NMSU banner ICSE-10 banner
Dr. Stefan Zollner, New Mexico State University, Las Cruces, NM, USA

Large File Depository

This server is used to store large files for downloading from the regular NMSU ellipsometry web page (now offline).

Older publications by Stefan Zollner (incomplete)
Complete list of publications and presentations by Stefan Zollner (created with HTLATEX or MAKE4HT).

FORTRAN programs for solid-state physics (need IMSL library)

  1. Phonon dispersion relations
  2. Electronic band structure with empirical pseudopotentials

MS Theses and Presentations

  1. Travis I. Willett-Gies, Lattice Dynamics of LaAlO3 and MgAl2O4, Spring 2014, M.S. thesis.
  2. Cesar A. Rodriguez, Electronic Properties of SrTiO3 Epitaxial Layers Investigated by Spectroscopic Ellipsometry, Summer 2016, M.S. thesis and slides.
  3. T. Nathan Nunley, Ellipsometric Studies of Simple and Complex Oxides from the Mid-Infrared to the Near Ultraviolet, Spring 2016, M.S. thesis and slides.
  4. Carola Emminger, Polarization dependent studies of linear and non-linear optical response, December 2017, Master's Thesis, Johannes-Kepler Universität Linz, Austria.

Ph.D. Theses and Presentations

  1. Lina S. Abdallah, Ellipsometry of Ni1-xPtx Alloys and Related Silicides, Summer 2014, Ph.D. thesis and slides.
  2. Nalin S. Fernando, Optical Characterization of Group-IV Semiconductor Alloys Using Spectroscopic Ellipsometry and High-Resolution X-Ray Diffraction, Spring 2017, Ph.D. thesis and slides.
  3. Farzin Abadizaman, Optical Characterization of Ni using Spectroscopic Ellipsometry at Temperatures from 80 K to 780 K, Fall 2020, Ph.D. thesis and slides.
  4. Nuwanjula Samarasingha, Optical Characterization of Compound Semiconductor Materials using Spectroscopic Ellipsometry, Fall 2021, Ph.D. thesis and slides and Recording.
  5. Rigo A. Carrasco, Molecular Beam Epitaxy and Optical Performance in Group IV and Group III/V Semiconductors for Photonic Applications, Fall 2021, Ph.D. thesis and slides.
  6. Carola Emminger, Ellipsometry of Semiconductors under Thermal and Laser Excitation, Spring 2022, Ph.D. thesis and slides.

