Farhana Anwar | Marquette University (original) (raw)

Papers by Farhana Anwar

IEEE Transactions on Quantum Engineering

Thin films with quantum defects are emerging as a potential platform for quantum applications. Qu... more Thin films with quantum defects are emerging as a potential platform for quantum applications. Quantum defects in some thin films arise due to structural imperfections, such as vacancies or impurities. These defects generate localized electronic states with unique optical and electronic properties. Crystal vacancies or defects that occur when atoms are missing from a crystal lattice can influence a material's quantum properties. In this study, we investigated inexpensive, complementary metal oxide semiconductor compatible materials with quantum defects suitable for room temperature applications. The experiments indicated 5, 15, and 17 ns relaxation times for aluminum nitride, aluminum oxide or alumina, and tin oxides, respectively. For all these materials, distinct resonant peaks are observed at approximately 1.1, 1.6, 2.2, and 2.7 GHz at room temperature (i.e., 21°C). These peaks exhibit slight frequency shifts, corresponding to known defect locations and thin film material properties. This discovery may lead the way to reliable, cost-effective quantum applications in our daily lives. INDEX TERMS Bandgap, microelectromechanical systems (MEMS), quantum information system (QIS), thin film, vacancy defect.

Phase Change Materials - Technology and Applications [Working Title]

Germanium telluride (GeTe) is a chalcogenide phase change material which is nonvolatile and chang... more Germanium telluride (GeTe) is a chalcogenide phase change material which is nonvolatile and changes its phase from amorphous state to a highly conductive crystalline state at approximately 180–230°C temperature, dropping the material’s resistivity by six orders of magnitude. These temperature-induced states lead to different physical and chemical properties, making it a suitable candidate for optical storage, reconfigurable circuit, high-speed switching, terahertz (THz), and satellite applications. Besides, GeTe-based devices offer complementary metal oxide-semiconductor (CMOS) compatibility and simplified, low-cost fabrication processes. In this chapter, three applications of GeTe will be discussed. They are as follows: (1) how GeTe can be utilized as DC and RF switching material with their high OFF/ON resistivity ratio, (2) how GeTe can contribute to current THz technology as split-ring resonators and modulators, and (3) effect of threshold voltage on GeTe for reconfigurable circu...

2019 IEEE Holm Conference on Electrical Contacts, 2019

In microelectromechanical systems (MEMS) ohmic contact switches, reliability is of great concern ... more In microelectromechanical systems (MEMS) ohmic contact switches, reliability is of great concern where billions of cycle operation is a requirement. Microcontact surface tribology plays the critical role in determining their reliability and performance. In this work, a novel, simple, quick and efficient test fixture has been designed and assembled to study the contact resistance, contact force, adhesion force, and contamination associated with the microcontact. In support of developing the test fixture, we evaluated the performance limitations of each components (i.e. piezoelectric actuators, force sensors, nanomax stage) independently. Force versus position, force versus voltage, and position versus voltage data have been collected for each test fixture components under direct current (DC) condition. A customized stage fixture has been 3D printed for holding the microcontact support structure. We use Thorlab’s state-of-the-art nanomax stage to provide nanometric positioning and precise alignment between the microcontact area and the force sensor on three orthogonal axes. We fabricate a novel contact support structure to test the feasibility of our test fixture and collect force and resistance data simultaneously at the rate of sim\simsim5 KHz using LabView. Data obtained from the test fixture will provide significant information to design a robust and reliable MEMS switch for future DC and RF applications.

