Two step synthesis of ultrathin transition metal tellurides
Abstract
Transition metal tellurides (TMTs) are an exciting group of two-dimensional materials with a wide variety of polytypes and properties. Here, we demonstrate a simple and versatile two-step method for producing MoTe2, WTe2, and PtTe2 films via tellurization of thin metals at temperatures between 400 and 700 °C. Across this temperature range, monoclinic 1T′ phase of MoTe2, orthorhombic Td phase of WTe2, and hexagonal 2H phase of PtTe2 were formed. Based on x-ray diffraction and Raman analysis, temperatures greater than 600 °C were found to produce the best quality MoTe2 and WTe2. In contrast, lower temperatures (400 °C) were preferred for PtTe2, which becomes discontinuous and eventually decomposes above 650 °C. The presence of H2 in the tellurization process was critical to facilitate the formation of H2Te, which is known to be more reactive than Te vapor. In the absence of H2, neither MoTe2 nor WTe2 formed, and although PtTe2 was formed under pure N2, the crystal quality was significantly reduced. Temperature-dependent resistivity (ρ) measurements were performed on the best quality TMT films revealing all films to be highly conductive. MoTe2 showed metallic behavior up to 205 K where it underwent a phase transition from the semimetallic Td to semiconducting 1T′ phase. WTe2 exhibited a consistent semiconducting behavior with a small positive increase in ρ with decreasing temperature, and PtTe2 showed a metallic dependence from 10 K up to room temperature. Spectroscopic ellipsometry for TMT films provides complex optical constants n and k from ultraviolet to infrared.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 21, 2022
- Source ID
- 10.1116/6.0001893
Entities
People
- Christopher Muratore
- David Moore
- E. M. Smith
- Michael J. Motala
- Michael Snure
- Nicholas R Glavin
- Shivashankar Vangala
- Timothy A. Prusnick
Organizations
- Air Force Office of Scientific Research
- Air Force Research Laboratory
- Air Force Research Laboratory Materials and Manufacturing Directorate
- University of Dayton