A quantum-tunneling metal-insulator-metal (MIM) diode is fabricated by atmospheric pressure chemical vapor deposition (AP-CVD) for the first time. This scalable method is used to produce MIM diodes with high-quality, pinhole-free Al 2 O 3 films more rapidly than by conventional vacuum-based approaches. This work demonstrates that clean room fabrication is not a prerequisite for quantum-enabled devices. In fact, the MIM diodes fabricated by AP-CVD show a lower effective barrier height (2.20 eV) at the electrodeinsulator interface than those fabricated by conventional plasma-enhanced atomic layer deposition (2.80 eV), resulting in a lower turn on voltage of 1.4 V, lower zero-bias resistance, and better asymmetry of 107.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201805533. dielectric layer sandwiched between two metal contacts. MIM diodes are capable of rectification in the high frequency range due to a femtosecond quantum-tunneling electron transport mechanism through the insulator, making them attractive for applications in solar rectennas, [1] infrared detectors, [2,3] and wireless power transmission. [4] However, the insulator layer in the MIM stack, which plays a crucial role in determining the diode performance, [5] is typically deposited using vacuum-based methods, such as sputtering, [6] anodic oxidation of sputtered films, [7] electron beam deposition, [8] and especially atomic layer deposition (ALD), [9] which is commonly used due to its ability to deposit nanoscale films with high accuracy and uniformity. High-throughput fabrication of MIM diodes is limited by slow deposition rates and the need for a vacuum environment. Scalable techniques are therefore needed for depositing nanoscale films for the next generation of integrated quantum devices. Some deposition processes have been introduced to fabricate thin films at atmospheric pressure for nanoelectronic devices that utilize quantum phenomena. Thermal and anodic oxidation, for example, have been used to grow thin CrO x and Nb 2 O 5 films on Cr and Nb layers for MIM diodes [7,10] ; atmospheric pressure metal organic vapor phase epitaxial growth (AP-MOVPE), or atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD), has been used to fabricate InGaAsP multiquantum-well structures for optical devices [11] ; the Langmuir Blodgett technique was used to deposit a ZnO film for a MIM diode [12] ; and a chemical vapor deposition (CVD) furnace operated at atmospheric pressure has been used to deposit a TiO 2 film in a tunneling transistor. [13] The need for high temperatures, specific metal films for oxidation, and complex compound precursors in these techniques, as well as challenges in reproducibility, highlight the need for new methods to reliably deposit enabling films for cost-effective quantum devices. Recently, atmospheric pressure spatial atomic layer deposition (AP-SALD) systems have been utilized to grow uniform films for different applications including solar cells...

biomedicine, [2,3] tribology, [4] photonics, [5] and electrocatalysis, [6] among others. Significant progress has been made recently in fabricating and functionalizing 2D nanosheets of transition metal dichalcogenides. [7] This progress has focused on the functionalization of mono-or few-layer nanosheets with lateral dimensions greater than 100 nm by combining chemical exfoliation, [8][9][10][11][12] micromechanical exfoliation, [13] or liquid exfoliation [14] with the reaction of functionalities. The formation and functionalization of smaller 2D nanoparticles or quantum dots, on the other hand, is still in its infancy.In what has been cited as the first direct evidence of covalent functionalization of a nanoscale transition metal dichalcogenide, Tuxen et al. produced MoS 2 monolayer nanoclusters in ultrahigh vacuum on a gold substrate and attached dibenzothiophene molecules to the clusters via controlled vapor exposure. [15,16] Beyond substrate-supported nanoclusters, the functionalization of nongraphene 2D nanoparticles suspended in solution was reported last year. Atkin et al. combined ultrasonication of WS 2 with microwave treatment in a citric acid-containing solution to produce monolayer WS 2 nanosheets ≈20-80 nm in diameter decorated with 2-5 nm carbon dots. [6] Jung et al. impinged BN flakes with super-heated nanoparticles then exposed them to water vapor to produce edge-hydroxylated BN quantum dots with 8 nm lateral size. [2] These techniques for fabricating and functionalizing 2D nanosheets and smaller nanoparticles are relatively slow (in some cases requiring several days), often require dangerous chemicals and elevated temperatures, and their demonstration has been material specific. In the case of functionalized 2D nanoparticles other than graphene, such as functionalized MoS 2 , WS 2 , and BN quantum dots, potentially exciting multifunctional optical properties have not been realized. The ability to produce a variety of hybrid 2D nanoparticles that possess the optical properties of both the host 2D material and functional groups would be extremely valuable for many of the aforementioned applications.We introduce a rapid femtosecond laser technique that simultaneously reduces the dimensions of flakes of 2D materials to a few nanometers and dissociates solvent molecules to bond with the edges of the freshly cleaved 2D sheets, in order to produce functionalized nanoparticles of 2D materials. Etha nol, a common and inexpensive solvent, is used to facilitate functionalization A general, rapid technique is introduced to simultaneously fabricate and functionalize nanoparticles of 2D materials. A femtosecond laser is used to irradiate flakes of 2D materials in an ethanol-containing solvent. The highly energetic laser pulses exfoliate and cleave the flakes into nanosheets with diameters of ≈3 nm and simultaneously dissociate the solvent molecules. The dissociated carbon and oxygen atoms bond with the freshly cleaved 2D nanoparticles to satisfy edge sites, resulting in the formation of hybrid 2D nanoparticles...

