My Research Experience I am describing very shortly about my research experience. Experimental Condensed Matter Physics is my research field of interest. There are three major parts in my research like active materials preparation, thin film device fabrication and electronic or optoelectronic device characterizations. Active materials are organic semiconductors (such as polymers, organic dye etc), binary quantum dots (such as CdSe, CdS, PbS, PbSe etc), metallic quantum dots (such as Au, Ag etc), doped and undoped metal oxide nanomaterials (such as ZnO, TiO2), hybrid organic-inorganic core/shell nanomaterials and graphene. These materials were prepared and functionalised by me in our research laboratory except organic molecules. Quantum dots were synthesised via aqueous or high temperature method regarding our requirements for hybrid materials preparation and device fabrication. Graphene is prepared from graphene oxide by using chemical exfoliation of graphite and microwave irradiation. I am also able to characterise these materials using standard techniques like XRD, HR-TEM, EDAX, FFT, FE-SEM, FT-IR, UV-vis, Photoluminescence etc for standardisation. Thin film device fabrication and characterisation is very important part of my research work. Techniques for thin film deposition are layer-by-layer electrostatic self assembly (LBL ESA), spin casting or vacuum deposition. The substrates are functionalised or cleaned ITO coated glass substrate or atomically flat highly doped silicon. I have characterised these thin films by using today’s advanced microscopy techniques like AFM, SEM and STM. For study the electrical properties and device applications, I have measured current-voltage characteristics of these device. I have shown electrical bistability and memory phenomenon of these devices. Using Scanning Tunnelling Microscope, I have measured tunnelling current of monolayer device to probe electrical properties at nanoscale. I have introduced how hybrid organic-inorganic core/shell nanomaterials can decouple the two gaps so that the transport gap of the quantum dots can be tuned without altering the optical gap.
Abstract: We report growth, monolayer formation, and (electrical bistability and memory phenomenon)
properties of hybrid coreshell nanoparticles. While inorganic quantum dots, such as CdS or CdSe, act as the core,
a monolayer of ionic organic dye molecules, electrostatically bound to the surface of functionalized quantum
dots, forms the shell. We form a monolayer of the coreshell hybrid nanoparticles via a layer-by-layer electrostatic
assembly process. Growth and monolayer formation of the organicinorganic hybrid nanoparticles have been
substantiated by usual characterization methods, including electronic absorption spectroscopy of dispersed
solution and atomic force microscope images of scratched films. Devices based on the hybrid nanoparticles have
exhibited electrical bistability and memory phenomena. From the comparison of these properties in coreshell
nanoparticles and in its components, we infer that the degree of conductance switching or on/off ratio is
substantially higher in the hybrid nanoparticles. Also, they (coreshell particles) provide routes to tune the
bistability and memory phenomena by choosing either of the components. A monolayer of hybrid nanoparticles
has been characterized by a scanning tunneling microscope tip as the other electrode. We show that a single
coreshell hybrid nanoparticle can exhibit bistability with an associated memory phenomenon. Charge
confinement, as evidenced by an increase in the density of states, has been found to be the mechanism of electrical
bistability.