In order to use Al-2 at%Nd as the source-drain electrode of hydrogenated amorphous silicon thin film transistors (a-Si:H TFTs) without diffusion barrier, the diffusion characteristics of Al-2 at%Nd into phosphorus-doped (n+) a-Si:H were studied, and diffusion between Al-2 at%Nd and phosphorous-doped poly-Si (n + poly-Si) was also investigated for comparison. The electric resistance variation of Al-2 at%Nd, n + a-Si:H, and n + poly-Si was measured by four-point probe method at every annealing step, and each surface was inspected by optical microscope. Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy were used to analyze atomic diffusion progress with the variation of annealing temperature. Through these analyses, we ascertain that the Nd element of Al-2 at%Nd hinders the diffusion between Al and Si, and n + a-Si:H is stable up to 300 degrees C and n + poly-Si is stable up to 400 degrees C against the diffusion of Al-2 at%Nd. Thus Al-2 at%Nd can be utilized as the source-drain electrode of a-Si:H TFTs below 300 degrees C and poly-Si TFTs below 400 degrees C without diffusion barrier. (C) 2011 Elsevier B.V. All rights reserved.