A novel process to synthesize plasmonic MoO3–X nanosheets is demonstrated, in which MoS2 powders suspended in ethanol/water are irradiated with pulses from a femtosecond laser, resulting in simultaneous Coulomb explosion, photoexfoliation, and oxidation. The oxidation process is found to start with the formation of hydrogen-bonded molybdenum oxide (H X MoO3), followed by the release of −OH2 groups to create oxygen vacancies, and finally, MoO3–X is oxidized to MoO3 after extended irradiation. The formation of H X MoO3 is the critical step to create enough oxygen vacancies for localized surface plasmon resonance (LSPR), and this step is attributed to H3 + dissociated from ethanol under femtosecond laser irradiation. It is found that 80–90% ethanol is the optimal concentration to synthesize plasmonic MoO3–X , where the balance of water facilitates the release of the −OH2 groups to create the required vacancies. It is shown that different organic solvents like methanol, 1-propanol, and isopropyl alcohol that were reported to generate large amounts of H3 + under femtosecond laser irradiation can also oxidize MoS2 into plasmonic MoO3–X . The LSPR properties of the synthesized MoO3–X are evaluated by UV–vis spectroscopy and photothermal conversion measurements. A photothermal conversion efficiency of 33% is observed under near-infrared irradiation, suggesting a potential application in photothermal cancer therapy.

Abstract-Hyper-heuristics are a class of high-level search techniques which operate on a search space of heuristics rather than directly on a search space of solutions. Early hyperheuristics focussed on selecting and applying a low-level heuristic at each stage of a search. Recent trends in hyper-heuristic research have led to a number of approaches being developed to automatically generate new heuristics from a set of heuristic components. This work investigates the suitability of using genetic programming as a hyper-heuristic methodology to generate constructive heuristics to solve the multidimensional 0-1 knapsack problem. A population of heuristics to rank knapsack items are trained on a subset of test problems and then applied to unseen instances. The results over a set of standard benchmarks show that genetic programming can be used to generate constructive heuristics which yield human-competitive results.

Graphene and its functionalized derivatives are unique and multifaceted novel materials with a wide range of applications in chemistry, healthcare, and optoelectronic engineering. 3D graphene materials exhibit several advantages over 2D (monolayer) graphene for a variety of devices applications. Here a novel and effective room temperature technique is introduced to convert an aqueous graphene oxide solution into a reduced graphene oxide gel with tunable physical and chemical properties comparable to a monolayer graphene sheet, without the need for any additives or chemical agents. The femtogel is synthesized by exposing an ultrahigh concentration graphene oxide solution with single‐layer flakes to high intensity femtosecond laser pulses. The femtosecond laser beam is focused on the air/aqueous solution interface to enhance the vaporization of functional groups and water, enabling femtogel formation. By controlling the pulsed laser intensity, beam focal parameters, and pulse duration, it is possible to produce several milliliters of femtogel in as little as 8 min. Through initial optimization of the irradiation parameters, a thin film is produced from a femtogel that demonstrates a surface roughness less than 6 nm, and more than 95% reduction in OH absorbance, as compared to a thin film produced from the unexposed graphene oxide solution.

Nanoscale films are integral to all modern electronics. To optimize device performance, researchers vary the film thickness by making batches of devices, which is time‐consuming and produces experimental artifacts. Thin films with nanoscale thickness gradients that are rapidly deposited in open air for combinatorial and high‐throughput (CHT) studies are presented. Atmospheric pressure spatial atomic layer deposition reactor heads are used to produce spatially varying chemical vapor deposition rates on the order of angstroms per second. ZnO and Al2O3 films are printed with nm‐scale thickness gradients in as little as 45 s and CHT analysis of a metal‐insulator‐metal diode and perovskite solar cell is performed. By testing 360 Pt/Al2O3/Al diodes with 18 different Al2O3 thicknesses on one wafer, a thicker insulator layer (≈7.0 nm) is identified for optimal diode performance than reported previously. Al2O3 thin film encapsulation is deposited by atmospheric pressure chemical vapor deposition (AP‐CVD) on a perovskite solar cell stack for the first time and a convolutional neural network is developed to analyze the perovskite stability. The rapid nature of AP‐CVD enables thicker films to be deposited at a higher temperature than is practical with conventional methods. The CHT analysis shows enhanced stability for 70 nm encapsulation films.

