Functional Electronic Devices Research Articles

Tunable Rectification in 2D Porphyrinic Metal–Organic Framework Nanosheets Molecular Heterojunctions

AbstractAs functional electrical devices advance, new strategies for regulating electrical properties are essential for achieving diverse electrical performance. In this study, molecular heterojunction rectifiers are constructed by connecting porphyrinic 2D metal–organic framework (2D MOF) nanosheets and oligophenylene thiols self‐assembled monolayers (OPT SAMs) within metal electrodes. The rectification characteristics can be tuned by the molecular length of OPT and the coordinated metal atom in the center of 2D MOFs. Specifically, a rectification ratio of more than 1.67 orders of magnitude is achieved in the heterojunction composed of 2D Zn‐TCPP MOF nanosheet (TCCP, tetrakis(4‐carboxyphenyl) porphyrin) and OPT3 SAM. Combining Kelvin probe force microscopy measurements and first‐principles calculations of the 2D MOF nanosheets, it elucidates that the rectification variations come from the adjustment of energy level alignment at OPT SAMs//2D MOF interface, leading to asymmetric charge transport with the voltage polarities. This strategy can be further extended to Cu‐MOF nanosheets, which also exhibit rectification behaviors when placed on OPT2 SAMs. This work provides a universal and flexible strategy for regulating the electrical behaviors of MOFs without the need for specific design and synthesis, paving the way for the development of MOF‐based functional electronic devices.

H-BN-assisted-transferred metal contacts to InSe for twodimensional multifunctional electronic devices

Abstract Metal contacts to two-dimensional semiconductors play a crucial role in determining the electrical performance of the electronic devices. However, traditional three-dimensional metal deposition processes will bring damage to two-dimensional semiconductors and cause significant Fermi-level-pinning effects. In this work, we report a hexagonal boron nitride (h-BN)-assisted-transferred method for metal contacts to few-layered InSe for construction of two-dimensional functional electronic devices. Using transferred Pt electrodes as the contact, p-type dominated ambipolar conduction behavior with the hole Schottky barrier height (SBH) approaching 0 meV was observed in field-effect transistors (FETs) based on multilayered InSe. Based on this, using a dual-gate modulating method, multiple types of InSe homojunctions, including p-p, n-n, p-n and n-p junctions, could be constructed. For InSe p-n homojunctions, a current rectification ratio of over 104 and optoelectronic detection capabilities were achieved. Furthermore, a complementary metal-oxide-semiconductor (CMOS) inverter with an ultra-high voltage gain exceeding 60 at VDD = -1 V was constructed. Our h-BN-assistedtransferred metal contact method can be easily extended to other two-dimensional semiconductors for the construction of complementary electronic and optoelectronic devices.

ProtonationDriven Polarization Retention Failure in Nano-Columnar Lead-Free Ferroelectric Thin Films.

Understanding microscopic mechanisms of polarization retention characteristics in ferroelectric thin films is of great significance for exploring unusual physical phenomena inaccessible in the bulk counterparts and for realizing thin-film-based functional electronic devices. Perovskite (K,Na)NbO3 is an excellent class of lead-free ferroelectric oxides attracting tremendous interest thanks to its potential applications to nonvolatile memory and eco-friendly energy harvester/storage. Nonetheless, in-depth investigation of ferroelectric properties of (K,Na)NbO3 films and the following developments of nano-devices are limited due to challenging thin-film fabrication associated with nonstoichiometry by volatile K and Na atoms. Herein, ferroelectric (K,Na)NbO3 films of which the atomic-level geometrical structures strongly depend on thickness-dependent strain relaxation are epitaxially grown. Nanopillar crystal structures are identified in fully relaxed (K,Na)NbO3 films to the bulk states representing a continuous reduction of switchable polarization under air environments, that is, polarization retention failures. Protonation by water dissociation is responsible for the humidity-induced retention loss in nano-columnar (K,Na)NbO3 films. The protonation-driven polarization retention failure originates from domain wall pinning by the accumulation of mobile hydrogen ions at charged domain walls for effective screening of polarization-bound charges. Conceptually, the results will be utilized for rational design to advanced energy materials such as photo-catalysts enabling ferroelectric tuning of water splitting.

Fast and Efficient Fabrication of Functional Electronic Devices through Grayscale Digital Light Processing 3D Printing.

