Dissolution Potentials and Activation Energies of InSb Single Crystals

Abstract

The rest (or corrosion) and dissolution potentials of normalInSb single crystals in normalHCl were determined. There is no potential difference (within error limits) between the inverse {111} faces in pure normalHCl . A difference of up to 44 mV and more develops as soon as the normalInSb electrode is anodically dissolved.The potential becomes less noble in the sequence In {111}, {100}, {110}, normalSbfalse{true1¯true1¯true1¯false} . The Tafel relationship is observed over three decades of current density. With additions of FeCl3 , FeCl2 , K3normalFefalse(CNfalse) 6 , K4normalFefalse(CNfalse) 6 , H2C4H4O6 to 2N normalHCl , the anodic potentials of both inverse {111} faces are shifted to more active values; the ɛ́Η of In{111} is always nobler than that of normalSbfalse{true1¯true1¯true1¯false} . There are indications that the various potentials observed are a function of current density within the pores of a protective layer, Sb4O5Cl2 . The apparent activation energy, ca. 20 kcal/mole, of the anodic dissolution reaction is nearly the same on all crystallographic planes of normalInSb . The rate of anodic dissolution of normalSbfalse{111false} in pure 2NnormalHCl is 3–7 times larger than that of the inverse face at the same potential.

Formation of porous layers on InSb(100) by anodization

“…From the AES profiles it is thus clear that in HCl and HBr a considerable amount of the InSb exposed during anodization is converted ito a layer of Sb-oxo-halogenide compounds. This is in line with findings suggesting a Sb 4 O 5 Cl 2 compound to form if In Sb is polarized in HCl (45,46).…”

“…It was reported that in 2M HCl under anodic polarization at current densities >70 mA/cm 2 a black layer is formed that is likely to consist of Sb 4 O 5 Cl 2 (45)(46).…”