Physical entropy sources that remain stable under extreme temperatures are essential for cryptography in emerging technological frontiers in deep space exploration, geothermal energy harvesting, and nuclear energy. However, conventional semiconductor platforms fail to generate stable and reliable cryptographic keys above 200 °C due to performance degradation. Here, we report a diamond-based cryptographic primitive that exploits the defect-rich sp2-bonded grain boundary network in nitrogen-incorporated ultrananocrystalline diamond (n-UNCD) film as a robust entropy source to generate cryptographic keys that remain operationally stable even after enduring extreme temperatures of 700 °C for 54 h while also surviving thermal cycling between room temperature and 700 °C for 48 h. The strength of the generated keys is assessed through several cryptographic metrics such as bit uniformity, entropy, hamming distances, and correlation coefficients, all of which are found to be near their respective ideal values. Moreover, the generated keys pass the NIST SP 800 and SP 800-90B tests and are also resilient to supply bias variations and a regression-based machine learning attack model based on the Fourier series. The robustness of the keys is attributed to the better thermal stability and chemical inertness of the n-UNCD film. This is supported by high-resolution energy-dispersive X-ray spectroscopy (EDS), which shows no significant lateral diffusion of metal atoms into the n-UNCD layer, and by Raman spectroscopy, which reveals no significant changes in the bonding configuration of the n-UNCD structure. Our findings highlight the remarkable potential of n-UNCD film for extreme environment cryptography by expanding the operational limits of conventional hardware security platforms.

MXenes are a rapidly expanding family of two-dimensional transition metal carbides and nitrides whose exceptional compositional, structural, and surface-chemical tunability has driven rapid growth across materials science, chemistry, physics, and engineering. This roadmap consolidates the current state of MXene research, spanning synthesis, processing, fundamental properties, computation, electrochemical energy storage, biomedical applications, electronics, optoelectronics, membranes, sensing, tribology, and extreme-environment technologies. By identifying key advances, persistent challenges, and emerging opportunities, the roadmap provides a forward-looking outlook for guiding MXenes from laboratory discovery toward transformative applications.

Protecting sliding surfaces from friction and wear remains a persistent engineering challenge. Graphene oxide (GO) and pristine graphene (PG), the two different carbon-based 2D materials, are attractive solid-lubricant coatings, but both are compromised by moisture. GO readily forms a protective transfer layer at the sliding contact through the reactive, adhesive chemistry of its oxygen-containing functional groups. These same groups, however, make it hydrophilic and humidity-sensitive, resulting in moisture-driven failure. PG is hydrophobic and chemically stable, yet its inert basal plane cannot sustain a persistent transfer layer, so it also loses durability under prolonged sliding in a humid environment. Here, we show that blending GO and PG, exploiting the compositional flexibility of solution-processed 2D coatings, turns this shared moisture vulnerability into a tunable design parameter. Across the full GO:PG composition range, the blended coatings sustain stable, low-friction sliding at humid sliding conditions, where both parent materials fail. In all cases, the improvement comes from keeping the carbonaceous transfer layer intact. GO and PG achieve this through complementary roles. In GO-rich blends, PG mitigates the moisture-induced failure of the GO-driven transfer layer against moisture, while in PG-rich films, GO enables the transfer-layer formation that PG alone cannot achieve. Representative GO-rich and PG-rich blends outperform their parent materials by one to two orders of magnitudes under the same humid conditions. The moisture sensitivity of graphene-derived coatings is therefore not a fixed material property but a compositionally tunable outcome, offering a practical route to moisture-tolerant solid lubrication.

