About

Paul J. Thomas is an Assistant Professor of Practice in the Department of Computer and Information Technology at Purdue University. He is responsible for teaching courses in systems development and project management. Prior to his current role, he served as an Assistant Professor at Kansas State University’s Department of Integrated Studies, where he taught programming and software engineering courses. He has over three years of industry experience as an analyst, with positions at Accenture and HUB International. Paul was a graduate student at Purdue University from 2015 to 2021, earning both a Master’s Degree in Computer and Information Technology and a PhD in Technology. His research interests include gamification, IT and project management education, and technology-supported active learning.

Research topics

• Materials science
• Physics
• Condensed matter physics
• Chemistry
• Physical chemistry
• Optoelectronics
• Computational chemistry
• Thermodynamics
• Mathematics
• Crystallography
• Composite material
• Quantum mechanics

Selected publications

• Oxygen vacancy-induced monoclinic dead layers in ferroelectric HfO2 with metal electrodes

  Journal of Applied Physics · 2025-04-08 · 11 citations

  articleOpen access1st authorCorresponding

  In this work, we analyze the dead layer comprising non-polar monoclinic (m) phase in HfO2-based ferroelectric material using first principles analysis. We show that with the widely used tungsten (W) metal electrode, the density and the spatial distribution of the oxygen vacancy across the cross section play a key role in dictating the favorability of m-phase formation at the metal–HfO2 interface. The energetics are also impacted by the polarization direction as well as the depth of oxygen vacancy, i.e., position along the thickness. At the metal–HfO2 interface with polarization pointing toward the metal, both interfacial relaxation and m-phase formation can lead to dead layers when (i) single vacancy forms at a trigonally bonded O atomic site or (ii) single and double vacancies form at trigonally and tetrahedrally bonded O atomic sites, respectively. For vacancies at other oxygen atomic sites and polarization direction, a dead layer is formed due to sole interfacial relaxation with the polar phase. Moreover, with electrodes consisting of a noble metal (Pt, Pd, Os, Ru, and Rh), a m-phase dead layer formation is less likely than W. Therefore, for these metals, a dead layer forms mainly due to the interfacial relaxation with the polar phase.

  PublisherDOI

• Physics-Based Compact Model of Ferroelectric Semiconductor Field Effect Transistors

  2025-12-06

  article1st authorCorresponding

  The presence of ferroelectric (Fe) and semiconducting properties in two dimensional (2D) In<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Se<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> has made it an interesting material in the field of ferroelectric devices. In particular, Ferroelectric Semiconductor Field Effect Transistors (FeSFET) offer great potential for memory and synaptic applications. In this work, we propose a physics-based compact model of In<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Se<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>-based FeSFET. We also present our experimental findings of clockwise (CW) & counter-clockwise (CCW) hysteresis which shows that CW loop is more favorable for high effective oxide thickness (EOT) and thinner In<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Se<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3.</inf> We show that our calibrated compact model is able to capture these experimental trends with respect to both EOT and In<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Se<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> thickness. The model also provides insights into the physics of CW and CCW hysteretic characteristics of FeSFET, shedding light onto the interplay between polarization switching, semiconductor electrostatics and multi-layer transport in the 2D FeS. Using our model, we analyze FeSFET-based memory array and provide insights into array-driven optimization of EOT and In<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Se<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> thickness to achieve high distinguishability of binary memory states.

  PublisherDOI

• Variability in Ferroelectric Hf_0.5Zr_0.5O₂: Physical Insights and Implications for Memory Applications

  2025-06-22

  article

  Ferroelectric (FE) hafnium-zirconium-oxide (Hf<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> Zr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> or HZO) is a promising candidate for next-generation electronics [1]. However, device-to-device variations in HZO remain a key challenge [1, 2]. Addressing this issue requires analyzing the interplay between polycrystallinity, multi-domain (MD) polarization switching and other HZO attributes [1, 2]. HZO exhibits an anisotropic crystal structure [3, 4], with alternating polar-spacer layers (APSL) in one lateral direction and continuous polar layers (CPL) in the other (Fig. 1a). This anisotropy affects polarization (P) domain formation [3] and leads to direction-dependent MD switching [4], which, in turn, affects variability in HZO. This work presents the physical insights into the mechanisms governing variability in HZO accounting for such unique attributes. We begin with first-principles simulations to provide atomic-scale insights. These findings are utilized to study metal-ferroelectric-insulator-metal (MFIM) capacitors using 3D phase-field simulations and analyze variability across different ferroelectric thicknesses ($T_{F E}$) and set voltages ($V_{S E T}$). Finally, we present how these variability trends affect the trade-offs between distinguishability of binary states and energy consumption for the SET operation in FE memories.

