Preparation And Electronic Transportation Properties Of One-dimension Graded Metal Nanowires

One-dimensional nanomaterials have received considerable attention over the past decades because of their novel physical and chemical properties and potential applications in future nanodevices. Many kinds of shape-controlled metal nanowires were synthesized with porous anodic aluminum oxide (AAO) template and provided the good foundation for the development of Nano-electronic devices. However, the electrical properties of the diameter-graded metal nanowires have been less studied. In this paper, we synthesized the graded metal nanowire arrays using AAO templates and investigated their electron transportation properties.1)We have improved the prepared method to fabricate the AAO template with the different nanochannels. The AAO template with a graded pore diameter was prepared through gradually changing the anodic voltage during an anodization in 0.3M oxalic acid. The remaining aluminum was removed by saturated CuCl solution and the alumina barrier layer at the bottom of the AAM was dissolved in 5 wt% phosphoric acid solution, respectively. Meanwhile, the alumina barrier layer also becomed thin through gradually decreasing the anodic voltage for electrochemical deposition,2) Based on these templates, the Ag nanowire arrays with graded diameter were electrochemically deposited into the pores of the AAO template. In order to compare their electronic properties, the Ag nanowire arrays and Fe nanowire arrays with straight diameter were also prepared. The presences of tartaric acid are considered to be critical factor for the appearance of the 4H structure during this process.3). Electronic transportation of one-dimension diameter-graded Ag nanowires in AAO was studied by the method of the volt-ampere. The results of measurement show that I-V curves of the diameter-graded Ag nanowires are nonlinear, which demonstrates the diameter-graded Ag nanowires transporet from metal to semiconductor along the straightion of the diameter. While, I-V curves of the straight Ag nanowires with 4H crystal structure and Fe nanowirs were nlinear. These results further show that semiconductor property of the diameter-graded metal was caused by the gradient change along the straightion of diameter. The coulomb blockade effects and the small size effects may results in these results.