The aim of this paper is to study the role of gold (Au) induced crystallization on amorphous silicon (a-Si) films produced by low pressure chemical vapor deposition (LPCVD) at low process temperatures (550 °C) to allow the use of glass substrates. Concerning the crystallization process Au was deposited by e-beam thermal evaporation over the silicon (Si), using different metal thickness, from 5 to 100 Å. The samples were then annealed at 450, 500 and 550 °C and the crystallization time was changed from 5 up to 30 h. The structure of the films was analyzed by X-ray diffraction (XRD) and spectroscopic ellipsometry (SE) while electrical conductivity measurements were performed to obtain the electrical properties of the films produced, namely the activation energy (EA) and how it changes with the Au thickness used. The data achieved show that the increase of the metal layer thickness decreases the time needed to get full crystallization. However this leads to lower conduction activation energy (EA) meaning that there is also an increase of Au incorporation that leads to the production of doped films. © 2004 Elsevier B.V. All rights reserved.

The aim of this paper is to study the role of different metals (aluminium, molybdenum, nickel and titanium) in inducing crystallization in films produced by LPCVD at high and low temperature processes and to compare the structural, morphological, optical and electrical properties of the various films produced. This work envisages the use of the most suitable conditions that lead to the production of films for optoelectronic applications such as solar cells. © 2003 Elsevier B.V. All rights reserved.

This work reports the use of undoped porous amorphous/nanocrystalline hydrogenated silicon (a/nc-Si:H) thin films produced by hot wire chemical vapour deposition (HW-CVD) as ethanol detector above 50ppm and as a primary fuel cell where a power of 4μW/cm2 was obtained in structures of the type glass/ITO/i-a-nc-Si:H/Al. The porous silicon looks like a sponge constituted by grains and cluster of grains that determines the type of surface morphology and the behaviour of the structure under the presence of vapour moisture. Apart from that, the detector/device performances will also depend on the type of interlayer and interfaces with the metal contacts. The sponge like structure adsorbs the OH groups in uncompensated bonds, which behave as donor-like carriers, leading to an increase in the current flowing through the material, directly dependent on the ethanol vapour pressure. The corresponding role of the components of the microstructure on this detector was investigated by spectroscopic impedance. The response time of the current of the sensor and its recovery time are in the range of 10-50s at room temperature. © 2004 Elsevier B.V. All rights reserved.

In this paper, we investigate the optoelectronic properties and the photodegradation of amorphous silicon films produced by the hot wire plasma assisted technique (HWPA-CVD). We observed that hydrogen dilution in the gas phase plays an important role in the time dependence of the photoconductivity, which is correlated with an enhancement of defect density. We also compare the degradation of these films with those produced by plasma enhanced and by hot wire chemical vapour deposition techniques (PECVD and HW-CVD) and we found lower time dependence for the photodegradation of the films produced by HWPA-CVD technique © 2003 Elsevier B.V. All rights reserved.

n/a

n/a

Despite of a growing interest in this material, until now the studies on polymorphous silicon (pm-Si:H) have been performed on small laboratory reactors working at 13.56 MHz. Envisaging an industrial application of pm-Si:H, the technology was transferred to a large area plasma enhanced chemical vapour deposition reactor (25 × 40 cm2) working at excitation frequencies of 13.56 and 27.12 MHz. The plasma was characterized by impedance probe measurements and the films were characterized by spectroscopic ellipsometry, infrared spectroscopy and hydrogen evolution experiments, which are techniques that allow a rapid and reliable identification of pm-Si:H structure. Conductivity measurements were also performed to determine their transport properties. The results show that scaling up using the 13.56 MHz was successfully done and pm-Si:H films were deposited at a growth rate of ≈ 12 nm/min. Moreover, by using the 27.12 MHz excitation frequency the growth rate was even further increased to above 18 nm/min, as desired for industrial production. © 2002 Elsevier Science B.V. All rights reserved.

This paper describes, for the first time, a method of producing polymorphous silicon (pm-Si:H) films by plasma-enhanced (PE) CVD, using an excitation frequency of 27.12 MHz. The aim is to produce, at high growth rates, nanostructured films that are more stable than the conventional amorphous or polymorphous silicon films grown by PECVD at 13.56 MHz. The processing data show that, at 27.12 MHz, the pm-Si:H films are produced close to the transition region from amorphous to microcrystalline silicon films, at a growth rate of about 0.3 nm s-1, using pressures above 160 Pa. Apart from that, the analysis of the exodiffusion, spectroscopic ellipsometry (SE), and micro Raman data reveal that these films are more dense and compact than the polymorphous films grown at 13.56 MHz.

This paper describes, for the first time, a method of producing polymorphous silicon (pm-Si:H) films by plasma-enhanced (PE) CVD, using an excitation frequency of 27.12 MHz. The aim is to produce, at high growth rates, nanostructured films that are more stable than the conventional amorphous or polymorphous silicon films grown by PECVD at 13.56 MHz. The processing data show that, at 27.12 MHz, the pm-Si:H films are produced close to the transition region from amorphous to microcrystalline silicon films, at a growth rate of about 0.3 nms-1, using pressures above 160 Pa. Apart from that, the analysis of the exodiffusion, spectroscopic ellipsometry (SE), and micro Raman data reveal that these films are more dense and compact than the polymorphous films grown at 13.56 MHz.

This work refers to a study performed on polymorphous silicon (pm-Si:H) at excitation frequencies of 13.56 and 27.12 MHz in a large area PECVD reactor. The plasma was characterised by impedance probe measurements, aiming to identify the plasma conditions that lead to produce pm-Si:H films. The films produced were characterised by spectroscopic ellipsometry, infrared and Raman spectroscopy and hydrogen exodiffusion experiments, which are techniques that permit the structural characterisation of the pm-Si films and to study the possible differences between the films deposited at 13.56 and 27.12 MHz. Conductivity measurements were also performed to determine the transport properties of the films produced. The set of data obtained show that the 27.12 MHz pm-Si:H can be grown at higher rates with less hydrogen dilution and power density, being the resulting films denser, chemically more stable and with improved performances than the pm-Si:H films grown at 13.56 MHz.