Department of Physics
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Item Study of Structural and Magnetic Properties of Doped LuFeO3 for Phase shifting Application using DFT(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2023) AMTUL MATEEN; CIIT/SP22-RPH-017/LHR; Dr. Muhammad Idrees; LHR TP 8781Lutetium iron oxide (LFO) is a type-II multiferroic material which exhibits ferroelectric and magnetic orders, making them interesting for various technological applications include spintronic, memory devices, sensors, and phase shifters. Shifting electric ordering makes LFO a promising material for phase shifting applications due to its unique ferroelectric behavior responsible for change in electronic properties i.e. dielectric constant. Doping strategy is one way to optimize the dielectric constant for specific phase shifting application. The primary aim of this research is to explore the structural and dielectric characteristics of La-doped h-LFO using DFT in CASTEP software. LFO, P63cm phase is investigated using first-principles calculations based on the GGA-PBE approximation with Hubbard U (GGA-PBE+ U) method in the frame of plane-wave pseudo-potential density functional theory (DFT). The indirect band gap of 0.54 eV is calculated from the band structure which converted into direct band gap with value 0.514 eV after doping lanthanum atom at A-site in LFO supercell. The reduction in band gap is due to increase in partial and total density of sates which have great influence on the electric and optical properties. Partial density of states shows increase in total density of states. Lanthanum contributes p-state in the valence band and small contribution from d-state in the conduction band. Substitution of La-atom at the A-site of LFO significantly decreases the dielectric constant from 19.2 to 18.7. A minimal change in electronic disorder is observed due to small difference in the oxidation states of the Lu3+ and La3+as the structure disorder associated with ionic size difference between dopant and substituted atom. The change in the refractive index is also observed from 4.38 to 4.32 and also reflectivity decreases from 0.634 to 0.627. vItem Investigation of Cobalt doped Bismuth Ferrite for Photocatalytic Activity(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2023) Hina Hashim; CIIT/SP22-RPH-032/LHR; Dr. Muhammad Idrees; LHR TP 8790Bismuth ferrite (BiFeO3) is a multiferroic material with a distorted perovskite structure. The advances of single-phase multiferroic BFO opens up exciting possibilities for the development of advanced photochemical catalysts through harnessing its distinctive spin-polarized electronic, magnetic, and dielectric characteristics. BFO exhibits promising photo-catalytic characteristics and has the potential to be employed in photo-catalytic water splitting and pollutant degradation. In this research project the first-principles calculations are performed to investigate structural, electronic and optical properties of pure and Co-doped bismuth ferrite (BFO) in the Cambridge Serial Total Energy Package (CASTEP) code using GGA-PBE functional and ultra-soft pseudopotential (USP). A large band gap has been observed in the pure BFO rhombohedral structure. The Co impurity atom is more favorable to decrease the band gap. The band gap 2.73eV (spin up), 0.09eV (spin down) and 0.376eV (spin up), 0.013eV (spin down) has been observed for pure and Co-doped BFO rhombohedral structures respectively. Electronic band structure analysis revealed that the BFO exhibit semiconducting behavior with indirect ban gap. The density of states (DOS) indicates considerable hybridization between O-2p and Fe-3d states in valence band (VB) and conduction band (CB). The high absorption and lower reflectivity suggest that Co-doped BFO could be a potential candidate photo-catalyst.Item Synthesis and Characterization of Metal Oxide Based Photothermal Material for Interfacial Evaporation(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Azeem Sarwar; CIIT/FA19-RPH-031/LHR; Dr. Muhammad Idrees; LHR TP 7264With the fast growth of population and increasing environmental problems, resources. The shortage has drawn global concerns in recent years. Conversion of renewable energy sources like solar energy to generate other resources such as could be a promising strategy to solve the resources issues. Among them, interfacial solar steam generation arises to be an attractive strategy to generate freshwater by utilizing only solar energy. Utilizing solar energy to evaporate water is one of the greens and promising approaches in addressing the issues of global freshwater shortage and water pollution. Conventional solar steam generation systems usually involve bulk-water heating with low efficiency due to the considerable thermal energy loss. Recently, interfacial solar evaporation systems using floating evaporators to absorb heat at the air-water interface have received wide interest. A low-cost, efficient, and durable solar absorber is vital for the development of solar steam generation. This study focuses on photothermal materials for applications in solar-thermal conversion for freshwater generation. TiO2 and carbon materials have gained extensive research attention for solar steam generation owing to their non-toxic nature and environmental