Preparation And Electrical Properties Of .ni / Si-npa Study

Using regularly patterned silicon nanoporous pillar array (Si-NPA) prepared by hydrothermal etching method as substrate in this thesis, Ni/Si-NPA nanocomposite system with different surface morphologies has been synthesized by immersion plating method through changing Ni²⁺ concentration,pH value of concentration,different oxidation status on the surface of Si-NPA substrate,depositing time. The results indicated that Ni²⁺ concentration,pH value,oxidation status on Si-NPA surface and depositing time have a very tremendous influence on the surface appearance and structure of Ni/Si-NPA. Its forming mechanism has been studied, meanwhile the dependence of morphology of Si-NPA and the component of Ni/Si-NPA on annealing condition were investigated. The electricity properties of Ni/Si-NPA nanosystems before annealing and after annealing are studied. Main points are concluded as follows:1. Immersion plating of nickel on freshly prepared Si-NPA in different solutions (alkaline- NiSO₄ solution and alkaline NiSO₄-NH₄F solution) were observed. The results indicate that although there is nickel depositing on Si-NPA surface from alkaline- MSO₄ solution, but the silicon pillars are etched seriously during the period of deposition. Meanwhile there is nickel depositing on Si-NPA, the basic pillar array structure of Si-NPA substrate has been maintained after nickel depositing in alkaline NiSO₄-NH₄F solution. Taking all these factors into consideration, alkaline MSO₄-NH₄F solution is chosen as immersing solution to prepare pattern array structure characteristic Ni/Si-NPA.2. In order to further optimized conditions that the design of the structural characteristics of the Ni/Si-NPA nano-composite system were prepared, we changed alkaline solution of Ni²⁺ concentration, pH value and different oxidation status of Si-NPA substrates, and deposition time. The results can be concluded as follows: (1) Ni²⁺ concentration has a very tremendous influence on the surface appearance and structure of Ni/Si-NPA: Ni/Si-NPA maintain Si-NPA regular array substrate structure features in the high Ni²⁺ concentration, whereas the regular array structure of Ni/Si-NPA was almost destroyed in low Ni²⁺ concentration. (2) Different pH value has a similar influence on the surface morphology and structure of Ni/Si-NPA. Silicon-dissolved in acidic environment is different from alkaline solution, that is middle and upper pillars partial dissolution rate is faster than the lower pillars in alkaline solution, meanwhile overall pillars dissolved and became thinner in acidic environment. (3) The pillars dissolved faster along with the increasing aging time and without ideal patterned structure when Ni/Si-NPA prepared on aging Si-NPA substrate. In conclusion, we obtained a suitable condition to prepareing ideal Ni/Si-NPA composite structure, such as Ni²⁺ concentration,pH value,substrate condition,etc. Then we studied depositing time influence on the surface morphology and structure of the samples prepared in above conditions.3. Ni/Si-NPA that prepared by the optimum conditions of section 2 were put into tube furnace annealed at 400℃, 600℃and 800℃, respectively, for two hours. Annealed samples maintained the surface regular array structure in micron level on the whole, but the sample surface chemical composition changed larger along with the increasing annealing temperature, that is, the sample surface particle size is increasing, and no change in chemical composition when annealing temperature below 600℃, Surface composition of the sample material was become nickel particles into nickel oxide particles when annealing temperature hihger than 600℃.4. I-V and C-V of Ni/Si-NPA/Si composite structure were studies, and the results indicates that the I-V test found the barrier height is greater than the C-V testing potential barrier height, and the cause was analyzed according. The influence of temperature on the ideal factor of Ni/Si-NPA/Si composite structure was studied, and the results indicated that the value of ideal factor became larger along with the temperature lower. The stability had been studied and I-V almost the same, that means the stability of the samples are good. 5. The I-V properties of Ni/Si-NPA, annealed in high-purity nitrogen atmosphere, had been tested test and found that the I-V relationship accorded with the I-V Schottky Junction, the composite structure of the ideal factor gradually decreased with the annealing temperature hoisting by fitting the ideal size factor.