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X-WR-CALDESC:Events for CeNSE
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TZID:Asia/Kolkata
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DTSTART:20250101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260409T090000
DTEND;TZID=Asia/Kolkata:20260417T170000
DTSTAMP:20260514T081350
CREATED:20260312T071521Z
LAST-MODIFIED:20260312T071521Z
UID:10082-1775725200-1776445200@www.cense.iisc.ac.in
SUMMARY:Foundational workshop on Semiconductor Manufacturing
DESCRIPTION:
URL:https://www.cense.iisc.ac.in/foundational-workshop-on-semiconductor-manufacturing/#new_tab
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260409T160000
DTEND;TZID=Asia/Kolkata:20260409T170000
DTSTAMP:20260514T081350
CREATED:20260324T111423Z
LAST-MODIFIED:20260324T111423Z
UID:10162-1775750400-1775754000@www.cense.iisc.ac.in
SUMMARY:[Thesis Colloquium] : Design\, Fabrication\, Characterization & Packaging of Large Area RF GaN HEMTs
DESCRIPTION:Thesis Title: "Design\, Fabrication\, Characterization & Packaging of Large Area RF GaN HEMTs"\n\nName of the Student: Mr. SHONKHO SHUVRO\n\nDegree Registered: Ph.D. Engineering \n\nAdvisors: Prof. Digbijoy Nath & Prof. Prosenjit Sen\, CeNSE\n\nDate: 9th April 2026\, (Thursday)\, 4 PM\n\nVenue : CeNSE Seminar Hall (Hybrid)\n\nAbstract:\n\nWide-bandgap Gallium Nitride (GaN)-based High Electron Mobility Transistors (HEMTs)\n are strong candidates for RF power amplifiers due to their high electron saturation \nvelocity\, wide bandgap\, and large critical electric field\, enabling high power handling\, \nand high-frequency operation. This work begins with the fabrication and characterization\nof baseline 2×50 µm RF GaN HEMTs on SiC substrates\, where performance is established through \nDC\, RF\, and load-pull measurements.\n\nBuilding on this baseline\, large-area scaling is enabled through a simple and robust \nair-bridge fabrication methodology for reliable source interconnects across wide device \nperipheries while reducing process complexity. To address current collapse caused by trapping \neffects\, a passivation-first approach along with post gate metallization anneal is implemented\, \nreducing drain lag from 21% to 10.4% for GaN-on-SiC with negligible knee walkout\, while on a \nnovel compensation free GaN-on-Si shows 15% collapse at knee. With reduced current collapse and \noptimized air-bridges\, output powers of 12 W (for GaN/SiC) and 8 W (for GaN/Si) are achieved at X-band (10 GHz).\n\nLinearity is then investigated using two-tone intermodulation measurements at 6 GHz on 2×125 \nµm devices. An OIP3/PDC of 15.06 dB is achieved for GaN-on-Si—the highest reported for C and \nX bands—while GaN-on-SiC shows ~10.2 dB\, comparable to literature.\n\nSubsequently\, a novel IR laser-assisted etching technique is introduced for substrates with \nlow etch rates\, or which are difficult to etch such as SiC\, Sapphire\, Diamond\, Ga₂O₃\, and Quartz.\n As a proof-of-concept\, embedded microfluidic channels has been etched in Ga₂O₃ which demonstrated \n48% temperature reduction with liquid cooling\, highlighting its potential for thermal management in Ga₂O₃ based devices.\n\nFinally\, to address self-heating in large-area devices\, microfluidic cooling is implemented \nusing channels on a bonded copper flange with DI water with a flow rate of 200 mL/min at room \ntemperature\, resulting in 46% RF power improvement (from 5.6 W to 8.1 W at 6 GHz) for GaN-on-Si.\n This approach is further extended to commercial GaN devices in a commercial RF package. \nBy etching the backside of the package\, the coolant is brought closer to the die hotspots\, \nenabling direct thermal management beneath the active region. Importantly\, this is achieved \nwithout altering the standard packaging process flow or having grounding issues\, making it a \npractical solution for integrating liquid cooling in packaged RF GaN devices.\n\nIn summary\, this work demonstrates a simple and robust air-bridge fabrication enabling \nlarge-area scaling\, along with reduced current collapse\, improved linearity\, and near-junction \ncooling\, collectively enabling high-performance RF GaN HEMTs.