International Journal of Renewable Energy Research

Thin film CdS/CdTe solar cell is one of the leading technologies for providing high power convers... more Thin film CdS/CdTe solar cell is one of the leading technologies for providing high power conversion efficiency at comparatively low manufacturing cost. We have done modeling and simulation of thin film CdS/CdTe solar cell and then used nanowire CdS layer instead of planar CdS layer using SCAPS-1D to demonstrate the fact that the use of CdS nanowires enhances the efficiency of the CdS/CdTe solar cells by ~3%. The scattering cross section of CdS nanowire was observed using Lumerical FDTD solutions to determine that diameter of 40-60nm is preferable for CdS nanowires for using as window layer of CdS/CdTe solar cell. For thin film CdS/CdTe solar cell the open circuit voltage was 0.69V and efficiency was 15.42%. For nanowire CdS/CdTe solar cell model the open circuit voltage was 0.82V and efficiency was 18.30%. Device parameters such as: temperature, interface state density, density of states, electron and hole mobility and metal work function were studied which can affect the efficiency of the nanowire CdS/CdTe solar cell. The rollover effect on nanowire CdS/CdTe solar cell was explained by varying the majority carrier barrier height of back contact from 0.4 to 0.7 eV. This indicates that when the barrier height is increased, a roll over effect occurs and the efficiency decreases. Effects of the parameters mentioned above were observed in order to ensure high efficiency performance from nanowire CdS/CdTe solar cell.

This work presents the only known SOI membrane approach, using Microelectromechanical systems (ME... more This work presents the only known SOI membrane approach, using Microelectromechanical systems (MEMS) fabrication techniques, to address viable water leakage sensing requirements at low cost. In this research, membrane thickness and diameter are used in concert to target specific stiffness values that will result in targeted operational pressure ranges of approximately 0-120 psi. A MEMS membrane device constructed using silicon-on-insulator (SOI) wafers, has been tested and packaged for the water environment. MEMS membrane arrays will be used to determine operational pressure range by bursting. Two applications of these SOI membranes in aqueous environment are investigated in this research. The first one is water pressure sensing. We demonstrate that robustness of these membranes depends on their thickness and surface area. Their mechanical strength and robustness against applied pressure are determined using Finite Element Analysis (FEA). The mechanical response of a membrane pressure sensor is determined by physical factors such as surface area, thickness and material properties. ACKNOWLEDGMENTS Farhana Anwar I would like to express my sincere gratitude to my advisor Dr. Coutu for his continuous support, patience, enthusiasm, and immense knowledge. His guidance helped me to conduct this research and thesis writing. I am grateful to my fellow lab mates, especially, Dr. Dushyant Tomer, Protap K. Mahanta and Gilmore Wesley for their assistance and valuable comments regarding my research. Also, I am thankful to Process Engineers from Wisconsin Centers for Nanoscale Technology and Pritzker Nanofabrication Facility for their help with my device fabrication. Special thanks go to my thesis committee members, Dr.

Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive... more Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive Copper Indium Gallium Selenide (CIGS) absorber layer due to its high efficiency, low-cost, non-radioactive and environmental friendly behavior. Potential buffer layers for CZTS solar cells like ZnO, ZnS, In2S3 and ZnSe along with conventional CdS buffer layer are numerically analyzed. Among these structures, ZnS/CZTS structure shows an optimum efficiency of 26.82% (with Voc = 0.724 V, Jsc = 53.312 mA/cm 2 and fill factor = 69.44 %).This paper explicitly reveals the most favorable CZTS layer thickness around 2.5 μm, whereas buffer layer thickness lies just below 50 nm. Absorber carrier density has its effect on Voc and Jsc and so on efficiency. With increasing carrier density Jsc decreases while Voc increases. An optimum density of 5×10 17 cm to 1×10 cm shows a great result. The achieved results can lead to the development of higher efficiency CZTS thin film solar cells. (Avoid the words...

International Journal of Photoenergy, 2017

Simulation has been done using SCAPS-1D to examine the efficiency of CH3NH3SnI3-based solar cells... more Simulation has been done using SCAPS-1D to examine the efficiency of CH3NH3SnI3-based solar cells including various HTM layers such as spiro-OMeTAD, Cu2O, and CuSCN. ZnO nanorod array has been considered as an ETM layer. Device parameters such as thickness of the CH3NH3SnI3 layer, defect density of interfaces, density of states, and metal work function were studied. For optimum parameters of all three structures, efficiency of 20.21%, 20.23%, and 18.34% has been achieved for spiro-OMeTAD, Cu2O, and CuSCN, respectively. From the simulations, an alternative lead-free perovskite solar cell is introduced with the CH3NH3SnI3 absorber layer, ZnO nanorod ETM layer, and Cu2O HTM layer.

