Thin-film growth and application prospects of metallic delafossites
T. Harada
Abstract
Metallic delafossites are fascinating layered materials with exceptionally high electrical conductivity and surface polarity. The high conductivity is produced by the two-dimensional Pd and Pt conductive layers stabilized in a layered oxide framework. In this review, I will discuss the current status of thin-film growth and application prospects of metallic delafossites. Thin-film growth will enable the fabrication of the heterostructures of metallic delafossites and other compounds. In such heterostructures, the surface polarity of metallic delafossites can play a significant role, owing to their layered crystal structure with positively and negatively charged layers. Surface polarity not only influences on the movement of electrons but also induces spin-dependent surface states. Polar surfaces and interfaces can be used for device functionality by making the heterostructures of metallic delafossites and functional materials such as semiconductors and magnets. Quantum and mesoscopic devices are another promising application of metallic delafossites, which exploit the very long mean free path and electron coherence length found in bulk single crystals. For such applications, thin films with exceptional quality are needed, which is a challenge for thin-film growth. The research on metallic delafossite thin films is still in its infancy, and this review can impart knowledge that can lead to innovations on heterostructures with various materials.