This work presents the development of novel fluorinated graphene (FG)-based resistive humidity sensor. The humidity sensor was fabricated by drop-casting FG suspension, as the humidity sensing material, on silver (Ag)-based interdigitated electrodes (IDEs). The silver-based IDEs were screen printed on a flexible polyimide substrate. The FG suspension was synthesized by uniform dispersion of FG in isopropyl alcohol (IPA), using the ultra-sonication process. The resistive response of the fabricated humidity sensors towards varying relative humidity (RH) levels was investigated, when the RH was varied from 20% to 80%, in steps of 10%, and at a temperature of 24 0C. A relative resistance change of 13.3% was observed when the RH was changed from 20% to 80%, with a sensitivity of 0.22%/%RH for the FG-based humidity sensor. Response time and recovery time of 82 s and 125 s, respectively, was obtained for the fabricated sensor. In addition, the effect of varying operating temperatures on the response of the fabricated humidity sensors was investigated. The average temperature coefficient of resistance of sensors was obtained as approximately -0.3%/:C. A linear relation between the temperature and the relative resistance change of sensors was observed. Further, first-principles study, employing density functional theory calculations, was performed to investigate interactions between the fluorine atom and graphene substrate, as well as humidity sensing behavior of the FG. DFT calculations showed that hydrogen atoms of the water molecule move towards the fluorine atom of the FG during the relaxation process, confirming the hydrogen bonding between FG and water molecules. The Eads of -0.50 eV was calculated for the adsorption of water molecule on the FG, demonstrating the strong humidity sensing property of the FG. The results demonstrate that FG, a highly stable derivative of graphene, is a potential material for humidity sensing applications.

The temperature coefficient of resistance (TCR) of thin metal lines is often used for applications in thermometry, bolometers, or thermal accelerometers. However, metal TCR is much degraded in nanometer-thin films due to strong surface scattering, preventing their use as fast thermal sensors, which simultaneously require low thermal mass and large TCR. In contrast, here we show that the TCR of doped two-dimensional (2D) semiconductors is large (∼0.3% K⁻¹ at 300 K in MoS₂ and MoTe₂) even at sub-nanometer thickness. This is larger than that of any metals with thicknesses up to ∼35 nm and larger than that of ∼95 nm thick Cu lines (0.25% K⁻¹) at 300 K. At 100 K, the TCR of these 2D materials is doubled, ∼0.6% K⁻¹. Comparison with detailed 2D transport models suggests that the TCR could be further enhanced (up to 0.45% K⁻¹ at 300 K and ∼2.5% K⁻¹ at 100 K) by reducing the density of Coulomb impurities and scattering centers. Such high TCR in atomically thin 2D semiconductors could lead to the design of fast thermal sensors.

A first-principles study was successfully employed to investigate the impact of different ratios of functional groups such as fluorine (-F), oxygen (-O), and hydroxyl (-OH) on ammonia (NH ₃ ) sensing of titanium carbide Mxene. Density functional theory (DFT) calculations were performed for studying the adsorption energy (E _ads ) and charge transfer (CT) between different gases (NH ₃ , CO ₂ , NO, H ₂ S and SO ₂ ) and Ti ₃ C ₂ T _x material with a high ratio of fluorine surface functional groups, Ti ₃ C ₂ (OH) _0.44 F _0.88 O _0.66 . DFT calculations showed more sensitivity to NH ₃ , with the highest CT (0.098 e) and the lowest E _ads (-0.36 eV) among the mentioned gases. The adsorption of NH ₃ on Ti ₃ C ₂ T _x MXene with a high and low ratios of fluorine surface functional groups, Ti ₃ C ₂ (OH) _0.44 F _0.88 O _0.66 (Substrate 1) and Ti ₃ C ₂ (OH) _0.66 F _0.22 O _1.11 (Substrate 2) respectively, resulted in adsorption energies of -0.36 eV and -0.49 eV, revealing a stronger adsorption of NH ₃ on Substrate 2 with low ratios of fluorine. In addition, the isosurfaces representation of charge difference illustrated that fluorine atoms have smaller charge transfer than oxygen atoms when interacting with NH ₃ molecules. The Bader charge difference for the closest oxygen and fluorine atoms to NH ₃ molecule showed that oxygen atoms have 60% to 180% larger Bader charge difference, when compared to fluorine atoms, supporting that Ti ₃ C ₂ T _x sensor with a lower ratio of fluorine surface termination has a stronger interaction with NH ₃ gas molecules.

Silicon's dominance in integrated circuits is largely due to its stable native oxide, SiO₂, known for its insulating properties and excellent interface to the Si channel. However, silicon-based FETs face significant challenges when further scaled, which inspires the search for better semiconductors. While 2D materials such as MoS₂, WSe₂, BP, and InSe are promising, they lack a stable and compatible native oxide. High mobility (812 cm² V^-1 s^-1) 2D Bi₂SeO₂ stands out in this regard, as it can be oxidized into different forms of Bi₂SeO₅, thereby forming compatible high-κ native oxides. Despite growing interest in this material system, a comprehensive understanding of its fundamental properties is lacking. This study uses density functional theory and molecular dynamics simulations to investigate the intrinsic properties of Bi₂SeO₂, its native oxides, and its interfaces. Additionally, scanning transmission electron microscopy is employed to complement these theoretical analyses, providing detailed insights into the atomic-scale structure and interfaces of these materials. Building on these findings, we model semiconductor-oxide heterostructures and extract their intrinsic properties. Our results demonstrate that the atomically sharp and clean interface between oxide and semiconductor, the high dielectric constant (>30) of the oxide, and the sufficiently large conduction band offsets between the semiconductor and the most relevant β-phase of its native insulator (1.13 eV for holes and 1.55 eV for electrons) make this material system a strong candidate for future transistor technologies. These properties mitigate the limitations of traditional semiconductors and enhance device performance at the ultimate scaling limit, positioning 2D Bi₂SeO₂ as a suitable choice for next-generation nanoelectronics.