Fabricating polymeric composites with desirable characteristics for electronic applications is a complex and costly process. Digital light processing (DLP) 3D printing emerges as a promising technique for manufacturing intricate structures. In this study, polymeric samples are fabricated with a conductivity difference exceeding three orders of magnitude in various portions of a part by employing grayscale DLP (g-DLP) single-vat single-cure 3D printing deliberate resin design. This is realized through the manipulation of light intensity during the curing process. Specifically, the rational resin design with added lithium ions results in the polymer cured under the maximum UV-light intensity exhibiting higher electrical resistance. Conversely, sections that are only partially cured retains uncured monomers, serving as a medium that facilitates ion mobility, consequently leading to higher conductivity. The versatility of g-DLP allows precise control of light intensity in different regions during the printing process. This characteristic opens up possibilities for applications, notably the low-cost, facile, and rapid production of complex electrical circuits and sensors. The utilization of this technique makes it feasible to fabricate materials with tailored conductivity and functionality, providing an innovative pathway to advance the accelerated and facile creation of sophisticated electronic devices.

Dual-Mode Reconfigurable Split-Gate Logic Transistor through Van der Waals Integration.

As silicon-based transistors approach their physical size limitations, two-dimensional material-based reconfigurable functional electronic devices are considered the most promising novel device architectures beyond Moore strategies. While these devices have garnered significant attention, they often require complex device fabrication processes and extra electric fields. Additionally, the device performance is usually limited by the metal-semiconductor interface properties. In this Letter, we have constructed a reconfigurable logic device based on a WSe2 transistor with a nanofloating gate and split-gates through van der Waals integration. This device achieves a small Schottky barrier height due to the van der Waals contacts. By varying the split-gate biases, we can realize volatile reconfigurable homojunctions as well as AND, OR, NOR, and NAND logic operations with just a single device. Furthermore, with the charge trapping effect of nanofloating gate, we can also achieve nonvolatile reconfigurable homojunctions, as well as AND and OR logic operations. The volatile and nonvolatile logic operations are similar to the short-term plasticity and long-term plasticity, respectively, of synapses in the human brain. This work offers a potential approach for creating novel reconfigurable functional electronic devices with a simple fabrication process and low cost.

Thermally Robust Aramid Triboelectric Materials Enabled by Heat‐Induced Cross‐Linking

AbstractThe rapid development of the Internet of Things has led to numerous functional electronic devices, making it a significant challenge to provide power for these distributed devices. Triboelectric self‐power technology is ideal for smart devices due to its material diversity and high energy efficiency. However, traditional triboelectric materials have weak electrostatic induction due to their low dielectric constant. Additionally, the thermionic emission effect reduces their electric output in high temperatures, limiting their applications. This study designes a thermally robust aramid triboelectric material with a high dielectric constant through heat‐induced cross‐linking heterogeneous interface engineering. This novel material not only achieves high triboelectric output but also maintains high performance across a wide temperature range. The heat‐induced cross‐linking process enhances the interaction between aramid nanofibers and Al2O3 nanosheets, significantly improving the electrical performance, and flame retardance of the material, and the relative dielectric constant increases 16‐fold. The triboelectric nanogenerator constructed with this material achieves a power density of 3.97 W m−2, and maintains high triboelectric output at 260 °C. Finally, a self‐powered detection system collects high‐temperature gas energy and drives sensors is designed. This research presents a novel strategy for high‐performance triboelectric materials, showing significant potential for self‐powered devices.

All-natural, thermally conductive, flame-retardant electrical insulating lignocellulose-mica composite film fabricated via in-situ mineralization

Miniaturized, integrated, and functional electronic devices generate a large amount of heat accumulation during operation, which significantly affects the reliability, durability, and safety of electronic devices. In severe cases, it may even lead to fires. Therefore, the development of insulation composite materials with thermal conductivity and flame-retardant properties is particularly important. In this study, we propose an in-situ mineralization strategy to prepare insulation composite materials with thermal conductivity and flame-retardant properties. By dissolving and preparing a gel film, Al3+ and Zn2+ retained inside the lignocellulose are in situ mineralized to form Al(OH)3 and ZnO, and introducing inorganic blocks with high insulation performance (industrial waste mica tailings and synthetic mica). The prepared film has excellent tensile strength (117.4 MPa), low dielectric loss, high dielectric strength (83.8 kV mm−1), high insulation resistance, four times higher thermal conductivity than the unmineralized film, and excellent flame-retardant properties. Meanwhile, the environmental impact of the composite film is much lower than that of petrochemical-based plastic films and can easily degrade under natural conditions within 32 days. It is a composite material that meets the standards of the new electrical insulation field, and the in-situ mineralization strategy can also provide ideas for the preparation of high-performance lignocellulose-based materials.