Two-dimensional (2D) semiconductors with narrow bandgaps are promising candidates for near- and far-infrared (IR) photodetection, particularly in the telecommunication spectral window. However, current low-bandgap IR photodetectors face significant challenges due to their high dark current, increased carrier recombination, and thermally generated noise. In this work, a hybrid phototransistor is demonstrated by integrating direct, contact-free palladium diselenide (PdSe2) as a highly responsive IR detection layer with a non-IR-absorbing molybdenum diselenide (MoSe2) field-effect transistor (FET), using a near-IR source at a wavelength of lambda = 1650 nm. Exfoliated PdSe2 flakes integrated into a back-gated FET architecture exhibit ambipolar transport behavior, with extracted hole and electron mobilities of 24.8 cm(2) V-1 s(-1) and 58.4 cm(2) V-1 s(-1), respectively. The devices show a clear photocurrent generation under the illumination of a lambda = 1650 nm laser source, achieving a notable responsivity of similar to 300 mA W-1 at an applied gate voltage of 15 V, which highlights the suitability of PdSe2 as a narrow-bandgap material for photodetection. Photoresponsivity saturates and does not have any effect above an applied gate voltage of 15 V. To further tune the photoresponsivity performance continuously with the applied gate voltage, we construct a van der Waals heterostructure phototransistor, where few layers of PdSe2 are directly transferred onto the 2D channel region of a MoSe2 FET, while avoiding any contact with the metal electrodes. In this heterostructure, PdSe2 works as the primary active IR-absorbing layer, while MoSe2 provides high-performance FET characteristics. This spatial separation of absorption and transport facilitates efficient interlayer charge transfer and charge separation, resulting in high responsivities of up to 972 mA W-1 at near-IR wavelengths and a low power density of 1.5 mW/mm(2). The responsivity of our photodetector is comparable to that of some state-of-the-art commercially available NIR photodetectors, highlighting the potential of PdSe2-based heterostructures as scalable, CMOS-compatible platforms for high-performance near-IR detection.

MXenes, an emerging class of two-dimensional van der Waals materials, have become the focus of research, demonstrating exceptional potential in electrochemical, biochemical and electronic applications. This chapter provides a brief overview of MXenes, covering their fundamental characteristics, synthesis methods and current challenges, with particular attention on synthesis methods.

Efficient thermal management in 2D-3D heterostructures hinges upon phonon transmission across weakly bound interfaces, yet how heteroatom doping of the 2D layer reshapes vibrational coupling remains unclear. Here, we combine nonequilibrium molecular dynamics (NEMD) simulation with vibrational spectral analysis and complementary density functional theory (DFT) calculations to investigate phonon-mediated thermal transport across graphene-diamond (Gr-D) interfaces as Gr is substitutionally doped with nitrogen (N), boron (B), and silicon (Si) at dopant concentrations of 5, 10, and 15% at 298 K. The undoped Gr-D heterostructure (control) exhibits an interfacial thermal conductance (ITC) of similar to 14 MW m-2 K-1. N-doping yields ITC values comparable to the control (similar to 11-14 MW m-2 K-1), while B-doping gives a modest increase of ITC up to similar to 16 MW m-2 K-1 at 15% dopant concentration. Remarkably, Si-doping of Gr produces a monotonic, large ITC enhancement from similar to 19 to 57 MW m-2 K-1 going from 5 to 15% dopant concentration, a 3-fold gain over the control. Frequency-resolved analysis shows a dopant-induced bimodal redistribution of the out-of-plane projected density of states (PDOS), reweighting from the 8-20 THz (mid) band into the 0-8 (low) and 20-40 THz (high) bands with Si causing the strongest shift and the largest Bose-Einstein (BE)-weighted spectral overlap with diamond. Out-of-plane BE-weighted overlap strongly correlates with ITC, indicating that spectral matching rather than intrinsic damping contributes to thermal phonon transport. DFT results show that Si-doping increases the interfacial interaction energy and produces localized charge accumulation between the protruded Si and topmost diamond C atoms, consistent with stronger vibrational coupling inferred from NEMD. Together, these results provide a mechanistic framework for understanding the role of dopants in simultaneously increasing out-of-plane spectral co-occupancy and strengthening interfacial coupling that can raise ITC in Gr-D and other similar 2D-3D heterostructures.

