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Preparation And Properties Of Manganin Piezoresistive Thin Film Sensor

Posted on:2022-07-08Degree:MasterType:Thesis
Country:ChinaCandidate:Y CaoFull Text:PDF
GTID:2518306539459124Subject:Mechanical engineering
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Since the sensing part of the discrete device sensor is always far away from the actual working part of the workpiece,it is diffcult to measure the applied pressure of the workpiece and mechanical parts(such as cutting tools,molds,bearings,and etc.).In this thesis,a piezoresistive thin film sensor based on Cu84Mn12Ni4 was fabricated using dc magnetron sputtering.This work studies the effects of deposition process such as substrate bias,substrate temperature,and deposition pressure on the microstructure and piezoresistive properties of the films;and then investigates the effects of film thickness and heat treatment time on the microstructure and piezoresistive properties of the films.Finally,the effects of Mn and Ni concentrations in films on the microstructure and piezoresistive properties of the films were evaluated.The main results of this thesis are listed as follows.1)With the increasing of substrate bias,the grain sizes refinement and density increase of the films are obtained.However,the piezoresistive coefficient of the films reaches the largest at a bias of-100 V,=12.57×10-4(6-1.However,the film indicates a poor repeatability during the piezoresistive test because of the coarser grains and increased structural defects.The increase of substrate temperature helps the grains of the film grow gradually,while the compactness of the film increases first and then decreases.Under the deposition temperature of 200?,the film shows a low amount of microporous defects,high compactness,and small surface roughness.The piezoresistive coefficient of film deposited at 200?is=7.9×10-4(6-1 with an excellent repeatability.The grain sizes of the Cu84Mn12Ni4 thin films increase with the increase of deposition pressure,while the compactness of the films decreases.These films with refined grains,high compactness,and small surface roughness can be deposited at a low pressure of 0.2 Pa.The corresponding piezoresistive coefficient is=8.63×10-4(6-1 with an excellent repeatability.Finally,the optimised working parameters for Cu84Mn12Ni4 thin film deposition are determined as follows:substrate bias voltage-100 V,deposition temperature200?,and deposition pressure 0.2 Pa.2)As the thickness of the film increases,the elemental compositions of the films remain stable and the surface grains/granules grow gradually.The films with the thickness of 0.4 to1.2?m maintain a relatively compact structure and no micropores in surface and cross-section can be observed.The piezoresistive coefficientd of the filmd are 13.75×10-4and 6.23×10-4(6-1at 0.4 and 1.2?m,respectively.However,a samll film thickness favors to grow a nonuniform surface structure of the film,which decreases the repeatability of the film compared to the thick film.After annealing,the grains of the films grow up and the defects in the film decrease,which improves the density of the films.The piezoresistive coefficient of the films annealed at 400?for 120 min is 23.36×10-4(6-1,which is70%higher compared to the unannealed film(13.74×10-4(6-1).The piezoresistive repeatability of the films after annealing is enhanced as well.3)The improment of Ni concentrations in Cu Mn Ni solution produces grain refinement and increases micropores or other defects in the films,resulting in the decrease of compactness and the increase of surface roughness of the film.The increased Ni leads to the transition of piezoresistive coefficient from positive to negative.The piezoresistive coefficients of 1.11×10-4 and-2.0×10-4(6-1 are obtained when the Ni contents are 0.18 at.%and 17.54 at.%,respectively.However,the absolute values of those piezoresistive coefficients are significant less than that of the Cu84Mn12Ni4.With the increase of Mn concentrations in Cu Mn Ni solution,grain refinement and increase of compactness can be detected.The surface roughness of the film decreases with the increase of the Mn concentrations.However,adding Mn component can enhance the positive piezoresistive effect of Cu Mn Ni.The film reaches the maximum piezoresistive coefficient of 23.81×10-4(6-1 when Mn content is 16.72 at.%.After heat treatment,the piezoresistive coefficient of the film increases to 35.78×10-4(6-1.The piezoresistive repeatability of the films after annealing is enhanced as well.
Keywords/Search Tags:Manganin thin film, Magnetron sputtering, Piezoresistive sensor, Piezoresistive coefficient
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