Abstract

A user-friendly software PRISA has been developed to determine optical constants (refractive index and extinction co-efficient), dispersion parameters (oscillator energy and dispersion energy), absorption co-efficient, band gap and thickness of semiconductor and dielectric thin films from measured transmission spectrum, only. The thickness, refractive index, and extinction co-efficient of the films have been derived using Envelope method proposed by Swanepoel. The absorption co-efficient in the strong absorption region is calculated using the method proposed by Connel and Lewis. Subsequently, both direct and indirect bandgap of the films is estimated from the absorption co-efficient spectrum using Tauc plot. The software codes are written in Python and the graphical user interface is programmed with tkinter package of Python. It provides convenient input and output of the measured and derived data. The software has a feature to cross check the results by retrieving transmission spectrum using the values of refractive index, extinction co-efficient, and thickness obtained from Envelope method. The performance of the software is verified by analyzing numerically generated transmission spectra of a-Si:H amorphous semiconductor thin films, and experimentally measured transmission spectra of electron beam evaporated HfO2 dielectric thin films as examples. PRISA is found to be much simpler and accurate as compared to the other freely available softwares. To help researchers working on thin films, the software is made freely available at https://www.shuvendujena.tk/download.

Highlights

  • Performance of most thin film optical coatings and optoelectronic devices depends on optical properties and thickness of thin films [1]

  • Hydrogenated amorphous silicon (a-Si:H) thin film is widely used in solar cells, while thin film of chalcogenide glass like As2Se3 is used in optical memory devices [5]

  • All the above mentioned commercial and free software do not have the features to estimate dispersion energy parameters (Ed, E0, and n0), Tauc plots, and band gap (Eg) of thin films. This encouraged us to develop a simple and userfriendly graphical user interface (GUI) software named PRISA that can derive n, k, Ed, E0, α, Eg, and d of thin films from the measured transmission spectrum, which will be useful to the researchers working in the area of thin films

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Summary

Introduction

Performance of most thin film optical coatings and optoelectronic devices depends on optical properties and thickness of thin films [1]. The high sensitivity of optical bandgap and refractive index of the semiconductor chalcogenide thin films to external factors such as laser, neutron, electron, and gamma irradiation has gathered significant attention over few decades [6] These photosensitive natures of such amorphous semiconductor thin films have found numerous applications in optoelectronics, optical imaging and recording, information storage, absorption filters, highresolution display devices, acousto-optic devices, and photolithography [7]. All the above mentioned commercial and free software do not have the features to estimate dispersion energy parameters (Ed, E0, and n0), Tauc plots, and band gap (Eg) of thin films This encouraged us to develop a simple and userfriendly graphical user interface (GUI) software named PRISA that can derive n, k, Ed, E0, α, Eg, and d of thin films from the measured transmission spectrum, which will be useful to the researchers working in the area of thin films. Details of the software distribution, and summary of the work are presented in Sec., and Sec. 6, respectively

Optical constants and thickness
Retrieval of transmission spectrum
Dispersion energy parameters
Software interface
Verification and performance
Numerical spectrum of a-Si:H semiconductor thin film
Experimental spectrum of HfO2 dielectric thin film
Limitations
Software distribution and future plans
Conclusion
References:
Full Text
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