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Study of the Dielectric Function of ZnS by Spectroscopic Ellipsometry
T. H. Ghong,김태중,김영동,S. J. Kim,데이비드에스프네스,Y. D. Choi,Y-. M. Yu 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
We report the best room-temperature dielectric function data for zincblende-type ZnS from 3.7 to 6.0 eV, obtained by spectroscopic ellipsometry together with real-time assessment of overlayer removal. These data were extended to 9.0 eV (without chemical etching) using a variable-angle system. This permits the first detailed analysis of the $E_2$ band gap of ZnS, revealing 3 bandgaps in this spectral region
Nondestructive analysis of coated periodic nanostructures from optical data.
Ghong, T H,Han, S-H,Chung, J-M,Byun, J S,Kim, T J,Aspnes, D E,Kim, Y D,Park, I H,Kim, Y-W Optical Society of America 2010 Optics letters Vol.35 No.5
<P>Optical data are essential for the accurate nondestructive determination of profiles of periodic structures in integrated-circuit technology. In rigorous coupled-wave analysis, the sample is generally modeled as layers consisting of a single material and the ambient. We extend present capabilities to the analysis of structures with overlayers and demonstrate our approach by determining quantitatively the thicknesses of top, sidewall, and bottom oxides of deliberately and naturally oxidized structures.</P>
Dielectric function and band gap study of ZnSe film
T. H. Ghong,김영동,윤재진,김태중,H. J. Kim,Y. C. Chang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.-
We present the dielectric function of zinc-blende ZnSe film, which has been determined by vacuum ultraviolet spectroscopic ellipsometry whose spectral range is from 0.7 to 9.0 eV at room temperature. In this work, we focus on determining the critical point (CP) energies above 6 eV, where the dielectric function has significant noise, by numerically calculating the second derivative of the spectrum with respect to energy. We calculate the band structure of ZnSe by using density-functional theory based on linear augmented Slater-type orbitals. From a comparison of data and theory, we can identify the experimentally obtained CP transition energies as E0, E0+Delta0, E1, E1+Delta1, E2, E2+Delta2, E2', E0' and E0'+Delta0'+Delta0 in the 0.7 - 9 eV region.
Roughness Analysis of the Critical Dimension by Using Spectroscopic Ellipsometry
T. H. Ghong,S.-H. Han,,J.-M. Chung,J.-M. Chung,Y. D. Kim,데이비드에스프네스 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.51
In semiconductor electronics applications, observation of the linewidth roughness (LWR) or the critical dimension roughness will become increasingly important. In this article, we study to analyze the roughness of a grating structure by using spectroscopic ellipsometry. A simple 1D patterned c-Si grating structure was measured from the zeroth-order diffraction response at a fixed angle of incidence, which result agreed with a theoretical prediction made by using a rigorous coupled-wave analysis (RCWA) calculation with an effective-medium approximation (EMA) for a structure with roughness.
Study on Interface Analysis by Using Spectroscopic Ellipsometry
김태중,김영동,T. H. Ghong,Y. W. Jung,윤재진 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6
Spectroscopic ellipsometry (SE) has been proved to be a powerful nondestructive method for analyzing multilayer structures. Recently, a new interface model, which utilizes a parametric model to describe the alloy dielectric function of an arbitrary alloy composition, was introduced. Even though the new model could reconstruct the experimental spectrum precisely, the resulting thickness value for each composite layer in the graded interface layers seemed to be unreasonably asymmetric. To check the validity of the new model, we performed z-contrast scanning transmission electron microscopy (STEM) and compared the result with those from SE, confirming that the SE analysis can be considered to be reliable.
Optical Properties of InP at a Higher Bandgap Region Studied at 25 K and 300 K by Using Ellipsometry
김태중,윤재진,T. H. Ghong,김영동 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3
The dielectric functions of InP at 25 K and 300 K were measured by using spectroscopic ellipsometry (SE) for the energy region from 1.3 to 6.57 eV. The values of the critical point (CP) energies were determined from numerically-calculated second energy derivatives of the data. We observed a significant blue shift and sharper CP structures at low temperatures. A separation of CP energies in the E2 peak energy region, which could not be detected at room temperature, was clearly observed at 25 K, so that we could identify the CP energies E0’(Γ), E0’(Δ), E2, and E0’ + Δ0’. We also report the observation of the CP energies E2’ and E1’ over a 5.5 eV photon energy region, which so far have not been observed using SE.
Ellipsometric Analysis on Interface Effects in CdMgTe and AlGaAs Multilayer Systems
김태중,Y. D. Kim,T. H. Ghong,Y. . Ihn 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.2
We report ellipsometric detectability of the existence of alloy-form interface layers in Cd1−xMgxTe and AlxGa1−xAs systems as examples of nanostructure and multilayer systems. We used previously reported experimental dielectric functions of Cd1−xMgxTe and AlxGa1−xAs alloys to interpolate those for arbitrary Mg and Al compositions by using a parametric semiconductor model which allows " to be calculated as a continuous analytic function of x. From these results, we conclude that the conventional ellipsometric analysis using effective medium approximation could not detect the existence of an interface layer whose thickness is in the range below 30 °A.
Optical Properties of InGaAs Alloy Films in the E2 Region by Spectroscopic Ellipsometry
영동 김,B. H. Koo,데이비드에스프네스,S. J. Kim,T. Yao,T. H. Ghong,Y. S. Ihn 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
We report pseudodielectric functions $<\epsilon>$ of In$_x$Ga$_{1-x}$As alloy films for several In composition $x$ from 0.00 to 0.66. Films were grown on (110) InP substrates by solid-source molecular beam epitaxy. We used chemical etching to remove overlayers and thereby to obtain the best approximation to the bulk dielectric responses $\epsilon$ of the films. The dependences of the ${E_0}'$, ${E_0}'$+$\Delta_0 '$, and $E_2$ critical point point energies on $x$ were obtained by analysis of second energy derivatives of the $<\epsilon>$ spectra.