Home Page of Dr. Oleg Rubel

Research group

Current members

Mitchell Albert (photo)
      

Project: Adhesion of poly(styrene-alt-maleic acid) to hydroxyapatite and titanium oxide

Currently, hip implants are constructed with titanium, then plasma coated with hydroxyapatite (HA), a mineral also found in bone. After the implant is inserted, the bond between bone and HA becomes so strong that the HA may strip from the implant, causing the implant to fall out. The polymer Poly(Styrene-Alt-Maleic Acid) may be able to adhere to both HA and the oxide layer of titanium better than plasma coating, making it a favourable alternative to the HA coating used in the past. By virtually modelling these interactions at the molecular level and calculating the change in surface energy at the interface, we are able to determine the favourability of the polymer to adhere to HA and titanium oxide. Should the bonds be both favourable and stronger than the HA plasma coating, then our research could change the way implants are constructed.


Mitchell Albert (Undergraduate Research Assistant)

Christopher Pashartis (photo)
      

Project: Effect of compositional disorder on performance of III-V semiconductor alloys in telecommunication applications

Disorder due to mixing of isotropic elements in III-V semiconductors is rarely discussed. Developing methods to study this disorder and predict future disorder is my main interest. By understanding the disorder introduced into a system we will gain greater understanding in engineering more efficient gain materials. We have already determined a unique statistical approach in quantifying electron localization in a material for WIEN2k - which is able to capture the disorder introduced. However, the ability to predict the amount of disorder in the system is currently under study. Currently, we hypothesize the disorder to have effect on the recombination efficiency of the system in both recombination rate and electron mobility.

Publications/presentations:

  • "Alloying strategy for 2D GaN optical emitters" arXiv:1707.04625 (2017)
  • "Localization of electronic states in III-V semiconductor alloys: a comparative study" Phys. Rev. Applied 121, 11977 (2017)
  • 59th Electronic Materials Conference (South Bend, Indiana, July 2017)
  • Canadian Association of Physics Congress (Ottawa, June 2016)
  • 28th Canadian Materials Science Conference (Hamilton, June 2016)
  • 23th International Wien2k Workshop (Hamilton, June 2016)

Awards:

  • Ontario Graduate Scholarship (2016-2017)
  • 2nd Place Poster in the Division of Condensed Matter and Materials Physics at the Canadian Association of Physics Congress (2016)


Christopher Pashartis (Master Student)

Chao Zheng (photo)
      

Project: Photovoltaic materials with polarization texture

Perovskite solar cells are one kind of very promising photovoltaics. The power conversion efficiency of perovskite solar cells are around 22%. Moreover, cheap to produce and easy to fabricate are another advantages. However, the stability of perovskite solar cells is one big challenge. Instability of perovskite solar cells shows in the form of decomposition of light-harvesting active perovskite layer. Our project is focused on improving instability of this perovskite structure. Currently, we proposed one new mechanism which can explain the instability of perovskite structure. And our next work will focus on finding some new perovskite materials which are stable and suitable for photovoltaics.

Publications/presentations:

  • "Ionization energy as a stability criterion for halide perovskites" J. Phys. Chem. C 121, 11977 (2017)
  • "Thermodynamic origin of instability in hybrid halide perovskites" Scientific Reports 6, 37654 (2016)
  • MRS Spring Meeting (Phoenix, Arizona, April 2017)
  • Canadian Association of Physics Congress (Ottawa, June 2016)
  • 28th Canadian Materials Science Conference (Hamilton, June 2016)
  • 23th International Wien2k Workshop (Hamilton, June 2016)

Awards:

  • Academic Excelence Graduate Dean's Scholarship (2016)
  • Academic Excelence Graduate Dean's Entrance Scholarship (2015)

Chao Zheng (PhD Student)

Alumni

Nitesh Mistry (photo)
      

Project: Finite element modelling of piezoelectric transducers for ultrasonic medical imaging

Piezoelectric materials are essential components for various applications; specifically, in medicine. In hospital ultrasound systems, the essential component to produce ultrasound waves utilizes the piezoelectric effect. This phenomenon is known to convert electric energy to mechanical energy or vice versa. My role was to investigate the behavior of transducer under different loading and boundary conditions. By developing 3D models and using the simulation feature of ANSYS, I was able to analyze the various acoustic powers that would be generated at different frequencies.

