A unique diffusion barrier structure, consisting of layers of a Ti nanorod array and Ti film, has been fabricated on Si substrate for a subsequent 2 at.% Ti-doped Mg film deposition using a combinational technique of multilayer growth, co-deposition and dynamic shadowing growth. The hydrogenation of the Ti-doped Mg film on such a barrier structure shows that the barrier can prevent direct Mg-Si contact and suppress the formation of Mg(2)Si alloy in a high-temperature process. When this film has been hydrogenated at temperatures T≤300 °C for approximately 150 h, tetragonal single-crystal MgH(2) nanowires are formed on the surface of the Ti-doped Mg film. The hydrogenation time and temperature are the two main factors for the nanowire formation. The doping of Ti also plays a significant role. This result reveals that complicated dynamic processes could occur during the hydrogenation of Ti-doped Mg film when Mg(2)Si formation can be eliminated by an effective diffusion barrier layer.