Sensors, 2019

In microelectromechanical systems (MEMS) switches, the microcontact is crucial in determining rel... more In microelectromechanical systems (MEMS) switches, the microcontact is crucial in determining reliability and performance. In the past, actual MEMS devices and atomic force microscopes (AFM)/scanning probe microscopes (SPM)/nanoindentation-based test fixtures have been used to collect relevant microcontact data. In this work, we designed a unique microcontact support structure for improved post-mortem analysis. The effects of contact closure timing on various switching conditions (e.g., cold-switching and hot-switching) was investigated with respect to the test signal. Mechanical contact closing time was found to be approximately 1 us for the contact force ranging from 10–900 μN. On the other hand, for the 1 V and 10 mA circuit condition, electrical contact closing time was about 0.2 ms. The test fixture will be used to characterize contact resistance and force performance and reliability associated with wide range of contact materials and geometries that will facilitate reliable, r...

Technologies, 2019

Liquid Crystals (LCs) are widely used in display devices, electro-optic modulators, and optical s... more Liquid Crystals (LCs) are widely used in display devices, electro-optic modulators, and optical switches. A field-induced electrical conductivity modulation in pure liquid crystals is very low which makes it less preferable for direct current (DC) and radio-frequency (RF) switching applications. According to the literature, a conductivity enhancement is possible by nanoparticle doping. Considering this aspect, we reviewed published works focused on an electric field-induced conductivity modulation in carbon nanotube-doped liquid crystal composites (LC-CNT composites). A two to four order of magnitude switching in electrical conductivity is observed by several groups. Both in-plane and out-of-plane device configurations are used. In plane configurations are preferable for micro-device fabrication. In this review article, we discussed published works reporting the elastic and molecular interaction of a carbon nanotube (CNT) with LC molecules, temperature and CNT concentration effects on electrical conductivity, local heating, and phase transition behavior during switching. Reversibility and switching speed are the two most important performance parameters of a switching device. It was found that dual frequency nematic liquid crystals (DFNLC) show a faster switching with a good reversibility, but the switching ratio is only two order of magnitudes. A better way to ensure reversibility with a large switching magnitude is to use two pairs of in-plane electrodes in a cross configuration. For completeness and comparison purposes, we briefly reviewed other nanoparticle-(i.e., Au and Ag) doped LC composite's conductivity behavior as well. Finally, based on the reported works reviewed in this article on field induced conductivity modulation, we proposed a novel idea of RF switching by LC composite materials. To support the idea, we simulated an LC composite-based RF device considering a simple analytical model. Our RF analysis suggests that a device made with an LC-CNT composite could show an acceptable performance. Several technological challenges needed to be addressed for a physical realization and are also discussed briefly.

Sensors 19(3):579, 2019

In microelectromechanical systems (MEMS) switches, the microcontact is crucial indetermi... more In microelectromechanical systems (MEMS) switches, the microcontact is crucial indetermining reliability and performance. In the past, actual MEMS devices and atomic forcemicroscopes (AFM)/scanning probe microscopes (SPM)/nanoindentation-based test fixtures havebeen used to collect relevant microcontact data. In this work, we designed a unique microcontactsupport structure for improved post-mortem analysis. The effects of contact closure timing on variousswitching conditions (e.g., cold-switching and hot-switching) was investigated with respect to thetest signal. Mechanical contact closing time was found to be approximately 1μs for the contact forceranging from 10–900μN. On the other hand, for the 1 V and 10 mA circuit condition, electrical contactclosing time was about 0.2 ms. The test fixture will be used to characterize contact resistance andforce performance and reliability associated with wide range of contact materials and geometries thatwill facilitate reliable, robust microswitch designs for future direct current (DC) and radio frequency(RF) applications.

(PDF) Novel Test Fixture for Characterizing MEMS Switch Microcontact Reliability and Performance. Available from: https://www.researchgate.net/publication/330744690_Novel_Test_Fixture_for_Characterizing_MEMS_Switch_Microcontact_Reliability_and_Performance [accessed Feb 08 2019].

