Electrical Resistivity Of Nanostructured Aluminum At Low Temperature

Due to the good thermal and electrical conductivity,corrosion resistance,excellent machinability and other properties,aluminum is widely used in the fields of industry,military,and aerospace and so on.With the rapid development of technology,the materials with better properties are highly required in many fields.The properties of nanostructured materials are improved obviously.For example,the hardness and strength of the nanostructured aluminum bulk was 3~11 times than that of coarse-grained aluminum.Inertial Confinement Fusion(ICF)experiment requires that the materials not only have the ability of cool storage,but also have a good anti-radiation.Compared with the coarse-grained aluminum,the nanostructured Al has the ability of cool storage and good anti-radiation.Therefore,the nanostrucrued Al is selected as the prior material for ICF experiments.Electrical resistivity is the physical property of the materials.So,studying on it not only can improve the nanostructured materials of physical properties,but also helps to explore the potential application value of aluminum nanocrystalline.The nanocrystalline aluminum sensor has the advantages of good anti-radiation,sensitivity and selectivity,which makes it to adapt more abominable industrial environment.In addition,the nanostructured films can be made into the micro heater thanks to the pimping space.Therefore,this paper analyzed temperature dependence of the electrical resistivity for nanocrystalline aluminum bulks and films at 8K~300K.The main research results are as follows:(1)At low temperature(8 K~30 K),the temperature dependent electrical resistivity(?(T))is a function of T4 for the coarse-grained bulk aluminum.Due to the phonon-electron scattering at grain boundary and surface,the electrical resistivity varies with the temperature not only in T4,but also in T3 for all nanostructured aluminum.(2)When the temperature is higher than 120 K,the electron mean free path for Al(about 60 nm)is less than the average grain size,and the electrons could not be scattered by grain boundary and surface.So the electrical resistivity of all samples(include the nanostructured aluminum and coarse-grained bulk aluminum)decreases linearly with the temperature down to about 120 K.(3)The residual resistivity(?residual)of the nanostructured aluminum samples is about 5.5×10-4 ?·m,5~6 orders magnitude larger than that of the coarse-grained bulk aluminum(2.01×10-10 ?·m)due to the electron scattering by the macroscopic defects of holes between nanoparticles,the amorphous alumina cladding and the grain boundary.(4)The average grain size increases with increasing of nanostrucrured Al films.Therefore,the electron scattering probability for intracrystalline phonon also increases,and the intensity for electron-grain boundary/surface scattering will be weaken.The results show that the magnitude of coefficient for the T4 term increases with the increasing of thickness and the probability of core electron-phonon scattering is more and more stronger.The magnitude of coefficient for the T3 term increases with the increasing of thickness,which expresses the probability of grain boundary/surface electron-phonon scattering become weak.(5)The residual electrical resistivity of nanofilms is found to be the 2~3 orders magnitude larger than that of the coarse-grained Al due to the surface scattering,grain boundary scattering,defect scattering and the impurity scattering.The electron-surface scattering is the dominant mechanism for the residual resistivity when the film thickness is smaller than the grain size and mean free path.The surface scattering will become weak when the thickness is larger than the grain size.Owing to the closely contact,high film density,and the low macroscopic defects such as holes for nanoparticles of nanostructured aluminum films,the residual electrical resistivity of nanostructured aluminum film(8.69×10-8 ?·m)is less than nanostructured aluminum bulk residual electrical resistivity(5.24×10-4 ?·m).