Kinetics of laser-induced low-temperature crystallization of amorphous silicon

A brief report on experimental and theoretical studies of the kinetics of the laser-induced crystallization (LIC) in undoped amorphous hydrogenated silicon is presented. It is shown that the LIC occurs at a substantially lower temperature and occurs at this temperature much faster compared to the thermal crystallization in a furnace. A nanoscopic kinetic electron-related model of the LIC is presented. The model explains the experimental observations as the integral effect of a huge amount of nanoscale picosecond atomic and electronic reconstructions leading to more stable material states which are generated by electron-assisted short-lived (picosecond) large energy fluctuations in nanometer material regions. (C) 2002 American Institute of Physics

ANHARMONIC INTERACTION IN ZINC SELENIDE

Experimental evidence of anomalous temperature dependence of the double phonon Raman spectrum is brought and explained by a 4th order anharmonic coupling between two 2-phonon states

Low Temperature Nanoscopic Kinetics of Hydrogen Plasma-Enhanced Crystallization of a-Si:H Films

A nanoscopic kinetic model of controlled plasma-assisted microcrystallite formation (PAmuCF) of Si in pre deposited a-Si:H films at low temperatures is proposed. The model suggests mechanisms for enhancement of the Si crystallization in a-Si:H films at low temperatures by treatment of the films in plasma. The model reveals certain kinetic advantages of hydrogen plasmas for the formation of Si crystalline nuclei in a-Si:H compared to other plasmas (Ar plasma, etc.). These advantages make the hydrogen plasma substantially more efficient in the PAmuCF of Si in a-Si:H films. The proposed mechanism for PAmuCF of Si is associated with the formation on the surface of the a-Si:H film and in the adjacent nanometer material layer of nanoscale (picosecond) short-lived hot spots of high energy density (or effective temperature). The hot spots are generated in the material by energetic plasma ions of energy epsilon(is)=20-100 eV accelerated by the electrical field in the thin plasma layer near the solid surface. The hot spots promote Si crystallization in a-Si:H. It is shown how the plasma composition, energy, mass, and fluxes of the plasma ions impinging on the surface of the a-Si:H film determine the Si nucleation rate and density of Si microcrystallization. (C) 2003 American Institute of Physics

PHONON-LINE-SHAPE AND DISORDER CORRELATION IN MIXED GaP1-xAsx

The disorder of GaP1-xAsx is evaluated from the double phonon spectrum and compared to the amorphous material

PROPRIÉTÉS OPTIQUES DU SULFURE DE ZINC CONTENANT DES MÉTAUX DE TRANSITION EN POSITION SUBSTITUTIONNELLE

Le manganèse se substitue au zinc dans le sulfure de zinc. Les fréquences des modes de vibration dus à la présence du Mn ont été déterminées par diffusion de la lumière. L'émission entre des niveaux électroniques 6A1 → 4T1 du Mn a été analysée à 2,4 K. Les modes récurrents qui assistent cette transition sont les modes de vibration de l'impureté. Celui qui a une symétrie Ɖ1 est prépondérant par rapport aux autres. Afin de déterminer la structure cristalline du ZnS : Mn, nous avons étudié l'émission du ZnS : Mn purement cubique et contenant des fautes d'empilement. Les propriétés vibratoires des impuretés substitutionnelles : Cr52, Mn55, Fe56, Ni59 et Co59 dans le ZnS, ont été analysées par diffusion Raman. Un comportement analogue à celui du manganèse a été observé. Un simple défaut de masse ne peut expliquer correctement nos résultats, et nous devons tenir compte de la variation des constantes de force.Manganese substitutes zinc in zinc sulfide. The Mn vibrational mode frequencies have been determined using Raman Scattering technics. The electronic transition emission between the 6A1 → 4T1 levels has been studied at 2.4K. The recurrents frequencies which assist this transition are the impurity vibrational modes ; the one with a Ɖ1 symmetry is preponderant with respect to the others. In order to determined the crystalline structure of ZnS : Mn, we have studied the emission of purely cubic ZnS : Mn and of material containing stacking faults. The Raman active vibrational modes of the substitutional ions : Cr52, Mn55, Fe56, Ni59, and Co59 in ZnS, have been studied. A behavior similar to that of the Mn has been observed. A single mass defect cannot explain our results and the variation of force constants has to be considered

Effects of doping on the kinetics of laser-induced low-temperature crystallization of amorphous silicon

Substantial effects of boron and phosphorus doping on the kinetics of laser-induced crystallization (LIC) in hydrogenated amorphous silicon (a-Si:H) are reported. A kinetic nanoscopic electron-related LIC model that suggests predictions and explanations of observed effects of B and P doping on the LIC temperatures and crystallite size in a-Si:H is presented. The LIC is considered to be the integral effect of a huge number of nanoscale picosecond material reconstructions, each of which is generated by a nanoscopic short-lived (picosecond) large-energy fluctuation. The LIC in doped a-Si:H occurs at temperatures substantially lower than those found in the crystallization in a furnace. Crystallite size in B-doped a-Si:H is half of that in P-doped and undoped material. (c) 2005 American Institute of Physics

Kinetics of CW laser-induced low temperature crystallization of amorphous silicon

A brief report on experimental and theoretical studies of the kinetics of the laser-induced crystallization (LIC) in undoped amorphous hydrogenated silicon is presented. It is shown that the LIC occurs at a substantially lower temperature and occurs at this temperature much faster compared to the thermal crystallization in a furnace. A nanoscopic kinetic electron-related model of the LIC is presented. The model explains the experimental observations as the integral effect of a huge amount of nanoscale picosecond atomic and electronic reconstructions leading to more stable material states which are generated by electron-assisted short-lived (picosecond) large energy fluctuations in nanometer material regions. (C) 2002 American Institute of Physics

PROPRIÉTÉS VIBRATOIRES DU SILICIUM DOPÉ PAR IMPLANTATION D'IONS

Les propriétés vibratoires du silicium implanté par des ions Si, P, A, Ga, As ont été étudiées par effet Raman. Les doses d'implantation varient de 1013 à 1016 ions/cm2 sous 80 keV. La perte d'énergie par unité de volume sous l'effet des processus nucléaires a été déterminée et est égale à 2,5 × 1024 eV/cm3. La profondeur de silicium rendu amorphe est comprise entre 500 et 1 000 Å. La température de guérison est comprise entre 550° et 595 °C.The vibrational properties of silicon implanted with Si, P, A, Ga and As have been studied using Raman spectroscopy. The implanted doses are included between 1013 and 1016 ions/cm2 under 80 keV. The energy deposited into nuclear processes per unit volume have been determined and is of the order of 2.5 × 1024 eV/cm3. The amorphous depth varies from 500Å to 1000 Å. The annealing temperature varies from 550 °C to 595 °C