Materials Science 2018, Atlanta, USA, 2018

Overview: A hybrid structure of Au/ZnO core-shell nanorod (NR) onto PbS quantum dot(QD) array is ... more Overview: A hybrid structure of Au/ZnO core-shell nanorod (NR) onto PbS quantum dot(QD) array is simulated for the power analysis of nanorods' size dependence of absorbed power using FDTD simulator Objective: Au/ZnO core-shell nanorod(NR) on an assembly of PbS quantum dot(QD) is proposed for light harvesting, nonlinear optics, and quantum information processing.

Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar ... more Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar cells including various HTM layers such as spiro-OMeTAD, Cu 2 O, and CuSCN. ZnO nanorod array has been considered as an ETM layer. Device parameters such as thickness of the CH 3 NH 3 SnI 3 layer, defect density of interfaces, density of states, and metal work function were studied. For optimum parameters of all three structures, efficiency of 20.21%, 20.23%, and 18.34% has been achieved for spiro-OMeTAD, Cu 2 O, and CuSCN, respectively. From the simulations, an alternative lead-free perovskite solar cell is introduced with the CH 3 NH 3 SnI 3 absorber layer, ZnO nanorod ETM layer, and Cu 2 O HTM layer.

Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has bee... more Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has been analyzed using the Finite-Difference Time-Domain (FDTD) simulation. The source used in the simulation is a Total-Field Scattered-Field (TFSF) which ranged from 300-900 nm. Strong scattering cross section (σ_scat) is observed from the σ_scat versus wavelength (λ) curve. Increase in absorption cross section is also observed due to Gallium Arsenide (GaAs) and Aluminium Gallium Arsenide (AlGaAs) having direct bandgaps. For core radii of 25 nm, 35 nm and 45 nm σ_scat increases respectively. The increase in thickness of AlGaAs layer elevated the scattering cross section far greater than the increase in thickness of the Au layer and the joint increase in thickness of the Au/AlGaAs layer increases the spectral linewidth. Shifts in wavelength (λ) is also observed as the radius of the core-multishell NW increases. Such high optical scattering properties can be used in infra-red lasing operations. Since there is a surface passivation of AlGaAs, the core multi-shell NW is also useful as photodetectors.

Thin film CdS/CdTe solar cells has become one of the leading technologies for providing high powe... more Thin film CdS/CdTe solar cells has become one of the leading technologies for providing high power conversion efficiency at comparatively low manufacturing cost. We have done modeling and simulation of thin film CdS/CdTe solar cell and then used nanowire CdS layer instead of planar CdS layer using SCAPS-1D to demonstrate the fact that the use of CdS nanowires enhances the efficiency of the CdS/CdTe solar cells by ~3%. The scattering cross section of CdS nanowire was observed using Lumerical FDTD solutions to determine the preferable diameter for CdS nanowires. For thin film CdS/CdTe solar cell the open circuit voltage was 0.69V and efficiency was 15.42%. For nanowire CdS/CdTe solar cell model the open circuit voltage was 0.82V and efficiency was 18.30%. Device parameters such as: temperature, parasitic series and shunt resistance interface state density, density of states, electron and hole mobility and metal work function were studied which can affect the efficiency of the nanowire-CdS/CdTe solar cell. The rollover effect on nanowire CdS/CdTe solar cell was explained by varying the majority carrier barrier height of back contact from 0.4 to 0.7 eV. This indicates that when the barrier height is increased, a roll over effect occurs and the efficiency decreases.

Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive... more Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive Copper Indium Gallium
Selenide (CIGS) absorber layer due to its high efficiency, low-cost, non-radioactive and environmental friendly behavior.
Potential buffer layers for CZTS solar cells like ZnO, ZnS, In2S3 and ZnSe along with conventional CdS buffer layer are
numerically analyzed. Among these structures, ZnS/CZTS structure shows an optimum efficiency of 26.82% (with Voc = 0.724 V,
Jsc = 53.312 mA/cm2 and fill factor = 69.44 %).This paper explicitly reveals the most favorable CZTS layer thickness around 2.5
μm, whereas buffer layer thickness lies just below 50 nm. Absorber carrier density has its effect on Voc and Jsc and so on
efficiency. With increasing carrier density Jsc decreases while Voc increases. An optimum density of 5×1017 cm-3 to 1×1018 cm-3
shows a great result. The achieved results can lead to the development of higher efficiency CZTS thin film solar cells.
(Avoid the words in abstract Ex. Recently in this work research)

