The Preparation Of High-pressure Sensor For Precision Ytterbium Film

Ytterbium is a special kind of piezoresistive material. Ytterbium thin film gauge has high sensitivity, fast response. It can be used to investigate the propagation and attenuation phenomena of shock pressure lower than 3GPa in rocks, soils, liquid mediums and structural materials. Ytterbium gauge is considered to be the best sensor to investigate explosion pressure in rocks or soils for it's high sensitivity under low dynamic pressure. Ytterbium gauge can also be used to measure pressures induced by laser-supported detonation, underwater detonation, hydrostatic pressure and high-rate dynamic loading on insensitive explosives. It is emergent needed in defense engineering.In this paper, low resistanceπ-shape ytterbium thin film gauges were fabricated by DC magnetron sputtering on polyimide sheet. The films were deposited under different conditions and the best results were obtained at 180℃and 120W for substrate temperature and sputtering power, respectively. The gauges were"in-material"structure and they were shock loaded in the pressure range from 600 to 700MPa in PMMA targets. The result showed the gauges fabricated at the same batch had excellent reproducibility. The variation of the piezoresistance coefficients was within±0.85%. The gauges deposited at different processing parameters also showed good reproducibility of±2.7%. The fastest response time was 80ns for unpackaged gauges.Yb thin film samples were annealed at 300℃for an hour in high vacuum environment. After annealing, the grain sizes increased from 206nm to 220nm. The film resistivity decreased from 47.5μΩ·cm to 41.3μΩ·cm. The influence of annealing on film grain size was not obvious. It was also founded that the structure of Yb thin films on PI substrates was not column structure, which was different from the previous report on Al2O3 substrates. The etching solution for ytterbium thin film was explored systematically. The best etching result was obtained with HCl and ethanol mixed solution with volume ratio of 1:30 at 20℃. Resistor pattern was realized by screen-printing to facilitate the coating of photoresist on PI flexible substrate. 50Ωhigh-resistance ytterbium thin film gauges were fabricated by this method.