# VIS-XUV Optical Constants and Electronic Band Parameters of a Tin-Oxo Cage Photoresist (Sn12O24C52H120)

## TL;DR

This paper measures optical and electronic properties of a Tin-Oxo cage photoresist using electron energy loss spectroscopy techniques.

## Contribution

The study provides new VIS-XUV optical constants and electronic band parameters for a Tin-Oxo cage material.

## Key findings

- An energy gap of E_g = 6.6 ± 0.5 eV was determined from the energy loss function onset.
- The electron affinity was calculated as χ = 3.3 ± 0.8 eV based on measured valence band and vacuum level data.
- The valence bandwidth was estimated to be E_v = 8.5 eV from coincidence data.

## Abstract

Energy band parameters and VIS-XUV optical constants
were measured
on a Tin-Oxo cage photoresist by employing reflection electron energy
loss spectra (REELS) and secondary electron–electron energy
loss spectroscopy (SE2ELCS). Different kinematic conditions were chosen
for the two reflection loss spectra in order to disentangle contributions
of volume and surface losses. The normalized differential inverse
inelastic mean free path (nDIIMFP) was extracted and fitted to a model
dielectric function, described as a sum of Drude-type oscillators.
The oscillator parameters were used to calculate the energy loss function
(ELF) and the electron inelastic mean free path (IMFP). An energy
gap of E
g = 6.6 ± 0.5 eV was determined
from the onset of the energy loss function. The energetic distance
between the valence band maximum (E
VBM, or highest occupied molecular orbital, HOMO) and the vacuum level
(E
vac) was established by electron-pair
spectroscopy by measuring the smallest energy loss leading to emission
of a secondary electron. This was found to be 9.9 ± 0.5 eV, giving
the electron affinity as χ = E
VBM – E
vac – E
g = 3.3 ± 0.8 eV. The valence bandwidth was estimated
from the coincidence data to be E
v = 8.5
eV.