Über den chemischen Zustand und das elektrische Moment der Oberfläche von Germanium in Kontakt mit wäßrigen Elektrolytlösungen

Steady-state and impedance investigations of anodic dissolution of p-Ge in alkali

“…The slopes give an acceptor concentration in the range N A ¼ 6 Â 10 15 to 7 Â 10 15 cm À3 ; using for the mobility the value 1900 cm 2 V À1 s À1 (probably overestimated for ordinary commercial crystals [21]) we obtain resistivity values around 0.5 X cm, in substantial agreement with the value indicated by the supplier. The estimated flatband position is E FB ffi À0:50 V SCE and E FB ffi À0:43 V SCE at pH 13 and 12, respectively, in substantial agreement with available literature data for an anodically polarised, hydroxyl covered surface [5,[22][23][24][25]. The observed dependence of E FB on pH can be attributed to the dissociation of surface acidic groups >Ge(OH) 2 [5,23].…”

“…The estimated flatband position is E FB ffi À0:50 V SCE and E FB ffi À0:43 V SCE at pH 13 and 12, respectively, in substantial agreement with available literature data for an anodically polarised, hydroxyl covered surface [5,[22][23][24][25]. The observed dependence of E FB on pH can be attributed to the dissociation of surface acidic groups >Ge(OH) 2 [5,23].…”

“…6 reproduces that proposed by Beck and Gerischer [3][4][5]. In this scheme some surface atoms are radical species, possibly present under dynamic anodic dissolution (the stable termination is actually represented by -H or -OH depending on potential [23][24][25]). Although the two Ge Å sites left behind by dissolution of Ge(IV) in step 3 are not equivalent to the starting Ge: species reacting in step 1, the process may be regarded as cyclic on average over a large number of individual reactions since Ge Å will be converted to Ge: by breaking of the bond with the adjacent surface Ge atom.…”

Analysis of the Hydrogen Formation at GaAs Electrodes by Impedance Spectroscopy Investigations

“…For instance, in the case of GaAs Brummer [13) has postulated a Volmer-Tafel mechanism whereas Gerischer [12) could interpret his results by a VolmerHeyrovsky mechanism. Difficulties arise because the surface may change from a hydroxide into a hydride surface leading to a change of the Helmholtz double layer, before the H 2-evolution occurs [10,11,16).…”

“…The latter result has not been much further investigated. Hrevolution has been studied at several semiconductor electrodes such as germanium [10,11], GaAs [12,13], InP…”