Electrochemical Preparation And Property Study Of One-dimensional Cu/Ni Multilayer Nanowires

In recent years, one-dimensional nanomaterials with their special performance have become a widely research object in physics, material sciences and electronics, etc. The magnetic/non-magnetic multilayer nanowire, as a member of one-dimensional nanomaterial, not only has important meaning in the field of basic application research and the application of nanomaterials, but also has potential applications in the field of nano-electronics device and GMR-sensors. Therefore, preparation of one-dimensional multilayer nanostructured materials with good periodic structure and study of the corresponding properties can provide the basic experiment data for current research and new idea for the development of related nanoscale devices.In this thesis, the Cu/Ni multilayer nanowires are prepared by electrochemical deposition alternately with ion-track membrane(polycarbonate PC) as template. The multilayer nanowires are characterized by scanning electron microscopy(SEM) and transmission electron microscopy(TEM) combine with the line scan of Energy Dispersive X-ray Spectroscopy(EDS)in order to obtain the details information of nanowires' diameter, layer thickness and crystal structure. After that we use ultraviolet visible near infrared spectrometer(UV-Vis-NIR) to measure the extinction spectrum of Cu/Ni multilayer nanowire, use vibrating sample magnetometer(VSM) to analyze the hysteresis loop, use comprehensive physical property measurement system(PPMS) to measure giant magnetoresistance effect(GMR). The Cu/Ni multilayer nanowires with different diameters, different periodicities and layer thicknesses are successfully fabricated in the ion-track template.During optical measurement, Cu/Ni multilayer nanowires exhibit a red shift with increasing periodicity in extinction spectra when the incident light is parallel to the nanowire arrays. The same red shift happens with increasing copper layer thickness and diameter due to the enhancement of Cu/Ni multilayer nanowires' surface plasmon resonance(SPR). With the increasing of periodicity of Cu/Ni multilayer nanowire, the extinction peak position exhibits a red shift because of “impurity effect” caused by the Ni layer. Red shift also happens with Cu layer thickness increasing for the existence of coupling effect. The enhanced phase delay effect can also introduce the red shift in extinction spectrum while increasing the nanowire's diameter.It is confirmed that the easy magnetic axis direction of multilayer nanowire arrays is parallel to the nanowires via the VSM measurement. When the applied external magnetic field is parallel to the nanowire arrays, the magnetic properties of multilayer nanowire show different performance in the case of different layer thicknesses, periodicities and nanowires' diameter. Due to shape anisotropy, the coercivity of multilayer nanowires increases with increasing Ni layer thickness and periodicity. The coercivity decreases with increasing Cu layer thickness and diameter, which is because the exchange coupling effect decreases between adjacent Ni layer and the magnetostatic coupling effect between adjacent nanowires. The saturated magnetic field decreases with decreasing Ni layer thickness and periodicity, similar to the coercivity, which is due to the decreasing magnetic Ni content between the two non-magnetic Cu layers.In addition, the Cu/Ni multilayer nanowire arrays with magnetic field perpendicular to the two-dimensional membrane surface, its GMR value in 300 k is smaller than 100 k. The GMR value decreases with increasing copper layer thickness while still in the range of diffusion length. When the temperature increases, the "electronic- phonon scattering" effect enhances and the GMR of Cu/Ni multilayer nanowires will reduce.