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< Back Harikrishnan Gopalakrishnan Post-Doc Researcher Curriculum Vitae Publications since 2025 Postdoctoral Researcher in Nano-spectroscopy group, Department of Physics, Sapienza University of Rome, Italy. Supervisor: Prof. Marta De Luca. 2023-2024 Postdoctoral Researcher in the Scanning Probe Microscopy and Plasmonics Group, School of Physics, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India. Project: Harnessing direct and indirect excitons in TMDCs for photo-stimulated device applications (STARS-MoE, Govt of India) PI: Prof. Joy Mitra. Project: Functionalizing the next-generation 2D semiconductors for optoelectronic and catalytic applications via ion irradiation (SPARC-UKIERI) PI’s: Prof. Ravi Silva, Director, ATI. Prof. Satheesh Krishnamurthy, Director, Ion Beam Center, University of Surrey, UK & Prof. Joy Mitra, IISER TVM 2017-2023 Ph.D. in Physics (INSPIRE Fellowship, Department of Science and Technology, Govt of India) School of Physics, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India. Supervisor: Prof. Joy Mitra. Thesis Title : Optoelectronic and Transport Properties of Nanostructured Hybrids of ZnO PEDOT:PSS and Ni-TiO2. Indo-Poland Joint Project (2020-2023) A novel heterostructure architecture for photodetection and photo-enhanced electron emission applications (Indo-Poland Project); Prof. Dorota A. Pawlak, Institute of Electronic Materials Technology, Department of Functional Materials, University of Warsaw, Poland. Exchange Visit Student (2018) Nanoscale writing of bespoke Graphene devices for electronic and plasmonic scalable technologies (UGC-UKIERI); Prof. Ravi P Silva, Advanced Technology Institute (ATI), University of Surrey, UK. 2016-2017 Project Assistant School of Physics, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India. Supervisor: Prof. Joy Mitra Project: Nanoscale Schottky Junction for sub-ppm hydrogen detection (DST-SERB Grant) 2011-2016 BS MS Integrated Dual Degree; Physics (Major) and Chemistry (Minor) Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India. Back to Top Sapienza University of Rome, Physics Department harikrishnan.gopalakrishnan@uniroma1.it Office: n° 349, third floor, Marconi building, Physics Department

< Back Muhammad Tahir PhD Student Curriculum Vitae Publications Since 2023 PhD Student, Nanospectroscopy Group, Department of PhysicsSapienza University of Rome, Italy. Currently focusing on tuning the optoelectronic and thermoelectric properties of indium nitride (InN) nanowires. 2018-2020 Master of Science (MSc) in PhysicsCOMSATS University Islamabad, Pakistan 2013-2017 Bachelor of Science (BSc) in PhysicsBahauddin Zakariya University, Multan, Pakistan Back to Top Sapienza University of Rome, Physics Department muhammad.tahir@uniroma1.it Office: n° 349, third floor, Marconi building, Physics Department

Projects Single photon emitters in GaAsN nanowire tubes Bandgap engineering and strain engineering by hydrogenation in dilute nitrides nanowires Defect engineering and bandgap control in InN nanowires Tunable quantum dots in GaAsP and InAsP nanowires Micro-ring resonator lasers by self-assembly in InP Size-controlled and site-controlled quantum rings in quantum wells Unveiling new crystalline defects in InP nanowires Spectroscopic investigations on Hybrid 2D Perovskites

