Silicon meets group-II metals in energy and electronic applications—How to handle reactive sources for high-quality films and bulk crystals

Abstract

In the present advanced information society, the group IV element Si is inevitably used for various high-performance devices, such as transistors and solar cells. When Si meets group-II elements such as Mg, Ca, Sr, or Ba, semiconducting silicides are formed, which are applicable to energy conversion devices such as thin-film solar cells and thermoelectric devices. In this Tutorial, we focus on two representative typical semiconducting silicides among them: Mg2Si and BaSi2 composed of earth-abundant elements. Mg2Si has been extensively studied for light-weight high-performance thermoelectric devices, whereas BaSi2 has been studied for thin-film solar cells, and recently has also been attracting attention as a thermoelectric material. However, these group-II elements are highly reactive with oxygen and water. Thus, we need to be careful when handling these elements. In this Tutorial, we provide guidance on how to handle these group-II elements and their compounds in an easy-to-understand manner for beginners. In addition, we introduce thin-film growth and bulk growth techniques, as well as the points to be considered when characterizing these materials.