The Reaction of Germanium with Aqueous Solutions

Abstract

The dissolution of germanium in water was studied as a function of oxygen partial pressure, temperature, crystallographic-orientation, and mobile-carrier density. It was found that, although thermodynamically feasible, germanium does not react with water, freed of oxygen, in the temperature range studied (up to 100~In the presence of oxygen the dissolution rate in pure water is a function of oxygen partial pressure, reaching a limiting value of the order of 1 t,g/cm~/hr at 35~ under oxygen partial pressures greater than approximately 0.5 atm. For a given oxygen pressure the dissolution rate is approximately trebled for a ten-degree temperature rise, the measured activation energy for the dissolution reaction being 19 __ 2 kcal/mole. The order of dissolution rates for the three principal crystallographic faces was found to be {1O0}> {110}> {111}. No effect on the dissolution rate was found to result from changes in mobile-carrier concentrations brought about by doping or illumination. From dissolution rates and potentials it is concluded that the dissolution process is under cathodic control and that the rate-determining step is the reduction of oxygen by germanium. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 192.236.36.29 Downloaded on 2015-04-12 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 192.236.36.29 Downloaded on 2015-04-12 to IP

Chemical Etching of Germanium in the System HF-H[sub 2]O[sub 2]-H[sub 2]O

“…For his derivation Camp used the expression Rj = ~ajCjp~ exp (--EJkT) [5] ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address.…”

“…[15] can be reduced to Camp's original expression, Eq. [5]. Using an analysis similar to his, it is possible to obtain a temperaturedependence relationship of the form Although the ~th reaction may be the rate-limiting step at a given temperature, it does not necessarily hold that this step is rate limiting at all temperatures.…”

Metal-assisted chemical etching of Ge surface and its effect on photovoltaic devices

“…Because Ge has a higher carrier mobility than Si at a given electric field, the nanostructures of Ge could be easily prepared by means of MaCE, which would enhance the fabrication of various types of Ge-based electronic and optical devices. However, MaCE of Ge is difficult due to the oxidation and dissolution of Ge, even on regions without metal particles [16]. During the MaCE process, the metal particles act as local cathodes, which reduces the solution by catalytic reactions, and the anode reaction takes place on the semiconductor surface that is in contact with the metal, thereby oxidizing and dissolving the semiconductor substrate [1,[17][18][19].…”

Crystalline Structure and Surface Reactivity

“…Stereohindrance also appears to play an important role in determining the adsorption characteristics of the atoms of surface defects (for example, edge dislocations)(16). For reasons which are not understood at present, germanium surfaces are inert to water free of dissolved oxygen(17), although the reaction between germanium and water is thermodynamically possible:Ge+ 2H20 -> GeO2 + 4H + 4e-E? =--0.15 Traces of oxygen provide a kinetic path for the reaction through the formation of a water-soluble oxide.…”