Nitesh Mistry (Undergraduate Research Assistant)

Lina Qamar (photo)
      

Project: Multiscale material simulation in modelling of solar cell performance

Taking a deeper look at the material design aspect of a simple Silicon solar cell. Material design for solar cells needs to focus on optimizing the material properties in order to attain the most efficient cells. Initially, using data gathered from First Principle calculations (DFT), devices can be simulated with great accuracy. Focusing on the effects of parameters such as The parameters studied were the following: Absorption, Bandgap, Lifetime of Carriers, Auger Recombination, and Electron and Hole mobility effect the efficiency of a simple Si solar cell.

Lina Qamar (Undergraduate Research Assistant)

Eric Tenuta (photo)
      

Project: Enhanced chemical stability of mixed halide perovskite photovoltaics

With the search for higher solar cell efficiencies and lower manufacturing costs scientists and engineers have come up with some ingenious materials and technologies. One of such materials is the methylammonium lead iodide perovskite that has gained significant attention in the past 5 years. My efforts this summer (2015) were directed at investigating the stability of the material and possibly providing some new changes to the material itself. Manipluation of the cation within crystal can be examined computational fairly quickly where as the same experiments would be far more strenuous. The crystallographic and stability calculations were done using Abinit while the band structures were created using Wien2k.

Publications/presentations:

Awards:

  • NSERC Undergraduate Student Research Award (2015)


Eric Tenuta (Undergraduate Research Assistant)

Anton Bokhanchuk (photo)
      

Project: Electronic structure of disordered solids

fold2Bloch is a new tool for studying the electronic structure of disordered solids. It enables "unfolding" of the band structure of supercells back to its conventional (Bloch) representation. For example, it can be useful for visualizing the band structure of compound alloys and quantify the extent of disorder. The software is able to interface with Wien2k all-electron DFT package. The interface with abinit is in progress and expected to be released by the end of 2014.

Publications/presentations:

Awards:

  • ELEKTA Student Travel Award (TBRRI, 2015)


Anton Bokhanchuk (Research Assistant, 2014-2015)

Nadiya Dragneva (photo)
      

Project: Molecular mechanisms of biocompatibility of syntectic materials

Biomaterials are widely used as an interface between implants and tissue in order to prevent the failure as a result of immune rejection. Implant rejection requires additional surgical intervention and, ultimately, increases health cost as well as recovery time. Within a few hours after implantation, the implant surface is covered with host proteins, which determines further immune response and, eventually, the biocompatibility of a given material. In this project we focus on modeling the interaction between artificial surfaces (such as graphene) and plasma proteins at the atomistic level taking into account the explicit biological environment. Our findings provide a foundation for development of novel coatings for implants with improved biocompatibility and bioadhesion.

Publications/presentations:

Awards:

  • ELEKTA Student Travel Award (TBRRI, 2014)
  • Best-of-the-best poster presentation at Research & Innovation Week (Lakehead University, 2014)
  • Ontario Graduate Scholarship 2013-2014

Co-supervisor: Dr. Wely B. Floriano


Nadiya Dragneva (PhD Biotechnology student, 2012-2015)

Dennis Stauffer (photo)
      

Project: Bioadhesive properties of polar surfaces

An increase in the use of artificial medical implants has created a need for the development of bio-compatible and bio-adhesive materials. Various properties of promising materials (such as graphene-based nanomaterials) can be analyzed through molecular dynamics software. This summer, I assisted in developing and analyzing a molecular model of a graphene-oxide surface. I gained valuable experience in working with molecular modeling software, various Matlab applications, super-computing, and many other forms of data analysis.

