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Research paper : A new density standard replaced from water (K. Fujii)−195 Synthesiology - English edition Vol.1 No.3 (2009) films with 10 to 100 nm thickness formed on silicon substrate is successfully measured with a relative uncertainty of about 0.1 %. Using this principle, it became possible to evaluate the density of oxide films that are vapor-deposited by different methods, and to specify a particular film manufacturing condition that gives highest density for the oxide films[38].Moreover, improvements were made to the magnetic suspension densitometer mentioned in Section 3.3.3, and a new PVT property (pressure-density-temperature relation) measurement technology was developed at the AIST[39]. It cancels out the effect of diamagnetism of the sample fluid itself near-completely. This new magnetic suspension densitometer employs dual sinkers using germanium single-crystals that has different density from that of silicon single-crystals. They are used as sinkers, and measurements of PVT properties for working fluids and alternative refrigerants are being conducted with high accuracy.Table 3 shows the examples of application of these measurement technologies used in the silicon density standard. Thy were created only after the density standard using silicon single-crystals became available, and it would have been extremely difficult to develop them from a standard system based on water.7 ConclusionSince silicon single-crystals with near-perfect crystalline structure have excellent properties such as form stability and density stability, it can be used as the material for the solid density standard. AIST developed the technology for the absolute measurement of density from diameter and mass measurements of silicon spheres, and constructed a new density standard system replaced from water, through integration of comparative measurement techniques of density. These density measurement technologies were not only employed in the Standard Instrument Testing and certification according to Measurement Law, but also realized the traceability of the density measurement in JCSS. It is now contributing to maintenance of traceability for densimeters used in industry. The number of calibrations of density measuring instruments by JCSS is thus increasing steadily.Future issue is to advance this solid density standard system by integrating it with new evaluation technologies for material science and thermophysical properties, and to actively apply them for semiconductor industry and energy conservation.AcknowledgementIn conducting this research, I would like to thank the following people: Dr. Akira Ono, Vice-President of AIST (formerly the Head of Thermophysical Metrology Department, National Research Laboratory of Metrology) who worked on the construction of traceability system of density; Dr. Mitsuru Tanaka, Director of the National Metrology Institute of Japan, AIST (formerly the Chief of Fluid Properties Section, Thermophysical Metrology Department, National Research Laboratory of Metrology) who worked to introduce a silicon sphere and hydrostatic weighing apparatus; Senior Researcher Dr. Atsushi Waseda, Researchers Dr. Naoki Kuramoto and Dr. Yohei Kayukawa, and all others of the Fluid Properties Section, Material Properties and Metrological Statistics Division, NMIJ.Terminology(41)−Table 3. Development and application of new measurement technology for density comparison.Control of carbon gas emissionProtection of earth environmentDevelopment of energy conservation technologyEvaluation of thermophysical properties of working fluids and alternative refrigerantsDensity measurement of gas and liquidEvaluation of density of flexible print substrateEvaluation of density of SAW deviceEvaluation of thin film manufacturing processEvaluation of defect in silicon crystalsEvaluation of density distribution in silicon crystalsExamples for applicationEmploy double sinker method with silicon and germanium single-crystalsPossible to measure density by cancelling out the effect of diamagnetic properties of fluids with unknown magnetic susceptibilityPrecise measurement of PVT propertiesDensity measurement of thin filmsRequire extremely precise temperature control (10 to 100 μK)Uncertainty of measurement of relative density difference is 10-7 to 10-8Detection of small density difference among silicon samplesCharacteristicsMagnetic suspension methodPressure-of-flotation methodMeasurement methodRelative combined standard uncertainty: The concept that expresses the quality of measurement was formerly called error. It is now summarized in the Guide to the Expression of Uncertainty in Measurement in ISO/IEC. The standard uncertainty of a quantity x is expressed as u(x) which is the variation in measurement of a certain quantity x, and it is determined by the standard deviation of the measurement. The relative combined standard uncertainty uc,r(y) = uc(y)/y is expressed as a relative quantity of the combined standard uncertainty uc(y) where the standard uncertainties of multiple input parameters are combined by error propagation equation.MRA (Mutual Recognition Arrangement): In measurement standard, the equivalence of standard provided by the national metrology institutes (NMIs) of countries or regions is mutually recognized, and calibration certificates issued by the NMIs are mutually recognized. The measuring instrument calibrated by a certain NMI can be used in other countries or regions without recalibration, to ensure one-stop service for users. Based on the TBT agreement, transparency in imposing mandatory regulation, voluntary regulation, or compatibility evaluation procedures is maintained, and international accord is promoted by international Term 1.Term 2.

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