Collaborations - Prof. F. Ishikawa, Hokkaido University (Japan) - Prof. S. Zhao and Prof. Z. Mi, Mc Gill University (Canada) - Prof. H. Tan and Prof. C. Jagadish, Australian National University (Australia) - Prof. A. Fontcuberta i Morral, EPFL (Switzerland) - Prof. L. Sorba, Dr. V. Zannier, CNR nano and Scuola Normale Superiore (Italy) - Dr. S. Rubini, CNR Tasc (Italy) - Prof. A. Sanchez, Warwick University (UK) - Dr. R. Rurali, ICMAB (Spain) - Prof. I. Zardo, University of Basel (Switzerland) - Prof. A. Polimeni and Prof. M. Felici, Sapienza University (Italy) Fundings GROUNDS : Growth and optical studies of tunable quantum dots and superlattices in semiconductor nanowires HELIOS : Bright telecom-band single photon sources in bottom-up nanowire waveguides Development of single photon quantum states based on quantum dots operating at different wavelengths NANOWHYR : Dots-in-NANOWires by near-field illumination: novel single-photon sources for HYbRid quantum photonic circuits

Our Goals Nanostructures, such as 2D materials or nanowires, have revolutionized the field of semiconductors, making it possible, among others, to transform indirect bandgap materials to direct bandgap materials, or making it possible for a crystal to grow in a crystal structure that does not exist in bulk. We work in close collaboration with several growth laboratories providing nanostructures, and we functionalize them by several methods, such as hydrogen or helium irradiation, laser heating, thermal annealing, nanoscale patterning etc. to achieve the desired properties. Working at the boundaries between fundamental physics and technological applications, our goal is to achieve new functionalities or explore new physical effects. Advances in Optics and Photonics 13 (2021): 242. However, in the Nano-spectroscopy group we are not happy to work just with nanostructures: we create nanostructures inside the nanostructures. In our vision the nanostructures are scaffolds embedding smaller quantum structures (quantum dots, point defects that emit single photons, quantum rings, quantum wells, etc.) with diverse dimensionalities (0D, 1D, and 2D). For example, in nanowire lasers, by embedding quantum confined structures as active gain media it is possible to enhance the gain and lower lasing threshold. Moreover, by embedding quantum dots in nanowires for quantum photonic applications based on single photon emitters, it can be possible to obtain a higher photon extraction than in standard self-assembled dots embedded in a 3D matrix, owing to the possibility to design the nanowire to act as a waveguide with a photon out-coupler. This makes quantum dots in nanowires the ideal building block of quantum photonic circuits. Furthermore, by embedding quantum rings in quantum wells, one can unveil the topological phase of charge carriers, by controlling the appearance of magnetic states expected due to the circular symmetry of the carrier wavefunction (Aharonov-Bohm effect). Explore our Projects Physics Today 1 September 2009; 62 (9): 38–43

Teaching You can find more information on the courses taught by Prof. Marta De Luca here . Physics for Biology Info here: e-learning Laboratory of Mechanics for Physicists Info here: e-learning