  PublisherDOI

• Formation and energetics of head-to-head and tail-to-tail domain walls in hafnium zirconium oxide

  Scientific Reports · 2024 · 10 citations

  1st authorCorresponding
  • Materials science
  • Crystallography
  • Physics

  domains walls (DWs) of head-to-head/tail-to-tail (H-H/T-T) type in ferroelectric (FE) materials are of immense interest for a comprehensive understanding of the FE attributes as well as harnessing them for new applications. Our first principles calculation suggests that such DW formation in hafnium zirconium oxide (HZO) based FEs depends on the unique attributes of the HZO unit cell, such as polar-spacer segmentation. Cross pattern of the polar and spacer segments in two neighboring domains along the polarization direction (where polar segment of one domain aligns with the spacer segment of another) boosts the stability of such DWs. We further show that low density of oxygen vacancies at the metal-HZO interface and high work function of metal electrodes are conducive for T-T DW formation. On the other hand, high density of oxygen vacancy and low work function of metal electrode favor H-H DW formation. Polarization bound charges at the DW get screened when band bending from depolarization field accumulates holes (electrons) in T-T (H-H) DW. For a comprehensive understanding, we also investigate their FE nature and domain growth mechanism. Our analysis suggests that a minimum thickness criterion of domains has to be satisfied for the stability of H-H/T-T DW and switching of the domains through such DW formation.

  PublisherOA PDFDOI

• Oxygen Vacancy-Induced Monoclinic Dead Layers in Ferroelectric $Hf_xZr_{1-x}O_2$ With Metal Electrodes

  arXiv (Cornell University) · 2024-12-09

  preprintOpen access1st authorCorresponding

  In this work, we analyze dead layer comprising non-polar monoclinic (m) phase in $Hf_xZr_{1-x}O_2$ (HZO)-based ferroelectric (FE) material using first principles analysis. We show that with widely used tungsten (W) metal electrode, the spatial distribution of the oxygen vacancy across the cross-section plays a key role in dictating the favorability of m- phase formation at the metal-HfO2 interface. The energetics are also impacted by the polarization direction as well as the depth of oxygen vacancy, i.e., position along the thickness. At the metal - $HfO_2$ interface, when polarization points towards the metal and vacancy forms at trigonally bonded O atomic site, both interfacial relaxation and m- phase formation can lead to dead layers. For vacancies at other oxygen atomic sites and polarization direction, dead layer is formed due to sole interfacial relaxation with polar phase. We also establish the relative favorability of the m-phase dead layer for different Zr concentrations (x=1 and x = 0.5) and metal electrodes. According to our analysis, 50% Zr doped $HfO_2$ exhibits less probability of m-phase dead layer formation compared to pure $HfO_2$. Moreover, with electrodes consisting of noble metal (Pt, Pd, Os, Ru, Rh), m-phase dead layer formation is less likely. Therefore, for these metals, dead layer forms mainly due to the interfacial relaxation with polar phase.

  PublisherOA PDFDOI

• Direction‐Dependent Lateral Domain Walls in Ferroelectric Hafnium Zirconium Oxide and their Gradient Energy Coefficients: A First‐Principles Study

  Advanced Electronic Materials · 2023 · 14 citations

  1st authorCorresponding
  • Materials science
  • Condensed matter physics
  • Composite material

  Abstract To understand and harness the physical mechanisms of ferroelectric hafnium zirconium oxide (HZO)‐based devices, there is a need for clear understanding of domain interactions, their dynamics, negative capacitance effects, and other multidomain characteristics. These crucial attributes depend on the coupling between neighboring domains quantified by the gradient energy coefficient ( g ). Furthermore, HZO has unique orientation‐dependent lateral multidomain configurations. To develop an in‐depth understanding of multidomain effects, there is a need for a thorough analysis of g . In this work, the energetics of multidomain configurations and domain growth mechanism corresponding to lateral domain walls (DWs) of HZO are analyzed and gradient energy coefficients are quantified using first‐principles density functional theory calculations. These results indicate that one lateral direction exhibits the following characteristics: i) DW is ultra‐sharp and domain growth occurs unit‐cell‐by‐unit‐cell, ii) the value of g is negative and in the order of 10 −12 V m 3 C −1 , and iii) g reduces (increases) with compressive (tensile) strain. In contrast, in the other lateral direction, the following attributes are observed: i) DW is gradual and domain growth occurs in quanta of half‐unit‐cell, ii) g is positive and in the order of 10 −10 V m 3 C −1 , and iii) g increases (reduces) with compressive (tensile) strain.