URL:https://www.cense.iisc.ac.in/event/thesis-colloquium-design-fabrication-characterization-packaging-of-large-area-rf-gan-hemts/
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260410T160000
DTEND;TZID=Asia/Kolkata:20260410T170000
DTSTAMP:20260514T081350
CREATED:20260402T091927Z
LAST-MODIFIED:20260402T091927Z
UID:10180-1775836800-1775840400@www.cense.iisc.ac.in
SUMMARY:[Thesis Colloquium] : Redefining Design Principles in Low-Dimensional Perovskite Solar Cells: Perovskite Bulk\, Interfaces\, and Charge Extraction Dynamics
DESCRIPTION:Thesis Title: "Redefining Design Principles in Low-Dimensional Perovskite Solar Cells: \nPerovskite Bulk\, Interfaces\, and Charge Extraction Dynamics"\n\nName of the Student: Ms. Bhumika Sharma\n\nDegree Registered: Ph.D. Engineering \n\nAdvisor: Prof. Sushobhan Avasthi\, CeNSE\n\nDate: 10th April 2026\, (Friday)\, 4 PM\n\nVenue: CeNSE Seminar Hall (Hybrid)\n\nAbstract:\n\nLow-dimensional perovskites exhibit enhanced stability against oxygen and moisture in comparison\n to their three-dimensional counterparts\, but it comes at the expense of efficiency. Several \nattempts such as additive engineering\, compositional engineering\, and the addition of interlayers \nto improve the efficiency have been made but understanding the fundamental differences and their \nimpact on devices remain incomplete. This thesis aims to re-define the design principles of \nlow-dimensional perovskite solar cells by investigating techniques which can be directly translated \nfrom three dimensional solar cells and identifying and amending the ones which need re-optimization. \nThe properties of perovskite bulk\, the hole transport layers (HTLs)\, and the interface between them \nis studied while paying attention to the optoelectronic processes that govern device performance.\n\nWe begin by examining the role of interfacial engineering by using ionic liquid to passivate perovskite\,\n without changing its bulk. This interlayer enhances carrier lifetime by suppressing non radiative \nrecombination\, which results in improved performance for low-dimensional solar cells. Another work \nwhich discusses the effect of interlayer uses self-assembled monolayer (SAM) as an HTL\, which are known \nto suffer from wettability issues. A seed layer of phenethylammonium iodide increases the wettability \nof SAM and its impact on the growth of low-dimensional perovskites is studied. The study reveals that \nchanges in nucleation and growth of perovskites influences morphology\, strain\, and bulk quality of perovskite. \nThe addition of interlayers either results in passivation or improves the perovskite bulk\, both of which \ncan be translated from three- to low-dimensional systems.\n\nBuilding on this\, the role of HTL is evaluated by using NiO𝑥 deposited via pulsed DC magnetron sputtering. \nThe NiO𝑥 optimized for three-dimensional perovskite results in inferior performance to the one specifically \noptimized for low-dimensional perovskite. The need for re optimization of transport layers is hence highlighted \nto elucidate the complete potential of low dimensional perovskites. The thesis further discusses the importance\n of intermediate size distribution in perovskite precursors in governing the growth dynamics of thin films. The \nintermediate size distribution is altered by redissolving perovskite powder prepared by inverse temperature \ncrystallization to form a precursor. The powder-processed precursor shows less viscosity and smaller intermediates \nleading to higher growth rates. This enhances carrier lifetime and perovskite bulk quality\, leading to devices \nhaving better efficiency and stability.\n\nIn conclusion\, this thesis establishes that moving beyond empirical optimizations and focusing on the fundamental\n mechanisms is essential to improve the quality and reproducibility of low dimensional solar cells. With careful \nconsideration of optoelectronic properties of perovskite\, the electrically coupled transport layers\, and interfaces\, \nthe design strategies can be modified to enhance the performance of low-dimensional cells to their true potential.
