Abstract
To improve the conductance of nano particulate indium tin oxide (In2O3:Sn, ITO) layers we have applied a number of treatments: post bake, infiltration by an ITO precursor solution with subsequent sol-gel transformation into ITO, treatment with etching agents as well as annealing in vacuum. We obtained a maximum conductance of 120 Omega(-1)cm(-1) by combining the precursor infiltration technique with vacuum annealing. Considering the layer thickness of 5.2 mu m, this value corresponds to a sheet resistance of about 16 Omega/square at a maximum transmittance of 83 %. These nano particulate layers should be applicable as electrodes in optoelectronics.
To understand the mechanisms behind the conductance improvement and to fathom the limits we did some investigations: long-term resistance measurements gave an insight in oxygen vacancy balance concentration. From infrared absorption measurements we inferred the free charge carrier density and at present we carry out XPS measurements which yield information about the alteration of oxygen vacancy concentration. Considering these data we discuss two conductance improving mechanisms: The increase of the free charge carrier density by a rise of oxygen vacancy concentration as well as a release of trapped charge carriers from the aggregate surfaces.