Mechanical stress dependence of the Fermi level pinning on an oxidized silicon surface

TL;DR

This study investigates how mechanical stress influences Fermi level pinning on oxidized silicon surfaces, revealing symmetric pinning behavior and quantifying energy changes under different stress conditions relevant to nano-device applications.

Contribution

It provides the first detailed measurement of stress-dependent Fermi level pinning on oxidized silicon surfaces using micro-Raman and XPS techniques.

Findings

Fermi level pinning remains symmetric under applied stress.

Pinning energy increases by 0.16 meV/MPa under compression.

Pinning energy increases by 0.11 meV/MPa under tension.

Abstract

A combination of micro-Raman spectroscopy and micro-XPS (X-ray photo-electron spectroscopy) mapping on statically deflected p-type silicon cantilevers is used to study the mechanical stress dependence of the Fermi level pinning at an oxidized silicon (001) surface. With uniaxial compressive and tensile stress applied parallel to the $\langle$110$\rangle$ crystal direction, the observations are relevant to the electronic properties of strain-silicon nano-devices with large surface-to-volume ratios such as nanowires and nanomembranes. The surface Fermi level pinning is found to be even in applied stress, a fact that may be related to the symmetry of the Pb$_0$ silicon/oxide interface defects. For stresses up to 160 MPa, an increase in the pinning energy of 0.16 meV/MPa is observed for compressive stress, while for tensile stress it increases by 0.11 meV/MPa. Using the bulk, valence band deformation potentials the reduction in surface band bending in compression (0.09 meV/MPa) and in tension (0.13 meV/MPa) can be estimated.