  PublisherOA PDFDOI

• Head-to-Head and Tail-to-Tail Domain Wall in Hafnium Zirconium Oxide: A First Principles Analysis of Domain Wall Formation and Energetics

  arXiv (Cornell University) · 2023-05-21

  preprintOpen access1st authorCorresponding

  180° domains walls (DWs) of Head-to-Head/Tail-to-Tail (H-H/T-T) type in ferroelectric (FE) materials are of immense interest for a comprehensive understanding of the FE attributes as well as harnessing them for new applications. Our first principles calculation suggests that such DW formation in Hafnium Zirconium Oxide (HZO) based FEs depends on the unique attributes of the HZO unit cell, such as polar-spacer segmentation. Cross pattern of the polar and spacer segments in two neighboring domains along the polarization direction (where polar segment of one domain aligns with the spacer segment of another) boosts the stability of such DWs. We further show that low density of oxygen vacancies at the metal-HZO interface and high work function of metal electrodes are conducive for T-T DW formation. On the other hand, high density of oxygen vacancy and low work function of metal electrode favor H-H DW formation. Polarization bound charges at the DW get screened when band bending from depolarization field accumulates holes (electrons) in T-T (H-H) DW. For a comprehensive understanding, we also investigate their FE nature and domain growth mechanism. Our analysis suggests that a minimum thickness criterion of domains has to be satisfied for the stability of H-H/T-T DW and switching of the domains through such DW formation.

  PublisherOA PDFDOI

• Contributors

  Elsevier eBooks · 2023-01-01

  book-chapter
  PublisherDOI

• Material, Device and Circuit-Compatible Modeling of Ferroelectric Devices

  IEEE Nanotechnology Magazine · 2023-06-14 · 1 citations

  article

  Ferroelectric devices have gained significant interest, owing to their diverse range of applications in fields such as non-volatile memories, steep-slope transistors, neuromorphic and in-memory computing. Accurate modeling of ferroelectric devices is crucial to optimize these devices for different applications and design high-performance circuits. This article presents an overview of the current state of ferroelectric modeling at material, device, and circuit levels. We examine the unique aspects and limitations of the current modeling techniques and highlight potential areas of further research to advance this field.

  PublisherDOI

• Direction-Dependent Lateral Domain Walls in Ferroelectric Hafnium Zirconium Oxide and their Gradient Energy Coefficients: A First Principles Study

  arXiv (Cornell University) · 2022-08-23

  preprintOpen access1st authorCorresponding

  To understand and harness the physical mechanisms of ferroelectric Hafnium Zirconium Oxide (HZO)-based devices, there is a need for clear understanding of domain interactions, their dynamics, negative capacitance effects, and other multi-domain characteristics. These crucial attributes depend on the coupling between neighboring domains quantified by the gradient energy coefficient (g). Furthermore, HZO has unique orientation-dependent lateral multidomain configurations. To develop an in-depth understanding of multi-domain effects, there is a need for thorough analysis of g. In this work, the energetics of multidomain configurations and domain growth mechanism corresponding to lateral domain walls of HZO are analyzed and gradient energy coefficients are quantified using first-principles Density Functional Theory calculations. These results indicate that one lateral direction exhibits the following characteristics: i) DW is ultra-sharp and domain growth occurs unit-cell-by-unit-cell, ii) the value of g is negative and in the order of $10^{-12} Vm^{3}C^{-1}$, and iii) g reduces (increases) with compressive (tensile) strain. In contrast, in the other lateral direction, the following attributes are observed: i) DW is gradual and domain growth occurs in quanta of half-unit-cell, ii) g is positive and in the order of $10^{-10} Vm^{3}C^{-1}$, and iii) g increases (reduces) with compressive (tensile) strain.

  PublisherOA PDFDOI

Frequent coauthors

• Quazi D. M. Khosru

  5 shared

• Sumeet Kumar Gupta

  5 shared

• Atanu Saha

  Central Mechanical Engineering Research Institute

  5 shared

• Peyman Fahimi

  Université Laval

  2 shared

• Sabu Thomas

  University of Johannesburg

  1 shared

• Yiyang Wu

  1 shared

• Jince Thomas

  1 shared

• P. Ábrahám

  Research Centre for Astronomy and Earth Sciences

  1 shared

Labs

• Paul J. Thomas's LaboratoryPI

Education

• MSc, Electrical and Electronic Engineering

  Bangladesh University of Engineering and Technology

Awards & honors

• 2025 Faculty and Staff awards celebrate excellence across Pu…
• Full list of Teaching Excellence award winners among Polytec…
• Professor, Ph.D. student use ChatGPT to develop undergrads’…
• Grad student, faculty mentors present on AI in business anal…
• Polytechnic faculty, staff celebrated at college-wide annual…