| As a next-generation semiconductor non-volatile memory, phase change memory has fast read and write speed, long cycle life, especially the dominant feature in the scaling properties. Phase change memory is one of the best alternative to flash memory devices. Phase change memory can store information by the phase change of phase change material between crystalline and amorphous. When the phase change material transforms from crystalline state to amorphous state, the process is called reset process.The excessive reset current is the major problem of phase change memory. Bismuth Telluride(Bi2Te3) is an important phase change material with low melting point, high electrical conductivity and low thermal conductivity. it's the key to achieve low current phase change memory. In addition, with the improving of the storage density, the small size effect of phase change nanomaterials will cause the significantly reducing of device operating current.This paper studies the controllable preparation of electrochemical deposition on different substrates. The morphology and component of Bismuth telluride films,nanowires and nanotubes that we prepared were characterized and analyzed.First, we studied the FTO conductive glass-based bismuth telluride thin films prepared by using electrochemical deposition method, and obtained the optimum technological parameters for the electrodeposition of bismuth telluride. Under the same electrolyte composition, surface morphology and the composition of the film is impacted by the current. When the current density is 2.5m A/cm2, the stoichiometry bismuth telluride film can be obtained.Then we prepared bismuth telluride nanowires in the porous alumina template by electrochemical deposition method using the technological parameters for the electrodeposition of bismuth telluride membrane. The porous alumina template was prepared by two-step anodization, after removing the barrier layer and depositing the gold electrode on one side, the high-density, long draw ratio, highly ordered bismuth telluride nanowires were prepared by using the parameters of the thin filmelectrodeposition experiment. Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy were used to characterize their morphology and structural components. The results showed that the nanowires had consistent diameter with the AAO template, and were continuous, uniform and dense, and had a monocrystalline or polycrystalline structure. Different single-crystal nanowires grew along different crystallographic orientation.Due to the preparation of porous alumina template need to remove the aluminum base and the barrier layer, the process is tedious and the yield is not high, in order to simplify the process, we use the order reduction current method to reduce the thickness of porous alumina barrier, as a result, the barrier layer had a structure with thick middle area and thin edge. In this porous alumina template with special structure, we used constant current electrochemical deposition to prepare bismuth telluride nanotubes. Field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy analysis were used to characterized the morphology and composition of the nanotubes. The test results showed that the outer diameter of nanotubes was about 50 nm, the thickness of tube wall was about 5nm, the length ranged from a few microns to tens of microns. XPS characterization results indicated that the binding energy peaks of 165 e V 159.5e V pointed to the Bi 4f7/2 peak and 4f5/2 peak, and the binding energy peaks of 583.85 e V 573.45 e V pointed to the Te of3d5/2 peak and 3d3/2 peak. The peak of oxygen was obviously, indicated that the surface of the nanotubes were heavily oxidized. At the same time we also got nanowires with diameters ranging from 3nm to 180 nm. We tested the content of Te in the nanowires with different diameters, the results showed that the content of Te increased when diameter increased. |
PDF Full Text Request