High-Performance Bismuth Antimony Telluride Thermoelectric Membrane on Curved and Flexible Supports
Liangwei Fu, Kwansu Park, Sang‐il Kim, Sang‐il Kim, Bongju Kim, Hyun Yong Song, Wooseon Choi, Young‐Min Kim, Jae‐Yeol Hwang, Kyu Hyoung Lee, Sung Wng Kim, Sung Wng Kim
Abstract
Separation of epitaxial thin films on a growth substrate and transfer onto other materials for functional heterostructures have boosted the transformative impact on science and technology. However, this scheme has proved challenging in thin-film thermoelectrics but promises a vast range of applications beyond the limited device configurations of bulk thermoelectrics. Here, the high-quality Bi0.5Sb1.5Te3 (BST) epitaxial thin film on a sapphire substrate grown by spontaneous van der Waals epitaxy (vdWE) is exfoliated and transferred onto versatile materials, creating high-performance thermoelectric membranes. Unprecedented millimeter-size vdWE BST membranes are produced by etching a pseudomorphic Te monolayer on the surface of a sapphire substrate in dilute HF solution. The intact exfoliation and direct transfer for vdWE BST membranes maintain the high-quality crystallinity, resulting in the remarkable zT value (∼0.9 at 300 K). These results represent the realization of long-pursued but undemonstrated high-performance thin-film thermoelectrics, paving the way for the design and fabrication of arbitrarily shaped thermoelectric devices.