The use of thin films as sensing elements for microsensor applications has been shown very attractive due to their low-cost fabrication, potential for integration with standard CMOS technologies and possibility of deposition on different substrate types. In particular, piezoresistive sensors based on thin films have been commonly developed because can be easily implemented using microfabrication processes and present the best relation between sensitivity and system complexity, which showing great advantages in term of device integration. In our previous works (Fraga et al. 2010(Fraga et al. , 2011a, we studied undoped and nitrogen-doped PECVD a-SiC thin films as alternative materials to replace the silicon piezoresistors in strain and pressure sensors for harsh environments. Here, we focused our attention on the piezoresistive properties of sputtered silicon carbide (SiC), diamond-like carbon (DLC) and titanium dioxide (TiO 2 ) thin films. These materials were evaluated in terms of sensitivity or gauge factor and of the influence of the temperature on this sensitivity, allowing a preliminary analysis of the applicability of these thin films in high temperature piezoresistive sensors.
In order to evaluate the potential of amorphous silicon carbide (a-SiC) films for piezoresistive sensors applications, a pressure sensor has been developed based on this material. The deposition conditions and properties of a-SiC films deposited on thermally oxidized (100) Si substrates by two techniques enhanced by plasma, PECVD (plasma enhanced chemical vapor deposition) and RF magnetron sputtering, are briefly described and compared. Among the SiC films produced, we choose the nitrogendoped PECVD SiC film to fabricate the piezoresistors of the sensor. The structure of the sensor consists of six a-SiC piezoresistors, configured in Wheatstone bridge, on a SiO 2 / Si square diaphragm. The sensor was tested for applied pressure ranging from 0 to 12 psi and supply voltage of 12 V. A preliminary study of the influence of the temperature on the performance of the sensor was performed by experimental measurements and theoretical investigations.
a Because of their outstanding characteristics, diamond-like carbon (DLC) thin films have been recognized as interesting materials for a variety of applications. For this reason, the effects of the incorporation of different elements on their fundamental properties have been the focus of many studies. In this work, nitrogen-incorporated DLC films were deposited on Si (100) substrates by DC magnetron sputtering of a graphite target under a variable N 2 gas flow rate in CH 4 + N 2 + Ar gas mixtures. The influence of high N 2 flow ratios (20, 40 and 60%) on the chemical, structural and morphological properties of N-DLC films was investigated. Different techniques including field emission gun-equipped scanning electron microscope (FEG-SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), profilometry, Rutherford backscattering spectrometry (RBS) and Raman spectroscopy (325-nm and 514-nm excitation) were used to examine the properties of the N-DLC films. Thus, the incorporation of nitrogen was correlated with the morphology, roughness, thickness, structure and chemical bonding of the films. Overall, the results obtained indicate that the fundamental properties of N-DLC films are not only related to the nitrogen content in the film but also to the type of chemical bonds formed.
Understanding the magnitude of contribution and relationships of industrial quality components to yield by nitrogen stimulation can drive strategies with benefits to the food industry. The objective of this study is to measure and interpret the contribution and relationship dynamics of the components of oat industrial quality with grain and industry yield by nitrogen stimulation, partitioning the correlation values in direct and indirect effects by path diagnosis, in proposing strategies that promote benefits to the food industry. The study was conducted from 2011 to 2016, in a randomized block design with four replications in 4x2 factorial for nitrogen rates (0, 30, 60 and 120 kg ha-1) and oat cultivars (Barbarasul and Brisasul) in separate environments soybean/oat and corn/oat succession system. The increase of nitrogen promoted greater change in the mass of caryopsis in soybean/oat system and the thousand grain mass and number of grains greater than 2 mm in corn/oat system, with a tendency of reduction. In soybean/oat system, grain and industry yields can be simultaneously incremented by direct increase via one thousand grain mass and indirect increase by caryopsis mass. In corn/oat system the grain yield does not show any relationship with industrial quality variables. However, the industral productivity is benefited by the increase of the number of grains larger than 2 mm. The management proposition in the improvement of the grain and industry productivity characteristics by nitrogen is dependent on the high succession and reduced N-residual release systems
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