Based On The Music Just Wave Magnesium Fluoride Waveguide Device Characteristics

Love wave sensor is a kind of surface acoustic wave sensor.Due to its highest mass sensitivity and application in liquid media,love wave sensor has a promising application in the future.Properties of guiding layer materials have an important influence on the performance of love wave sensors.Both theory and experiment have shown that guiding layer materials could have a good flexibility and low sound absorption,in addition to having low shear velocity and density.A new material MgF₂ used for love wave device guiding layer material is extensively discussed in this thesis.In this thesis,MgF₂ thin films were prepared on quartz substrates by thermal evaporation.The deposition parameters such as substrate temperature,evaporation current,and heat treatment temperature were systematically studied.The films prepared with different parameters were characterized by X-ray diffraction(XRD) and scanning electron microscope(SEM).MgF₂ thin films with low surface roughness,uniform crystal grain,and unique crystalline orientation were obtained when the evaporation current was 100A and the substrate temperature was 300℃.After heat treatment at 300℃for one hour,film grain sizes increased slightly,but surface roughness and tightness concentration did not change obviously.In addition,MgF₂(110) peak was enhanced,while(220) peak and(211) peaks appeared simultaneously.The mass and thickness of MgF₂ films were measured by QCM and SEM respectively.As a result,the film density of MgF₂ film was 2.9g/cm³ deduced.Love wave devices with different thickness of guiding layer were tested by network analyzer,and the relationship of gttiding layer thickness with frequency, insertion loss,Q value and mass sensitivity were discussed.The results showed that minimum insertion loss of-23.93dB and maximum Q value of 2193.8 were achieved with 2.5μm thick guiding layer,and the maximum sensitivity up to 416.7cm²g^-1 of guiding layer with thickness was 6.5μm.love wave devices were annealed at different temperature,the results showed that the Q value and mass sensitivity of the devices increased with increasing annealing temperature,but reverse tendency was observed for insertion loss.At last,a novel multilayer structure,consisting of PMMA/MgF₂/quartz, were evaluated for love wave device.The results indicated that for a certain thickness of MgF₂ layer,mass sensitivity and insertion loss of the device increased with increasing thickness of PMMA layer.For a certain thickness of guiding layer,Love wave device with PMMA/MgF₂ guiding layer has a higher mass sensitivity than that with MgF₂ guiding layer.