Surface Enhanced Raman Spectroscopy of Group IV Semiconductor Electrodeposition and Deoxygenation Stephen Maldonado, Department of Chemistry, University of Michigan
The overarching thesis of this work is to develop non-energy-intensive synthetic methods for crystalline, inorganic semiconductor materials with desirable optoelectronic properties. In the initial stages of this work, we discovered a fundamentally new and unexplored strategy for electrochemically synthesizing crystalline semiconductors from aqueous solutions containing dissolved oxide precursors. Through the use of a liquid metal electrode that simultaneously acts as an electrode (i.e. electron source for the reduction of dissolved, oxidized species) and as a solvent for recrystallization, we have demonstrated and reported the electrosynthesis of crystalline Ge from an aqueous solution of dissolved GeO2 at room temperature. We have dubbed this as an electrochemical liquid-liquid-solid (ec-LLS) proces. This method is not specific to either the target semiconductor or liquid metal, as we have successfully produced crystalline Ge, Se, and GaAs with several lowmelting point metals. The essence of this process is a dissolution of the initial amorphous electrodeposit, followed by supersaturation, and then precipitation/crystallization. Under the auspice of electrochemical control, these steps can be regulated and the resultant properties of the crystallized semiconductor can be tuned. We successfully demonstrated the ec-LLS process can yield Ge films that function as high-capacity electrodes in electrochemical energy storage technologies as-prepared.
Intensity / a.u.
(111) 20
40
60
80
2q / degree
1
X(s) 2
3
X(dissolved) Liquid Electrode
4
100
120
Intensity / a.u.
Xn+
Si prepared via ec-LLS
Intensity / a.u.
Liquid Electrolyte
As-electrodeposited crystalline Ge used as a battery device electrode
Ge at liquid Ga Ge at solid Ga
200
Si prepared via ec-LLS (220)
(311)
20
300
30 40 50 400 500 600 2q/ degree
Raman Shift / cm
-1
60 700
