arXiv subjects

Vishakha Kaushik

Publications and source records attributed to Vishakha Kaushik.

5 recordsLinked to original sources

arXiv2026

Modification of Surface Properties in Ruthenium Thin Films through Nitrogen Ion Irradiation

Surface modification is an important strategy for tailoring the physical and chemical properties of materials for advanced technological applications. In thin films, changes in surface structure, roughness, and composition can strongly influence their functional behavior. In this work, we studied the effect of N+-ion irradiation at 20 keV energy on Ru thin films of two different thicknesses, 100 Å and 1000 Å, over a fluence range of ~1014 to 1017 ions/cm2. The main objective of this study is to investigate the evolution of the structural and wettability properties of Ru thin films of different thicknesses under increasing ion fluence. Overall, the results reveal that increasing ion fluence promotes surface roughening in both film thicknesses, which is correlated with an increase in contact angle. This indicates a clear transition from hydrophilic to hydrophobic behaviour, with the highest contact angle of ~95.54° observed at a fluence of 1017 ions/cm2. TRIM simulations reveal that for the 100 Å film, the projected ion range exceeds the film thickness, allowing interaction with the bottom substrate, whereas in the 1000 Å film, ion penetration remains largely confined within the Ru layer. GIXRD confirms fluence-dependent structural modification, including peak broadening with preferred orientation changes from Ru (101) to (002). Overall, this study demonstrates that N+-ion irradiation serves as an effective route for tuning both the surface morphology and wettability of Ru thin films, enabling controlled enhancement of hydrophobicity.

cond-mat.mtrl-sci↗

arXiv2026

Influence of oxygen ion implantation on magnetic microstructure in Pt/Co/Pt multilayers with perpendicular magnetic anisotropy

The interaction of oxygen with cobalt and cobalt-based alloys has been a very important topic in the field of spintronics as it leads to enhanced orbital anisotropy and interfacial Dzyaloshinskii-Moriya interaction (DMI), which are crucial in the context of applications such as magnetic tunnel junctions (MTJs) based data storage and domain wall (DW) motion. To understand the complex and interesting relationship between oxygen and ferromagnetic (FM)/heavy metal (HM) interfaces, we studied controlled oxygen ion implantation in a cobalt layer located in a Pt/Co 1.2 /Pt (nm) multilayer with a specific structure. At high implantation fluence, the perpendicular anisotropy was lost, as verified by in-plane hysteresis measurements. Under low magnetic field conditions, the DW dynamics of Co/Pt multilayers were analyzed, highlighting key parameters such as DW velocity, roughness amplitude, and roughness exponent. After O+-ion implantation, the DW velocity increased by more than 50 times, rising from 5 um/s to 300 um/s compared with the as-deposited multilayer. The fundamental cause of this improvement is the structural and magnetic changes brought by the implantation, which successfully lower the energy barriers preventing DW movements. The results show how oxygen implantation can be used to precisely tailor the ferromagnetic interfaces, leading to promised improvements in the functionality of next-generation spintronic devices.

cond-mat.mtrl-sci↗

arXiv2025

Engineered Inclined Energy Landscapes Enabling Free Flow of Magnetic Microstructures for Artificial Neuron Applications

Spintronic-based brain-inspired neuromorphic computing has recently attracted significant attention due to the exceptional properties of magnetic microstructures, including nanoscale dimensions, high stability, and low energy consumption. Despite these advantages, the practical integration of such microstructures into functional devices remains challenging. Fabrication processes are often complex and prone to stochastic effects, such as unwanted pinning and thermal-induced instabilities, which limit device reliability and scalability. Addressing these challenges is crucial for advancing spintronic neuromorphic architectures toward real-world applications. Thus, to reduce these effects we have proposed a design which is experimentally feasible and require less energy as compared to existing one. By engineering the system anisotropy into a sawtooth-type energy landscape, we have achieved free flow of these microstructures and successfully emulated integrate and fire (IF) function of biological neuron. Thus, proposed design presents an experimentally reliable and energy efficient external stimuli approach for tailoring magnetic microstructures dynamic behaviours, resulting in low energy consumption of 23.66 fJ per spike paving the way for the development of skyrmion-based futuristic neuromorphic computing device applications.

physics.comp-ph↗

arXiv2025

Electrical Control of Excitons in Bare-MoSe2 and MoSe2/NbSe2 Heterostructure

Monolayer transition metal dichalcogenides (TMDCs) are promising materials for next-generation optoelectronic devices, owing to their strong excitonic responses and atomic thickness. Controlling their light emission electrically is a crucial step towards realizing practical nanoscale optoelectronic devices such as light-emitting diodes and optical modulators. However, photoluminescence (PL) quenching in van der Waals TMDC/metal heterostructures, caused by ultrafast interlayer charge or energy transfer, impedes such electrical modulation. Here, we investigate monolayer-MoSe2/bulk-NbSe2 heterostructures and demonstrate that a vertical electric field can effectively recover the PL intensity up to ~ 80% of bare-MoSe2. Furthermore, our analysis reveals that the room temperature PL intensity can be tuned by nearly three orders of magnitude in bare-MoSe2 and by about one order of magnitude in MoSe2/NbSe2 heterostructures. First-principles calculations incorporating spin-orbit coupling reveal that the perpendicular electric fields drive a transition from a direct to an indirect bandgap, fundamentally altering the optical response in the heterostructure. Unlike bare-MoSe2, the heterostructure exhibits a pronounced thermal dependence of the enhancement factor, implying that exciton lifetime dominates over interfacial transfer processes. Our findings demonstrate reversible, electric-field-driven PL control at a TMDC/metal interface, providing a pathway to electrically tunable light emission and improved contact engineering in two-dimensional optoelectronic devices.

physics.app-ph↗

arXiv2014

Micro-Raman and field emission studies of silicon nanowires prepared by metal assisted chemical etching

Micro-Raman scattering and electron field emission characteristics of silicon nanowires (SiNWs) synthesized by metal assisted chemical etching (MACE) are investigated. Scanning electron microscopy images reveal the growth of well aligned vertical SiNWs. Raman shift and size relation from bond-polarizability model has been used to calculate exact confinement sizes in SiNWs. The Si optical phonon peak for SiNWs showed a downshift and an asymmetric broadening with decreasing diameter of the SiNWs due to quantum confinement of optical phonons. The field emission characteristics of these SiNWs are studied based by carrying out current-voltage measurements followed by a theoretical analysis using Fowler-Nordheim equation. The electron field emission increased with decreasing diameter of SiNWs. Field emission from these SiNWs exhibits significant enhancement in turn-on field and total emission current with decreasing nanowire size. The reported results in the current study indicate that MACE is a simple technique to prepare well-aligned SiNWs with potentials for applications in field emission devices.

cond-mat.mes-hall↗