Memristive switching in the surface of a charge–density–wave topological semimetal

Owing to the outstanding properties provided by nontrivial band topology, topological phases of matter are considered as a promising platform towards low-dissipation electronics, efficient spin-charge conversion, and topological quantum computation. Achieving ferroelectricity in topological materials enables the non-volatile control of the quantum states, which could greatly facilitate topological electronic research. However, ferroelectricity is generally incompatible with systems featuring metallicity due to the screening effect of free carriers. In this study, we report the observation of memristive switching based on the ferroelectric surface state of a topological semimetal (TaSe4)2I. We find that the surface state of (TaSe4)2I presents out-of-plane ferroelectric polarization due to surface reconstruction. With the combination of ferroelectric surface and charge-density-wave-gapped bulk states, an electric-switchable barrier height can be achieved in (TaSe4)2I-metal contact. By employing a multi-terminal-grounding design, we manage to construct a prototype ferroelectric memristor based on (TaSe4)2I with on/off ratio up to 103, endurance over 103 cycles, and good retention characteristics. The origin of the ferroelectric surface state is further investigated by first-principles calculations, which reveal an interplay between ferroelectricity and band topology. The emergence of ferroelectricity in (TaSe4)2I not only demonstrates it as a rare but essential case of ferroelectric topological materials, but also opens new routes towards the implementation of topological materials in functional electronic devices.

Dynamic strain coupling driven by structural phase transition in mixed-dimensional 2H-MoS2/VO2 van der Waals heterointerfaces

Mixed-dimensional van der Waals (vdW) heterostructures, integrated two-dimensional (2D) atomic crystals with three-dimensional (3D) functional materials, offer a powerful means to manipulating physical properties and generating unprecedented functionalities. Understanding interfacial couplings at those hetero (homo)-interfaces is indispensable for exploring new optical and electronic devices. Herein, we investigated dynamically phase-transition-driven strain coupling across a vdW heterointerface through integrating 2D layered 2H-MoS2 nanoflakes onto 3D phase-change VO2 epitaxial thin films. The Raman peak positions of the in-plane and out-of-plane vibration modes E2g1 and A1g from the 2H-MoS2 nanoflakes show a phonon softening and reversible hysteresis loop as a function of temperature in this mixed-dimensional vdW 2H-MoS2/(1¯11)-VO2/(11¯02)-Al2O3 heterostructure, originating from the co-action of temperature-dependent anharmonicity in 2H-MoS2 and reversible structural phase transition (SPT)-induced in-plane tensile strain from the VO2 thin film. Accordingly, the integrated Raman scattering intensity of these two feature peaks of the 2H-MoS2 nanoflakes increased (decreased) as the temperature increased (decreased), exhibiting a hysteresis loop in the SPT and metal–insulator transition region of VO2. Additionally, the peak integrated intensity enhancement ratio of the E2g1 and A1g vibration modes was approximately 2.3 and 2.8, respectively. These results indicate that the dynamically SPT-driven in-plane tensile strain from the bottom VO2 layer interfacially couples with the adjacent 2H-MoS2 nanoflakes and results in a reduction in the electronic transition energy, leading to an enhancement in the Raman scattering intensity of 2H-MoS2. Our work holds promise for dynamic strain control of lattice dynamics and electron–phonon interaction of 2D materials for functional electronic and photoelectronic devices.

Light-Responsive Soft Robot Integrating Actuation and Function Based on Laser Cutting.

