Towards dielectric relaxation at a single molecule scale

Vitalii Stetsovych,Michal Šámal,Bareld Wit,Radovan Vranik,Ivo Starý,Jindřich Nejedlý,Stefan Müllegger,Eva Rauls,Simon Feigl

doi:10.1038/s41598-022-06684-9

Abstract

Dielectric relaxation lies at the heart of well-established techniques of dielectric spectroscopy essential to diverse fields of research and technology. We report an experimental route for increasing the sensitivity of dielectric spectroscopy ultimately towards the scale of a single molecule. We use the method of radio frequency scanning tunneling microscopy to excite a single molecule junction based on a polar substituted helicene molecule by an electric field oscillating at 2–5 GHz. We detect the dielectric relaxation of the single molecule junction indirectly via its effect of power dissipation, which causes lateral displacement. From our data we determine a corresponding relaxation time of about 300 ps—consistent with literature values of similar helicene derivatives obtained by conventional methods of dielectric spectroscopy.

Highlights

Dielectric relaxation lies at the heart of well-established techniques of dielectric spectroscopy essential to diverse fields of research and technology
RFSTM combines scanning probe microscopy with complementary concepts borrowed from microwave resonance spectroscopy, resulting in a powerful combination of high spatial resolution of < 10−9 m with simultaneous energy resolution of < 10−7 eV for spectroscopy
RFSTM methods have been developed that utilize an external modulation of the electric field across the tunnel junction at MHz to GHz frequencies; in particular, they have enabled the successful thermometry at the nanometer s cale[4], magnetic resonance spectroscopy at the single spin level[5–7], noise s pectroscopy[8], addressing single-atom m agnets[9,10], ferromagnetic r esonance[11] as well as spectroscopy of high-frequency mechanical motion of molecules[4,12]

Summary

Introduction

Dielectric relaxation lies at the heart of well-established techniques of dielectric spectroscopy essential to diverse fields of research and technology. We use the method of radio frequency scanning tunneling microscopy to excite a single molecule junction based on a polar substituted helicene molecule by an electric field oscillating at 2–5 GHz. We detect the dielectric relaxation of the single molecule junction indirectly via its effect of power dissipation, which causes lateral displacement. The phenomenon of dielectric relaxation describes the response of a dielectric substance to an external oscillating electric field and lies at the heart of dielectric spectroscopy[1,2] The latter is a well-established technique indispensable for diverse fields of research and technology, including molecular sciences, biophysics, medicine as well as petroleum-related industry. We report an experimental route for increasing the sensitivity of dielectric spectroscopy towards the scale of a single molecule For this we use the method of radio frequency (RF) scanning tunneling microscopy (STM)[3]. Our results may impact the fabrication of high frequency single molecule devices in the future[15]

Methods

Results

Discussion

Conclusion