URL:https://www.cense.iisc.ac.in/event/thesis-colloquium-redefining-design-principles-in-low-dimensional-perovskite-solar-cells-perovskite-bulk-interfaces-and-charge-extraction-dynamics/
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DTSTART;TZID=Asia/Kolkata:20260417T160000
DTEND;TZID=Asia/Kolkata:20260417T170000
DTSTAMP:20260514T081350
CREATED:20260324T055031Z
LAST-MODIFIED:20260324T055259Z
UID:10151-1776441600-1776445200@www.cense.iisc.ac.in
SUMMARY:[Thesis Colloquium] : Static and Dynamic Defects in Ferroic Materials: Pathways to Functional Responses
DESCRIPTION:Thesis Title: "Static and Dynamic Defects in Ferroic Materials: Pathways to Functional Responses"\n\nName of the Student: Mr. Shubham Kumar Parate\n\nDegree Registered: Ph.D. Engineering \n\nAdvisor: Prof. Pavan Nukala\, CeNSE\n\nDate: 17th April 2026\, (Friday)\, 4 PM\n\nVenue: CeNSE Seminar Hall\n\nAbstract:\n\nCrystalline materials are often described as periodic atomic arrangements\, yet real solids invariably \ncontain defects spanning multiple length scales\, from point vacancies to extended structural \nheterogeneities. Rather than acting only as imperfections\, such defects can reshape the energy \nlandscape of functional materials\, enabling enhanced responses and stabilizing new structural states. \nIn ferroic materials\, where coupled order parameters such as polarization and strain govern functional \nbehavior\, defects can strongly influence switching dynamics\, electromechanical response\, and phase \nstability. This thesis investigates how defects serve as a unifying thread linking property enhancement\, \nmesoscale transformations\, and long-range phase evolution in ferroic oxides and layered chalcogenides\, \nwith particular emphasis on the contrast between static defectlandscapes and dynamically evolving \ndefect networks.\n\nThe first part of this work focuses on defect-engineered BaTiO3\, where predominantly static vacancy \nconfigurations modify lattice anharmonicity and electromechanical coupling. It is shown that \nnon-stoichiometric BaTiO₃ can exhibit a giant electromechanical response even in the absence of \nclassical ferroelectric switching. By tuning defect concentration and distribution\, electric fields \ngenerate unusually large reversible strain\, establishing defect-mediated electrostriction as a pathway \nto strong functionality in nominally non-ferroelectric systems. Complementary in-situ bias transmission \nelectron microscopy studies further attempt to directly visualize polarization switching in BaTiO₃\, \nrevealing how static defect structures guide domain nucleation and propagation.\n\nThe thesis then shifts to layered In2Se3 nanowires\, where defects are not static but dynamically \nreorganize under external stimuli and are explored through combined ex-situ and in-situ transmission \nelectron microscopy.Electrical bias induces coupled interactions among polarization\, interlayer sliding\, \nand strain localization\, while evolving defect intersections act as nucleation sites for structural \ninstability. This results in cascading amorphization events that propagate over long distances\, \ndemonstrating how dynamic defect networks convert local perturbations into collective structural collapse.\n\nThe subsequent chapters further investigate electrically (reversible)\, optically and thermally \ninduced transformations in polymorphs of In₂Se₃. These studies show that defect redistribution \nand mesoscale strain fields govern transformation pathways and reversibility\, with electric bias \nand heat acting as controllable parameters for tuning phase stability.\n\nTogether\, these studies establish a unified framework in which both static and dynamic defects \nfunction as active structural elements that mediate electromechanical coupling\, nucleate phase \ntransitions\, and control switching pathways.This work provides design principles for energy-efficient \nfunctional materials based on metastability and defect-engineered energy landscapes.
