Ajit Kumar Katiyar

Two-dimensional (2D) transition metal dichalcogenides (TMDs) offer a promising pathway for next-generation electronics due to their exceptional electrical characteristics at atomically thin thickness. Nevertheless, the realization of high-quality p-type 2D-FETs remains a significant challenge for CMOS device integration due to surface damage and unintended n-doping induced during dielectric deposition. In this work, we report the wafer-scale synthesis of p-type WSe ₂ films using metal-organic chemical vapor deposition and the fabrication of top-gate p-FETs through a buffer layer strategy, which provides superior electrostatic control and channel stability. The transistors exhibit excellent p-type performance, achieving a hole mobility of 10.49 ± 2.35 cm ² V ⁻¹ s ⁻¹ with on/off current ratio exceeding 10 ⁹ . By leveraging the process’s scalability, which ensures uniform and damage-free fabrication, we successfully produced reliable wafer-scale PMOS logic circuits. This study provides a scalable, damage-free integration solution for 2D electronics, paving the way for the practical realization of all 2D-based high-density electronics and circuits.

N-annulated perylene tetraester-functionalized Zn _{1− x} Ag _x O nanocrystals offer a promising approach to CO ₂ capture, contributing to carbon emission mitigation and advancing materials-based strategies toward a sustainable, net-zero future.

The advent of 2D materials has revolutionized condensed matter physics and materials science, offering unprecedented opportunities to explore exotic physical phenomena, engineer novel functionalities, and address critical technological challenges across diverse fields. Over the past two decades, the exploration of 2D materials has expanded beyond graphene, encompassing a vast library of atomically thin crystals and their heterostructures. These materials exhibit extraordinary electronic, optical, thermal, mechanical, and chemical properties, and hold promise for breakthroughs in electronics, optoelectronics, quantum technologies, energy storage, catalysis, thermal management, filtration and separation, and beyond. Many exciting new physics and phenomena continue to emerge, while select 2D materials, such as graphene, h-BN, and the semiconducting transition metal dichalcogenides (TMDCs), are transitioning from laboratory-scale demonstrations to industrial applications. In this context, a holistic understanding of synthesis, structure-property relationships, integration, and performance optimization is essential. This roadmap reviews the multifaceted challenges and opportunities in 2D materials research, focusing on the synthesis, properties and applications of representative systems including graphene and its derivatives, TMDCs, MXenes as well as their heterostructures and moiré systems.

Two-dimensional (2D) semiconductors, such as MXenes, transition metal dichalcogenides, black phosphorus, and emerging van der Waals heterostructures, have revolutionized the field of optoelectronics by offering exceptional electrical, optical, and mechanical properties at atomic-scale thickness. Their unique features, including tunable bandgaps, high absorption coefficients, and strong excitonic effects, enable a wide range of light detection and light emission applications, making them key materials for next-generation functional optoelectronic devices. This review explores recent breakthroughs in light detection technologies using 2D materials. As photodetectors, they offer ultrafast response rates and high sensitivity across a broad spectral range. In solar cell applications, 2D materials contribute to the development of lightweight, flexible, and efficient photovoltaic devices with enhanced charge transport. Image sensors based on 2D materials exhibit superior spatial resolution and spectral selectivity, while their integration into biomedical imaging platforms enables non-invasive diagnostics due to their biocompatibility. Furthermore, novel morphable light-tracking devices leverage the mechanical flexibility and photoresponsivity of 2D materials for adaptive photonic systems in wearable and robotic applications. On the emission front, 2D semiconductors are emerging as active light-emitting materials in LEDs, lasers, and quantum emitters, benefiting from direct bandgaps in monolayers and strong quantum confinement effects. Additionally, their application as backplane driving circuits in flexible displays is gaining momentum due to their high mobility, mechanical robustness, and transparency, enabling foldable and stretchable display technologies. Despite these advancements, practical implementation faces persistent intrinsic challenges such as high contact resistance, environmental instability, difficulties in controlled doping, and a lack of scalable, reproducible synthesis methods. These issues hinder device reliability and integration. This review also outlines the perspective toward commercialization, emphasizing the need for advancements in heterostructure engineering, and interface optimization. Through interdisciplinary collaboration and innovative material processing, 2D semiconductors are poised to reshape the landscape of optoelectronics, bridging the gap between fundamental science and practical technologies.

Strain engineering is a powerful strategy that can strongly influence and tune the intrinsic characteristics of materials by incorporating lattice deformations. Due to atomically thin thickness, 2D materials are excellent candidates for strain engineering as they possess inherent mechanical flexibility and stretchability, which allow them to withstand large strains. The application of strain affects the atomic arrangement in the lattice of 2D material, which modify the electronic band structure. It subsequently tunes the electrical and optical characteristics, thereby enhances the performance and functionalities of the fabricated devices. Recent advances in strain engineering strategies for large‐area flexible devices fabricated with 2D materials enable dynamic modulation of device performance. This perspective provides an overview of the strain engineering approaches employed so far for straining 2D materials, reviewing their advantages and disadvantages. The effect of various strains (uniaxial, biaxial, hydrostatic) on the characteristics of 2D material is also discussed, with a particular emphasis on electronic and optical properties. The strain‐inducing methods employed for large‐area device applications based on 2D materials are summarized. In addition, the future perspectives of strain engineering in functional devices, along with the associated challenges and potential solutions, are also outlined.

Although Si is extensively used in micro-nano electronics, its inherent optical absorption cutoff at 1100-nm limits its photonic and optoelectronic applications in visible to partly near infrared (NIR) spectral range. Recently, strain engineering has emerged as a promising approach for extending device functionality via tuning the material properties, including change in optical bandgap. In this study, the reduction in bandgap with applied strain was used for extending the absorption limit of crystalline Si up to 1310 nm beyond its intrinsic bandgap, which was achieved by creating the crumpled structures in Si nanomembranes (NMs). The concept was used to develop a prototype NIR image sensor by organizing metal-semiconductor-metal–configured crumpled Si NM photosensing pixels in 6 × 6 array. The geometry-controlled, self-sustained strain induction in Si NMs provided an exclusive photon management with shortening of optical bandgap and enhanced photoresponse beyond the conventional Si absorption limit.

Recent advances in two-dimensional semiconductors, particularly molybdenum disulfide (MoS₂), have enabled the fabrication of flexible electronic devices with outstanding mechanical flexibility. Previous approaches typically involved the synthesis of MoS₂ on a rigid substrate at a high temperature followed by the transfer to a flexible substrate onto which the device is fabricated. A recurring drawback with this methodology is the fact that flexible substrates have a lower melting temperature than the MoS₂ growth process, and that the transfer process degrades the electronic properties of MoS₂. Here we report a strategy for directly synthesizing high-quality and high-crystallinity MoS₂ monolayers on polymers and ultrathin glass substrates (thickness ~30 µm) at ~150 °C using metal–organic chemical vapour deposition. By avoiding the transfer process, the MoS₂ quality is preserved. On flexible field-effect transistors, we achieve a mobility of 9.1 cm² V⁻¹ s⁻¹ and a positive threshold voltage of +5 V, which is essential for reducing device power consumption. Moreover, under bending conditions, our logic circuits exhibit stable operation while phototransistors can detect light over a wide range of wavelengths from 405 nm to 904 nm.

The absorption range of Si is extended to essential wavelength range of lidar sensor for self-driving car via strain engineering.