Conference Presentations by Farhana Anwar

IEEE Transactions on Quantum Engineering

Phase Change Materials - Technology and Applications [Working Title]

2019 IEEE Holm Conference on Electrical Contacts, 2019

International Journal of Renewable Energy Research

International Journal of Photoenergy, 2017

Sensors, 2019

Technologies, 2019

Sensors 19(3):579, 2019

Materials Science 2018, Atlanta, USA, 2018

Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive... more Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive Copper Indium Gallium
Selenide (CIGS) absorber layer due to its high efficiency, low-cost, non-radioactive and environmental friendly behavior.
Potential buffer layers for CZTS solar cells like ZnO, ZnS, In2S3 and ZnSe along with conventional CdS buffer layer are
numerically analyzed. Among these structures, ZnS/CZTS structure shows an optimum efficiency of 26.82% (with Voc = 0.724 V,
Jsc = 53.312 mA/cm2 and fill factor = 69.44 %).This paper explicitly reveals the most favorable CZTS layer thickness around 2.5
μm, whereas buffer layer thickness lies just below 50 nm. Absorber carrier density has its effect on Voc and Jsc and so on
efficiency. With increasing carrier density Jsc decreases while Voc increases. An optimum density of 5×1017 cm-3 to 1×1018 cm-3
shows a great result. The achieved results can lead to the development of higher efficiency CZTS thin film solar cells.
(Avoid the words in abstract Ex. Recently in this work research)

Cadmium sulfide (CdS) and cadmium telluride (CdTe) are two leading semiconductor materials used i... more Cadmium sulfide (CdS) and cadmium telluride (CdTe) are two leading semiconductor materials used in the fabrication of thin film solar cells of relatively high power conversion efficiency and low manufacturing cost. Numerical simulations of current-voltage characteristics of thin film CdS/CdTe solar cell and nanowire CdS/CdTe solar cell were performed as a function of temperature using SCAPS-1D to demonstrate the fact that use of CdS nanowires enhances the efficiency of the CdS/CdTe solar cells. For the simulation of nanowire CdS/CdTe solar cell we changed some parameters (thickness, bandgap, electron and hole mobility) of the simulation of thin film CdS/CdTe solar cell. The Optical properties (absorption and scattering cross section) of CdS nanowire were observed to determine the preferable diameter for CdS nanowires. Simulations for realizing the absorption and scattering cross sections for various diameters of CdS nanowire were done using Lumerical FDTD solutions. From simulation results it was evident that nanowire CdS design was superior to planar CdS film due to enhanced performance in the CdS/CdTe solar cell through higher open circuit voltage and higher efficiency as for thin film CdS/CdTe solar cell the open circuit voltage was 0.6908V and efficiency was 14.15%. For nanowire CdS/CdTe solar cell model the open circuit voltage was 0.7889V and efficiency was 15.07%. Device parameters such as: thickness, bandgap, interface state density, density of states, electron and hole mobility, trap density, metal work function, temperature, parasitic series and shunt resistance were studied which can affect the efficiency of the nanowire-CdS/CdTe solar cell. The rollover effect on nanowire CdS/CdTe solar cell was explained by varying the majority carrier barrier height of back contact from 0.4 to 0.7 eV. It proves that change of barrier height at the contact can cause rollover effect. The crossover effect was observed by varying the thickness of CdS nanowire layer and removing defect of i-SnO2 layer. It was evident that the removal of defect in i-SnO2 is responsible for producing the crossover effect. Though SCAPS-1D is basically designed for simulation of thin film solar cells, it can be concluded that SCAPS-1D can also provide realistic simulation for nanowire CdS/CdTe solar cells.

This is to certify that the 4 th year project on "Simulation and performance study of Nanowire Cd... more This is to certify that the 4 th year project on "Simulation and performance study of Nanowire CdS/CdTe Solar Cell" has been submitted for the award of the degree of B.Sc. in Electrical and Electronic Engineering from the University of Dhaka, carried out by exam roll-1255 and exam roll-1257, under my supervision. According to my knowledge and as per declaration, the whole work and project report has been prepared by the student and has not been submitted to anywhere else for any degree. The project report can be considered for evaluation.