Electrochemical properties of silicon deposited on patterned wafer

摘要

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 LiPF_6 in EC/DMC, electrolyte/lithium metal, counter electrode (EC = ethylenecarbonate; DMC = dimethyl carbonate). A patterned silicon (100) 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 mu m/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 mu A cm~(-2), the silicon electrodes yield an initial capacity of 327 (mu Ah (cm~2 mu m)~(-1). After 100 cycles, the capacity is 285 mu Ah (cm~2 mu m)~(-1) and the capacity retention is 86 percent. Capacity retention is 76 and 61 percent at cycles 200 and 300, respectively.