synthesis and characterization of novel 2d heterostructure materials

Open Access
Author:
Markman, Brian David
Area of Honors:
Materials Science and Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Joshua Alexander Robinson, Thesis Supervisor
  • Robert Allen Kimel, Honors Advisor
Keywords:
  • 2d
  • hexagonal boron nitride
  • tungsten disulfide
  • photoelectron spectroscopy
  • chemical vapor deposition
  • monolayer
Abstract:
Hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMD) have received increased attention in recent years due to graphene’s lack of bandgap. Hexagonal boron nitride exhibits some key advantages over 3D dielectrics such as its atomically smooth surface and lack of dangling bonds. Monolayer transition metal dichalcogenides exhibit interesting properties as compared to their multilayer counterparts. Most notable is the indirect-direct bandgap transition that TMDs undergo with layer thinning. This thesis presents the CVD growth of h-BN on Cu foil and the ARPES investigation of h- BN grown in UHV on Pt(110). Growths in UHV demonstrate the possibility of low temperature (630°C) ordered growth. Additionally, intercalation of Au to reach a quasi-free standing state was demonstrated and direct growth of WS2 on h-BN grown on Au and Ni(111) was also demonstrated. Direct growth of WS2 in UHV on various substrates (metallic and insulating) was also demonstrated. Low temperature growths (120°C) resulted in a disordered metallic phase while annealing to 400°C resulted in an irreversible phase transformation to the thermodynamically, semiconducting phase. The direct growth of the metallic phase occurred preferentially on quasi- free standing h-BN as compared to Au due to reduced coupling between layers and reduced adherence of residual S to the surface.