APEX is the successor to the Japanese Journal of Applied Physics (JJAP) letter section, JJAP Part 2, and not only has inherited the world-wide recognition of JJAP Part 2 (Letters and Express Letters), but also further promotes its strength in high scientific quality and prompt publication. In the journal policy, special emphasis is placed on high scientific and/or technological impact of its published papers. APEX is a sister journal of JJAP and is published by the Japan Society of Applied Physics (JSAP) through the Institute of Pure and Applied Physics (IPAP).