Cover Picture: Epitaxial phase‐change materials (Phys. Status Solidi RRL 11/2012)

Ge–Sb–Te (GST) alloys lying along the GeTe–Sb2Te3 pseudo-binary tie line have proven to be among the most auspicious classes of materials for storage applications. Their success is related to the rapid and reversible phase-change from the crystalline to the amorphous state, whose strongly different optical and electrical properties can be used to encode information. The main technique used to produce phase-change material (PCM) thin films, both in academia and in industry, is physical vapor deposition (PVD). The layers fabricated by PVD are polycrystalline in the crystalline state. In their Rapid Research Letter on pp. 415–417, Peter Rodenbach et al. demonstrate the successful molecular beam epitaxy (MBE) of PCM thin films in the quasi-binary GeTe–Sb2Te3 system on slightly (GaSb) as well as largely (Si) lattice-mismatched substrates with (111) orientation. MBE growth is anticipated to allow the control of the alloy composition at the atomic level of the different chemical species. The perfect spatial order of epitaxial layers opens new horizons for investigation of the unique properties of PCMs, that may lead to the development of conceptually new memory devices.