Employing mix-and-match lithography of I-line stepper and e-beam direct writing, independent double-gated poly-Si nanowire thin film transistors with channel lengths ranging from 70 nm to 5 µm were fabricated and characterized. Electrical measurements performed under cryogenic ambient displayed intriguing characteristics in terms of length dependent abrupt switching behavior for one of the single-gated modes. Through simulation and experimental verification, the root cause for this phenomenon was identified to be the non-uniformly distributed dopants introduced by ion implantation.