Analysis of the Electrodeposition and Surface Chemistry
of CdTe, CdSe, and CdS Thin Films through Substrate-Overlayer Surface-Enhanced
Raman Spectroscopy
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Abstract
The substrate-overlayer approach
has been used to acquire surface
enhanced Raman spectra (SERS) during and after electrochemical atomic
layer deposition (ECALD) of CdSe, CdTe, and CdS thin films. The collected
data suggest that SERS measurements performed with off-resonance (i.e.
far from the surface plasmonic wavelength of the underlying SERS substrate)
laser excitation do not introduce perturbations to the ECALD processes.
Spectra acquired in this way afford rapid insight on the quality of
the semiconductor film during the course of an ECALD process. For
example, SERS data are used to highlight ECALD conditions that yield
crystalline CdSe and CdS films. In contrast, SERS measurements with
short wavelength laser excitation show evidence of photoelectrochemical
effects that were not germane to the intended ECALD process. Using
the semiconductor films prepared by ECALD, the substrate-overlayer
SERS approach also affords analysis of semiconductor surface adsorbates.
Specifically, Raman spectra of benzenethiol adsorbed onto CdSe, CdTe,
and CdS films are detailed. Spectral shifts in the vibronic features
of adsorbate bonding suggest subtle differences in substrate-adsorbate
interactions, highlighting the sensitivity of this methodology