Schottky barrier formation and band bending revealed by first- principles calculations.

Yang Jiao,Mikael Käll,Anders Hellman,Yurui Fang,Shiwu Gao

doi:10.1038/srep11374

Abstract

The formation of a Schottky barrier at the metal-semiconductor interface is widely utilised in semiconductor devices. With the emerging of novel Schottky barrier based nanoelectronics, a further microscopic understanding of this interface is in high demand. Here we provide an atomistic insight into potential barrier formation and band bending by ab initio simulations and model analysis of a prototype Schottky diode, i.e., niobium doped rutile titania in contact with gold (Au/Nb:TiO2). The local Schottky barrier height is found to vary between 0 and 1.26 eV depending on the position of the dopant. The band bending is caused by a dopant induced dipole field between the interface and the dopant site, whereas the pristine Au/TiO2 interface does not show any band bending. These findings open the possibility for atomic scale optimisation of the Schottky barrier and light harvesting in metal-semiconductor nanostructures.

Highlights

The band structure of isolated and combined Au and rutile TiO2 slab
In order to explore the effect of chemical composition on the SB, a large number of different atomic structures were calculated based on the lattice alignment and orientation of Au nanoparticles on thin film rutile (110) TiO230
The SBH reduction is 0.58 eV for εS = 10 (0.15 eV for εS = 60), which deviates from the calculated SBH reduction (Fig. 4), and does not explain the dependence on the dopant position (Fig. 3). This qualitative and quantitative discrepancy between the SBH prediction obtained from the uniform dopant Schottky model and our results clearly indicate the importance of an atomistic description of the interface

Summary

Introduction

The red dashed line is the Fermi level. The TiO2 bands shift up by 0.4 eV owing to the contact with Au. Nb dopants are known to induce small lattice relaxations[28] which makes this particular system suitable for atomistic simulations. We found that the pristine Au/TiO2 interface has a relatively large barrier height, but shows no band bending. The band bending and decay length is instead determined by the precise locations of the dopant. Our results show that the band bending is inhomogeneous and highly localised to the defect region. We calculated the dopant position dependent barrier height and show that it can be qualitatively understood by the deep level (DL) barrier model[29]. Our results reveal the origin and nature of inhomogeneity of the SBH and shed light on the mechanisms of electron transmission across the metal-semiconductor interfaces

Methods

Results

Conclusion