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J. Campmany

Bio: J. Campmany is an academic researcher from University of Barcelona. The author has contributed to research in topics: Thin film & Amorphous silicon. The author has an hindex of 8, co-authored 23 publications receiving 186 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the effects of plasma processing conditions on the microstructural properties of silicon powders are presented, which reveal an increase in hydrogen content and a reduction in volume/surface ratio as the modulation frequency of RF power increases.
Abstract: The effects of plasma processing conditions on the microstructural properties of silicon powders are presented. Hydrogenated nanophase silicon powders were prepared using low-pressure and low-temperature square wave modulated RF plasma (13.56 MHz) using pure silane gas. Plasma parameters such as pressure, RF power, plasma modulation frequency, and gas flow rate were varied. In situ analysis by quadrupolar mass spectroscopy and ex situ analysis of the silicon powders by Fourier transform infrared spectroscopy (FTIR) and thermal desorption spectrometry of hydrogen were performed. The thermal desorption spectrometry results show the fundamental differences between the concentrations of hydrogen weakly and strongly bonded in silicon powders as compared to amorphous silicon films. The FTIR analysis also determined the microstructural characteristics of powders and hence their volume/surface ratio. This parameter was determined from the balance of Pj probabilities of having one of the Hj-Si-Si4-j bond arrangements in the powder particles. These results reveal an increase in hydrogen content and a reduction in volume/surface ratio as the modulation frequency of RF power increases. In consequence, higher compactness of silicon powders is associated with long particle residence times inside the plasma as a result of ion bombardment. TEM analysis indicated a considerable dispersion of particle size and some degree of structure of the silicon powder characterized by intergrain linkage. We point out the dominant presence of hydrogen on the particle surfaces (external voids), which may cause the high reactivity of grains, increasing the degree of intergrain linkage.

36 citations

Journal ArticleDOI
01 Oct 1994-Vacuum
TL;DR: In this article, nanoscale amorphous silicon powder was prepared in a specially designed plasma reactor, operating with square-wave modulation (SQWM) of the rf power at low pressure and low temperature.

18 citations

Journal ArticleDOI
TL;DR: In this paper, a qualitative model is presented, which points up the importance of plasma negative ions in the deposition of hydrogenated amorphous silicon (a•Si:H) from SQWM rf discharges through their influence on powder particle formation.
Abstract: Hydrogenated amorphous silicon (a‐Si:H) thin films have been obtained from pure SiH4 rf discharges by using the square wave modulation (SQWM) method. Film properties have been studied by means of spectroellipsometry, thermal desorption spectrometry, photothermal deflection spectroscopy and electrical conductivity measurements, as a function of the modulation frequency of the rf power amplitude (0.2–4000 Hz). The films deposited at frequencies about 1 kHz show the best structural and optoelectronic characteristics. Based upon the experimental results, a qualitative model is presented, which points up the importance of plasma negative ions in the deposition of a‐Si:H from SQWM rf discharges through their influence on powder particle formation.Hydrogenated amorphous silicon (a‐Si:H) thin films have been obtained from pure SiH4 rf discharges by using the square wave modulation (SQWM) method. Film properties have been studied by means of spectroellipsometry, thermal desorption spectrometry, photothermal deflection spectroscopy and electrical conductivity measurements, as a function of the modulation frequency of the rf power amplitude (0.2–4000 Hz). The films deposited at frequencies about 1 kHz show the best structural and optoelectronic characteristics. Based upon the experimental results, a qualitative model is presented, which points up the importance of plasma negative ions in the deposition of a‐Si:H from SQWM rf discharges through their influence on powder particle formation.

16 citations

Journal ArticleDOI
J. Campmany1, J.L. Andújar1, Adolf Canillas1, J. Cifre1, Enric Bertran1 
TL;DR: In this paper, a comparative study of the vibrational properties of PECVD amorphous silicon nitride films obtained from SiH 4 + NH 3 and SiH4 + N 2 precursor gas mixtures has been performed by FT-IR transmission spectroscopy.
Abstract: A comparative study of the vibrational properties of PECVD amorphous silicon nitride films obtained from SiH 4 + NH 3 and SiH 4 + N 2 precursor gas mixtures has been performed by FT-IR transmission spectroscopy. The bonded hydrogen, calculated from the absorption spectra, shows important quantitative and qualitative differences depending on the precursor gas mixtures used. The hydrogen content of near-stoichiometric films obtained from SiH 4 + N 2 mixture is 10 times lower than that of films prepared from SiH 4 + NH 3 mixture. In addition, hydrogen is mainly bonded to nitrogen atoms in films from SiH 4 + NH 3 , whereas it is mainly bonded to silicon atoms in films from SiH 4 + N 2 . These low-hydrogenated silicon nitride films, obtained from mixtures containing N 2 , have been applied as insulator layers in the preparation of amorphous silicon thin-film transistors (a-Si TFTs). The TFTs were of normal staggered type composed of the structure Al/a-SiN:H/a-Si:H grown on NiCr source and drain electrodes deposited on glass substrates. TFTs with a 0.2 μm thick a-Si:H layer and 10 μm channel length have on-off current ratios of 5 × 10 4 , electron field-effect mobilities of about 1.5 cm 2 /V s and threshold voltages around 5 V.