Publications/presentations:

Awards:

  • NSERC Undergraduate Student Research Award (2014)
  • NSERC Undergraduate Student Research Award (2013)

Co-supervisor: Dr. Wely B. Floriano


Dennis Stauffer (Undergraduate Research Assistant, 2013-2014)

Ayman Alahmar (photo)
      

Project: Ferroelectric materials for high-power therapeutic applications

Ferroelectric materials used for high-power ultrasonic actuators are generally driven at their resonance frequencies in order to maximize their mechanical power output. There are three power loss mechanisms in ultrasonic transducers: mechanical, dielectric, and piezoelectric losses. The mechanical losses are considered dominant under resonant excitation and cause a reduction in the mechanical quality factor (Q) that ultimately limits the output power. The mechanical losses represent the mechanical energy dissipation properties of the actuator�s material under cyclic stress, and they cause a reduction in Q much below its intrinsic quantum limit. In this research, we attempt to model the quantum limit of Q by calculating the relevant material's properties that define this limit using first-principle methods.

Co-supervisor: Dr. Laura Curiel


Ayman Alahmar (PhD Material Science student, 2013-2014)

Sheikh J. Ahmed (photo)
      

Project: Computer simulation of functional materials for therapeutic ultrasound applications.

The performance of ultrasonic transducers for high-power applications, such as high-intensity focused ultrasound, is affected by a dielectric dissipation that results in a risk of thermal runaway. The aim of this thesis is twofold: to establish a microscopic origin of the dielectric loss in ferroelectric materials and, secondly, to propose approaches for its reduction. The modern theory of polarization was combined with a first principle electronic structure method in order to determine relevant material properties. Our study of a ferroelectric switching at the microscopic level has lead to the development of a new method for driving ferroelectric crystals with a minimized energy loss. The anticipated implications of this work are a reduction of the risk of thermal damage to the tissue at the interface with the transducer, an improvement to the working stability of the transducer and further miniaturization of ultrasonic actuators with limited access to thermal sink. Sheikh was actively involved in developing a software "BerryPI" - an additional software package for WIEN2k density-functional theory code, which enables calculation of polarization related properties of crystalline solids using Modern theory of polarization.

Publications/presentations:

Co-supervisor: Dr. Samuel Pichardo

Email:


Sheikh Jamil Ahmed (MSc Physics student, 2011-2013)

Jeremy Cole (photo)
      

Project: Marble game with ferroelectric switching

Ferroelectric materials yield an abundance of applications largely due to their piezoelectric property. One such application is High-Intensity Focused Ultrasound (HIFU), which offers a minimally invasive method to destroy cancerous tissue, assist in drug delivery, and many other medical functions. Over the course of the summer I engaged in a variety of tasks all leading to the discovery of the potential profile for ferroelectric materials. With my background in computer science I was able to create several file manipulation and parsing programs to accelerate the process. Additionally, I created many real-time interactive simulations to better visualize what was occurring at the atomic level of these materials. I have gained an immense amount of knowledge in the fields of crystallography, mathematics, and computer graphics throughout the summer, and I am forever grateful for the opportunities that the Thunder Bay Regional Research Institute has presented.

Publications/presentations:

Awards: NOHFC Youth Internship and Co-Op Scolarship

Co-supervisors: Drs. Samuel Pichardo and Laura Curiel

Email:


Jeremy Cole (Summer co-op student, 2013)

Ali Darbandi (photo)
      

Project: Microscopic modelling of high-field transport in amorphous selenium.

Electrons avalanche multiplication has lead to the development of avalanche-based photodiodes. The latter have found a wide variety of applications in the electronics market including laser range finders, TV camera tubes, fiber optic telecommunications and potential use in medical imaging detectors. Recently, there has been a growing interest to use amorphous semiconductors instead of crystalline since amorphous production is economically more favorable than crystalline. Selenium is the only material that has been reported clearly to feature avalanche phenomenon in the amorphous phase at a practical electric field. My intriguing project is an attempt to understand the physics behind the uniqueness of amorphous Selenium in representing the impact ionization process. The latter was undertaken by first principle studying of the electronic structure and the electron-phonon interaction in Selenium.