friendliness. In this work, TiO2-carbon nanocomposites were synthesized by hydrothermal method and employed as a solar absorber for enhancing water evaporation. Raman spectroscopy and FTIR use for structural and vibrational studies of TiO2-carbon nanocomposites.Item Synthesis and Characterization of Transition Metal Oxide Resistive Random-Access Memory(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Muhammad Shahbaz; CIIT/FA19-RPH-052/LHR; Dr. Muhammad Idrees; LHR TP 7263With the huge advancement in memory storage devices, non-volatile memory is encouraging data storage and processing devices. Nonvolatile memory has a wide advantage over silicon-based flash memory such as SRAM, DRAM, etc. This special type of memory requires no external power supply to maintain store data than another silicon-based flash volatile memory. In recent years various nonvolatile memories (NVMs) have been studied such as FeRAMs, MRAMs, STTRAMs, RRAMs. But resistive random-access memory (RRAM) has a greater advantage over other non- volatile memory due to scalability and other performance parameters. In this thesis a Fe doped nickel oxide-based RRAM is designed and investigated, this cell develops either valence change mechanism (VCM) based conduction filament or electrochemical metallization-based filament. The vibrational mode of the NiO/FTO film has been carried out using Raman Spectroscopy. The Energy band calculates by using the Tauc Relation from the absorbance result of the Ultraviolet-Visible Spectroscopy. The optical characteristics of the deposited films were investigated by photoluminescence spectroscopy.Item Synthesis of iron doped nickel oxide (NiO) by Co- precipitation method(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2020) Ayesha Liaqat , Asma Aziz; FA16-BPH-017 , FA16-BPH-047; Dr. Muhammad Idrees; LHR TP 5927The rapid development of nanotechnology and electronics during this period Ni was an interesting element because it is an oxidized form with semiconductor properties allows several applications, such as gas sensors, painted sensitized photocathodes and electrodes in alkaline batteries. In addition, NiO has recently been used as a resistor Switching (RS) is used as an electrochromic (EC) smart window that saves memory and energy. The study of the transition properties of NiO or Fe-doped NiO in resistive random cassation (RRAM) devices is easily possible using optical or magnetic techniques, so physical properties such as optical or magnetic properties are also of interest in this thesis. In this thesis study, the physical properties of NiO and Fe-Doped NiO were determined experimentallyItem Synthesis of LaFeO3 by Carbon Containing and Carbon free Precursors and Characterization(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2020) Sufyan Ahmad; CIIT/FA17-RPH-038/LHR; Dr. Muhammad Idrees; LHR TP 6067In this work, Auto-combustion method and co-precipitation method is used to prepare LaFeO3. The Nano powder was successfully synthesized using chelating agent, precipitating agent and nitrates of iron and lanthanum. To explore the thermal growth of the crystalline phases, the as burnt sample and dry precipitates were kept in a furnace at 450oC, 600oC, 800oC and at 1000oC (in co-precipitation method) for four hours at each temperature. X-ray diffraction technique revealed that at temperature 450oC only the Fe (OH)3 and La (OH)3 were present there in powder dominantly in amorphous form. Increasing the treatment temperature caused the decomposition of these hydroxides into Fe2O3 and La2O3 accompanied by the formation of LaFeO3. The formation of LaFeO3 incomplete up to 800oC in Co-precipitation method and found crystalline LaFeO3 in combustion method at same temperature. LaFeO3 was obtained at 1000°C indicating that heating at 1000oC changes it into complete transformation of the oxides and hydroxides (of Fe and La) to LaFeO3 in co-precipitation method. For the sake of exploring the effect of variations in microstructure of samples prepared by precipitation method, the powder treated at 1000°C was pressed into several pellets of circular shape having the diameter of 10 mm and 1 mm thickness. The sintering temperature of the pellets was 1000oC selectively for 4, 8, 12 and 16 hours and were named as LF4, LF8, LF12 and LF16, respectively. Scanning electron microscopy (SEM) revealed that the particles possess spherical symmetry. The average grain size of LaFeO3 was found 200 nm and the grain size continue to grow by increasing the treatment time. The stability of carbonate residual precursors in combustion method has been explored by TGA. FTIR analysis of both method’s samples was done after treatment of heat at various temperatures. During heat treatment the continuous decomposition of these residuals occurred. The room temperature dielectric properties of LaFeO3 were analyzed and examined thoroughly at frequencies from 1 Hz to 10 MHz of both method’s samples and explored the effect of residual carbonate precursors on dielectric properties of combusted samples. The dielectric properties of combusted samples strongly affected by these amorphous carbonate residues. It was found that the value of dielectric constant improved wi th the rise in the t ime of heat t reatment . This increase in cryst al l ini ty shows higher value of di el ect ri c const ant .