The mechanical and tribological properties of MXene coatings have gained notable attention in recent years due to their promising friction and wear performance. However, the chemical stability of MXenes under tribomechanical stress, a critical factor for ensuring long-term reliable lubrication, remains largely unexplored. In this study, we investigate the tribological behavior of a multi-layer molybdenum-based carbide MXene (ordered double transition metal Mo2TiC2Tx), highlighting its exceptional performance as a solid lubricant in dry nitrogen atmosphere when sliding against a diamond-like carbon (DLC) counterface at macroscale. Our findings reveal sustained superlubricity, with an impressively low friction coefficient of 0.005, and remarkable wear rate (5.11x10-10 mm3 N- 1 m- 1) over a prolonged linear sliding distance of 86 km without any sign of failure, outperforming all previously tested MXenes and 2D materials under similar conditions. Comprehensive characterization, along with molecular dynamics simulations, reveals the formation of a carbon-rich tribolayer, enabled by the enhanced tribo-catalytic activity of Mo under tribo-mechanical stress, which facilitates prolonged superlubricity. The exceptional durability and superlubricious performance of Mo2TiC2Tx coatings with negligible wear pave the way for the development of more robust and catalytically active MXenes with extended wear life and offer a promising alternative to oil-based lubricants in tribology.

Graphene oxide (GO) is a promising solid tribology material owing to its excellent wear resistance, yet its tribological performance is highly sensitive to humidity, leading to frictional instability and premature failure under humid environments. Despite extensive studies, the water-driven degradation of tribological properties and the strategy to overcome it remains unclear. Here, the effect of humidity on tribological properties of GO was investigated and a structural design guideline was proposed by blending hydrophilic GO and hydrophobic pristine graphene (PG) to control internal compactness and interfacial chemistry. It is revealed that blending PG into GO matrix suppresses water-driven degradation, while incorporating GO into PG matrix promotes transfer layer formation, enabling 2D-2D friction interface. An optimal compositional regime balances GO’s reactive transferability and PG’s hydrophobic stability against interfacial water, yielding both low friction (COF ~0.12) and lifetime improvements up to two orders of magnitude under 50% RH. These findings establish a structural design framework of 2D materials composite films for solid tribology applications, offering a new pathway toward reliable operation in diverse environmental conditions.

High Entropy Alloys (HEAs) have garnered attention due to their remarkable tribological attributes. Predominantly, failure mechanisms in HEAs emanate from stress‐induced dislocations, culminating in crack propagation and film delamination. In this study, we report on the synthesis of 2D HEA of (MoWNbTaV) 0.2 S 2 which facilitates shear‐induced energy dissipation at sliding interfaces. The ball‐on‐disk tribological investigations demonstrate unprecedentedly low average coefficients of friction (0.076) and wear rates (10 −9 mm 3 (N∙m) −1 ) under high contact pressures (0.936 GPa) within ambient conditions. Employing multi‐scale characterizations alongside molecular dynamic simulations, we elucidate that the presence of the HEA triggers tribocatalytic activity under high contact pressures emerging as a pivotal factor in extending lubricant lifespan during tribological tests. The resilient lubriciousness coupled with the facile spray coating methodology of (MoWNbTaV) 0.2 S 2 in ambient environments paves the way for the development of a new class of solid lubricants based on 2D HEA.

To assess the efficacy of a mixed-dimensional van der Waals (vdW) heterostructure in modulating the optoelectronic responses of nanodevices, the charge transport properties of the transition-metal dichalcogenide (TMD)-based heterostructure comprising zero-dimensional (0D) WS2 quantum dots (QDs) and two-dimensional (2D) MoS2 flakes are critically analyzed. Herein, a facile strategy was materialized in developing an atomically thin phototransistor assembled from mechanically exfoliated MoS2 and WS2 QDs synthesized using a one-pot hydrothermal route. The amalgamated photodetectors exhibited a high responsivity of ∼8000 A/W at an incident power of 0.05 nW of white light, surpassing that of the pristine MoS2 devices. Furthermore, the detectivity of pristine MoS2, which was on the order of 1010, increased to 1012 Jones for the WS2 QDs/MoS2 heterostructure photodetector, outperforming other WS2-based materials. The quasiparticle band gap and density of states (DOS) are further analyzed to elucidate the photophysics of the WS2 QD/MoS2 hybrid assembly. The difference in the work function between MoS2 and WS2 QDs gives rise to an electric field across the 0D-2D interface, facilitating effective charge separation and migration and contributing to the enhancement of photoresponsivity. The analysis of optical responses using density functional theory (DFT) revealed stronger absorption and less reflection over a broader spectrum of wavelengths for the heterostructure compared to the pristine materials. The estimated optical conductivity aligns well with the experimentally predicted maximum photoresponsivity under visible light, which is attributed to the high absorbance of 2D MoS2. Combining diverse spectroscopic and imaging techniques with quantum simulation provides insights that clarify the pertinence of 0D-2D TMDs in designing phototransistors.

