My experiments with thin films—the nanostate of matter

Abstract

The black art of thin films exhibiting whimsical properties and thus called ‘the fourth state of matter’ enticed the author to a challenge to unravel the mysteries of matter createdab-initio on a nanoscale. Nucleation and growth studies of evaporated and sputtered films (both polycrystalline and epitaxial) and the effects of kinetic energy, angle of incidence, electric field, substrate agitation, formation of metastable and amorphous structures, etc led to exciting discoveries. The fields of amorphous metal alloy and semiconducting films were thus born. Electron and optical transport investigations on pure and doped metal, semiconducting, oxide and polymer films established a variety of new phenomena of which the mean free path effects and specular scattering of conduction electrons in epitaxial metal films, giant thermopower in quenched metal films, sputter quenching, giant photocontraction effect in amorphous Ge-chalcogenide films, enhancement of superconducting transition temperature in transition metal films, nanosize multi layer coating (the first known superlattices) are noteworthy. A variety of new deposition processes such as solution growth of polymer films, solution growth of chalcogenide and oxide films, spray pyrolysis, coprecipitation of multicomponent oxides (for thick films), activated reactive evaporation/magnetron sputtering were innovated. This lecture will share the excitement of the contributions by the author, his 60 Ph.D students and a number of post doctoral fellows and faculty members at the Thin Film Laboratory, IIT Delhi and the Microscience Laboratory at IIT Kharagpur.