# Reflectivity

Topics: Electron, Refraction, Refractive index Pages: 15 (3147 words) Published: January 9, 2013
CHARACTERISATION OF THIN FILM AND MULTILAYERS BY X-RAY REFLECTIVITY

Submitted by Rajshekhar Bar Supervisor: Dr. Sanjeev Kumar Srivastava

In partial fulfilment of the M.Sc.(2yr) degree in Physics

Department of Physics and Meteorology Indian Institute of Technology Kharagpur,721302,India May,2012

ACKNOWLEDGEMENT
First and foremost, I thank my advisor Prof. Sanjeev kumar Srivastava for the many useful suggestions and pieces of advice that he has given me. I am also thankful to all faculties of Department of physics and Meteorology for creating a comforting study environment for all its students. I would like to thank to Mr. Uttam Das and Mr.Rakesh Das who helped me in the laboratory for making films. I would also like to thank to all my friends who helped for the understanding of many things and for many fruitful discussions. Finally, all errors and limitations remaining in this report are mine alone.

Date: 02/05/2012

Rajshekhar Bar 10PH40026 Department of Physics and Meterology IIT Kharagpur

ABSTRACT
Now a days x-ray reflectivity is a very useful method for the study of thin films and multilayer. This method is based on total external reflectivity. Using this method we can calculate the thickness of the film electron density profile of the material and roughness of the film surface. After a short introduction of Fresnel’s reflectivity, the Parratt formulation is used for the calculation reflectivity for a stratified film. Then after discussing the experimental technique, we have calculated the thickness, electron density and roughness from the experimental curve.

CONTENTS

Introduction---------------------------------------------------------------[1] 2) Film deposition-----------------------------------------------------------[2] 3) Basic principle of x-ray reflectivity-------------------------------------[3] 4) Reflection and refraction at the boundary----------------------------[5] 5) X-ray reflectivity measurement-----------------------------------------[6] 6) Principle and calculation procedure of x-ray reflectivity-----------[7] 7) Reflectivity from a single layer-----------------------------------------[7] 8) Thickness calculation----------------------------------------------------[8] 9) Reflectivity from multilayer---------------------------------------------[9] 10) Experimental reflectivity curve----------------------------------------[10] 11) Various effects on reflectivity------------------------------------------[12] 12) Conclusions---------------------------------------------------------------[13] 13) References-----------------------------------------------------------------[13] 1)

●Intrtoduction:
In light of the recent growth of rapid utilization of thin films in microelectronics, it becomes very useful to understand the intrinsic properties of the thin film. The recent development of commercial analytical instruments in microelectronics demands to characterise thin film. There are several methods for the characterisation of thin films. Among them optical methods of thin film characterisation are widely used because they are applicable to both opaque and transparent films. Generally by using this method we can measure the thickness of the film very accurately. X-ray reflectivity is one of the best optical method by which we can measure the film thickness, the roughness of the surface layer and the electron density of the layer with high accuracy. The x-ray wavelength of around 1 Å is of the same order of magnitude as most interatomic distances. Apart from this property it has the same physical property as the optical wave and that’s why x-ray is very useful for the surface characterisation. Typically layer thickness around 5Å to 400 nm and surface roughness around 0 to 20Å can be measured by this method.

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●Film deposition:
There are several types of deposition processes depending on the requirement of the film. The basic film deposition processes are Physical Vapour...

References: 1. X-ray and Neutron Reflectivity analysis of thin flims and superlattices. H. Zabel , Appl Phys.A 58.159-168(1994) 2. Method of X-Ray and Neutron scattering in Polymer sciences. R.J.Roe 3. X –ray and Neutron reflectivity : Principles and applications. Alain Gibaud, Jean Daillant. 4.Materials science of thin film. Milton Ohring,2nd edition.
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