Nitrogen-incorporated ultrananocrystalline diamond (n-UNCD) films offer tremendous potential for diverse electronic applications. However, the absence of a reliable Ohmic contact at room temperature limits their practical integration and broader applicability. Here, we investigate the room temperature specific contact resistivity ρc of Ti/Pt/Au metal stack deposited on n-UNCD films grown on an intrinsic single crystal diamond substrate using a microwave plasma chemical vapor deposition system. We employ a circular transfer length model (c-TLM) and find the room temperature ρc to be ∼4.67×10−5 Ω cm2, which is among the lowest reported value for n-UNCD films. High temperature vacuum annealing conducted at 700 and 800 °C results in an initial improvement, followed by a minor degradation in ρc values, respectively. The electrical contacts remain highly Ohmic for all measurements. Furthermore, cross-sectional transmission electron microscopy analysis suggests formation of conductive titanium carbide layer with no significant inter metallic diffusion. Overall, the electrical contacts demonstrate robust thermal stability, both of which are critical for attaining high-performance nanocrystalline diamond-based electronic devices.

The high-power density energy storage device is one of the critical components of future microelectronics. The dielectric capacitors possess high power density but low energy density. Here, we explored a few-micrometer geometry hybrid dielectric capacitor using ionic liquid coupled with 2D dielectric materials to enhance the capacitive energy storage. The in-plane capacitors were fabricated on the Si/SiO 2 substrate with a 285 nm oxide layer used to apply the electric field to enhance the capacitance of the dielectric capacitor. Using the back gate geometry through SiO 2 layer, we able to enhance the capacitance significantly. We will discuss a detail study of the capacitance, storage energy density and power density of this hybrid micro-capacitor and their potential applications in future technology.

In recent studies of two-dimensional (2D) nanomaterial-based solid lubricants, the importance of durability has been emerging for real engineering-scale applications. To achieve this, a transfer layer formation is essential to prevent the wear of the mechanical systems. However, it has been challenging for pristine graphene (PG) to induce a material transfer due to chemical inertness. In this study, we suggest an easy-to-process strategy to promote the huge material transfer of the PG onto the counterpart contacting material. We utilized graphene oxide (GO) as a gluing layer between the PG film and the counterpart contact surface to realize the superior tribological performance. The high interaction energy of the GO from its functional groups makes a contribution to the material transfer of PG, which is unveiled by a systematic analysis of the counterpart contact surface and the wear track. The huge solid transfer layer not only makes a wear-resistant contact interface between the transfer layer and the underlying film by densification and oxidation, but also reduces surface interaction energies, finally resulting in a significant improvement in durability.

The growing need for renewable energy has drawn significant attention to the development of energy storage systems with ultra-high capacity and efficiency. Polymer-based dielectric capacitors are important in modern electronics and energy storage systems because of their inherent flexibility, fast charge-discharge capabilities, low dielectric loss, and high power density. However, the conflicting relationship between dielectric polarization and electric breakdown behavior frequently hinders further advancements in energy storage performance. In this study, we incorporated mechanically exfoliated 2D mica as nanofillers into a poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) or PTC polymer to fabricate multilayered heterostructure capacitors and arranged them in a PTC/mica/PTC (PMP) and PTC/mica/PTC/mica/PTC (PMPMP) configuration. PMP and PMPMP nanocomposite films exhibit maximum discharged energy densities of 50 J cm-3 (E = 750 MV m-1) and 45 J cm-3 (E = 625 MV m-1), respectively, compared to the typical PTC capacitor with a maximum discharged energy density of 15 J cm-3 (E = 500 MV m-1). The PMPMP capacitors demonstrate a discharge time of 6.64 mu s with high cyclic stability (98%) after thousands of cycles at an applied voltage of 400 V. This study provides a comprehensive understanding of the development of polymer- and 2D nanofiller-based capacitors for industrial applications.