Selected Recent Journal Articles

  1. T. Nathan Nunley, Nalin S. Fernando, Nuwanjula Samarasingha, Jaime M. Moya, Cayla M. Nelson, Amber A. Medina, and Stefan Zollner, Optical constants of germanium and thermally grown germanium dioxide from 0.5 to 6.6 eV via a multi-sample ellipsometry investigation, J. Vac. Sci. Technol. B 34, 061205 (2016).
  2. Rigo A. Carrasco, Cesy M. Zamarripa, Stefan Zollner, Jose Menendez, Stephanie A. Chastang, Jinsong Duan, Gordon J. Grzybowski, Bruce B. Claflin, and Arnold M. Kiefer, The direct bandgap of gray α-tin investigated by infrared ellipsometry, Appl. Phys. Lett. 113, 232104 (2018).
  3. Stefan Zollner, Pablo P. Paradis, Farzin Abadizaman, and Nuwanjula S. Samarasingha, Drude and Kukharskii mobility of doped semiconductors extracted from Fourier-transform infrared ellipsometry spectra, J. Vac. Sci. Technol. B 37, 012904 (2019).
  4. Rigo A. Carrasco, Stefan Zollner, Stephanie A. Chastang, Jinsong Duan, Gordon J. Grzybowski, Bruce B. Claflin, and Arnold M. Kiefer, Dielectric function and band structure of Sn1-xGex (x<0.06) alloys on InSb, Appl. Phys. Lett. 114, 062102 (2019).
  5. Aakash Mathur, Dipayan Pal, Ajaib Singh, Rinki Singh, Stefan Zollner, and Sudeshna Chattopadhyay, Dual ion beam grown silicon carbide thin films: variation in refractive index and band gap as a function of film thickness, J. Vac. Sci. Technol. B 37, 041802 (2019).
  6. Alireza Kazemi, Qingyuan Shu, Vinita Dahiya, Zahra Taghipour, Pablo Paradis, Christopher Ball, Theodore J. Ronningen, Stefan Zollner, Steven M. Young, Jordan Budhu, Kevin A. Grossklaus, Thomas E. Vandervelde, Anthony Grbic, Sanjay Krishna, Subwavelength antimonide infrared detector coupled with dielectric resonator antenna, in Infrared Technology and Applications XLV, Proc. SPIE 11002, 434-441 (2019).
  7. Shirly Espinoza, Steffen Richter, Mateusz Rebarz, Oliver Herrfurth, Rüdiger Schmidt-Grund, Jakob Andreasson, and Stefan Zollner, Transient dielectric functions of Ge, Si, and InP from femtosecond pump-probe ellipsometry, Appl. Phys. Lett. 115, 052105 (2019).
  8. Farzin Abadizaman and Stefan Zollner, Optical constants of polycrystalline Ni from 0.06 to 6.0 eV at 300 K, J. Vac. Sci. Technol. B 37, 062920 (2019).
  9. Carola Emminger, Farzin Abadizaman, Nuwanjula Samarasingha, Thomas E. Tiwald, and Stefan Zollner, Temperature dependent dielectric function and direct band gap of Ge, J. Vac. Sci. Technol. B 38, 012202 (2020).
  10. Steffen Richter, Oliver Herrfurth, Shirly Espinoza, Mateusz Rebarz, Miroslav Kloz, Joshua A. Leveillee, André Schleife, Stefan Zollner, Marius Grundmann, Jakob Andreasson, and Rüdiger Schmidt-Grund, Ultrafast dynamics of hot charge carriers in an oxide semiconductor probed by femtosecond spectroscopic ellipsometry, New Journal of Physics 22, 083066 (2020).
  11. B. Claflin, G. J. Grzybowski, A. M. Kiefer, M. E. Ware, and S. Zollner, Process for growth of group-IV alloys containing tin by remote plasma enhanced chemical vapor deposition, Front. Mater. 7, 44 (2020).
  12. Nuwanjula S. Samarasingha, Stefan Zollner, Dipayan Pal, Rinki Singh, and Sudeshna Chattopadhyay, Thickness dependence of infrared lattice absorption and excitonic absorption in ZnO layers on Si and SiO2 grown by atomic layer deposition, J. Vac. Sci. Technol. B 38, 042201 (2020).
  13. Matthew J. Hilfiker, Megan Stokey, Rafal Korlacki, Ufuk Kiliç, Zbigniew Galazka, Klaus Irmscher, Stefan Zollner, and Mathias M. Schubert, Zinc gallate spinel dielectric function, band-to-band transitions, and Γ-point effective mass parameters, Appl. Phys. Lett. 118, 132102 (2021).
  14. Carola Emminger, Farzin Abadizaman, Nuwanjula S. Samarasingha, José Menéndez, Shirly Espinoza, Steffen Richter, Mateusz Rebarz, Oliver Herrfurth, Martin Zahradník, Rüdiger Schmidt-Grund, Jakob Andreasson, Stefan Zollner, Analysis of temperature-dependent and time-resolved ellipsometry spectra of Ge, IEEE Photonics Society Summer Topicals Meeting Series, online (2021).
  15. Nuwanjula S. Samarasingha and Stefan Zollner, Temperature dependence of the optical phonon reflection band in GaP, J. Vac. Sci. Technol. B 39, 052201 (2021).
  16. Dominic Imbrenda, Rigo A. Carrasco, Ryan Hickey, Nalin S. Fernando, Stefan Zollner, and James Kolodzey, Band structure critical point energy in germanium-tin alloys with high tin contents, Appl. Phys. Lett. 119, 162102 (2021).
  17. Carola Emminger, Nuwanjula Samarasingha, Melissa Rivero Arias, Farzin Abadizaman, Jose Menendez, and Stefan Zollner, Excitonic effects at the temperature-dependent direct band gap of Ge, J. Appl. Phys. 131, 165701 (2022). DOI: 10.1063/5.0080158
  18. Farzin Abadizaman, Jaden Love, and Stefan Zollner, Optical constants of single-crystalline Ni(100) from 77 K to 770 K from ellipsometry measurements, J. Vac. Sci. Technol. A 40, 033202 (2022). DOI: 10.1116/6.0001763
  19. Carola Emminger, Shirly Espinoza, Steffen Richter, Mateusz Rebarz, Oliver Herrfurth, Martin Zahradník, Rüdiger Schmidt-Grund, Jakob Andreasson, and Stefan Zollner, Coherent acoustic phonon oscillations and transient critical point parameters of Ge and Si from femtosecond pump-probe ellipsometry, phys. stat. solidi RRL 16, 220058 (2022). DOI: 10.1002/pssr.202200058
  20. Stefan Zollner, Farzin Abadizaman, Carola Emminger, and Nuwanjula Samarasingha, Spectroscopic ellipsometry from 10 to 700 K, Adv. Opt. Techn. 11, 117-135 (2022). DOI: 10.1515/aot-2022-0016
  21. Melissa Rivero Arias, Carlos A. Armenta, Carola Emminger, Cesy M. Zamarripa, Nuwanjula S. Samarasingha, Jaden R. Love, Sonam Yadav, and Stefan Zollner, Temperature dependence of the infrared dielectric function and the direct band gap of InSb from 80 to 725 K, J. Vac. Sci. Technol. B 41, 022203 (2023). DOI: 10.1116/6.0002326. Optical constants for InSb and its native oxide for J.A. Woollam WVASE32 software.
  22. Stefan Zollner, Shivashankar R. Vangala, Vladimir L. Tassev, Duane Brinegar, and Samuel Linser, Infrared dielectric function of GaAs1-xPx semiconductor alloys near the reststrahlen bands, Appl. Phys. Lett. 123, 172102 (2023). DOI: 10.1063/5.0173978
  23. Stefan Zollner, Excitonic Effects in the optical absorption of gapless semiconductor α-tin near the direct band gap, J. Vac. Sci. Technol. B 42, 022203 (2024). DOI: 10.1116/6.0003278
  24. Bruce Claflin, Gordon J. Grzybowski, Stefan Zollner, Bridget R. Rogers, Timothy A. Cooper, and David C. Look, Remote plasma-enhanced chemical vapor deposition of GeSn on Si (100), Si (111), sapphire and fused silica substrates, J. Vac. Sci. Technol. B 42, 052204 (2024). DOI: 10.1116/6.0003689
  25. Stefan Zollner, Carlos A. Armenta, Sonam Yadav, and José Menéndez, Conduction band nonparabolicity, chemical potential, and carrier concentration of intrinsic InSb as a function of temperature, J. Vac. Sci. Technol. A 43, 012801 (2025). Supplementary Material. DOI: 10.1116/6.0003929

