title: Quantifying charge carrier concentration in ZnO thin films by Scanning Kelvin Probe Microscopy.
abstract: In the last years there has been a renewed interest for zinc oxide semiconductor, mainly triggered by its prospects in optoelectronic applications. In particular, zinc oxide thin films are being widely used for photovoltaic applications, in which the determination of the electrical conductivity is of great importance. Being an intrinsically doped material, the quantification of its doping concentration has always been challenging. Here we show how to probe the charge carrier density of zinc oxide thin films by Scanning Kelvin Probe Microscopy, a technique that allows measuring the contact potential difference between the tip and the sample surface with high spatial resolution. A simple electronic energy model is used for correlating the contact potential difference with the doping concentration in the material. Limitations of this technique are discussed in details and some experimental solutions are proposed. Two-dimensional doping concentration images acquired on radio frequency-sputtered intrinsic zinc oxide thin films with different thickness and deposited under different conditions are reported. We show that results inferred with this technique are in accordance with carrier concentration expected for zinc oxide thin films deposited under different conditions and obtained from resistivity and mobility measurements.
authors.affiliation: Institute Center for Energy (iEnergy), Masdar Institute of Science and Technology, Abu Dhabi, UAE.
authors.forename: C
authors.initials: C
authors.lastname: Maragliano
authors.affiliation: Institute Center for Microsystems (iMicro), Masdar Institute of Science and Technology, Abu Dhabi, UAE.
authors.forename: S
authors.initials: S
authors.lastname: Lilliu
authors.affiliation: Institute Center for Microsystems (iMicro), Masdar Institute of Science and Technology, Abu Dhabi, UAE.
authors.forename: M S
authors.initials: MS
authors.lastname: Dahlem
authors.affiliation: Institute Center for Energy (iEnergy), Masdar Institute of Science and Technology, Abu Dhabi, UAE.
authors.forename: M
authors.initials: M
authors.lastname: Chiesa
authors.affiliation: Institute Center for Energy (iEnergy), Masdar Institute of Science and Technology, Abu Dhabi, UAE.
authors.forename: T
authors.initials: T
authors.lastname: Souier
authors.affiliation: Institute Center for Energy (iEnergy), Masdar Institute of Science and Technology, Abu Dhabi, UAE.
authors.forename: M
authors.initials: M
authors.lastname: Stefancich
mesh_terms: D003217:Conductometry / Q000379:methods*; D004553:Electric Conductivity; D004579:Electron Transport; D008422:Materials Testing / Q000379:methods; D008567:Membranes, Artificial; D020527:Microscopy, Scanning Probe / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry*; D055672:Static Electricity; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D008567:Membranes, Artificial; D015034:Zinc Oxide