Search

Hydrogenated microcrystalline silicon (μc-Si:H) thin films were prepared by remote low frequency inductively coupled plasma (ICP) chemical vapor deposition system, and the effect of silane/hydrogen ratio on the microstructure and electrical properties of μc-Si:H films was systematically investigated. As silane/hydrogen ratio increases, the crystalline volume fraction Fc decreases and the ratio of the intensity of (220) peak to that of (111) peak drops as silane flow rate is increased. The FTIR result indicates that the μc-Si:H films prepared by remote ICP have a high optical response with a low hydrogen content, which is in favor of reducing light-induced degradation effect. Furthermore, the processing window of the phase transition region for remote ICP is much wider than that for typical ICP. The photosensitivity of μc-Si:H films can exceed 100 at the transition region and this ensures the possibility of the fabrication of microcrystalline silicon thin film solar cells with a open-circuit voltage of about 700 mV. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hydrogenated silicon (Si:H) thin films were fabricated on glass substrates by low frequency inductively coupled plasma-assisted chemical vapor deposition using a silane precursor with low hydrogen dilution at room temperature. The crystallinity and microstructure properties of the Si:H thin films deposited at different inductive radio-frequency (rf) power density were systematically studied by Raman spectroscopy, x-ray diffraction, and scanning electron microscopy. We found that at a low rf power density of 16.7 to 20.8 mW/cm3, the structure of silicon thin films evolves from a completely amorphous phase to an intermediate phase containing both amorphous and microcrystalline silicon. As the power density is increased to a moderate value of 25 mW/cm3, a highly crystallized (111)-preferred hydrogenated microcrystalline silicon (μc-Si:H) film featuring a vertically aligned cone-shaped structure, is emerging. Both the crystallinity and deposition rate exhibit a monotonic increase with the increase in the rf power density, reaching a maximum value of 85% and 1.07 nm/s, respectively, at a power density of 41.7 mW/cm3. Scanning electron microscopy reveals that continuous and dense μc-Si:H films with grain size of tens to hundreds nanometers can be achieved deterministically without the formation of amorphous incubation layer, and this is of great importance for synthesis of multilayer structures in p-i-n solar cells. The formation mechanism of the μc-Si:H films and the elimination of the amorphous incubation layer are explained in terms of the high electron density and the plasma-surface interactions. [ABSTRACT FROM AUTHOR]

Anomalous hysteresis loops measured by longitudinal and polar magneto-optical Kerr effects (MOKE) were observed in a Co/NiO/Cu/Co/Cu structure. After excluding other possible mechanisms, we explain the anomalous hysteresis loops in terms of the opposite rotation angles for the top- and bottom-Co layers. Ultimately, the opposite rotation angles are likely caused by the different incidence angles for the top- and bottom-Co layers. [ABSTRACT FROM AUTHOR]

The influence of a nano-nitride-layer (NNL) doped at different interfaces in the structure of Cu/Co/Cu/Co/Cu on magnetoresistance (MR) is investigated. As the NNL is doped at the inner interfaces of the core Co/Cu/Co sandwich, an inverse MR is observed. This contrasts sharply with that doping at the two outer interfaces between the core sandwich (Co/Cu/Co) and the buffer or/and the capping layers. The result arises from the negative spin asymmetry induced by the NNL doping under different interfacial circumstances. Moreover, the MR value increases in magnitude as temperature is decreased from room temperature to 4.2 K. [ABSTRACT FROM AUTHOR]