1,720,961 research outputs found
Formation mechanism of crystallites in the as-deposited mixed-phase low pressure chemical vapor deposition silicon thin films
No full textTransmission electron microscopy study on the microstructure of silicon thin films, deposited at temperature ranges of 565 degrees C similar to 600 degrees C and at 200 mTorr by low pressure chemical vapor deposition and annealed at 570 degrees C, was carried out so that the formation mechanism of crystallites observed in as-deposited mixed-phase silicon thin films could be proposed. Crystallites were observed only at the Si/SiO2 interface in the as-deposited silicon thin film deposited at 570 degrees C for 28 min. Their size was about 20 nm and they had an irregular shape. Areal density of crystallites in the as-deposited film was about 4 X 10(10)/cm(2), but that in the film deposited as an amorphous phase and annealed at 570 degrees C for 2 h was about 2x10(9)/cm(2). No remarkable crystal growth occurred in the film deposited at 570 degrees C for 28 min and then annealed at 570 degrees C for 1 h. Two kinds of crystallites were observed in the film annealed at 570 degrees C for 3 h. The first, observed only at the Si/SiO2 interface, had an irregular shape, and the second, grown through the entire thickness of the film, had an elongated elliptical shape. On the basis of above results? it was proposed that crystallites observed in as-deposited silicon thin films were formed not because silicon films deposited as an amorphous phase had been annealed during the deposition process, but because silicon films were deposited as a crystalline phase at the initial stage of the deposition process and then deposited as an amorphous phase after the initial stage of the deposition process. (C) 1996 American Institute of Physics
Fabrication of thin film transistors using a Si/Si1-xGex/Si triple layer film on a SiO2 substrate
No full textA novel approach that can reduce the thermal budget in the fabrication of thin film transistors (TFT's) using a Si/Si0.7Ge0.3/Si triple film as an active layer was proposed. The crystallization behavior of the triple film was described and device characteristics of Si/Si0.7Ge0.3/Si TFT's were compared with those of Si TFT's and of SiGe TFT's. The triple film was completely crystallized only after a 25-h anneal at 550 degrees C, N-channel polycrystalline Si/Si0.7Ge0.3/Si TFT's had a field-effect mobility of 57.9 cm(2)/Vs and an I-on/I-off ratio of 5.7 x 10(6). This technique provides not only a shorter time processing capability than Si TFT's technology but also superior device characteristics compared to SiGe TFT's
Structural modification of a trench by hydrogen annealing
No full textThe structural change of a trench by hydrogen ambient thermal annealing was investigated from the viewpoint of crystallographic orientation change and stress relaxation. By short-time hydrogen ambient annealing, structural stresses within sharp corner regions were relaxed, and new crystal planes were formed by surface energy minimization. The thermal oxide thickness difference at the corner region diminished mainly with the annealing temperature. Surface migration of silicon atoms was confirmed by the reduction in the surface roughness on the sidewall after the hydrogen annealing and by the crystalline reorientation of the silicon surface at the concave corner region. Migrated atoms on the crystal surfaces formed specific crystal planes, such as the (111) and the (113) low-index planes. On surfaces where atomic migration occurred, steps were mainly formed on (111) plane groups. By applying hydrogen annealing to the trench process, we were able to achieve stress relaxation and reliable oxide growth because of silicon atomic migration
INFLUENCE OF TIAS PRECIPITATE FORMATION ON MORPHOLOGY DEGRADATION OF THE TISI2/AS-DOPED POLYSILICON SYSTEM
No full textThe formation of TiAs precipitates between TiSi2 with C54 structure and arsenic-doped polysilicon and the influence of TiAs and silicon resulting from the reaction TiSi2 + As --> TiAs + 2Si on layer morphology degradation have been studied. The formation of TiAs precipitates has been revealed by X-ray diffraction in a sample annealed at 900-degrees-C for 60 min and a sequential increase in sheet resistance with increasing annealing time has been observed. Cross-sectional scanning electron microscopy of the sample annealed for 60 min has shown irregular-shaped protrusions. Point analyses by Auger electron spectroscopy and cross-sectional transmission electron microscopy of the same sample have shown the presence of TiAs precipitates and extra silicon near the TiSi2 - polysilicon interface under the protrusion area. From the results it has been found that TiAs precipitates and extra silicon resulting from the reaction TiSi2 + As --> TiAs + 2Si lead to morphology degradation of this system
THIN-FILM TRANSISTORS WITH POLYCRYSTALLINE SILICON PREPARED BY A NEW ANNEALING METHOD
No full textA new annealing method, nucleation by rapid thermal annealing (RTA) and grain growth in furnace annealing, has been developed to obtain high-quality polycrystalline silicon (poly-Si) and to reduce the long annealing time for solid-phase crystallization (SPC) of amorphorus silicon (a-Si) film without a decrease in grain size. Poly-Si thin-film transistors (TFTs) were fabricated using this method and the electrical properties of poly-Si film were evaluated. We obtained higher field effect mobility (25 cm2/(V.s)) and better uniformity (less-than-or-equal-to 5% in 5-inch wafer) than those obtainable by the conventional furnace annealing
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
STRUCTURAL AND OPTICAL-PROPERTIES OF MICROCRYSTALLINE SILICON FILMS DEPOSITED BY PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION
No full textHydrogenated microcrystalline (mu c) silicon films were prepared by plasma enhanced chemical vapour deposition using an Ar-diluted SiH4 gas at various deposition conditions. The substrate temperature and RF power were varied from 150 to 400 degrees C and from 10 to 120 W, respectively. Structure and microstructure were examined by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Hydrogen bonding and optical properties were investigated by FTIR spectra and UV transmission spectra. The crystal fraction of the films increased as the deposition temperature decreased and RF power increased. More definite columnar morphology was developed with increasing crystal fraction. The existence of mu c-Si above a critical RF power ( > 30 W) suggests that SiH2 radical in plasma plays an important role for the formation of columnar morphology and mu c-Si. IR absorption analysis showed that the SiH2/SiH bonding ratio in the silicon films increased as the crystal fraction increased. The UV absorption coefficient of the films became smaller as the deposition temperature and RF power increased
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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