Heterostructured Thin Films of Coordination Polymers: Study on Growth and Electrical Conductance

Abstract

The thesis entitled “Heterostructured Thin Films of Coordination Polymers: Study on Growth and Electrical Conductance” primarily focuses on the fabrication of lattice-matched and lattice-mismatched heterostructured thin films of CPs and thorough investigation of electrical transport properties across the thin films. Herein, we have fabricated the lattice-matched and lattice-mismatched heterostructured thin films of CPs involving metals with different oxidation states Cu(II) or Cu(I) and different ligands with distinctive functionalities or coordination motifs on functionalized Au and FTO substrates by employing LbL method. Electrical transport measurements were conducted for the first time to explore the emergence of interfacial properties on heterostructured CP thin films. Overall, four Cu-based heterostructured thin films of CPs are explored in this thesis, with one lattice-matched and three lattice-mismatched structures. In chapter-2, lattice-mismatched heterostructure thin films of Cu(II)-BTC (BTC = 1,3,5-benzenetricarboxylate) and Cu(I)-TCNQ (TCNQ = 7,7,8,8- tetracyanoquinodimethane) have been studied and electrical transport measurements across the thin films revealed rectification of current assigned to be due to the formation of p-n junction interface. Similarly, a current rectification was realized in a lattice-matched heterostructured thin film of Cu(II)-BTC and TCNQ@Cu-BTC with the formation of p-n junction in chapter-3. In chapter-4, an unusual metallic conduction was identified in the lattice-mismatched heterostructure thin film of Cu(II)-BPyDC (BPyDC = 2,2′-bipyridine-4,4′-dicarboxylate) and Cu(I)-TCNQ, attributed to be due to charge-transfer across the interface and in chapter-5, an interesting effect of current rectification along with resistive switching at elevated temperature was observed in a lattice-mismatchedheterostructured thin film of Cu(II)(Cys)2 (Cys = Cysteine) and Cu(I)-TCNQ where both CPs show thermally driven resistive switching behaviour. In all the cases, emergence of unique interfacial properties was realized in resultant heterostructured thin films. Therefore, the obtained results open up new avenues for the design and development of functional materials in thin film configurations for various electronic and electrochemical device applications, specifically, flexible electronics (flexible displays, sensors, and wearable electronics), memory devices (resistive switching or phase change), field-effect transistors (FET), photodetectors and photovoltaics.