15 citations

Journal ArticleDOI
TL;DR: In this paper, phase modulated spectroscopic ellipsometry in the UV-visible range was used to characterize silicon dioxide and silicon oxynitride thin films on crystalline silicon substrates.

14 citations


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Journal ArticleDOI
TL;DR: In this article, the authors review the advances in the development of plasma processes and plasmasystems for the synthesis of thin film high and low index optical materials, and in the control of plasma surface interactions leading to desired film microstructures.
Abstract: Plasma enhanced chemical vapor deposition(PECVD) is being increasingly used for the fabrication of transparent dielectric optical films and coatings. This involves single-layer, multilayer, graded index, and nanocomposite optical thin filmsystems for applications such as optical filters, antireflective coatings, optical waveguides, and others. Beside their basic optical properties (refractive index, extinction coefficient, optical loss), these systems very frequently offer other desirable “functional” characteristics. These include hardness, scratch, abrasion, and erosion resistance, improved adhesion to various technologically important substrate materials such as polymers, hydrophobicity or hydrophilicity, long-term chemical, thermal, and environmental stability, gas and vapor impermeability, and others. In the present article, we critically review the advances in the development of plasma processes and plasmasystems for the synthesis of thin film high and low index optical materials, and in the control of plasma–surface interactions leading to desired film microstructures. We particularly underline those specificities of PECVD, which distinguish it from other conventional techniques for producing optical films (mainly physical vapor deposition), such as fabrication of graded index (inhomogeneous) layers, control of interfaces, high deposition rate at low temperature, enhanced mechanical and other functional characteristics, and industrial scaleup. Advances in this field are illustrated by selected examples of PECVD of antireflective coatings, rugate filters, integrated optical devices, and others.

542 citations

Journal ArticleDOI
TL;DR: An overview of dynamic self-organization phenomena in complex ionized gas systems, associated physical phenomena, and industrial applications is presented in this paper, where the most recent experimental, theoretical, and modeling efforts to understand the growth mechanisms and dynamics of nano- and micron-sized particles, as well as the unique properties of the plasma-particle systems (colloidal, or complex plasmas) and the associated physical effects are reviewed and the major technological applications of micro- and nanoparticles are discussed.

322 citations

Journal ArticleDOI
TL;DR: In this paper, a multichannel spectroscopic ellipsometer based on the rotating-compensator principle was developed and applied to measure the time evolution of spectra (1.5 − 4.0 eV) in the normalized Stokes vector of the light beam reflected from the surface of a growing film.
Abstract: A multichannel spectroscopic ellipsometer based on the rotating-compensator principle was developed and applied to measure the time evolution of spectra (1.5–4.0 eV) in the normalized Stokes vector of the light beam reflected from the surface of a growing film. With this instrument, a time resolution of 32 ms for full spectra is possible. Several advantages of the rotating-compensator multichannel ellipsometer design over the simpler rotating-polarizer design are demonstrated here. These include the ability to: (i) determine the sign of the p-s wave phase-shift difference Δ, (ii) obtain accurate Δ values for low ellipticity polarization states, and (iii) deduce spectra in the degree of polarization of the light beam reflected from the sample. We have demonstrated the use of the latter spectra to characterize instrument errors such as stray light inside the spectrograph attached to the multichannel detector. The degree of polarization of the reflected beam has also been applied to characterize the time evo...

195 citations

Patent
17 Jun 2005
TL;DR: In this paper, a method for the synthesis of single-crystal semiconductor nanoparticles, including photoluminescent silicon nanoparticles with diameters of no more than 10 nm, is described.
Abstract: Methods and apparatus for producing nanoparticles, including single-crystal semiconductor nanoparticles, are provided. The methods include the step of generating a constricted radiofrequency plasma in the presence of a precursor gas containing precursor molecules to form nanoparticles. Single-crystal semiconductor nanoparticles, including photoluminescent silicon nanoparticles, having diameters of no more than 10 nm may be fabricated in accordance with the methods.

191 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the application of LPCVD and PECVD in microstructures and their application in functional and ion sensitive films, including passivation films.
Abstract: After discussion of the basic aspects of CVD and its reaction kinetics LPCVD and PECVD will evolve as techniques commonly used at high temperature and lower temperature , respectively. Films deposited by these two techniques differ in several aspects, i.e., thickness, uniformity, purity, density, electrical properties, adhesion, step coverage, etc. Reactor designs are discussed in brief for optimization of the process parameters to yield optimized film properties. Then each of the major film materials such as polysilicon, SiN, , , SiC and some exotics such as diamond films are discussed with respect to their application in microstructures and their film properties in dependence on the deposition technique and follow-on processing, e.g., internal stresses due to imperfection in structure and composition or clamping, film density, pinhole density, and etchability. The discussion then moves to the application of LPCVD and PECVD in microstructures. A few typical examples will be presented for functional layers: films for membranes, cantilevers, etc in mono- and heterostructures, or ion sensitive films including passivation films as used in many sensors (e.g., microphones) and actuators (e.g., micromotors), especially such as fabricated by surface micromachining. Some room is also given to SiC, a new micromechanical material. A summary and weighting of the two CVD techniques is given.

160 citations