Soft robots with good deformability and adaptability have important prospects in the bionics and intelligence field. However, current research into soft robots is primarily limited to the study of actuators and ignores the integrated use of functional devices and actuators. To enrich the functions of soft robots and expand their application fields, it is necessary to integrate various functional electronic devices into soft robots to perform diverse functions during dynamic deformation. Therefore, this paper discusses methods and strategies to manufacture optical stimuli-responsive soft actuators and integrate them into functional devices for soft robots. Specifically, laser cutting allows us to fabricate an optically responsive actuator structure, e.g., the curling direction can be controlled by adjusting the direction of the cutting line. Actuators with different bending curvatures, including nonbending, can be obtained by adjusting the cutting depth, cutting width, and the spacing of the cutting line, which makes it easy to obtain a folded structure. Thus, various actuators with complex shape patterns can be obtained. In addition, we demonstrate a fabrication scheme for a worm-like soft robot integrated with functional devices (LEDs are used in this paper). The local nonbending design provides an asymmetric structure that provides driving power and avoids damage to the functional circuit caused by the large deformation during movement. The integration of drive and function provides a new path for the application of soft robots in the intelligence and bionics field.

Aging and degradation of transparent copper iodide thin film electrodes for functional electronic devices

Transparent CuJ copper iodide thin-film electrodes are widely used in various optoelectronic devices, such as solar cells, electroluminescent displays, touch screens, multifunctional photoconverters, etc. Their advantages are high transparency, because CuJ absorbs light in a limited range of wavelengths, which allows them to transmit visible light, making them ideal for transparent devices, low cost, because copper iodide is an inexpensive material, making it economically viable for mass production, simplicity fabrication, as CuJ can be easily deposited on various substrates using simple film deposition techniques such as vacuum deposition and magnetron sputtering. However, transparent CuJ type thin-film electrodes are subject to aging and degradation, which can reduce their performance and service life. The main factors affecting the aging and degradation of CuJ are the processes of oxidation, diffusion, degradation under the influence of light, and humidity. Despite numerous studies in the direction of obtaining high-quality thin films of copper iodide, today there is a need for a detailed study of the processes of their aging and degradation of properties. Therefore, in this article, we investigated the degradation processes of transparent upper copper iodide electrodes of thin-film multicomponent semiconductor heterostructures. This article shows the features of the use of film copper iodide in multilayer thin-film semiconductor structures. The influence of atmospheric conditions and lighting on the values of the rates of degradation of electrical resistance of copper iodide in semiconductor thin-film structures was studied. It has been found that atmospheric exposure to oxygen, moisture and other factors increases the electrical resistance of the copper iodide top electrode, and the use of Elastosil sealant does not lead to appreciable improvement. Heterostructures in vacuum are minimally affected by external factors, and therefore a significant increase in their CuJ upper electrode resistance values indicates the predominant role of aging of copper iodide films, which is not related to atmospheric conditions. It was established that natural sunlight significantly increases the degradation of copper iodide films, which should be taken into account when forming and using the corresponding thin film structures.

Design and fabrication of wearable electronic textiles using twisted fiber-based threads.

Mono-dimensional fiber-based electronics can effectively address the growing demand for improved wearable electronic devices because of their exceptional flexibility and stretchability. For practical applications, functional fiber electronic devices need to be integrated into more powerful and versatile systems to execute complex tasks that cannot be completed by single-fiber devices. Existing techniques, such as printing and sintering, reduce the flexibility and cause low connection strength of fiber-based electronic devices because of the high curvature of the fiber. Here, we outline a twisting fabrication process for fiber electrodes, which can be woven into functional threads and integrated within textiles. The design of the twisted thread structure for fiber devices ensures stable interfacing and good flexibility, while the textile structure features easily accessible, interlaced points for efficient circuit connections. Electronic textiles can be customized to act as displays, health monitors and power sources. We detail three main fabrication sections, including the fabrication of the fiber electrodes, their twisting into electronic threads and their assembly into functional textile-based devices. The procedures require ~10 d and are easily reproducible by researchers with expertise in fabricating energy and electronic devices.

Ultraclean Interface of Metal Chalcogenides with Metal through Confined Interfacial Chalcogenization.