which is reflected in the sheer number of review articles on the topic. [1-9] Detection of VOCs in exhaled breath has been particularly useful for the diagnosis of a broad range of diseases such as diabetes, liver and lung disorders, and different forms of cancer. [10] 2D nanomaterials such as graphene oxide (GO), molybdenum disulfide (MoS 2), and tungsten disulfide (WS 2) are viable candidates for use in chemical gas sensors due to their large specific surface area that can be tailored for analyte adsorption. 2D nanomaterials have been primarily used for the detection of toxic gasses and pollutants such as nitrogen dioxide (NO 2), hydrogen disulfide (H 2 S), carbon monoxide (CO), and carbon dioxide (CO 2), [1-3,11] while the detection of VOCs by these materials has been limited. GO, [12,13] MoS 2 , [14,15] and WS 2 [16,17] have all shown a response to water vapor or relative humidity changes. Without the aid of other compounds or dopants, graphene oxide has shown a response to ethanol [18,19] and toluene vapors. [20] Similarly, MoS 2 and WS 2 have shown a response to vapors of ethanol, acetone, hexane, toluene, and benzene. [21-23] In most of these reports, the sensing material is casted over a set of interdigitated electrodes to form a chemoresistive sensor. The interaction between analyte vapors and the sensing material (i.e., through

transparency thus connected networks of 1D nanomaterials [5] have been studied as a viable alternative to thin films of indium tin oxide, which suffer from drawbacks such as brittleness and indium scarcity. [6] Materials such as graphene and transition metal dichalcogenides (TMDs) exhibit excellent electrical properties due to their "flat" 2D chemical structure. Sheets or flakes of these materials can allow for large area coverage with high conductivity but typically at the expense of transparency. [7,8] An approach to improving transparency is utilizing these materials in 1D nanorod-like structures. Carbon nanotubes (CNTs) are the most popular 1D variant of graphene and have been utilized to form large area conducting films, although challenges remain with respect to their purification [9,10] and aggregation. [5] As an alternative to CNTs, the synthesis of carbon-based nanorods has been reported by utilizing arc discharge [11] and microwave plasma chemical vapor deposition (CVD) [12] methods. However, the arc discharge method requires an extensive filtering (Soxhlet extraction) and drying process, while the CVD method requires a high power and temperature (e.g., 850 °C). The growth of graphene nanoribbons has also been reported by ultrahigh vacuum thermal evaporation [13] and hydrothermal techniques, [14] yielding lengths of 20-450 nm and widths of 2-40 nm.In regards to TMDs, molybdenum disulfide (MoS 2 ) nanorods have been synthesized via a redox reaction in an aqueous solution (yielding a nanorod mixture of binary oxides (Mo x O y ) and binary sulfides (Mo x S y )), [15] hydrothermal synthesis, [16] and hydrothermal synthesis of MoO 3 nanorods combined with sulfurization. [17] Similar to MoS 2 , the synthesis of tungsten disulfide (WS 2 ) nanorods has been accomplished by lengthy hydrothermal [18,19] and sulfidation [20] methods. Zhang et al. used high energy ball milling of WS 2 powder for 122 h, after which the powder was used as a precursor in a hydrothermal reaction for nanorod growth. [21] Ball milling methods have also been used to produce boron nitride (BN) nanorods. Boron carbide powders were milled for 100 h and subsequently treated with nitrogen at high temperature to produce BN nanorods. [22][23][24] In another approach, Museur et al. synthesized BN nanorods embedded in amorphous boron suboxides (B x O y ) through UV laser irradiation of a compacted BN powder pellet in a high-pressure nitrogen environment. [25] Table 1 summarizes these previous efforts to fabricate nanorods of 2D materials. Many of these methods require Herein, the previously unrealized ability to grow nanorods and nanotubes of 2D materials using femtosecond laser irradiation is demonstrated. In as short as 20 min, nanorods of tungsten disulfide, molybdenum disulfide, graphene, and boron nitride are grown in solutions. The technique fragments nanoparticles of the 2D materials from bulk flakes and leverages molecular scale alignment by nonresonant intense laser pulses to direct their assembly into nanorods up to several micrometers i...