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|Title:||The Surface Modification of Single Crystal Semiconductors via Solubility Equilibria|
|Author(s):||Farmer, Deborah Jo|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||The surface modification of semiconductors is an area of considerable interest because of their potential use in solar energy cells. Stabilization of the semiconductor against dissolution, corrosion, and surface passivation in ionic solutions is of particular importance in the development of efficient, long-lived liquid junction cells. This study demonstrated that solubility equilibria provide a simple, versatile means of modifying the surface of a semiconductor.
Undoped single crystal cadmium sulfide and indium phosphide were etched and immersed in solutions containing ions with which one of the semiconductor constituents can react to form an insoluble precipitate. The semiconductor surface was characterized by Auger electron spectroscopy and X-ray photoelectron spectroscopy.
An insoluble layer containing iron formed on the InP surface after treatment with either Fe(CN)(,6)('3-) or Fe(CN)(,6)('4-). Other cyanide complexes produced similar layers on both InP and CdS surfaces. The InP surface was not modified by Co(CN)(,6)('3-). Oxygen-containing anions also produced an insoluble layer on the InP surface.
Several factors influenced surface modification. At high pH, InP was not modified by anions other than OH('-), presumably because of In(OH)(,3) formation. The pH also controlled the chemical identity of the species in solution available for modification. Oxidizing agents modified InP through the formation of a surface phosphate.
Cations and neutral species did not modify InP, but cations did modify CdS. Cations whose corresponding sulfide has a K(,sp) significantly higher than that of CdS did not modify the surface. Photoassisted cation penetration into the CdS lattice was observed. The penetration was more extensive on the (0001)A, or Cd, face than the (0001)B face. Adding EDTA to the modifying solution inhibited this penetration.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.
|Date Available in IDEALS:||2014-12-15|