The Reaction of Germanium with Aqueous Solutions

Abstract

The dissolution of single-crystal germanium has been studied in electrolyte solutions containing dissolved oxygen. The following electrolytes were considered: KF, KC1, KBr, KI, NaNOs, Na~SO,, CsC1, BaCh, and LaCh. In the range 10 -6 to 1.0N, the dissolution rate typically goes through a maximum as ExperimentalThe experimental techniques employed were, in many respects, similar to those described earlier (1). The reagent grade salts employed were not further purified, since consistent results were obtained with such salts from different sources. The KHF~ was purified by recrystallization. Certain improvements in the procedure for single-crystal samples, as well as the technique employed with powdered samples, will be described briefly. Powdered samples.--These experiments were performed using a conventional Warburg apparatus. 65 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.192.114.19

Anodic Tafel Slopes for N-Type Germanium

“…Over the current range, 2.3-1000 #a, and under the measurement conditions used, no change of slope was observed during the course of a single run to denote a shifting of the surface composition from that characteristic of the freshly etched surface to that typical of the pre-anodized surface. This apparent retention of initial surface condition may be similar to the effect of specific anion adsorption on the kinetics of chemical (not anodic) dissolution of germanium observed by Harvey and Gates (6). However, either prolonged anodization at relatively low currents (100 ~a for 30 min) or short anodization at relatively high currents (1000-3000 ga) will suffice to change the Tafel slope from the 0.087 • range to the 0.106 • region.…”

“…It is felt that the two significantly different Tafel slopes measured in this work reflect two different compositions of the germanium anode surface. The surface of germanium, freshly etched with CP-4 or CP-4A, is probably covered with adsorbed HF molecules (6). Pre-anodization presumably brings about replacement of these with hydroxyl groups.…”

On the Mechanism of Chemically Etching Germanium and Silicon

“…Figure 2 shows three things: (a) increasing pH shifts the electrode potential in the negative direction; (b) an appreciable potential difference is observed between n and p-type Ge and Si when the solution rapidly corrodes the semiconductor; and (c) p-type Ge or Si is always positive in potential with respect to n-type when a potential difference does exist. The effect of pH on the electrode potential of Ge has been observed many times before (5,6). Cretella and Gatos (7) have observed n-type Ge to be positive in potential with respect to p-type Ge in nitric acid solutions more dilute than 6N.…”

“…[2] is multiplied by 3 and Eq. [5] by 4 for the necessary charge balance) is as follows: 3St +4HNO, + 18HF-~ 3H~SiF~ + 4NO + 8H~O + 3(4--n)e + + 3(4--n)e- [6] The mole ratio of HNO~ to HF for this reaction is 4/18 or 1/4.5. This agrees very well with the HNO~-HF composition which gives the maximum rate of etching shown in Fig.…”

Wet chemical treatments of high purity Ge crystals for γ-ray detectors: Surface structure, passivation capabilities and air stability

“…Indeed, only GeeOH and GeeO species resulting from hydroxylation or simple oxidation of surface Ge atoms are expected. A possible interpretation arises from the pioneering work of Harvey and Gatos on the reaction of germanium with aqueous solutions [27]. They considered water dissolved oxygen as electron acceptor, thus behaving as follows:…”