URL:https://www.cense.iisc.ac.in/event/thesis-colloquium-static-and-dynamic-defects-in-ferroic-materials-pathways-to-functional-responses/
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260421T100000
DTEND;TZID=Asia/Kolkata:20260421T110000
DTSTAMP:20260514T081350
CREATED:20260416T111234Z
LAST-MODIFIED:20260416T111234Z
UID:10272-1776765600-1776769200@www.cense.iisc.ac.in
SUMMARY:[Thesis Colloquium] : Probing quantum transport of weak topological insulators\, engineered heterostructures of strange metals with strong topological insulators and 3D Dirac semimetals
DESCRIPTION:Thesis Title: "Probing quantum transport of weak topological insulators\, engineered heterostructures of \nstrange metals with strong topological insulators and 3D Dirac semimetals."\n\nName of the Student: Mr. Nirmal K Sebastian\n\nDegree Registered: Ph.D. Engineering \n\nAdvisor: Prof. Anil Kumar P.S (Physics)  and  Dr. Shivakumara. C (SSCU)\n\nDate: 21st April 2026\, (Tuesday)\, 10:00 AM\n\nVenue:  CeNSE Seminar Hall \n\nAbstract:\n\nTopological materials are known for hosting unusual electronic states that come mainly from strong \nspin-orbit coupling(SOC) and band topology. In this work\, we study three different yet\, closely related \ntopological phases to understand how weak antilocalization (WAL)\, weak localization (WL)\, and quantum interference \nappear in them\, along with the nature of quantum oscillations in surface states with high mobility.\n\n\nIn the first part of this thesis\, we find that thin films of Bi₂Te₃ grown in the R3m phase behave like a weak \ntopological insulator. When the magnetic field is applied perpendicular to the side surface\, we clearly observe \nShubnikov-de Haas quantum oscillations in electrical resistivity at very high magnetic fields. Interestingly\, \nthe quantum oscillations only appear for this geometry\, indicating that the side surface states play the dominant \nrole here and has much larger charge carrier mobility compared to the bulk and the other surfaces. The extracted \noscillatory part after a background subtraction is fitted well with Lifshitz Kosevic equations that validates the \nvery large mobility and associated physical properties of the side surface. This highlights how the side surfaces of \nweak TIs are quite crucial if we want to use them in devices later. Accessing the side surfaces of weak topological \ninsulators is very essential in harnessing their true potential. We also observe WAL feature that fits nicely to the \n2D Hikami-Larkin-Nagaoka (HLN) expression. This further confirms the existence of strong SOC for the side surfaces. \nThis work experimentally realizes the emergence of a weak TI phase in R3m phase of Bi₂Te₃.\n\nIn the next part of this thesis\, we look at thin films of YBa₂Cu₃O₇−δ/Bi₂Se₃ heterostructures\, where YBa₂Cu₃O₇−δ is \nin the strange metal phase. Here\, we see a crossover from WAL to WL with increasing magnetic field and temperature. \nBy fitting the magnetoconductance to a two-component HLN model\, we find competing length scales such as dephasing length\,\nspin-orbit scattering length\, and mean free path. At low temperatures\, the conductance changes logarithmically with \ntemperature\, which suggests that electron-electron interaction effects are also important. This shows that when a correlated \nphase like strange-metal YBCO is placed in close proximity to a topological insulator\, the quantum interference properties \nof the TI surface states can be tuned quite strongly\, and strong correlations can be induced upon proximity of a TI surface \nto a strongly and non-locally entangled electronic species like a strange metal.