Effects of tin doping on crystallization of amorphous silicon were studied using Raman scattering, Auger spectroscopy, scanning electron microscopy, and X-ray fluorescence techniques. Formation of silicon nanocrystals (2–4 nm in size) in the amorphous matrix of Si1−xSnx, obtained by physical vapor deposition of the components in vacuum, was observed at temperatures around 300 °C. The aggregate volume of nanocrystals in the deposited film of Si1−xSnx exceeded 60% of the total film volume and correlated well with the tin content. Formation of structures with ∼80% partial volume of the nanocrystalline phase was also demonstrated. Tin-induced crystallization of amorphous silicon occurred only around the clusters of metallic tin, which suggested the crystallization mechanism involving an interfacial molten Si:Sn layer.

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This paper reviews the impact of doping silicon with substitutional tin impurities on the formation of intrinsic and extrinsic lattice defects. The two major topics covered are ͑i͒ the effect on the diffusivity and aggregation/precipitation of interstitial oxygen in Czochralski ͑CZ͒ silicon and ͑ii͒ the formation of stable radiation defects in irradiated Sn-doped material. As demonstrated, the compressive stress associated with incorporating a large Sn atom on a lattice site is the basic feature governing the interactions with point defects. Consequently, Sn acts as a selective vacancy trap, while, in contrast, not affecting interstitial reactions. This leads to a reduced formation of oxygen thermal donors in n-type Si and lowers the concentration of vacancy-oxygen and divacancy centers in irradiated material. Enhanced oxygen precipitation has been noted around 750°C in p-type CZ silicon. Furthermore, specific Sn-related radiation defects are introduced, which question the use of doping with tin as a technique for substrate hardening.

A deep level transient spectroscopy study of defects created by 61 MeV proton irradiation of tin-doped n-type Czochralski silicon is reported. A comparison is made with the deep levels observed in irradiated p–n junction diodes fabricated in n-type float-zone silicon, without tin doping. The main conclusions are that in Sn-doped material, at least two additional deep radiation centers are introduced at 0.29±0.01 and 0.61±0.02 eV below the conduction band. From annealing experiments, it is concluded that these electron traps dissociate below 120 °C, which is lower than observed before for Sn–V related levels. It is demonstrated that the introduction rates of the well-known radiation defects are significantly smaller in Sn-doped material.

Formation of Si nanocrystals in amorphous Si-metallic Sn film structures has been studied experimentally, by using the Auger spectroscopy, electron microscopy, and Raman scattering methods. The results are analyzed in comparison with recent results on the crystallization of tin-doped amorphous Si. A mechanism of silicon transformation from the amorphous to the nanocrystalline state in the eutectic layer at the Si-Sn interface is proposed. The mechanism essence consists in a cyclic repetition of the processes of formation and decay of the Si-Sn solution. The application aspect of this mechanism for the fabrication of nanosilicon films used in solar cells is discussed. K e y w o r d s: silicon, nanocrystals, thin films, metal-induced crystallization, tin, solar cell.

An efficient technique for low temperature metal-induced nanocrystalline silicon fabrication is presented. The technique is based on laser annealing of thin films of “amorphous silicon-tin” composites combined with in situ control and monitoring with Raman technique. Laser annealing was shown to provide the possibility of fine-tuning the nanocrystals size and concentration, which is important in photovoltaic and thermoelectric devices fabrication.

Abstract

The beneficial influence of Sn doping of Si materials on the radiation hardness has triggered interest in this material. It is therefore essential to have a good insight in the impact of Sn on the fundamental defect behavior. This report gives a systematic study of the effect of the Sn impurities on the generation and annealing kinetics of oxygen-containing thermal donors formed during a 450ЊC anneal step. Special attention is given to the influence of a thermal preheat treatment at 800ЊC and the important role played by oxygen microfluctuations. The latter act as precursors for the thermal donor formation. The original Kaiser-Frisch-Reiss model, developed for explaining the experimental results in Sn-free Czochralski Si and based on hetero-and homogeneous precipitation processes, points to the beneficial role of Sn doping on the thermal donor properties.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-08 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-08 to IP