Design and production of antireflection coating for Ge, ZnSe and ZnS in 8-12 micrometer wavelength region

Üçer, Begüm
This thesis describes the works done during the design and deposition process of the antireflection coating for the materials commonly used as refractive optical elements in thermal imaging systems. These coatings are quite necessary to reduce reflection losses from the surface of the optics and stray light that directly affects the image quality. Germanium, zinc sulfide and zinc selenide were used as substrate material and their optical properties were investigated with infrared ellipsometry and FTIR. Antireflection coatings for each material operating in 8-12 μm range were designed with Needle Synthesis Technique. In order to shorten the optimization time, commercial software; “The Essential Macleod” was used. In order to reduce the reflectance losses multilayer structure was used in the coating design, and zinc selenide and lead telluride were used as low and high index materials. In this study the necessary theoretical background and common deposition techniques are reviewed. Samples were produced using the magnetron sputtering. To optimize the v thicknesses of the deposited layers, growth period and rate was controlled. Thicknesses of the samples, following to the deposition were also measured by thickness profilometer. A 3-layer coating, PbTe/ZnSe/PbTe, on ZnS and 2-layer coating PbTe/ZnS on Ge having more than 90% transmittance in 9.7-10.3 μm wavelength region have been successfully produced. Although, the measured range for 3 and 2- layer coating is narrower than the aimed one, it has been shown that, the method developed in this thesis would yield AR-coatings with broader spectral response if a system having better control on deposition parameters is used. For example, our design and optimization work has suggested that a 7-layer AR coating on germanium, with alternating high and low index layers is expected to give transmittance value greater than 93% in the studied wavelength region.


Structural, electrical and optical characterization of ge-implanted gase single crystal grown by Bridgman Method
Karaağaç, Hazbullah; Akınoğlu, Bülent Gültekin; Department of Physics (2005)
In this work, structural, electrical and optical characterization of as-grown, Ge-implanted, and annealed GaSe single crystals grown by using 3-zone vertical Bridgman-Stockbarger system, have been studied by carrying out X-ray Diffraction (XRD), electrical conductivity, Hall effect, photoconductivity, and spectral transmission measurements. The temperature dependent electrical conductivity of these samples have been measured between 100 and 400 K. As a result, it was observed that upon implanting GaSe with ...
Development of atomic force microscopy system and kelvin probe microscopy system for use in semiconductor nanocrystal characterization
Bostancı, Umut; Turan, Raşit; Department of Physics (2007)
Atomic Force Microscopy (AFM) and Kelvin Probe Microscopy (KPM) are two surface characterization methods suitable for semiconductor nanocrystal applications. In this thesis work, an AFM system with KPM capability was developed and implemented. It was observed that, the effect of electrostatic interaction of the probe cantilever with the sample can be significantly reduced by using higher order resonant modes for Kelvin force detection. Germanium nanocrystals were grown on silicon substrate using different g...
Development of software for calculations of the reflectance, transmittance and absorptance of multilayered thin films
Şimşek, Yusuf; Esendemir, Akif; Department of Physics (2008)
The aim of this study is to develop a software which calculates reflection, transmission and absorption of multilayered thin films by using complex indices of refraction, as a function of both wavelength and thickness. For these calculations matrix methods will be considered and this software is programmed with the matrix method. Outputs of the program will be compared with the theoretical and experimental results studied in the scientific papers.
Physics and technology of the infrared detection systems based on heterojunctions
Aslan, Bülent; Turan, Raşit; Department of Physics (2004)
The physics and technology of the heterojunction infrared photodetectors having different material systems have been studied extensively. Devices used in this study have been characterized by using mainly optical methods, and electrical measurements have been used as an auxiliary method. The theory of internal photoemission in semiconductor heterojunctions has been investigated and the existing model has been extended by incorporating the effects of the difference in the effective masses in the active regio...
Density functional investigation of nano-structures
Üzengi Aktürk, Olcay; Tomak, Mehmet; Department of Physics (2010)
In this thesis, we first investigate the physical properties of some metal atoms, molecules and their clusters. We then study the interaction of these with silicon and graphene surfaces. The adsorption of NH3 and H2S molecules on Au3Pt3 is also studied. We calculate the equilibrium atomic structures of metal clusters using density functional theory (DFT) up to eight atoms. The electronic structures of these free and adsorbed clusters are also calculated in detail. We find that the adsorption generally modif...
Citation Formats
B. Üçer, “Design and production of antireflection coating for Ge, ZnSe and ZnS in 8-12 micrometer wavelength region,” M.S. - Master of Science, Middle East Technical University, 2009.