Research On Surface Electrical Characteristics Of Polymer By Scanning Probe Microscope

Research of surface electrical characteristics of polymer in submicron is very valuable in the theory construction and has a number of potential applications value.In recent years,adopt reliable experimental means effectively to characterization of these performance in submicron scale has become focal point in the field of nano-dielectric materials research field.Study surface electrical properties of dielectric material in submicron scale structure,has important scientific significance and practical value for improve and raise the level of properties and applications of nano-dielectric materials.Scanning Probe microscopy(SPM)is an effective means to test the structure and property information on the surface of the material in submicron.In this paper,author studies the surface properties of nano-composite polymer materials by using SPM.Research the surface structure and electrical characteristics of the interface region between the two kinds of different materials.A method of injecting charge stability on the surface of polymer submicron regional using microprobe with conductive coating by scanning probe microscope was designed.Make the polymer surface charged stability by touch with charged tip,then we use the different working modes of SPM,including Electric Force Microscopy(EFM)and Kelvin Force Microscopy(KFM),to study the effect of experimental parameters on the experimental results,such as coating of tip,injecting voltage polarity.Next,using above method,a contrastive research was used to analyze surface charge properties on two kinds of polyimide film,original polyimide(100HN)and corona-resistance polyimide(100CR).Based on the phase signal of EFM and the electric potential signal of KFM analysis shows that the differences in two kinds of materials.For 100CR,due to doping of Al2O3 made the injection barrier increases and the resistivity decreases than 100HN.Surface charge accumulation on 100CR is reduced to 50%of that on100HN,and dissipate quickly for the former.Time constant of exponential decay on 100HN is four to five times to the 100CR.These factors lead to the corona resistant performance is enhanced.Established a method to compare different dielectric constant of the material surface in submicron based on the EFM.It can be distinguish the different of the dielectric constant at the micro interface area between the two kinds of materials.The means improved overcomes the original defects of lack spatial resolution of the dielectric spectrum measurement.Changing the DC voltage is applied to the tip(VEFM),we can obtained the vibration phase offset(??)f tip.And then calculate the characteristic curve:tan(??)—VEFM.There is a increasing function relationship between the quadratic term coefficient of characteristic curve and the dielectric constant on material surface,(?)a/(?)?>0.The dielectric constant in single or two phase materials,such as polyethylene,mica,graphite and their interface,are quantitatively analyzed by above method.Put forward a method to measuring surface electric potential by EFM different from the past KFM.It solves the problem that the limited the scope of KFM.The advantage of the method:First,the range of measurement of surface potential has increased without increasing the hardware.Senond,the phase and surface potential were detected in the same working mode.It reduces the drift caused by the resetting in various work modes.Last but not least,when the surface potential beyond the measuring range,we can estimate the size of surface potential through characteristic curve obtained by mathematical modelingThese experimental method extends the field of research on electrical property of material by SPM,provides a more effective means for further research on nano-dielectric material.