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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Microsystem technologies 5 (1999), S. 151-156 
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract  Recent improvements in the quality of diamond films grown by Chemical Vapour Deposition (CVD) have made synthetic diamond a very attractive material for detection applications. In this paper, polycrystalline diamond films synthesised by microwave plasma enhanced CVD using a CH4–CO2 gas mixture, previously investigated as particle detectors, have been characterised by X-ray diffraction and Raman spectroscopy. The detector response was measured in vacuo under irradiation with 5.5 MeV α-particle from a 241Am source. A systematic study of the influence of the film structural properties on the detector performance has been carried out by changing the methane concentration in the growth plasma and the deposition temperature. The existence of a correlation between growth conditions, film texturing and detector performance has been demonstrated. Independently of the substrate temperature, (1 0 0) orientated films exhibit the lowest detection efficiencies. The meas ured collection distances are smaller than the average grain sizes and seem to be limited by trapping centres within the grains. These results are confirmed by Raman analysis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract  A detailed Raman analysis is carried out in order to explain the results of the systematic morphological and mechanical characterisation of unhydrogenated and hydrogenated amorphous carbon films prepared by the pulsed laser deposition at substrate temperatures ranging from 25 to 600°C. The carbon bonding modifications produced by the different deposition conditions are discussed via the quantitative analysis of the changes correspondingly induced into the shape of the Raman spectra. The indications coming from scanning electron microscopy, atomic force microscopy and hardness measurements are understood in terms of the different sp3- to sp2-bonding fraction attained and the role of both substrate temperature and growth ambient on the quality of the deposited films is clarified. The existence is demonstrated of a very narrow temperature window for the achievement of a high sp3-bond percentage in hydrogen-free films resulting in relevant hardness values and a correlation between mechanical strengths and shape of the Raman spectrum is tentatively established.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Microsystem technologies 1 (1994), S. 23-29 
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract The Π theorem of Dimensional Analysis, usually applied to the inference of physical laws, is for the first time applied to the derivation of interpolation curves of numerical data, leading to a simplified dependence on a reduced number of arguments Π, dimensionless combination of variables. In particular, Monte Carlo modelling of electron beam lithography is considered and the backscattering coefficient η addressed, in case of a general substrate layer, in the elastic regime and in the energy range 5 to 100 keV. The many variables involved (electron energy, substrate physical constants and thickness) are demonstrated to ultimately enter in determining η through asingle dimensionless parameter Π0. Thus, a scaling law is determined, an important guide in microsystem designing, indicating, if any part of the configuration is modified, how the other parameters should change (or “scale”) without affecting the result. Finally, a simple law η=83 Π0 is shown to account for all variations of the parameters over all substrates of the periodic table.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract  A detailed structural characterisation of synthetic diamond films, previously investigated as UV photodetectors, has been carried out by SEM, X-ray diffraction, catholuminescence (CL), micro-Raman spectroscopy and micro-photoluminescence. The films were deposited by microwave plasma enhanced chemical vapour deposition using a CH4–CO2 gas mixture. The effect of a systematic change of the methane concentration on film morphology, preferential orientation and crystal quality has been investigated at two different substrate temperatures, 750°C and 850°C. A strong decrease of both band-A CL and width of the diamond Raman line at 1332 cm-1 has been observed, at lower substrate temperature, going towards (1 0 0) texturing, consistent with the attribution of band-A luminescence to the presence of structural defects such as dislocations. A strong correlation between methane-induced texturing and UV detector performance has been evidenced: poorly oriented films exhibit a better UV photoresponse than highly textured films. Raman and luminescence measurements suggest that the limiting factor for the detector performance is related, rather than to structural defects to centres of different nature, whose density strongly depends on the sample preferential orientation.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 523-535 
    ISSN: 0392-6737
    Keywords: Electron scattering ; Numrrical approximation and analysis ; Distribution theory and Monte Carlo studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The typical problem is addressed of system and process modelling depending on a large number of variables. Demonstration is given that the number of independent variables can be dramatically reduced, by a modified application of Buckingham's theorem of dimensional analysis, resulting in a simplified formulation of the problem in terms of a limited number of dimensionless arguments. This simplified formulation eventually leads, by interpolation of numerical data, to the derivation of practical approximants to the physical laws governing the system or process. This approach is demonstrated, in case of electron scattering, through a general layer in the elastic regime, as modelled by Monte Carlo methods. In particular, a single dimensionless quality factor is introduced, allowing remarkable simplification both in forward and backward scattering analysis. Hence, Buckingam approximants are derived, effectively describing the scattering by universal laws, applicable to all elements of the periodic table and all variations of electron energy and layer thickness, in the ranges 5 to 150 keV and 1 to 3000 nm. The proposed method may be considered as a physical approximation, compared to purely mathematical methods, such as for example Padé approximants. As a consequence, the method is understandably highly effective, and may be extensively applied to all systems and processes susceptible to being described by mathematical modelling.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 10 (1988), S. 901-914 
    ISSN: 0392-6737
    Keywords: Multiphoton processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Il metodo della «space translation» (ST) usato frequentemente nell'interazione radiazione-materia in regimi di alta intensità è riconsiderato. Alcune limitazioni del programma di lavoro della ST nel calcolo delle ampiezze di transizione sono messe in evidenza. Viene anche considerata la teoria della diffusione da potenziale nell'ambito del metodo della ST e viene discusso un recente trattamento approssimato.