Publication List Articles Published or under revision in Peer-Reviewed Journals < Back Poster : “Nitrogen-induced strain in highly mismatched III-V heterostructured nanowires: a Raman spectroscopy investigation” Conference: Nanowire Week 2025 Date, where: 25 – 29/08/2025, St John’s College, University of Cambridge, Cambridge, UK Authors: Riccardo Pallucchi (presenter), Akant Sagar Sharma, Nadine Denis, Paolo De Vincenzi, Francesca Santangeli, Ilaria Zardo, Fumitaro Ishikawa, Riccardo Rurali and Marta De Luca. Poster : “Localized annealing: a step toward post-growth, site-controlled quantum dots in III-V semiconductor nanowires” Conference: PLASMONICA – International School of Plasmonics and Nano-optics at Lake Como School of Advanced Studies Date, where: 03-07/06/2024, Como Authors: Riccardo Pallucchi (presenter), Akant Sagar Sharma, Paolo De Vincenzi, Nadine Denis, Francesca Santangeli, Antonio Polimeni, Fumitaro Ishikawa, Riccardo Rurali, Marta De Luca Subject: toward post-growth, site-controlled QDs in semiconductor nanowires through laser and SNOM localized annealing on III/V nanowires (NWs). Preliminary Raman and PL spectroscopies results on bandgap tuning by hydrogenation and annealing, and investigation of the vibrational properties of mismatched, strained heterostructures. Oral contribution: “Real-time light transmission spectroscopy: quantitative time-resolved investigation of colloidal aggregation dynamics” Conference: ECIS2023 – 37th Conference of the European Colloid & Interface Society (https://www.ecis2023.eu/) Date, where: 03-08/09/2023, Napoli Authors: Angela Capocefalo, Riccardo Pallucchi, Greta Peruzzi, Federico Bordi, Paolo Postorino, Barbara Ruzicka, Claudia Fasolato (presenter) Subject: Time-resolved optical transmission spectroscopy for the study of colloidal systems subjected to external stimuli. Results of the investigation on the aggregation stimulated by acidity variations in plasmonic and polymeric colloidal systems functionalized with different ligands. Poster: “Surface Enhanced Raman Scattering studies on biocompatible pH responsive nanosystems” Conference: ECIS2023 – 37th Conference of the European Colloid & Interface Society (https://www.ecis2023.eu/) Date, where: 03-08/09/2023, Napoli Authors: Greta Peruzzi, Sara Cerra, Angela Capocefalo, Riccardo Pallucchi, Francesco Cappelluti, Ilaria Fratoddi, Claudia Fasolato (presenter) Subject: Functionalization of silver nanoparticles with two different pH-responsive thiols, stable under physiological conditions; characterization of the surrounding molecular layer at different acidity levels by surface-amplified Raman spectroscopy. Poster: “Quantitative aggregation dynamics of responsive plasmonic colloids by real-time light transmission spectroscopy” Conference: Plasmonica – 9th edition of the Workshop on Plasmonics and Nano-optics (https://www.plasmonica.it/2023) Date, where: 05-07/07/2023, Milano Authors: Angela Capocefalo, Riccardo Pallucchi (presenter), Greta Peruzzi, Federico Bordi, Paolo Postorino, Barbara Ruzicka, Claudia Fasolato Subject: study of the aggregation and diffusion dynamics of plasmonic colloidal systems subjected to external stimuli through real-time measurements of optical transmission spectroscopy. Results of quantitative measurements of optical extinction on a colloidal system of gold plasmonic nanoparticles with different ligands to investigate their aggregation stimulated by variations in acidity. Oral contribution on invitation: “Real-time light transmission spectroscopy: quantitative investigation of colloids and aerosols for environmental applications” Conference: DEUPAS “Ultrasensitive monitoring of VOCs and pathogens by spectroscopy – Innovative solutions and sensor systems for air-quality monitoring” Date, where: 04-05/07/2023, Frascati Authors: Claudia Fasolato (presenter), Angela Capocefalo, Riccardo Pallucchi, Greta Peruzzi, Federico Bordi, Barbara Ruzicka, Paolo Postorino Subject: optical extinction measurements for real-time characterization of particulate matter produced by combustion in diesel engines. Presentation of an original setup for time-resolved extinction measurements and preliminary results performed on colloidal systems for the study of the aggregation dynamics induced by pH variations. Discussion of the potential and limitations of the setup in the context of air quality monitoring. Poster: “All-optical investigation of biocompatible plasmonic colloids: surface chemistry, colloidal stability and pH responsivity” Conference: VISPEC2023 – International Summer School on Vibrational Spectroscopy – School and Conference (https://vispec2023.weebly.com/) Date, where: 12-16/06/2023, Perugia Authors: Greta Peruzzi (presenter), Sara Cerra, Angela Capocefalo, Riccardo Pallucchi, Francesco Cappelluti, Ilaria Fratoddi, Barbara Ruzicka, Claudia Fasolato Subject: synthesis of silver nanoparticles with two hydrophilic thiols characterized by amino and sulfhydryl groups, and subsequent study of the surrounding molecular layer under varying pH conditions by means of surface-amplified Raman spectroscopy. Poster: “Real-time light transmission spectroscopy: quantitative investigation of colloidal aggregation dynamics” Conference: Interchall2023 – Interdisciplinary challenges: from non-equilibrium physics to life science (https://www.interchall2023.com ) Date, where: 17-21/04/2023, Roma Authors: Riccardo Pallucchi (presenter), Angela Capocefalo, Greta Peruzzi, Paolo Postorino, Barbara Ruzicka, Claudia Fasolato Subject: Development of a time-resolved optical transmission spectroscopy instrument designed to investigate the evolution of colloidal systems subjected to external stimuli through quantitative scattering measurements. Presentation of the results related to the aggregation of plasmonic gold nanoparticles with different functionalizations in response to pH variations.

