n^+-Si在HF溶液中的阳极极化行为和阻抗谱

Anodic Polarization Behavior and Impedance Response of n^+Si in Hydrofluoric Acid Solution

n^(+)-Si在0.25～1.0%HF溶液中无光照和光照下的伏安曲线均明显地分为三段:在低极化下呈线性关系,对应于硅的阳极溶解,形成多孔硅层 (PSL);在中间电位区,电极部分表面为硅氧化物所覆盖,阳极溶解和非均匀电抛光过程同时进行;在高极化区,全部表面为硅氧化物所覆盖,发生均匀的电抛光过程.在上述三个区域中由交流阻抗测得的特征电容环和电感应环的变化,揭示了由单—阳极溶解逐渐转变为均匀抛光过程的一些细节,定性地说明了n^(+)-Si上进行的竞争性反应的速率是随电位而改变,并受光照影响.

The voltammetric curves of heavily doped n-Si(n+-Si) closely related to the concentration of HF solution and the irradiation were investigated. There are generally three regions on each i-ψ curve: porous silicon formation at low potentials, electropolishing at high potentials and a transition region located in between. The corresponding complex plane impedance plots of n+-Si at above three potential regions imply that the rate of the following competitive reactions:Si + 2HF+2h+→SiF2+2H+Si + 2H2O + 4h+→SiO2 +4H+is dependent on the potential and light illumintion. The former reaction is nominative one at low potentials, the reaction of latters is accelerated at higher potentials until the electrode surface is covered completely with SiO2. The influence of the illumination on the impendance were measured and discussed.