Acquisition of defect-free transition metal dichalcogenides (TMDs) channels with clean heterojunctions is a critical issue in the production of TMD-based functional electronic devices. Conventional approaches have transferred TMD onto a target substrate, and then apply the typical device fabrication processes. Unfortunately, those processes cause physical and chemical defects in the TMD channels. Here, a novel synthetic process of TMD thin films, named confined interfacial chalcogenization (CIC) is proposed. In the proposed synthesis, a uniform TMDlayer is created at the Au/transition metal (TM) interface by diffusion of chalcogen through the upperAu layer and the reaction of chalcogen with the underlying TM. CIC allows for ultraclean heterojunctions with the metals, synthesis of various homo- and hetero-structured TMDs, and in situ TMD channel formation in the last stage of device fabrication. The mechanism of TMD growth is revealed by the TM-accelerated chalcogen diffusion, epitaxial growth of TMD on Au(111). We demonstrated a wafer-scale TMD-based vertical memristors which exhibit excellent statistical concordance in device performance enabled by the ultraclean heterojunctions and superior uniformity in thickness. CIC proposed in this study represents a breakthrough in in TMD-based electronic device fabrication and marking a substantial step toward practical next-generation integrated electronics.

Giant piezoelectricity and ferroelectricity in two-dimensional ThOTe monolayer

Two-dimensional flexible materials with both piezoelectric and ferroelectric properties are regarded as the holy grail for realizing ultrathin functional electronic devices, which can be used in electronic flexible skins, high-performance...

A universal chemical approach to the growth of self-assembled vanadium dioxide nanostructures

Vanadium dioxide (VO2) nanocrystalline materials are of great interest as for modern electronics and photonics as well as for energy saving technologies. Nevertheless, there still remains a challenge to realize their controllable synthesis, as evidenced by the low rate of implantation of existing technologies into mass production. Here, a hydrothermal reaction in a water-ethylene glycol (EG) solution has been coupled with the post-deposition annealing, yielding a range of phase-pure vanadium dioxide nanostructures on single-crystal r-sapphire substrate. A directed change in the viscosity of the precursor solution by using a change in the EG : H2O ratio makes it possible to control the nucleation rate and thus form VO2 isolated nanocrystals, as well as their ordered ensembles with regular distribution and uniform films on the substrate. The obtained nanostructures were extensively characterized by Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy combined with energy-dispersive X-ray spectroscopy. Continuous VO2 nanostructures demonstrated a metal-insulator transition (MIT) with a jump in resistivity of about 103–104, as well as a giant terahertz (THz) modulation depth up to 86 % (in the range from 0.3 to 2.0 THz), which confirms their high-quality and the possibility of their use in the creation of functional electronic and THz optical devices.

Epitaxial Growth of 1D Te/2D MoSe2 Mixed‐Dimensional Heterostructures for High‐Efficient Self‐Powered Photodetector

AbstractMixed‐dimensional heterostructures provide additional freedom to construct diverse functional electronic and optoelectronic devices, gaining significant interest. Herein, highly‐aligned pseudo‐1D tellurium is epitaxially grown on 2D monolayer transition metal dichalcogenides (TMDs), including MoSe2, MoS2, and WS2. A one‐pot chemical vapor deposition (CVD) technique eliminates the normally required transfer steps, thereby producing mixed‐dimensional heterostructures with an ultraclean interface. The controllable epitaxial growth of Te/TMD heterostructures are verified by Raman, scanning probe microscopy (SPM), and transmission electron microscopy (TEM) observation. The photoluminescence results indicate that the emission from TMDs is quenched in the heterostructure, confirming the efficient transfer of photogenerated carriers from TMDs to Te. Additionally, the mixed‐dimensional p‐n Te/MoSe2 heterojunction photodetector presents self‐driven behavior with high responsivity (328 mA W−1), external quantum efficiency (79%), and specific detectivity (8.2 × 109 Jones). The modified facile synthesis strategy and proposed growth mechanism in this study shed light on synthesizing mixed‐dimensional heterojunctions. This opens avenues for fabricating functional devices with reduced sizes and high densities, further enabling miniaturization and integration opportunities.

Portable triboelectric-electromagnetic hybrid biomechanical energy harvester for driving various functional light-emitting diodes with a wide range of wavelengths

