Materials Chemistry and Physics, Vol.139, No.2-3, 756-764, 2013
Electrochemical isotropic texturing of mc-Si wafers in KOH solution
Boron doped multicrystalline Si-wafers were anodically polarized in 2 M KOH and 4 M KOH at 40 degrees C and 50 degrees C. The applied potentials were 25 V, 30 V, 40 V and 50 V. The morphology of the textured surfaces, the surface products and the light reflectivity were analyzed by utilizing SEM, XPS and Lambda UV/Vis/NIR spectrophotometer, respectively. Isotropic texturing was obtained. The lowest average reflectivity, 17%, was achieved after pre-etching for 10 min and polarization at 40 V for 10 min in 4 M KOH at 50 degrees C. That reflection value is half of that measured on a chemical pre-etched surface, 34%. By increasing the voltage to 50 V the reflectivity rises to 28%. Polarizations to 25 V and 30 V at 50 degrees C in both solutions give local pores in the gm-range. The etch attack initiation is located at protrusions on the surface. At 40 V and 50 V in both solutions the pores are extended onto the entire surface. The width of the pores is about 10 mu m. Inside the micro-pores, nm-pores are formed; their lateral size is in the range 100 nm-200 nm. A mechanism for the anodic dissolution reactions is discussed. (C) 2013 Elsevier B.V. All rights reserved.