    Abstract: Резюме Заново рассмтривается метод трансляции пространства, часто используемый для изучения взаимодействия излучения с веществом в области высоких интенсивностей. Отмечаются ограничения обычного метода трансляции пространства, а также трудности, возникающие при вычислении амплитуд переходов. Исследуется теория потенциального рассеяния в присутствии сильного поля излучения в рамках метода трансляции иространства, а также обсуждаются недавние приближенные рассмотрения.
    Notes: Summary The space translation (ST) method frequently used to treat the radiation-matter interaction in the high-intensity domain is reconsidered. Limitations of the usual ST working program are pointed out together with the related difficulties in the evaluation of transition amplitudes. The theory of potential scattering in the presence of a strong radiation field within the ST method is considered as well, and a recent approximate treatment discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 663-676 
    ISSN: 0392-6737
    Keywords: Plasma production and heating by laser beams ; Other multiphoton processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The energy absorption rate by a classical homogeneous plasma irradiated by a strong fluctuating laser field via inverse bremsstrahlung is considered. A chaotic-field model is used and comparison is made with the fundamental model of a purely coherent field. In the present analysis, the emphasis is put on the interplay between the laser field statistics and the plasma electron energy distribution. Numerical calculations are concerned with the dependence of the energy absorption rates on laser intensity and frequency. Laser intensity values up to 4.6\1015 W/cm2 are considered. The multiphoton structure of the energy absorption is analysed as well. Concerning the joint influence of the radiation and particle statistics on the absorption rate, the basic result may be stated as follows. For situations where the particle thermal velocityv T is larger than the oscillatory velocityv 0 imparted by the field (v T ≥v 0, relatively weak field), the absorption rate is only weakly dependent on the field statistics. For situations, instead, whenv 0≫v T , which occurs for very high intensities, the reverse becomes true: now the initial particle velocity distribution plays the modest role of a velocity spread of an electron beam oscillating atv 0. In general, for very high intensities (v 0≫v T ), the energy absorption via bremsstrahlung becomes less effective because the high oscillatory velocityv 0 reduces the time available to electrons for the interaction with the ions, the third body which makes possible the exchange for energy between electrons and a radiation field. We report also, for the first time, results on the Marcuse effect for the case of a chaotic laser field, along with calculations of the absorption rate for a directed electron beam.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 15 (1993), S. 1345-1359 
    ISSN: 0392-6737
    Keywords: Integrated electronics ; VLSI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary An additive process using the three-level resist scheme for X-ray mask fabrication by electron beam lithography is analysed by Monte Carlo simulation of electron scattering. The resist exposure is calculated for specific e-beam test patterns aimed at 0.2μm resolution. The time evolution of the developed resist profiles is simulated by using a string model for dissolution. Relevant process variables such as e-beam energy (25 to 50 keV) and resist thickness are investigated. Simulation results demonstrate that 50 keV is altogether a preferred condition, compared to 25 keV, leading however to different pattern transfer techniques, according to resist thickness. The process modelling is compared with previously reported experimental results. Good qualitative agreement is found, indicating that modelling can be used as an effective aid in the quantitative evaluation of the process.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 15 (1993), S. 531-539 
    ISSN: 0392-6737
    Keywords: Integrated electronics ; VLSI ; Simulation and modeling of fabrication processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary In this paper the physical mechanisms of electron scattering in solids are studied, emphasis being placed on the processes relevant in electron spectroscopy and lithography. The essential features of the Monte Carlo approach to electron penetration are reviewed. Lithography applications are briefly discussed.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 1049-1059 
    ISSN: 0392-6737
    Keywords: Integrated electronics ; VLSI ; Simulation and modelling of fabrication processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Theoretical understanding of electron scattering phenomena is essential to the implementation of X-ray lithography. In this paper we theoretically investigate electron scattering effects in X-ray mask-making, by means of a subtractive process, in the 0.2 μm region. The results of Monte Carlo simulation are utilized in order to calculate radial absorbed energy distributions and resist development profiles with respect to some cases of practical interest. Relevant process variables are considered, such as electron-beam energy (10 to 30 keV) and spot sizes. The results show how, by choosing appropriate working conditions, high-resolution patterns can be obtained. Favourable process conditions are found at the low electron energy limit. However, it is shown that suitable electron-beam spot sizes are required in order to take fully advantage of the favourable properties of the scattering.
    Type of Medium: Electronic Resource
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