Publication List Articles Published or under revision in Peer-Reviewed Journals < Back Poster: “Hydrogenation-Driven Bandgap Engineering in InN Nanowires for Quantum Technologies and Optoelectronic Devices” Conference: Nanowire Week 2025 Date, where: 25 – 29/08/2025, St John’s College, University of Cambridge, Cambridge, UK Authors: Muhammad Tahir, Francesca Santangeli, Pietro Todesco, Ernesto Placidi, Marco Sbroscia, Zetian Mi, Songrui Zhao, Antonio Polimeni, and Marta De Luca.

Organized Conferences Marta co-organizes the IEEE Nanotechnology Materials and Devices Conference in October 2023, Paestum, Italy . Symposium ‘Fundamentals and applications of nanotubes, nanowires, quantum dots and other low dimensional materials’ Marta co-organizes the CLEO/Europe Focus Meeting (ECOC, European Conference on Optical Communication) in September 2022, Basel, Switzerland. Symposium ‘Novel Photonic Materials & Effects’ Invited Talks Marta gives a talk for the International Symposium on Semiconductor Optoelectronics and Nanotechnology (ISSON) in the Department of Electronic Materials Engineering of the Australian National University on the 9.11.2024. Marta gives an invited talk for the Quantum Science & Technology Seminars in the Physics Department of Federico II University in Naples (Italy) on the 27.10.2023. Marta gives an invited talk at the IEEE Nanotechnology Materials and Devices Conference (NMDC) in Paestum (Italy) on the 24.10.2023. https://ieeenmdc.org/past-conferences/nmdc-2023/ Marta gives an invited talk at the Phonons Conference 2023 in Paris (France) on the 05.07.2023 https://phonons2023.sciencesconf.org/ Marta gives an invited talk at the International Conference on Solid State Devices and Materials (SSDM) in Chiba (Japan) on 27.09.2022 https://ssdm.jp/2022/ Marta gives an invited talk at the Rank Prize symposium on Nanowire Photonics in Grasmere in Lake District (UK) on 08.11.2022 https://www.rankprize.org/symposia/nanowire-photonics-2/