The metal-to-insulator phase transition (MIT) in two-dimensional (2D) materials under the influence of a gating electric field has revealed interesting electronic behavior and the need for a deeper fundamental understanding of electron transport processes, while attracting much interest in the development of next-generation electronic and optoelectronic devices. Although the mechanism of the MIT in 2D semiconductors is a topic under debate in condensed matter physics, our work demonstrates the tunable percolative phase transition in few-layered MoSe2 field-effect transistors (FETs) using different metallic contact materials. Here, we attempted to understand the MIT through temperature-dependent electronic transport measurements by tuning the carrier density in a MoSe2 channel under the influence of an applied gate voltage. In particular, we have examined this phenomenon using the conventional chromium (Cr) and ferromagnetic cobalt (Co) as two metal contacts. For both Cr and Co, our devices demonstrated n-type behavior with a room-temperature field-effect mobility of 16 cm2 V-1 s-1 for the device with Cr-contacts and 92 cm2 V-1 s-1 for the device with Co-contacts, respectively. With low temperature measurements at 50 K, the mobilities increased significantly to 65 cm2 V-1 s-1 for the device with Cr and 394 cm2 V-1 s-1 for the device with Co-contacts. By fitting our experimental data to the percolative phase transition theory, the temperature-dependent conductivity data show a transition from an insulating-to-metallic behavior at a bias of similar to 28 V for Cr-contacts and similar to 20 V for Co-contacts. This cross-over of the conductivity can be attributed to an increase in carrier density as a function of the gate bias in temperature-dependent transfer characteristics. By extracting the critical exponents, we find that the transport behavior in the device with Co-contacts aligns closely with the 2D percolation theory. In contrast, the devices with Cr-contacts deviate significantly from the 2D limit at low temperatures.

Diamond has tremendous potential for power electronics, due to its superior thermal conductivity, large electric field strength, and high carrier mobilities. However, the absence of a reliable room temperature n-type transport has impeded any advancements in diamond-based electronics. Here, we circumvent this bottleneck by integrating n-type two-dimensional (2D) monolayers of molybdenum disulfide (MoS2) with boron doped p-type single crystal diamond and demonstrate 2D/3D heterostructure-based PN junction diodes that operate at room temperature with excellent rectification characteristics. Our diodes achieve a maximum forward current density (JD) of ∼4000 A/cm2, an ideality factor (η) value of ∼3.7, and a rectification ratio (RR) of 106. We find that the origin of current rectification stems from the interlayer recombination of majority carriers driven by direct tunnelling (DT) and Fowler Nordheim (FN) tunnelling mechanisms. Our demonstration can open new avenues for diamond-based power electronics through its integration with 2D materials.

Two-dimensional (2D) materials offer significant potential for applications in energy-harvesting devices, batteries, sensors, and transistors. However, their intrinsic brittleness makes them prone to mechanical failure, limiting their practical use. In this work, we perform in situ transmission electron microscopy (TEM) fracture tests on monolayer MoSe2 and uncover an extrinsic toughening effect induced by an ultrathin adsorbed polystyrene adlayer. This adlayer substantially enhances the fracture resistance of the 2D flakes. Through a combination of molecular dynamics simulations and finite element analysis, we elucidate the molecular mechanism behind this toughening effect. It arises from the active crack-bridging behavior of entangled polymer chains and the formation of a fracture process zone that stabilizes crack propagation and increases the energy required for crack extension. The proposed toughening mechanism offers a pathway to improving the mechanical reliability of 2D material-based devices by mitigating the risk of sudden failure.

Methyl ammonium lead iodide (MAPbI(3)) was one of the earliest perovskite formulations examined, which created tremendous interest in these materials given their stupendous rise in power conversion efficiency (PCE). Beyond MAPbI(3), new perovskite formulations have emerged, such as the triple cation (Cs(0.05)FA(0.79)MA(0.16)PbI(2.45)Br(0.55)) absorbers, which have further advanced research in emerging photovoltaics in addition to other types of optoelectronics sensors. In this work, we explore how an environmental ambient with nitrogen influences the rate of device degradation using a triple cation absorber during in-use testing with maximum power point tracking (MPPT) over the course of 51 hours. We compare our results to an ambient comprised largely of air, and our results confirm the rapid degradation of the device parameters in an uncontrolled environmental ambient, even with the intrinsically more stable triple cation absorber.