Determination of refractive index of crystalline silicon in the
infrared region on the basis of interference pattern observed
in thick slab

J 2025

Determination of refractive index of crystalline silicon in the infrared region on the basis of interference pattern observed in thick slab

VOHÁNKA, Jiří; Jiří VEČEŘE; Daniel FRANTA and Ivan OHLÍDAL

Basic information

Original name

Determination of refractive index of crystalline silicon in the infrared region on the basis of interference pattern observed in thick slab

Authors

VOHÁNKA, Jiří (203 Czech Republic, guarantor, belonging to the institution); Jiří VEČEŘE (203 Czech Republic, belonging to the institution); Daniel FRANTA (203 Czech Republic, belonging to the institution) and Ivan OHLÍDAL (203 Czech Republic, belonging to the institution)

Edition

Infrared Physics and Technology, Elsevier B.V. 2025, 1350-4495

Other information

Language

English

Type of outcome

Article in a journal

Field of Study

10305 Fluids and plasma physics

Country of publisher

Netherlands

Confidentiality degree

is not subject to a state or trade secret

References:

URL

Impact factor

Impact factor: 3.400 in 2024

Organization unit

Faculty of Science

DOI

https://doi.org/10.1016/j.infrared.2025.105889

UT WoS

001488821100001

EID Scopus

2-s2.0-105004265952

Keywords in English

Silicon; Infrared spectroscopy; Refractive index; Ellipsometry

Abstract

In the original language

The precise values of the refractive index of crystalline silicon are determined in the infrared region based on the measurements of the interference pattern in 0.25 mm thick wafer. The interference pattern observed for one particular incidence angle allows us to determine the optical thickness precisely, however, the wafer thickness and refractive index, whose product gives the optical thickness, can be determined with much worse accuracy. This limitation could be overcome by using several incidence angles because if the dependence of the period of interference pattern on the incidence angle is considered, it is possible to determine both the thickness and refractive index with high accuracy. The FTIR infrared ellipsometer is used for measurements at oblique incidence angles, while the FTIR spectrophotometer is utilized for measurements at near-normal incidence. To correctly interpret the experimental data, it is necessary to consider the influence of the finite spectral resolution and beam divergence of the instruments and the thickness non-uniformity of the sample. These effects significantly alter the observed interference patterns. The formulae needed to accomplish this task are derived in this work. The values of the refractive index determined using the proposed method for the crystalline silicon show differences smaller than 10-3 from the values obtained by the minimum deviation method.

Links

LM2023039, research and development project

Name: Centrum výzkumu a vývoje plazmatu a nanotechnologických povrchových úprav

Investor: Ministry of Education, Youth and Sports of the CR

Cite

VOHÁNKA, Jiří; Jiří VEČEŘE; Daniel FRANTA and Ivan OHLÍDAL. Determination of refractive index of crystalline silicon in the infrared region on the basis of interference pattern observed in thick slab. Infrared Physics and Technology. Elsevier B.V., 2025, vol. 149, September, p. 1-11. ISSN 1350-4495. Available from: https://doi.org/10.1016/j.infrared.2025.105889.

@article{2499782,
   author = {Vohánka, Jiří and Večeře, Jiří and Franta, Daniel and Ohlídal, Ivan},
   article_number = {September},
   doi = {https://doi.org/10.1016/j.infrared.2025.105889},
   keywords = {Silicon; Infrared spectroscopy; Refractive index; Ellipsometry},
   language = {eng},
   issn = {1350-4495},
   journal = {Infrared Physics and Technology},
   title = {Determination of refractive index of crystalline silicon in the infrared region on the basis of interference pattern observed in thick slab},
   url = {https://doi.org/10.1016/j.infrared.2025.105889},
   volume = {149},
   year = {2025}
}

TY  - JOUR
ID  - 2499782
AU  - Vohánka, Jiří - Večeře, Jiří - Franta, Daniel - Ohlídal, Ivan
PY  - 2025
TI  - Determination of refractive index of crystalline silicon in the infrared region on the basis of interference pattern observed in thick slab
JF  - Infrared Physics and Technology
VL  - 149
IS  - September
SP  - 1-11
EP  - 1-11
PB  - Elsevier B.V.
SN  - 13504495
KW  - Silicon
KW  - Infrared spectroscopy
KW  - Refractive index
KW  - Ellipsometry
UR  - https://doi.org/10.1016/j.infrared.2025.105889
N2  - The precise values of the refractive index of crystalline silicon are determined in the infrared region based on the measurements of the interference pattern in 0.25 mm thick wafer. The interference pattern observed for one particular incidence angle allows us to determine the optical thickness precisely, however, the wafer thickness and refractive index, whose product gives the optical thickness, can be determined with much worse accuracy. This limitation could be overcome by using several incidence angles because if the dependence of the period of interference pattern on the incidence angle is considered, it is possible to determine both the thickness and refractive index with high accuracy. The FTIR infrared ellipsometer is used for measurements at oblique incidence angles, while the FTIR spectrophotometer is utilized for measurements at near-normal incidence. To correctly interpret the experimental data, it is necessary to consider the influence of the finite spectral resolution and beam divergence of the instruments and the thickness non-uniformity of the sample. These effects significantly alter the observed interference patterns. The formulae needed to accomplish this task are derived in this work. The values of the refractive index determined using the proposed method for the crystalline silicon show differences smaller than 10-3 from the values obtained by the minimum deviation method.
ER  -

VOHÁNKA, Jiří; Jiří VEČEŘE; Daniel FRANTA and Ivan OHLÍDAL. Determination of refractive index of crystalline silicon in the infrared region on the basis of interference pattern observed in thick slab. \textit{Infrared Physics and Technology}. Elsevier B.V., 2025, vol.~149, September, p.~1-11. ISSN~1350-4495. Available from: https://doi.org/10.1016/j.infrared.2025.105889.

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