Presentations at Conferences and Institutions

  1. Stefan Zollner, Accurate measurements and models of temperature-dependent optical constants for infrared detector materials, 2024 IEEE Photonics Conference, Rome, Italy, 10-14 Nov 2024.
  2. Stefan Zollner, Femtosecond pump-probe ellipsometry and screening of two-dimensional excitons in Ge, Quantum Materials from Theory to Practice, Austin, TX, 26 October 2024.
  3. Stefan Zollner, Matrix elements and excitonic effects in the direct gap absorption of semiconductors, LXVII Congreso Nacional de Fisica, Sociedad Mexicana de Fisica, Chihuahua, Mexico, 09 October 2024. abstract and slides.
  4. Stefan Zollner, Carlos A. Armenta, Sonam Yadav, Yoshitha Hettige, Jaden R. Love, Haley B. Woolf, Atlantis K. Moses, and Danissa P. Ortega, Optical spectroscopy of materials for mid-wave infrared detector applications, 7th Tri-Service Workshop on GeSn and GeSiSn, Colorado Springs, CO, 16-17 September 2024.
  5. Stefan Zollner, Relaxation, band filling, and screening in the transient dielectric function of Ge determined with femtosecond ellipsometry, 9th European Light Infrastructure Summer School, Szeged, Hungary, 05 September 2024. Abstract and slides.
  6. Stefan Zollner, Matrix elements and excitonic effects in the direct gap absorption of semiconductors, abstract and slides, 2024 Nebraska/Lund Ellipsometry Lecture Mini Series, 07 February 2024.
  7. Stefan Zollner, Carola Emminger, and Jose Menendez, Excitonic absorption in semiconductors with low and high carrier densities, 2023 Fall Materials Research Society Meeting, Boston, MA, 26 November to 01 December 2023.
  8. Stefan Zollner, Bridget Rogers, Carlos A. Armenta, Gordon J. Grzybowski, and Bruce Claflin, Characterization of buffer layers for remote plasma-enhanced chemical vapor deposition of germanium-tin epitaxial layers, Sixth Annual Tri-Service Workshop on GeSn and SiGeSn, 25-26 October 2023, Colorado Springs, Co.
  9. Stefan Zollner, Perspective on femtosecond ellipsometry, Satellite Meeting on Time-Resolved Ellipsometry, 12th AKE Workshop on Spectroscopic Ellipsometry, 22 September 2023.
  10. Stefan Zollner, Theory of direct band gap absorption in highly excited semiconductors, 12th AKE Workshop on Spectroscopic Ellipsometry, 20 September 2023, Praha, Czech Republic.
  11. Stefan Zollner, Intravalence Band Transitionsin Gapless Topological Insulators, abstract and slides, seminars given at University of Nebraska, Lincoln, and University of Arkansas, Fayetteville, in August 2023.
  12. Stefan Zollner, Spectroscopic ellipsometry studies of optical constants in highly excited semiconductors, DPG SKM Spring Meeting, Dresden, Germany, 30 March 2023.
  13. Stefan Zollner, Spectroscopic ellipsometry studies of optical constants in highly excited semiconductors, Technische Universität Ilmenau, Ilmenau, Germany, 24 March 2023.
  14. Stefan Zollner, Impact of stress and strain on optical spectra of semiconductors, seminar at European Synchrotron Radiation Facility (ESRF), Grenoble, France, 13 March 2023.
  15. Stefan Zollner, Optical properties of infrared detector materials, 5th Tri-Service Workshop on GeSn and GeSiSn, Dayton, OH, 10-11 January 2023.
  16. Jaden R. Love, Optical and structural properties of CaF2, NMSU URCAS, 29 April 2022, Powerpoint and PDF slides and video.
  17. Melissa Rivero Arias, Temperature dependence of the direct bandgap of InSb, NMSU URCAS, 29 April 2022, Powerpoint and PDF slides and video.
  18. Haley Woolf, Optical and X-Ray Characterization of Ge1-ySny alloy on GaAs, NMSU URCAS, 29 April 2022, Powerpoint and PDF slides and video.
  19. Carola Emminger, Excitonic effects at the direct band gap of Ge, 2021 AFRL Workshop on GeSn alloys (online), slides and recording.
  20. Carola Emminger, Accurate temperature-dependent optical constants for germanium near the direct band gap, 2020 AFRL Workshop on GeSn alloys (online), slides and recording.
  21. Stefan Zollner, Time-resolved ellipsometry: a historical perspective, ELIps Workshop, Prague Czech Republic, October 10-12, 2016.

