The Electrode Process of Titanium Subchlorides and Electrodeposition of Titanium in LiCl-KCl Fused Salts

The electrochemical behaviour of Ti(Ⅲ) and Ti(Ⅱ) in LiCl-KCl eutectic system has been studied by cyclic voltammetry and chronoamperometry.The cathodic reduction of Ti(Ⅲ) and Ti(Ⅱ) has been found to be stepwise:Ti(Ⅲ)+e=Ti(Ⅱ),Ti(Ⅱ)+2e =Ti.The reductions are diffusion controlled.When an equilibrium between Ti subchlorides and excess metallic Ti was estab- lished by reaction 2TiCl_3+Ti=3TiCl_2 in LiCl-KCl melt at 475℃,then the average valence of Ti is less than 2.1.In this system the diffusion coefficient for Ti(Ⅱ) ion was calculated as D=2.5×10^(-5)cm^2·s^(-1).The chronoamperometric studies showed that the initial nucleation stage and growth of nuclei were observed when Ti ions were electrodeposited on low carbon steel substrate. The investigation of nucleation of metal may provide the method for obtaining smooth,coherent and adherent deposits of titanium.

A Study on the Kinetics of the Europium Electrochemistry Reduction 1.The Polarization Properties of Europium Reduced at the Cathode

This article studies the polarization properties of the cathode reduction of Eu in the Sm-Eu-Gd chloride system by using a constant potential method.As the feed concentration,temperature,and stirring rate of the system change,the system can gradually turn from chemical polarization to concentration polarization,and there would be a higher limiting current.As to the effects of acidity,only at a rather higher pH there will be a typical polarization property.The study can give some bases for the Eu electroreduction technlolgy parameter selection.

The effect of oxygen plasma ashing on the resistance of TiN bottom electrode for phase change memory

Phase change memory （PCM） has been regarded as a promising candidate for the next generation of nonvolatile memory. To decrease the power required to reset the PCM cell, titanium nitride （TIN） is preferred to be used as the bottom electrode of PCM due to its low thermal and suitable electrical conductivity. However, during the manufacture of PCM cell in 40 nm process node, abnormally high and discrete distribution of the resistance of TiN bottom electrode was found, which might be induced by the surface oxidation of TiN bottom electrode during the photoresist ashing process by oxygen plasma. In this work, we have studied the oxidation of TiN and found that with the increasing oxygen plasma ashing time, the thickness of the TiO2 layer became thicker and the state of the TiO2 layer changed from amorphous to crystalline, respectively. The resistance of TiN electrode contact chain with 4-5 nm TiO2 layer was confirmed to be almost three-orders of magnitude higher than that of pure TiN electrode, which led to the failure issue of PCM cell. We efficiently removed the oxidation TiO2 layer by a chemical mechanical polishing （CMP） process, and we eventually recovered the resistance of TiN bottom electrode from 1×10^5Ω/via back to 6×10^2 Ωvia and successfully achieved a uniform resistance distribution of the TiN bottom electrode.