As the application range of light-emitting diode (LED) has rapidly expanded in various fields and functional LED-implanted electronic devices have deeply permeated human daily lives, research on the electrically off-grid power supply method for LEDs is being widely conducted around the world in order to further strengthen and utilize the strong points of LEDs. In this study, a shaft-shared triboelectric-electromagnetic hybrid portable energy harvester (STEP) considering the electromotive force-based hybridization is proposed to drive various functional LEDs with a wide range of wavelengths using biomechanical energy. The respective roles and functionalities of triboelectric nanogenerator (TENG) and electromagnetic generator (EMG) in a hybrid energy harvester are experimentally and visually demonstrated by comparative investigation in parallel and series circuits. Then, based on the experimental result, the necessity of hybridization of TENG and EMG is described from the perspective of both electromotive force and current for the LED-involved devices. When the STEP operation speed is 500 rpm, the average output voltage and current of the TENG and EMG parts are experimentally characterized, and the average output voltage from TENG is 238 V and the average output current from EMG is 18 mA. The maximum peak powers of TENG and EMG are 1.92 and 26.7 mW when the external load resistances are 30 MΩ and 400 Ω, respectively. STEP is portable in size and weight, and it can be operated by human force thanks to an optimally designed gearbox. When STEP is driven by human power, it can power a variety of functional LEDs ranging from 275 to 850 nm of wavelengths, including 250 visible, 50 infrared, and dozens of UV LEDs. Given that the superior functionalities of LEDs have been validated, and that the synergistic effect through convergence with electrical grid-independent power supply technology is thought to have great potential in a variety of fields, STEP is expected to serve as a guideline for effective energy supply strategy to various functional LEDs in related fields such as lighting, engineering, security, and healthcare industries.

Ultra-flexible silver/iron nanowire decorated melamine composite foams for high-efficiency electromagnetic wave absorption and thermal management

Nowadays, functional electronic devices with excellent flexibility and thermal management capability for effective electromagnetic wave absorption are urgently in demand. Herein, a novel and highly flexible silver nanowire (AgNW)/iron nanowire (FeNW) decorated melamine composite foam (AgFe-MF) was prepared via simple dip-coating process. Owing to optimal impedance matching, synergistic dielectric and magnetic losses as well as three-dimensional porous structure, the AgFe-MF with an ultra-low filler content (0.22 vol%) exhibited an outstanding minimum reflection loss of −69.61 dB, and the best effective absorption bandwidth (EAB) could reach up to 6.37 GHz. Importantly, the EAB of long-time working AgFe-MF was enhanced to 7.01 GHz after 1000 compress-release cycles under 40 % strain. Besides, it also featured considerate Joule heating capacity and achieved a saturation temperature of over 85.7 ℃ under 2.6 V voltage. The impressive thermal isolation and long-term stability ensured the safety used as portable heater. Therefore, this work will provide a vital slight for fabricating smart wearable electronic devices with integrated anti-electromagnetic radiation and personalized thermal management performances towards potential thermal and health threats.

Laser-induced structural modulation and superconductivity in SrTiO3

Under normal conditions, stoichiometric SrTiO3 is an excellent dielectric. It shows a structural phase transition, from cubic to tetragonal, below 105 K. In this structure, well separated domains hosting tetragonal phases with different long axes exist giving rise to the so-called X, Y, and Z domains. At very low temperatures, it becomes a quantum paraelectric in which local ferroelectric domains are found at the X, Y, and Z domain boundaries. Creation of oxygen vacancy in SrTiO3 makes it conducting with low carrier density which also undergoes an unconventional superconducting transition at sub-kelvin temperatures. We have created structural phase separation with clear domain boundaries (as in the X, Y, and Z domains) at room temperature on single crystals of SrTiO3 by irradiating the surface with high power density excimer laser pulses. We find that the domain boundaries are dominantly conducting, and the irradiated crystals undergo a superconducting phase transition below 180 mK indicating that the superconducting phase appears at the domain boundaries. This concurrence of local ferroelectricity and superconductivity in lightly doped SrTiO3 supports a ferroelectric fluctuation mediated Cooper pairing in the system. The results also point out the possibility of controlling ferroelectricity and superconductivity in functional electronic devices through surface engineering.

Highly doped graphene on ion-exchanged glass

Engineering the doping level in graphene is essential to realizing functional electronic and optoelectronic devices. While achieving strong p-doping is relatively straightforward, electrostatic or chemical approaches to negatively dope graphene have yielded electron densities (ns ) of −9.5 × 1012 cm−2 or below. In this work, we demonstrate very high ns (−1013 to −1014 cm−2) in graphene, on an ion-exchanged glass substrate, which is widely used in touch screen displays (e.g. smart phones). Moreover, the proposed method, which is easy to implement and scalable, leads to relatively stable graphene doping, with about a 40% increase in sheet resistance over 5 months at ambient conditions.