Posters

  1. Haley B. Woolf, Matt Kim, Carola Emminger, Carlos Armenta, and Stefan Zollner, Optical and X-ray Characterization of Ge1-ySny Alloy on GaAs, 2022 APS March Meeting, 14-18 March 2022, Chicago, IL.
  2. Melissa Rivero Arias, Carola Emminger, and Stefan Zollner, Temperature Dependence of the Dielectric Function of Indium Antimonide, 2022 APS March Meeting, 14-18 March 2022, Chicago, IL.
  3. Jaden R. Love, Nuwanjula, S. Samarasingha, Carlos Armenta, Stefan Zollner, and H. Kim, Properties of CaF2 using X-Ray Diffraction and IR Ellipsometry, 2022 APS March Meeting, 14-18 March 2022, Chicago, IL.

Lecture Series: Optical Properties of Solids (Summer 2023)

  1. Polarized Light and the Dielectric Tensor
    Light is described by electric and magnetic fields, which are governed by Maxwell's Equations. For simplicity, we Fourier-transform these fields, which reduces Maxwell's Equations to vector identities. The propagation of light in vacuum is then given by the wave equation, which has plane wave solutions. Plane waves with an angular frequency ω and wave vector k are described by the complex electric field amplitude vector E0 (because the magnetic field strength can be calculated from Faraday's Law). If we normalize the intensity of the field, ignore the absolute phase (which is not accessible experimentally), and consider the transversality of the wave, the six real parameters of E0 can be reduced to two. They are written as a Jones vector with two real parameters known as the ellipsometric angles ψ and Δ. Incoherent superposition of waves (with different absolute phases) leads to depolarization. Such a superposition of waves (a monochromatic ray of light) is described with four Stokes parameters (with the total light intensity called S0). When a ray is transmitted or reflected by an optical element or sample, the change of the ray's polarization state is described by a Jones or Mueller matrix. To describe the propagation of light inside a homogeneous medium, Maxwell's Equations need to be modified with the introduction of dielectric and permeability tensors. At optical frequencies, one usually sets μ=1 and ignores the permeability. Spatial dispersion is not usually important.
  2. Reflection of Light by Stratified Planar Structures
    The reflection of light by stratified planar structures (a series of layers on a substrate) can be described with a 4x4 Berreman matrix approach. This approach relates the Jones or Mueller matrix of the sample to the dielectric tensor of each layer. I did not prepare a lecture on this subject, because this is not my specialty. This task is usually handled by the software that comes with commercial ellipsometers, based on a method developed by Mathias Schubert in his Ph.D. thesis.
  3. Infrared Response of Free Carriers and Lattice Vibrations
    A bound charge will oscillate resonantly under the influence of an AC electric field. These oscillations lead to a susceptibility (dielectric tensor) that can be described with a Lorentz oscillator model. Different damping rates for transverse and longitudinal vibrations can be described by adding an anharmonic imaginary term in the numerator. Unbound charges in metals are described with a Lorentz model. Examples will be given for semiconductors (GaAs, GaP, and their alloys; GaN, ZnO), complex metal oxides (LaAlO3, spinel), anisotropic oxides (sapphire, gallium oxide), and metals such as Al, gold, Ni, and doped germanium.
  4. Interband Optical Transitions
    Peaks and other features in optical spectra are closely related to the electronic band structure of solids. I will review the van Hove singularities and critical points in the dielectric function and its derivatives. Several parametric models can be used to model such singularities. The lowest band gap can usually be described within a simple k⋅p model, including excitonic effects. Such interband optical transitions are also important for metals. In the transparent region, a simple Sellmeier model consisting of poles in the IR and UV are usually sufficient. Many examples will be given.

