Kelvin probe force microscopy of the nanoscale electrical surface potential barrier of metal/semiconductor interfaces in ambient atmosphere

Petr Knotek,Jan Smolík,Milan Vlček,Jiří Navrátil,Petr Kutálek,Čestmír Drašar,Tomáš Plecháček,Filip Dvořák

doi:10.3762/bjnano.10.138

Abstract

This study deals with the preparation and characterization of metallic nanoinclusions on the surface of semiconducting Bi2Se3 that could be used for an enhancement of the efficiency of thermoelectric materials. We used Au forming a 1D alloy through diffusion (point nanoinclusion) and Mo forming thermodynamically stable layered MoSe2 nanosheets through the reaction with the Bi2Se3. The Schottky barrier formed by the 1D and 2D nanoinclusions was characterized by means of atomic force microscopy (AFM). We used Kelvin probe force microscopy (KPFM) in ambient atmosphere at the nanoscale and compared the results to those of ultraviolet photoelectron spectroscopy (UPS) in UHV at the macroscale. The existence of the Schottky barrier was demonstrated at +120 meV for the Mo layer and −80 meV for the Au layer reflecting the formation of MoSe2 and Au/Bi2Se3 alloy, respectively. The results of both methods (KPFM and UPS) were in good agreement. We revealed that long-time exposure (tens of seconds) to the electrical field leads to deep oxidation and the formation of perturbations greater than 1 µm in height, which hinder the I–V measurements.

Highlights

Increasing energy demand and the negative effects of current energy technologies on the environment lead to increased interest in alternative energy technologies
We demonstrated local changes of the work function/surface contact potential as a consequence of metal nanoinclusions on the surface of Bi2Se3
These Schottky barriers can be realized in the form of separated metal nanoparticles through dc sputtering, or through the local reaction/diffusion of a metallic layer irradiated with electrons or UV photons

Summary

Introduction

Increasing energy demand and the negative effects of current energy technologies on the environment lead to increased interest in alternative energy technologies. Size, homogeneity of distribution and chemical composition as the basic characteristics are studied by using electron microscopy (SEM+TEM), there is a high probability that the NPs diffuse into the TE matrix due to the e-beam interaction. These characterizations are performed by using scanning tunneling microscopy (STM) [27,28] or by using AFM in the semicontact mode. In the present study we demonstrate that the Schottky barrier (surface contact potential) value and the polarity can be controlled by the barrier-forming metal NPs (Au, Mo) and can reflect their different chemical behavior with the Bi2Se3 matrix. A monoatomic argon ion source was utilized with energy of 2 keV, ion current 10 μA, raster area 1 × 1 mm and sputtering time 30 s

Results and Discussion

Conclusion

48. Nanomaterials