\n\nFinally\, we study the electrical transport properties of Bi₄Se₃\, which is expected to be a 3D Dirac semimetal. Previous reports \nhave shown it to be a 3-D Dirac semimetal via DFT calculations\, but the electrical transport is still lacking. Here\, we report \nelectrical transport studies of Bi₄Se₃ for the first time. The variation of resistivity with temperature shows a semimetallic nature.\nFurthermore\, upon applying various strengths of magnetic fields\, the Dirac cone doesn’t gap out in bulk\, which is indicative of true \n3-D nature of the Dirac fermions. We also observe a clear WAL signal that is best fit using a 3D version of the HLN model\, \nsupporting that bulk Dirac fermions with strong spin-orbit coupling and a Berry phase of π are present. \nThe structure consists of alternating Bi₂Se₃ layers and Bi bilayers\, and it belongs in the R-3m space group\, \nsimilar to some layered telluride systems. Also\, the variation of the characteristic length scales follow a power \nlaw decaying behaviour\, where the exponent describes dephasing via 3-D electron-electron interactions. All these results \nconfirm that Bi₄Se₃ is a 3-D Dirac semimetal.\n\nTogether\, these results give a more complete picture of how strong SdH oscillations can arise from side surfaces \nof weak TIs\, the elusive nature of competition between WAL and WL for the surface states of strong TIs in proximity \nto a strange metal\, and nature of quantum diffusion and 3-D WAL in 3D Dirac semimetals. Understanding how these \ntopological effects evolve is useful for designing hybrid systems for topological quantum computing and low-dissipation \nelectronic/spintronic applications.
URL:https://www.cense.iisc.ac.in/event/thesis-colloquium-probing-quantum-transport-of-weak-topological-insulators-engineered-heterostructures-of-strange-metals-with-strong-topological-insulators-and-3d-dirac-semimetals/
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260424T160000
DTEND;TZID=Asia/Kolkata:20260424T170000
DTSTAMP:20260514T081350
CREATED:20260410T052615Z
LAST-MODIFIED:20260410T052820Z
UID:10250-1777046400-1777050000@www.cense.iisc.ac.in
SUMMARY:[Seminar] : Reconfigurable Microwave Devices using Insulator-Metal Phase Transition in Vanadium Dioxide
DESCRIPTION:Speaker: Dr Amit Verma\, Associate Professor\, Department of Electrical Engineering\, IIT Kanpur.\n\nTitle: "Reconfigurable Microwave Devices using Insulator-Metal Phase Transition in Vanadium Dioxide"\n\nDate: Friday\, 24th April 2026 - Time: 4 PM\n\nHi Tea & Coffee: 5 PM\n\nVenue: CeNSE Seminar Hall\n\nAbstract:\n\nVanadium dioxide (VO2) is a phase-transition material which exhibits a reversible structural and \nan associated insulator-metal phase transition at 68 ºC. This phase transition is accompanied by \na large change in VO2 resistivity and dielectric-response properties\, enabling a host of \nelectromagnetic switching applications from microwave to THz\, Infra-red\, and visible wavelengths. \nIn this talk\, several reconfigurable microwave devices realised using VO2 will be presented along \nwith detailed modelling of the experimentally observed characteristics.\n\nBiography:\n\nAmit Verma is currently an Associate Professor in the Department of Electrical Engineering and \nProf. T. R. Vishwanathan Young Faculty Fellow at IIT-Kanpur.  He also holds an Adjunct Faculty \nposition in the Material Science Program at IIT Kanpur. His research interests include thin film \ngrowth\, fabrication\,and characterisation of devices based on wide-bandgap semiconductors and \nphase-change materials.\n\n\nHost Faculty:  Prof. Sreetosh Goswami
URL:https://www.cense.iisc.ac.in/event/seminar-reconfigurable-microwave-devices-using-insulator-metal-phase-transition-in-vanadium-dioxide/
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