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Highly conductive grain boundaries in copper oxide thin films

Deuermeier, Jonas and Wardenga, Hans F. and Morasch, Jan and Siol, Sebastian and Nandy, Suman and Calmeiro, Tomás and Martins, Rodrigo and Klein, Andreas and Fortunato, Elvira (2016):
Highly conductive grain boundaries in copper oxide thin films.
In: Journal of Applied Physics, 119 (23), p. 235303, ISSN 0021-8979,
[Online-Edition: http://dx.doi.org/10.1063/1.4954002],
[Article]

Abstract

High conductivity in the off-state and low field-effect mobility compared to bulk properties is widely observed in the p-type thin-film transistors of Cu2O, especially when processed at moderate temperature. This work presents results from in situ conductance measurements at thicknesses from sub-nm to around 250 nm with parallel X-ray photoelectron spectroscopy. An enhanced conductivity at low thickness is explained by the occurrence of Cu(II), which is segregated in the grain boundary and locally causes a conductivity similar to CuO, although the surface of the thick film has Cu2O stoichiometry. Since grains grow with an increasing film thickness, the effect of an apparent oxygen excess is most pronounced in vicinity to the substrate interface. Electrical properties of Cu2O grains are at least partially short-circuited by this effect. The study focuses on properties inherent to copper oxide, although interface effects cannot be ruled out. This non-destructive, bottom-up analysis reveals phenomena which are commonly not observable after device fabrication, but clearly dominate electrical properties of polycrystalline thin films.

Item Type: Article
Erschienen: 2016
Creators: Deuermeier, Jonas and Wardenga, Hans F. and Morasch, Jan and Siol, Sebastian and Nandy, Suman and Calmeiro, Tomás and Martins, Rodrigo and Klein, Andreas and Fortunato, Elvira
Title: Highly conductive grain boundaries in copper oxide thin films
Language: German
Abstract:

High conductivity in the off-state and low field-effect mobility compared to bulk properties is widely observed in the p-type thin-film transistors of Cu2O, especially when processed at moderate temperature. This work presents results from in situ conductance measurements at thicknesses from sub-nm to around 250 nm with parallel X-ray photoelectron spectroscopy. An enhanced conductivity at low thickness is explained by the occurrence of Cu(II), which is segregated in the grain boundary and locally causes a conductivity similar to CuO, although the surface of the thick film has Cu2O stoichiometry. Since grains grow with an increasing film thickness, the effect of an apparent oxygen excess is most pronounced in vicinity to the substrate interface. Electrical properties of Cu2O grains are at least partially short-circuited by this effect. The study focuses on properties inherent to copper oxide, although interface effects cannot be ruled out. This non-destructive, bottom-up analysis reveals phenomena which are commonly not observable after device fabrication, but clearly dominate electrical properties of polycrystalline thin films.

Journal or Publication Title: Journal of Applied Physics
Volume: 119
Number: 23
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Surface Science
Date Deposited: 17 Jun 2016 05:54
Official URL: http://dx.doi.org/10.1063/1.4954002
Identification Number: doi:10.1063/1.4954002
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