Preparation Of Magnetic Nanowire Array Based On AAO/Si Composite Templates

One-dimensional nanostructured materials have been extensively studied because of their unique morphological structure,which are different from the block,particle,and film materials.In recent years,one-dimensional nanomaterials are not limited to the preparation,but are expected to be applied in practical devices.The construction of nanostructured devices requires orderly assembly of one-dimensional materials,while the vast majority of prepared nanomaterials are disorder which limits their application.Studying the way of arranging the nano-materials into an array system is the frontier and hot spot of nanomaterials and nanostructures research.Compared with the disordered nanomaterials,the ordered array system has better performance for its low-dimensional nanoscale effects and highly ordered,which is the base material for the next generation of nanostructured devices.Therefore,the preparation of one-dimensional"free standing"magnetic nanowire arrays is studied in this paper.The magnetic nanowires were prepared by template-assisted electrochemical deposition technology,while obtained loose and disordered nanowires after removed the template,which makes it difficult to study the effect of different array structures on the performance of magnetic nanowires.Therefore,in order to achieve"free standing"and ordered assembly of nanowires,this paper focuses on the preparation process of AAO/Si composite template,and mainly studies the influence of experimental parameters?electrolyte type,anodizing voltage,oxidation time,etc.?on surface morphology and pore parameters of the template.?1?Assembled AAO/Si composite template:A double-pass AAO is prepared from an aluminum sheet,then the AAO template is physically attached to a conductive substrate.The results show that the pore distance and pore diameter are closely related to the type of electrolyte,and the optimal anode voltage for different electrolytes is different.The optimal oxidation voltage of oxalic acid electrolyte and phosphoric acid+oxalic acid electrolyte are 40 V and 195 V respectively.AAO/Si composite template with a wide range of thickness and pore diameter can be adjusted by controlling oxidation time and pore expansion time.AAO template has poor adhesion to Si substrate.At the same time,the double-pass AAO template prepared by phosphoric acid+oxalic acid electrolyte,the minimum value of the pore diameter was reduced from the original 300 nm to 230 nm using physical filling technology?polycarbonate,PMMA?.?2?Growth AAO/Si composite template:The Al/Ti/Si composite film is firstly prepared by coating technology,then the aluminum film is anodized to form an AAO/Ti/Si composite template.The results show that in phosphoric acid+oxalic acid electrolyte,the template morphology and structure are poorly.In the oxalic acid electrolyte,the thickness of the AAO template and the diameter of the pore are adjusted by controlling the oxidation time and the pore expansion time.The range of thickness and pore diameter is much smaller than the assembled AAO/Si composite template,but the binding force with the substrate is much better than it.Finally,the obtained two composite templates were used to electrochemically deposition of Co Fe₂?CF?and Co Fe₂O₄?CFO?nanowire arrays.The results show that the nanowires prepared by the growing type template have a better binding force with the substrate than the assembled type AAO/Si composite template,not easy to fall off.When the height of the nanowire is less than 2?m,it parallels to each other and freely stands on the substrate,showing a hexagonal arrangement.When the height of the nanowire is longer than 5?m,it occurs top agglomeration phenomenon.The CF nanowires showed poor crystallinity or even no crystallization,while CFO showed good crystallinity and obtained a magnetically anisotropic free-standing ferrite nanowire array with a remanence ratio of 0.42 and coercive force of 553 Oe.