Improved contacts on a porous silicon layer by electroless nickel plating and copper thickening

Abstract

In this paper stable, low-resistance contacts on porous silicon have been realized by electroless nickel deposition from a very weakly alkaline solution followed by copper thickening. The porous silicon layer after nickel deposition has been analysed by x-ray diffraction, which shows that a porous silicon nickel structure is successfully achieved from the bath. FESEM studies have been performed which show that the surface morphology of the porous silicon layer remains intact after nickel-copper plating. The mean roughness of the porous silicon surface has been found to improve after nickel plating from the AFM studies. Electrical characterization shows that the J-V characteristics of the nickel-copper-plated porous silicon lateral structure contact is fairly linear up to a certain value of applied voltage. Specific contact resistance of the nickel on porous silicon has been measured for the first time and has been found to be of an order of magnitude lower than that of other metals. No significant ageing is visible in this electroless nickel contact contrary to the vacuum-evaporated nickel contact.

Li15Si4Formation in Silicon Thin Film Negative Electrodes

“…It is well known that Si bonds strongly to Ni, 19 and, as a result, Ni is used as a bonding layer for Si wafer contacts in solar cells. 20,21 Good Si-Ni adhesion likely results in good cycling performance of the Si film on Ni foil, even when it is roughened. Figure 8 shows the delithiation capacity, Li 15 Si 4 peak area, and the change in average half-cycle potential (from the first cycle) plotted against cycle number for all the Si films on the different substrates shown in Figure 7.…”

Nanocrystalline Porous Silicon

“…Chemical etching of silicon using chemical solutions of HF, HNO 3 and water (Vasquez et al, 1992), NaNO 2 and HF or CrO 3 and HF (Beale et al, 1986;Zubko et al 1999) are employed for PS formation. However, the most widely used method is the electrochemical etching of silicon crystal in an electrolyte solution of HF and ethanol or methanol (Saha et al, 1998;Kanungo et al, 2006) or HF and water or HF and N, N dimethyl formamide (DMF) (Archer et al, 2005) by passing current for a fixed duration of time. Hummel et al (Hummel & Chang, 1992) utilized a new spark erosion technique for PS formation, which does not involve any aqueous solution or fluorine contaminants in air or in the other gases.…”

XPS study of palladium sensitized nano porous silicon thin film

“…We applied an etching current density of 10 mA/cm 2 for 40 min. The porosity and thickness of around 55% and 5 μm, respectively were measured gravimetrically (Kanungo et al 2006(Kanungo et al , 2009) using a precision semi-microbalance (290-9842/K, PAG OERLIKONAG CH-DIETKON, Switzerland).…”