Thermo-compression Synthesis And Size-dependent Optical And Piezoelectric Properties Of Ultrathin Two-dimensional Materials

Ultrathin two-dimensional?2D?nanomaterials have now emerged as a key class of materials that have shown promising outcomes in many areas such as electronics/optoelectronics,energy storage and conversion,sensors and catalysts,to name a few.These outcomes acted as a thrust behind the comprehensive research efforts towards the expansion of 2D family by realizing new functional 2D materials and requires innovative synthesis routes.To this point,layered materials of 2D family have been the focus of studies so far,largely due to their comparatively weak interplanar van der Waals forces which makes them feasible to isolate into 2D nanomaterials,where,liquid and mechanical exfoliation come into play.Such materials include semimetallic graphene,semiconducting monolayer TMDs?e.g.Mo S₂,Mo Se₂,WSe₂ etc.?,and insulator hexagonal boron nitride?h-BN?.Unfortunately,numerous functional materials,such as,semi-metals/metalloids,polymers and most metal oxides,owing to their non-layered lattice structure,have not been well studied due to the lack of facile fabrication mechanism that helps realizing their 2D nanostructures.In this dissertation,we propose a unique thermo-compression synthesis mechanism developed especially to realize ultrathin 2D nanostructures out of materials with non-layered crystal structure involving both the inorganic and organic?macromolecular?material systems,by systematically studying non-layered semimetal Bismuth?Bi?,layered semiconducting Bismuth Telluride?Bi₂Te₃?,semi-crystalline,molecular?polyvinyledene fluoride?PVDF polymer and 1D van der Waals?vd W?layered Tellurium?Te?.We further discuss implications of the proposed strategy on as-prepared 2D materials by investigating the size effects?thickness-dependence?in their optical and piezoelectric properties.Studies on substrate effects are also carried out in order to define the role of substrates and their implications on structural and therefore,optical properties with reference to the proposed thermo-compression synthesis mechanism.At the end,other developed thermo-compression synthesis techniques have been proposed for realizing large yield of 2D metal nanostructures,especially for materials with high melting points.