Electrical properties of Si-XII and Si-III formed by nanoindentation

Conventional silicon devices and integrated circuits are fabricated in the diamond cubic phase of silicon, so-called Si-I. Other phases of silicon can be formed under pressure applied by indentation and these phases are metastable at room-temperature and pressure. As we demonstrate, such phases behave entirely differently to normal diamond-cubic silicon (Si-I) having different electrical properties. Two such phases, Si-III (BC8) and Si-XII (R8), can be formed by indentation but little is known about their electrical properties. Theoretical studies predict Si-III to be a semimetal [1] and Si-XII to be a narrow band gap semiconductor [2]. We report the first electrical measurements on these phases, which we have formed by nanoindentation. We demonstrate that Si-XII is a semiconductor that can be electrically doped with boron and phosphorus at room temperature. We also demonstrate early devices formed by nanoindentation at room temperature.