  We have investigated the gate-voltage dependence and the temperature
dependence of the magnetoconductivity of amorphous indium-gallium-zinc-oxide
thin-film transistors. A weak-localization feature is observed at small
magnetic fields on top of an overall negative magnetoconductivity at higher
fields. An intriguing controllable competition between weak localization and
weak antilocalization is observed by tuning the gate voltage or varying the
temperature. Our findings reflect controllable quantum interference competition
in the electron systems in amorphous indium-gallium-zinc-oxide thin-film
transistors.
