Electron microscopy study of Ni induced crystallization in amorphous Si thin films

The crystallization of amorphous silicon is studied by transmission electron microscopy. The effect of Ni on the crystallization is studied in a wide temperature range heating thinned samples in-situ inside the microscope. Two cases of limited Ni source and unlimited Ni source are studied and compared. NiSi2 phase started to form at a temperature as low as 250 degrees C in the limited Ni source case. In-situ observation gives a clear view on the crystallization of silicon through small NiSi2 grain formation. The same phase is observed at the crystallization front in the unlimited Ni source case, where a second region is also observed with large grains of Ni3Si2. Low temperature experiments show, that long annealing of amorphous silicon at 410 degrees C already results in large crystallized Si regions due to the Ni induced crystallization.