The invention discloses a
thin film transistor, a preparation method thereof, an array substrate and a
display device. The
thin film transistor, the preparation method thereof, the array substrate and the
display device resolve the problems that an
electrode or a wire made of Cu causes poor or abnormal display of the
display device due to high
diffusion capacity or easy oxidation. The
thin film transistor comprises a grid
electrode made of pure
copper, a grid
electrode insulation layer, an
active layer, a source electrode, a drain electrode and a
copper alloy film layer, wherein the
copper alloy film layer is arranged on the surface, facing the
active layer, of the grid electrode. The thin film
transistor, the preparation method thereof, the array substrate and the display device have the advantages that the
copper alloy film layer is arranged on the surface, facing the
active layer, of the grid electrode of the thin film
transistor, accumulation of
alloy elements at the
crystal boundary, the
crystal surface and the surface can prevent
diffusion of copper atoms towards the active layer, the
oxidation resistance of the grid electrode is improved, and therefore the problem of poor or abnormal display of the display device caused when the thin film
transistor fails or the display device has a Mura defect is avoided.