It incorporates referee's comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The

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This work reports upon the dilution effect of Ar + H2 on the microstructures, optical, and photovoltaic properties of the hydrogenated nanocrystalline silicon (nc-Si:H) thin films. High crystallinity (up to 82.6%) nc-Si:H thin films were fabricated from silane diluted by Ar + H2 in a low-frequency inductively coupled plasma (LFICP) facility at a low temperature of 300 °C. The substitution of H2 by Ar in the diluent gas leads to an increase of the deposition rate, grain size, and crystallinity, and a decrease of the optical bandgap. Varying the Ar content caused a fluctuation of the H concentration and a change of the preferential orientation from (111) to (220) in the synthesized thin films. These effects physically originated from changes of the Ar + H2 + SiH4 plasma environment in the LFICP system. The enhancement of the dissociation of SiH4/H2 molecules by ion Ar+ and the metastable state Ar* were discussed in terms of related chemical reactions between the diluent gases and silane. Furthermore, it was found that a heterojunction solar cell prototype based on the as-deposited nc-Si:H thin films exhibits an excellent photovoltaic response.

Nano-crystalline Si/SiO 2 multilayers were prepared by alternately changing the ultra-thin amorphous Si film deposition and the in situ plasma oxidation process followed by the post-annealing treatments. Well-defined periodic structures can be achieved with 2.5 nm thick SiO 2 sublayers. It is shown that the size of formed nano-crystalline Si is about 3 nm. Room temperature electroluminescence can be observed and the spectrum contains two luminescence bands located at 650 nm and 520 nm. In order to improve the hole injection probability, p-i-n structures containing a nanocrystalline Si/SiO 2 luminescent layer were designed and fabricated on different p-type substrates. It is found that the turn-on voltage of p-i-n structures is obviously reduced and the luminescence intensity increases by 50 times. It is demonstrated that the use of a heavy-doped p-type substrate can increase the luminescence intensity more efficiently compared with the light-doped p-type substrate due to the enhanced hole injection.

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Hydrogenated silicon suboxide (SiO x  : H) thin films are fabricated by a low-frequency inductively coupled plasma of hydrogen-diluted SiH4 + CO2 at a low temperature (100 °C). Introduction of a small amount of oxygen into the film results in a predominantly amorphous structure, wider optical bandgap, increased H content, lower conductivity and higher activation energy. The minority carrier lifetime in the SiO x  : H-passivated p-type Si substrate is up to 428 µs with a reduced incubation layer at the interface. The associated surface recombination velocity is as low as 70 cm s−1. The passivation behaviour dominantly originates from the H-related chemical passivation. The passivation effect is also demonstrated by the excellent photovoltaic performance of the heterojunction solar cell with the SiO x  : H-based passivation and emitter layers.

Raman spectroscopic imaging is a powerful label-free tool for studying cells and tissues in biology and medicine, but it suffers from extremely slow data acquisition. In this Letter, a novel multi-channel Raman imaging technique is proposed to speed up Raman acquisition. Wide-field Raman images are taken in multiple narrow-band channels, each through a different bandpass filter, simultaneously in one camera frame. Then Wiener estimation is used to quickly reconstruct the full Raman spectrum at each pixel from narrow-band measurements. The proposed system with four channels was evaluated in the mixtures of two and three chemicals exhibiting strong Raman scattering because of convenience in the verification of reconstructed spectra. This new technique is expected to overcome the limitation of traditional Raman spectroscopic imaging in speed, and expand its applications in the label-free analysis of both biological and non-biological samples, where potential species are known and fast imaging is required to investigate temporally varying events.

Amorphous and microcrystal hydrogenated intrinsic silicon (a-Si:H/μc-Si:H) thin films with good silicon surface passivation effect were deposited using a precursor gases of silane and hydrogen, which were discharged by low frequency inductively coupled high density plasma source. With regard to silicon surface passivation, the effect of discharge power on thin films properties, including the optical band gap, the crystal fraction, and bond configuration, as well as the deposition rate were thoroughly investigated. It was found that the best passivation effect was obtained at the region near the transition regime from a-Si:H to μc-Si:H with a minimized incubation layer between the passivation layer and substrate. Cz-silicon wafer passivated by as-deposited μc-Si:H thin films without any post-deposition thermal annealing possesses minority carrier lifetime of about 234 μs. This is attributed to the chemical annealing from the high-density hydrogen plasma during the deposition process. Subsequent thermal annealing in hydrogen flow increased the lifetime to 524 μs with a suppressed maximum surface recombination velocity of as low as 60 cm/s. Throughout the process flow covering the pre-deposition H plasma treatment, the film deposition from H2 diluted feedstock gases and the post-deposition annealing, hydrogen plays a vital role to enhance the minority carrier lifetime by improving the interface properties. The injection level dependent surface recombination velocity was also extracted from the lifetime measurement. The effectivity of the a-Si:H/μc-Si:H for silicon surface passivation in a practical heterojunction solar cell was further validated by the excellent photovoltaic performance.