Electrochemical properties of silicon deposited on patterned wafer

An amorphous silicon thin-film deposited on a patterned wafer is prepared by radio-frequency (rf) magnetron sputtering and is characterized by X-ray diffraction, galvanostatic cycle testing and field emission scanning electron microscopy. The specimen is assembled in cell of configuration: silicon working electrode/1 M LiPF6 in EC/DMC, electrolyte/lithium metal, counter electrode (EC = ethylenecarbonate; DMC = dimethyl carbonate). A patterned silicon (1 0 0) wafer prepared by photolithography and KOH etching is used as the electrode substrate. The size of the patterns, which are composed of arrays of the negative square pyramids, is 5 μm/side. The patterned specimen (silicon film on patterned substrate) is compared with a normal specimen (silicon deposited on a flat substrate). The rate of capacity fade on cycling is monitored as a function of the voltage window and current density. The patterned specimen displays better cycle behaviour at a high current density (high C-rate). During the cycle tests at 200 μA cm−2, the silicon electrodes yield an initial capacity of 327 μAh (cm2 μm)−1. After 100 cycles, the capacity is 285 μAh (cm2 μm)−1 and the capacity retention is 86%. Capacity retention is 76 and 61% at cycles 200 and 300, respectively.