annealing and their structural characteristics

Cited by 20 publications

References 11 publications

Structural and optical characterization of pure Si-rich nitride thin films

Structural and optical characterization of pure Si-rich nitride thin films

Silicon‐based nanocomposites for thermoelectric application

Spectroscopic and X-Ray Diffraction Study of Structural Disorder in Cryomilled and Amorphous Griseofulvin

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