Publications/presentations:

Email:


Ali Darbandi (MSc Physics student 2010-2012)

�lise Devoie (photo)
      

Project: Modelling the electron-hole pair generation by ionizing radiation in selenium.

Selenium is an amorphous (disordered) material used in medical imaging applications mainly as an x-ray detector. Though it has many applications, little is know about the structure and intrinsic properties of selenium. During my term here, I was involved in modelling the electron-hole-pair creation in selenium, as well as creating a rudimentary model for its disordered structure. My work consisted mainly of the development and implementation of mathematical algorithms in MatLab, as well as high-performance computing using abinit software. From this work, not only did I learn an incredible amount, but relevant intrinsic values for the electron-hole-pair creation energy and Fano factor in selenium were determined, while the work on the amorphous structure is still ongoing. I am very grateful for the knowledge I have gained and the opportunities that the Thunder Bay Regional Research Institute has offered me, it was a wonderful way to spend a summer.

Publications/presentations:

Awards: 2nd prize winner - Summer Student Presentations Competition 2012


�lise Devoie (Summer co-op student, 2012)

Kaci Karter (photo)
      

Project: Computer simulation of functional materials for therapeutic ultrasound applications.

This summer I worked on the design of piezoelectric materials for therapeutic ultrasound focussing on increasing the efficiency of the piezoelectric ceramic in an ultrasound transducer in order to improve High Intensity Focussed Ultrasound treatment. I was able to calculate multiple elastic constants for commonly studied compounds in order to show that density functional theory can be used for accurate calculations. I was also able to gain hands on experience by performing two experiments in order to measure the efficiency of ultrasound transducers. I liked how I could do both theoretical calculations and hands on experiments in the lab. I have gained a lot of knowledge and experience through this summer research project and I am very thankful to have been a part of the Thunder Bay Regional Research Institute this summer.

Awards: NSERC Undergraduate Student Research Award

Co-supervisor: Dr. Laura Curiel


Kaci Karter (Summer student, 2012)

Olivia Di Matteo (photo)
      

Project: Recombination of geminate charge carriers in the presence of disorder

The problem of the dissociation of geminate electron-hole pairs and the problem of injection of electrons into a semiconductor from a metallic contact are among the most often discussed topics in the field of disordered systems, particularly amorphous and organic disordered materials. The central question in both cases is how charge carriers escape from the Coulomb potential well created by their counterparts via a series of noncoherent hopping transitions between spatially localized states or in a diffusion manner. It has been shown that an energetic disorder, which arises from structural imperfections, significantly affects the dissociation probability. Recently an analytical solution was obtained for the specified problem in the 1D case. The goal of this project was to extend the model to higher dimensions (2D and 3D), which makes the model more relevant to experiments. A solution of the dissociation and injection problems is of vital importance for the physics of molecular solar cells, organic light emitting diodes, polymer field effect transistors, and other optoelectronic devices.

Publications/presentations:

Awards: 2nd prize winner - Summer Student Presentations Competition 2011; NSERC Undergraduate Student Research Award


Olivia Di Matteo (Summer student, 2011)

Andrew Potvin (photo)
      

Project: Modelling the avalanche multiplication in disordered semiconductors

Andrew significantly advanced the accuracy and simplified mathematically the lucky-drift model model of avalanche multiplication for disordered semiconductors.

Publications/presentations:

Andrew Potvin (Summer student, 2010)

Daniel Laughton (photo)
      

Project: Modelling the avalanche multiplication in disordered semiconductors

Daniel made a key contribution to uncovering the physics behind uniqueness of avalanche multiplication in amorphous selenium, in particular relating this phenomenon to features of the electronic structure.

Publications/presentations:

Daniel Laughton (Summer student, 2009)

© by O. Rubel