Fractal formation in a-Si:H/Ag/a-Si:H films after annealing

Abstract

The crystallization behavior of a-Si:H/Ag/a-Si:H sandwich films has been studied in detail. Fractals of Si caused by metal enhanced crystallization appear after annealing at 350–600 °C. The fractal dimension decreases (the Si fractals become more open) with the increasing annealing temperature. The number density of fractals increases at 350–450 °C and turns to decrease at 500–600 °C. The average fractal size increases from 350 to 550 °C and shows a decreasing tendency at 600 °C. The formation of fractals can be explained by a random successive nucleation and growth model. The x-ray energy dispersive spectroscopy (EDS) microanalysis indicates that although there is lateral interdiffusion of Ag and Si atoms, the thicknesses of the fractal region and the matrix remain nearly the same. At the same time, EDS shows that there are also Ag aggregates extending out of the films. It is suggested that besides the preferred nucleation at the Ag/Si interface the break of Si—H bonds may also stimulate the crystallization of a-Si:H so that the crystallization temperature of an a-Si:H/Ag system is much lower than that of an a-Si/Ag system.

Crystallization of sputtered amorphous silicon induced by silver–copper alloy with high crystalline volumeratio

“…Ag-induced crystallization of a-Si is also reported by some researchers. Bian et al [18] reported recrystallization of a-Si with 3:1 Ag to Si ratio. Scholz et al [19] reported the recrystallization of a-Si with 3:4 Ag to Si ratio and tens of hours of annealing at 530 1C.…”

Thermal annealing of a-Si/Au superlattice thin films

“…Presence of certain metal layers e.g., Al, Ag, Ni, and Au on amorphous Si (a-Si) films helps to crystallize a-Si [1][2][3][4]. The process is known as metal induced crystallization (MIC) which lowers the crystallization temperature of amorphous semiconductors [5,6].…”

Low-temperature crystallization of amorphous silicon using Cu field-aided lateral crystallization at 350°C

“…Russell et al 3 reported the crystallization of a-Si at about 485°C using an a-Si/Cu layer. Bian et al 4 reported the crystallization of hydrogenated a-Si (a-Si:H) in an a-Si:H/Ag/a-Si:H structure above 350°C. In these studies, the metal-silicide phase, which acts as a source to degrade the electrical characteristics, could remain at the center region of the transistor channel after the completion of the crystallization, and the crystallization velocity is completely dependent on the thermal diffusivity of the metal-silicide crystallization mediator.…”