Real-Time Spectroscopic Ellipsometry for Flux Calibrations in Multi-Source Co-Evaporation of Thin Films: Application to Rate Variations in CuInSe₂ Deposition

Authors

Dhurba R. Sapkota, University of Toledo
Balaji Ramanujam, University of Toledo
Puja Pradhan, University of Toledo
Mohammed A. Razooqi Alaani, University of Toledo
Ambalanath Shan, University of Toledo
Michael J. Heben, University of Toledo
Sylvain Marsillac, Old Dominion UniversityFollow
Nikolas J. Podraza, University of Toledo
Robert W. Collins, University of Toledo

Document Type

Article

Publication Date

2024

DOI

10.3390/ma17164048

Publication Title

Materials

Volume

17

Issue

16

Pages

4048 (1-27)

Abstract

Flux calibrations in multi-source thermal co-evaporation of thin films have been developed based on real-time spectroscopic ellipsometry (RTSE) measurements. This methodology has been applied to fabricate CuInSe₂ (CIS) thin film photovoltaic (PV) absorbers, as an illustrative example, and their properties as functions of deposition rate have been studied. In this example, multiple Cu layers are deposited step-wise onto the same Si wafer substrate at different Cu evaporation source temperatures (TCu). Multiple In₂Se₃ layers are deposited similarly at different In source temperatures (TIn). Using RTSE, the Cu and In₂Se₃ deposition rates are determined as functions of TCu and TIn. These rates, denoted Reff, are measured in terms of effective thickness which is the volume per planar substrate area and accounts for surface roughness variations with deposition time. By assuming that all incident metal atoms are incorporated into the films and that the atomic concentrations in the deposited material components are the same as in single crystals, initial estimates of the Cu and In atom fluxes can be made versus T_Cu and T_In. Applying these estimates to the co-evaporation of a set of CIS films from individual Cu, In, and Se sources, atomic concentration corrections can be assigned to the Cu and In₂Se₃ calibration films. The corrections enable generation of a novel calibration diagram predicting the atomic ratio y = [Cu]/[In] and rate R_eff within the T_Cu-T_In plane. Using this diagram, optimization of the CIS properties as a PV absorber can be achieved versus both y and Reff.

Rights

© 2024 by the Authors.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License (CC BY 4.0).

Data Availability

Article states: "Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request."

Original Publication Citation

Sapkota, D. R., Ramanujam, B., Pradhan, P., Alaani, M. A. R., Shan, A., Heben, M. J., Marsillac, S., Podraza, N. J., & Collins, R. W. (2024). Real-time spectroscopic ellipsometry for flux calibrations in multi-source co-evaporation of thin films: Application to rate variations in CuInSe₂ deposition. Materials, 17(16), 1-27, Article 4048. https://doi.org/10.3390/ma17164048

Repository Citation

Sapkota, Dhurba R.; Ramanujam, Balaji; Pradhan, Puja; Razooqi Alaani, Mohammed A.; Shan, Ambalanath; Heben, Michael J.; Marsillac, Sylvain; Podraza, Nikolas J.; and Collins, Robert W., "Real-Time Spectroscopic Ellipsometry for Flux Calibrations in Multi-Source Co-Evaporation of Thin Films: Application to Rate Variations in CuInSe₂ Deposition" (2024). Electrical & Computer Engineering Faculty Publications. 480.
https://digitalcommons.odu.edu/ece_fac_pubs/480

ORCID

0000-0003-0826-8119 (Marsillac)