Year: 2018
Type: article
Abstract: Polytypism, or the ability for materials to crystallize with different stacking sequences, often leads to fundamentally different properties in families of two-dimensional materials. Here, we show that is possible to control the polytype of GeH, a representative two-dimensional material that is synthesized topotactically by first controlling the polytype sequence of the precursor Zintl phase. 1T, 2H, and 6R GeH can be prepared by the topotactic deintercalation of 1T EuGe 2, 2H α-CaGe 2, and 6R β-CaGe 2, respectively. The 6R and 1T GeH polytypes exhibit remarkably similar properties and feature band gaps of 1.63 and 1.59 eV, respectively. However, the 2H CaGe 2 precursor forms due to the incorporation of small amounts of In flux in the germanium lattice, which is retained when converted to GeH. Consequently, 2H GeH has a reduced band gap of 1.45 eV. Finally, temperature dependent diffraction of 6R GeH shows a negative coefficient of thermal expansion along the a -axis and a positive coefficient of thermal expansion along the out-of-plane c -axis.
Source: Chemistry of Materials
Institutions: The Ohio State University, University of Delaware
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, Camille and Henry Dreyfus Foundation, Ohio State University, Office of Science, Materials Research Science and Engineering Center, Harvard University, Division of Materials Research, Division of Emerging Frontiers in Research and Innovation, Basic Energy Sciences, Argonne National Laboratory
Awards: G102163711, G107546177, G1286251239, G1313983767, G1608797791, G1664757510, G2287611682, G2487199047, G262962599, CAREER: Synthesis and Structural Characterization of Lanthanide-Based Silicides and Germanides, G3075337988, G3589692066, G3723821865, G426311843, Center for Emergent Materials, G4815212387, G498139845, G513797252, Acquistion of Multiuser X-Ray Photoelectron Spectrometer for Materials Research and Education, G5387317844, G5430360074, Collaborative Research: Synthesis, Structural Characterization and Electrochemical Studies of Framework Substituted Silicon, Germanium and Tin Clathrates, G6012531032, G6336286406, G635677031, G6492027905, G6671297155, G6848031779, G6884130749, G6918803902, G6921884059, G7583137537, G7696246063, EFRI 2-DARE: Enhancing Electronic and Thermal Properties in Epitopotaxial Ge/Sn Graphane Heterostructures, G969889393, G993149817
OpenAlex ID: W2787198481