Department of Physics
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Item Fabrication of Electronic Devices Based on Near Percolation Nanotube Networks(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Muhammad Tayyab Idrees; CIIT/SP20-RPH-045/LHR; Dr. Abdul Sattar; LHR TP 7694Electronic gadgets that are efficient, compact, light, and cost-effective are in high demand. The fundamental objective of the researchers is to improve the performance of FETs, which are the building blocks of microelectronics. However, the trade-off between mobility and ION/IOFF remains a problem in today's FETs, lowering their performance. The Problems such as the instability of gate dielectric to withstand high threshold voltage in currently used CNTFETs are still unresolved. Also, single CNT based transistors are hard to realize for commercial used due to complexity of the fabrication method. To overcome these problems, firstly, self-assembled Monolayers (SAMs) can be used as a gate dielectric. Secondly to achieve single path CNT active region, lowest possible area coverage of carbon nanotubes much closer to percolation nanotube networks can be used. To overcome this, SWCNTs were used as an active region, and Self Assembled Monolayer (SAM) was used as a gate dielectric. Three different SAMs of different dielectric constants (Octanedithiol (ODT), Dodecanethiol (DDT), Cyclohexanethiol (CHT)) were employed as a gate dielectric in SWCNT-FET. Two different concentrations of SWCNTs were used. SAMs were grown by immersion method while SWCNTs were deposited by the drop-casting method. After the preparation of SWCNT-FET, various analyses were performed using different characterization tools. Electrical measurements were done by Keithley source meter. It was observed that CNTFETs with low concentrations had ten times better properties as compared to high concentration ones. Among SAMs, DDT with low concentration showed an optimum balance between ION/IOFF ratio and mobility. The effective deposition of SWCNTs and SAMs in fabricated devices was confirmed by Raman and FTIR spectroscopy. When CNTFETs were analyzed with SAMs as the only gate dielectric, they performed exceptionally well. Using pure semiconducting CNTs as a channel and passivating the channel surface with SAMs to prevent oxidation and contamination from the environment can boost the device's performance even further.Item DFT Studies of Electrical and Optical Properties of Graphene Quantum Dot Based Devices(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Shabnum Rani; CIIT/SP20-RPH-013/LHR; Dr. Abdul Sattar; LHR TP 7710Graphene quantum dots (GQD) are tiny particles, which have novel properties. These properties play a vital role in innovative devices like sensors, energy storage and solar cell. Transition metal dichalcognised combining with graphene quantum dots have unique photoluminescence properties. Photovoltaic, photodectors and spintronic are examples of TMDCs with graphene quantum dot based devices. Density Functional Theory (DFT) is an essential tool to understand and explore the electronic and optical properties of TMDC/GQD. To study many-body electronic system Atomistic tool kit (ATK) package will be used along with local density approximation (LDA) and Generalized Gradient Approximation (GGA) as exchange and correlation function. Simulated data would be used to determine the I-V characteristic, density of states and structural arrangement. We will calculate the density of state, band structure, transmission spectra, optical spectrum, Eigen state and projected density of state, to understand the best results of TMDCs i.e. (MoS2, MoSe2, WS2, WSe2) with Graphene quantum dot. This project will try to pin-point the ideal configuration of a modified GDQs for its application in photodectors and spintronic.Item Synthesis and Characterization of Graphene Quantum Dots for Electronic and Photonics Devices(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Ammara Javed; CIIT/SP20-RPH-063/LHR; Dr. Abdul Sattar; LHR TP 7720People interpret the term "micro world" in a variety of ways. The surface-to-volume relationship is defined as the intermediary between atoms and solids. When chemists first introduced nanotechnology, no one knew what it was. They used physicists to alter the structures. Richard Feynman, a physicist, was awarded a Nobel prize for his contributions to nanotechnology in 1959. After winning the Nobel Prize for his amazing invention, the Noble Prize laureate declared during an American Physical Society meeting that "there is plenty of room at the bottom." Biology has traditionally been molecular, with important multidisciplinary study areas such as DNA, protein, and cellular machinery. The nanoworld idea is founded on the convergence of a genuine scientific or technological combination. Despite the fact that the wave-corpuscle duality-based principles of quantum physics are not clearly apparent. With the exception of semiconductors and lasers. Quantum effects will be applied in a variety of applications in the future. "Nano-Technology is a science, engineering, and technology that takes place on the nanoscale, which ranges from 1 to 10 nanometers." A billionth of a meter, or 10-9 of a meter, is one nanometer, which is difficult to comprehend. The capacity to observe and manipulate individual atoms and molecules is required. Atoms make up everything on the planet. However, seeing a nanometer-sized object with the naked eye is impossible. As a result, microscopes such as the Scanning Tunneling Microscope (STM).