Abstract: A process is disclosed for producing microporous crystalline silicon which has a band-gap substantially increased relative to that of normal crystalline silicon. This process involves the preparation of quantum wires of silicon by means of a chemical attack method carried out on silicon that has been doped such that it conducts electricity substantially via the effective transport of electric charge by means of so-called holes. The microporous crystalline silicon thus produced is in the form of a discrete mass having a bulk-like, interconnected crystalline silicon structure of quantum wires whose band-gap is greater than normal crystalline silicon. Because of this increased band-gap this microporous crystalline silicon may be used as an active element in applications such as tandem solar cells.

Abstract: A method for forming a thin crystal layer of silicon on top of a insulating layer that is supported by a silicon wafer used for electronic device applications. Carbon ions are implanted in a silicon wafer in order to form an etch stop. Said wafer is bonded to a supporting wafer that has an insulating surface layer of silicon oxide or silicon nitride. The silicon substrate of the implanted wafer is removed using an alkaline etching solution or grinding and alkaline etching. The remaining carbon implanted layer forms the thin silicon layer.