Publication List Articles Published or under revision in Peer-Reviewed Journals < Back 1. Surfactant Free Platinum Nanoclusters as Fluorescent Probe for the Selective Detection of Fe(III) Ions Anu George, Harikrishnan G., Sukhendu Mandal* (Sens.Actuators B 243 (2017)332- 337). 2. Negative photoresponse of ZnO-PEDOT:PSS nanocomposites and photogating effects Harikrishnan G.*, Sesha Vempati, K Bandopadhyay, K. Prajapati, Vijith Kalathingal and J. Mitra* (Nanoscale Advances,1 (2019)2435). 3. Epsilon-near-zero response in Indium Tin Oxide thin fims: Octave span tuning and IR plasmonics Ben Johns, Navas M P, Harikrishnan G., Akhileshwar Mishra, Ravi Pant, J. Mitra* (Journal of Applied Physics 127(4):043102(2020)). 4. Enhancement in electrical conductivity of a porous indium based metal-organic framework upon 12 uptake: combined experimental and theoretical investigations Mani Prabhu, Mandal Nilangshu, Roopesh Mekkat, Harikrishnan G., Datta Ayan, Mandal Sukhendu* (Journal of Materials Chemistry C 8(14):4836-4842(2020)). 5. Controlling the macroscopic electrical properties of reduced graphene oxide by nanoscale writing of electronic channels Arijit Kayal, Harikrishnan G.,K. Bandopaghyay, Amit Kumar, S. Ravi P. Silva, J.Mitra* (Nanotechnology, 2021.32(17):p.175202). 6. Mobility enhancement in CVD-grown monolayer MoS2 via patterned substrate induced non-uniform straining Arijit Kayal, Sraboni Dey, Harikrishnan G., Nadarajan Renjith, Chattopadhyay Shashwata, J.Mitra* (Nano Lett. 2023, 23, 14, 6629-6636). 7. Anomalous Photoresponse in a Reduced Metal- Semiconductor Hybrid of Nickel and Titanium Oxide Harikrishnan G., K. Bandopadhyay, K. Kolodziejak, Vinayak B Kamble, Dorota A. Pawlak, J.Mitra * (arXiv:2309.17427 [physics.app-ph]). 8. Negative resistance and anomalous transport properties of a porous anisotropic (Ni- TiO2) hybrid system Harikrishnan G., Shashwata Chattopadhyay, K. Bandopadhyay, K. Kolodziejak, Dorota A. Pawlak, J.Mitra * (arXiv:2310.02976 [cond-mat.mtrl-sci]). Poster : “Comprehensive Raman toolkit to probe crystal quality, geometry, and vibrational properties of InN nanowires” Conference: Nanowire Week 2025 Date, where: 25 – 29/08/2025, St John’s College, University of Cambridge, Cambridge, UK Authors: Harikrishnan Gopalakrishnan, Francesca Santangeli, Pietro Todesco, Muhammad Tahir, Ernesto Placidi, Francesco Mura, Zetian Mi, Songrui Zhao, and Marta De Luca.

