Mesotaxy by nickel diffusion into a buried amorphous silicon layer

Formation of nickel nanoparticles on amorphous silicon thin film and its effect on crystallization

“…5,6 Erokhin et al 7 also observed similar phenomena. They 6,7 suggested that crystallization is enhanced by solid-phase transport of Si through the silicides. However, in a Ni/a-Si/ c-Si layered system, Mohadjeri et al 8 presented another possibility of crystallization mechanism than in the previous results: 6,7 During annealing at various temperatures between 350 and 425°C, nickel monosilicide ͑NiSi͒ forms at the Ni/ a-Si interface and Ni diffuses toward at the a-Si/ c-Si interface through the a-Si layer.…”

“…The NiSi 2 precipitates are observed to migrate in the a-Si films, leaving c-Si needles behind ͑NiSi 2 -mediated crystallization͒. 5,6 Erokhin et al 7 also observed similar phenomena. They 6,7 suggested that crystallization is enhanced by solid-phase transport of Si through the silicides.…”

“…Bulk amorphous silicon ͑a-Si͒ crystallizes at about 600-700°C ͑e.g., Ref. 1͒ and this intrinsic crystallization temperature is lowered by addition of metal impurities, such as Au, 2 Al, 3 and Sb, 4 which form eutectics with Si, and Ni, [5][6][7] which forms various silicides with Si. For the eutecticforming metals, Radnoczi et al suggested that Au, Sb, and Al dissolved in the a-Si film may loosen the covalent bonding in the a-Si and make the a-Si even unstable, enhancing crystallization.…”

“…3 Unlike eutectic-forming metals, for the silicide-forming metal, such as Ni, silicides are reported to mediate crystallization. [5][6][7] Hayzelden and co-workers 5,6 observed that after NiSi 2 precipitates with CaF 2 structure, which has a close lattice match to Si ͑−0.4% ͒, form in a-Si in the shape of octahedra bounded by eight ͕111͖ faces at about 400°C, then at a higher temperature of 500°C, the c-Si is epitaxially nucleated on one or more of the NiSi 2 ͕111͖ surfaces. The NiSi 2 precipitates are observed to migrate in the a-Si films, leaving c-Si needles behind ͑NiSi 2 -mediated crystallization͒.…”

Solid-Phase Crystallization of Amorphous Silicon Films

“…Diffusion of Ni through c-Si to reach the a-Si in Figure 18 is consistent with previous experiments on Ni-assisted Si epitaxy. Erokhin et al [45] deposited a film of Ni on a c-Si/a-Si structure and observed Ni diffusion to the c-Si/a-Si interface to form NiSi 2 after annealing for 43 h at 350°C . Decomposition of NiSi 2 at the NiSi 2 /c-Si interface with Ni diffusion into the a-Si was suggested as a mechanism for Si crystallization.…”