Video Series: Optical Properties of Solids (Spring 2019)

  1. Introduction and overview; spectroscopy; Slides and Video
  2. Crystal structures; symmetry; point and space groups; Wyckoff positions; Slides and Video
  3. Electromagnetic waves in vacuum; polarized light; Jones and Mueller matrix; Slides and Video
  4. Electrodynamics of continuous media; Lorentz and Drude model; Slides and Video
  5. Applications of Lorentz and Drude model to metals and insulators; Slides and Video
  6. Continuation of Lecture 5: Dispersion; poles and Cauchy model; analytical properties of ε; Slides and Video
  7. Electronic band structure; direct and indirect gaps; Slides and Video
  8. Optical interband transitions; Tauc plot; Slides and Video
  9. Indirect gap absorption; experimental techniques; critical points; Slides and Video
  10. Excitons; ionization of excitons; excitons in low dimensions; Slides and Video
  11. Applications I: Emission spectroscopy; hot carriers and high density effects; quantum wells, wires, dots; Slides and Video
  12. Applications II: quantum nanostructures; carbon nanotubes; defects in insulators and semiconductors; stress, strain, deformation potentials; Slides and Video

MATLAB scripts

  1. Excitonic absorption in Ge with and without screening
  2. Nonparabolic 8x8 k.p band structure of alpha-tin
  3. Intervalence band absorption of alpha-tin
  4. Calculate Fermi level of intrinsic InSb as a function of temperature for parabolic bands
  5. Calculate thermal expansion coefficient of InSb
  6. Calculate band structure of InSb for nonparabolic bands in different approximations
  7. Calculate Fermi level of intrinsic InSb as a function of temperature for nonparabolic bands
  8. Calculate Murnaghan's equation of state for Si under hydrostatic pressure
  9. Calculate electron distribution of GaSb with nonparabolic bands in different conduction band minima

Videos

  1. Roughening the back surface of sample with a sand blaster to allow ellipsometry measurements below the band gap, Aaron Lopez Gonzalez, 03 October 2023.
  2. Dirac rotations by 4π of macroscopic objects, Juan Gil Fraile, 11 December 2024.

Course Materials

  1. Applications of Group Theory to Condensed Matter Physics: Course Notes, Stefan Zollner, Iowa State University, 20 July 1995.

Internal NMSU Documents

  1. NMSU Research and Creativity Week 2023 Centers and Institutes Powerpoint and PDF slides.
  2. Comprehensive Exam question 2024: Quantum Mechanics.

Recruiting Materials

  1. Physics Undergraduate Studies Brochure 2024
  2. Engineering Physics Recruiting video spring 2024
  3. Optical Science and Engineering at UNC Charlotte (courtesy of Professor Jay Matthews)
  4. Physics Recruiting Video Summer 2020
  5. Physics Department Brochure large or small
  6. Physics Undergraduate Studies Brochure 2022 large or small
  7. Physics Graduate Studies Brochure 2022 large or small
  8. Engineering Physics Undergraduate Studies Brochure 2022 large or small
  9. Physics and Engineering Physics 2017
  10. Physics Graduate Studies Brochure 2017

Physics Department Newsletters (Quantum Times)

Dr. Stefan Zollner, Head, Department of Physics, New Mexico State University, 25 September 2024.
Maintained with support from the National Science Foundation under Award No. DMR-2423992.