PRIN Project Nanowires (NWs) are quasi-1D crystals with nanoscale diameters and several microns in length. This project aims at growing and thoroughly investigating quantum dots (QDs) and superlattices (SLs) in two different III-V NW heterostructures: GaAsP/GaP NWs, for photonic and optoelectronic applications in the visible-near infrared range, and InAsP/InP NWs, for telecom-wavelengths applications. The well-known vapor-liquid-solid growth approach will be employed to realize bottom-up NWs incorporating QDs of controllable size, position and chemical composition. In particular, we will use the chemical beam epitaxy technique, which combines the advantages of ultra-high-vacuum epitaxial growth with the ease of use and flexibility given by metalorganic precursor gas sources. The controlled NW morphology and diameter will be exploited for the optimization of the waveguiding properties of NWs for the nested QDs. Scanning electron microscopy (SEM) for morphology characterization and energy dispersive x-ray spectroscopy (EDX) for compositional analysis are performed in-house with a field emission gun (FEG) electron microscope operating up to 30 kV. Electron Beam Lithography (EBL) for substrate patterning is performed instead with a dedicated FEG SEM equipped with an interferometric stage. The CNR unit in Pisa has a remarkable expertise in the growth and structural characterization of III-V semiconductor nanowires, axial and radial nanowire heterostructures, and selective area nanostructures. The Chemical Beam Epitaxy (CBE) system and the cleanroom facility of the National Enterprise for nanoScience and nanoTechnology (NEST) Laboratory of Scuola Normale Superiore, where the Nanoscience institute of CNR is headquartered are fully available for the project.The CBE is equipped with a Riber Compact-21 growth chamber with an integrated Reflection of High Energy Electron Diffraction (RHEED) system for in-situ monitoring and an optical pyrometer for the substrate temperature measurement. Available group-V materials are arsenic (TBAs), phosphorous (TBP), and antimony (TDMASb and TMSb); for group III there are indium (TMIn), gallium (TEGa), and aluminium (TMAl) precursors. Transmission electron microscopy (TEM) to investigate the nanowires structural quality (crystal phase, interface sharpness, strain distribution) is also performed by the CNR unit, in collaboration with the Center for Instrument Sharing (CISUP) of the University of Pisa. R. Sorodoc, P. De Vincenzi, ACS Appl. Mater. Interfaces 16, 47 (2024) The growth and the structural characterization of the NWs performed at the CNR unit is cross-correlated to advanced optical spectroscopy experiments (inelastic light scattering and photoluminescence) carried out at Sapienza University. The optical measurements are performed also with a photon-correlation setup to probe the properties of the grown QDs. The close synergy of the two units allows a continuous flow of samples and information. In this way, a full picture of the structural, electronic, and optical properties of the QDs and SLs in NWs is achieved and controllably tuned. Single QDs in NWs with high brightness and low multi-photon emission probability are being realized within this project, as well SLs with a tunable period, in order to determine the new type of band alignment arising in the SL and show the potential of these SLs for NW-based optoelectronic applications such as photodetectors. Furthermore, NWs with GaAsP (with varying concentrations of As and P) in the wurtzite phase were created to study the new optical and electronic properties of the material in this new crystalline phase. The results of this study are then used as a starting point to better understand the effects of quantum confinement in the previously mentioned samples. Team members: Dr. Valentina Zannier, CNR researcher Prof. Marta De Luca, Sapienza University professor Prof. Lucia Sorba, CNR research director Robert Andrei Sorodoc, CNR fellow Paolo De Vincenzi, PhD student of Sapienza University Giada Bucci, PhD student of Scuola Normale Superiore Publications: Tunable GaAsxP1-x quantum dot emission in wurtzite GaP Nanowires . R. Andrei Sorodoc+, P. De Vincenzi+, A. Sagar Sharma, G. Bucci, M. Roggi, E. Mugnaioli, L. Sorba, M. De Luca and V. Zannier (+ equal contribution). ACS Appl. Mater. Interfaces 16, 47 (2024) Zincblende InAsxP1–x/InP Quantum Dot Nanowires for Telecom Wavelength Emission. G. Bucci*, V. Zannier, F. Rossi, A. Musiał, J. Boniecki, G. Sęk, L. Sorba. ACS Appl. Mater. Interfaces 16, 20 (2024) InAs–InP Superlattice Nanowires with Tunable Phonon Frequencies, V. Zannier, J. Trautvetter, A. K. Sivan, F. Rossi, D. de Matteis, B. Abad, R. Rurali, L. Sorba, I. Zardo. Advanced Physics Research 3, 6 (2024) Revealing Inclined Twin Related Defects in III–V Nanowires Grown in Popular Alternative Crystallographic Directions, H. A. Fonseka, N. Denis, J. A. Gott, X. Yuan, R. Beanland, H. H. Tan , C. Jagadish, A. M. Sanchez, M. De Luca*. J. Phys. Chem. C 2024, 128, 50 (2024)

Team Members Marta De Luca Principal Investigator Office: n° 350, third floor, Marconi building, Physics Department Read More Francesca Santangeli PhD Student Office: n° 349, third floor, Marconi building, Physics Department Read More Muhammad Tahir PhD Student Office: n° 349, third floor, Marconi building, Physics Department Read More Akant Sagar Sharma Post-Doc Researcher Office: n° 349, third floor, Marconi building, Physics Department Read More Paolo De Vincenzi PhD Student Office: n° 312, third floor, Marconi building, Physics Department Read More Isabella Santanchè Master Student Office: n° 312, third floor, Marconi building, Physics Department Read More Harikrishnan Gopalakrishnan Post-Doc Researcher Office: n° 349, third floor, Marconi building, Physics Department Read More Riccardo Pallucchi PhD Student Office: n° 349, third floor, Marconi building, Physics Department Read More Alumni Research Assistant Xiangyu Lin Read More Master Student Pietro Todesco Read More Master Student Mario Roggi Read More