Ionic tunneling conductivity mechanism for growing colloidal gold quantum dots

Background. For experimental studies of fundamental physical effects in systems of ultrafine nanoparticles(UFNP) in a dielectric matrix, as well as for instrumental applications it is necessary to develop a technology of controlled growth of UFNP of set sizes in the ultra-thin dielectric film, that is relevant for both precise nanoelectronics and modern nanomedicine. The purpose of this work is to study the features of the tunneling volt-ampere characteristics(CVC), obtained for growing colloidal gold quantum dots in the combined atomic-force and scanning tunnel microscope(AFM/STM), as well as to investigate conditions of possible contribution of 2D - dissipative tunneling in the tunneling CVC. Materials and methods. The experimental methods correspond to methods of the authors from the University of Kobe(Japan)[12]. Formation of gold particles in films of Au(III) - SiO2/TiO2 was performed using an atomic force microscope. The theoretical work was carried out in the theory of dissipative tunneling using the instanton method. Results. In this work the authors obtained the tunneling CVC for growing colloidal gold quantum dots in the AFM/STM system. The tunneling CVC with the theoretical curve of field dependence of probability of 2D - dissipative tunneling was compared with the influence of two local phonon modes of the wide-band matrix. Qualitative matching of the experimental and theoretical curves indicates the possible contribution of dissipative tunneling in the tunneling current through a quantum dot at the cantilever tip, which can be amplified in clusters ranging in size from 1 to 5 nm in thinner films. Conclusions. Qualitative comparison of the tunneling CVC for growing clusters of colloidal gold in the AFM/STM system and the theoretical curve for field dependence of the probability of 2D - dissipative tunneling with the influence of two local phonon modes shows the presence of possible contribution of dissipative tunneling in the tunneling current through a growing QD at the initial stage of growth. It has been found that the ionic conductivity mechanism will prevail over the tunnel one when the magnitude of tension, induced by the electric field of positive gold ions, exceeds the value of the external electric field.