Feasibility of Tellurium-oxygen Ion Exchange in Tungsten Oxide Thin Films for Synthesis of Tungsten Telluride Crystals

Open Access
Author:
Bersch, Brian M
Area of Honors:
Engineering Science
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Joshua Alexander Robinson, Thesis Supervisor
  • Reginald Felix Hamilton, Honors Advisor
  • Judith A Todd, Faculty Reader
Keywords:
  • tungten telluride
  • WTe2
  • tungsten oxide
  • WO3
  • tellurization
  • transition metal dichalcogenides
  • two dimensional materials
Abstract:
This body of work outlines the feasibility of a tellurium-oxygen ion exchange in tungsten oxide (WO3) thin films as a means of synthesis for tungsten telluride (WTe2) crystals. Tungsten telluride belongs to a class of layered, two dimensional materials called transition metal dichalcogenides (TMDs) which have garnered an enormous amount of attention in recent years due to their unique material properties at the nanoscale and their many exciting applications, particularly in the next generation of scaled down and high performance semiconductor devices. The large majority of existing scientific literature on WTe2 is dated and solely focuses on the synthesis of either powdered or single crystal bulk WTe2 samples. To date, no research has been conducted on the nanoscale synthesis of WTe2 by a conventional thin film deposition method. This lack of investigation into a promising next generation semiconductor material combined with the rapidly growing interest in MoS2 and similar tungsten TMD compounds such as WS2 and WSe2 is impetus for research into the synthesis, characterization, and application of WTe2. This tellurium-oxygen exchange reaction, or tellurization, of WO3 thin films has been pursued in this research as an avenue for WTe2 growth because it is a synthesis technique very similar to the sulfurization and selenization of molybdenum and tungsten oxides for successful growth of MoS2, MoSe2, WS2, and WSe2. However, this research has found that the various processing conditions attempted for tellurization of WO3 thin films in this thesis did not yield WTe2 crystals. Unfortunately, tellurization of WO3 does not seem to be a viable or practical synthesis method for WTe2 nanosheets, and research focuses should perhaps be devoted elsewhere. Yet, this research will hopefully shed light on the kinetics of WTe2 thin film growth and provide meaningful insight into future work suggestions.