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The ability to deposit conformal catalytic thin fi lms enables opportunities to achieve complex nanostructured designs for catalysis. Atomic layer deposition (ALD) is capable of creating conformal thin fi lms over complex substrates. Here, ALD-MnO x on glassy carbon is investigated as a catalyst for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), two reactions that are of growing interest due to their many applications in alternative energy technologies. The fi lms are characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, ellipsometry, and cyclic voltammetry. The as-deposited fi lms consist of Mn(II) O, which is shown to be a poor catalyst for the ORR, but highly active for the OER. By controllably annealing the samples, Mn 2 O 3 catalysts with good activity for both the ORR and OER are synthesized. Hypotheses are presented to explain the large difference in the activity between the MnO and Mn 2 O 3 catalysts for the ORR, but similar activity for the OER, including the effects of surface oxidation under experimental conditions. These catalysts synthesized though ALD compare favorably to the best MnO x catalysts in the literature, demonstrating a viable way to produce highly active, conformal thin fi lms from earth-abundant materials for the ORR and the OER.

Flexible and disposable sensors have great potential toward applications such as medical diagnostics, food safety and environmental monitoring. [ 1 , 2 ] Radio frequency identifi cation (RFID) tags were originally developed for identifi cation and tracking purposes. When RFID tags are combined with fl exible organic sensors, they could function as wireless sensors while possessing the merits of organic electronics, such as mechanical fl exibility, light weight and low cost. Remote temperature sensors would offer the possibility of monitoring temperature of human body, perishable food and medicine by simply attaching a fl exible tag. Several types of temperature sensors have been fabricated on fl exible substrates, such as thermocouples, [ 3 ] resistive temperature detectors (RTDs), [ 4 ] and organic diodes. [ 5 ] Thermocouples are based on the Seebeck effect and typically generate a voltage change between 40 to 70 μ V/ ° C. [ 3 , 6 ] As the resistance change of a standard 100 Ω RTD is only 0.4 Ω / ° C, [ 3 , 6 ] the readout of these temperature sensors requires hihgly accurate and complex electronic circuits, i.e. high gain amplifi ers and high precision analog to digital converters (ADCs), [ 7 ] making it diffi cult for integration and hence increases the overall cost in their fabrication process.In this work, we developed Ni microparticle-fi lled binary polymer composites as temperature sensors with greater improved reproducibility compared to single polymer composites. These materials showed a much higher sensitivity than other types of fl exible temperature sensors. In addition, the higher improved sensitivity enabled us to fabricate a wireless temperature sensor by integrating it with a passive RFID antenna. Our temperature sensor consists of a Ni microparticle-fi lled binary polymer composite with polyethylene (PE) and polyethylene oxide (PEO) as the matrix designed to be highly sensitive for monitoring human body temperature. Conductive particle-fi lled polymer composites have already been widely used commercially as antistatic and electromagnetic interference shielding materials. [ 8 ] In addition, it has also been shown that some polymer composites showed several orders of resistivity change with temperature. This phenomenon has been explored for self-limiting heating elements, over-current protectors and resettable fuses. [ 9 ] However, conductive particle-fi lled polymer composites have yet been used as temperature sensor. This is primarily due to the diffi culty in achieving a reproducible temperature sensing response. [10][11][12] Additionally, the sensitive ranges previously reported were > 70 ° C, [13][14][15] which is much higher than the temperature range needed for medical diagnostics, food safety and environmental monitoring.In our system, we chose a matrix polymer blend with both semi-crystalline PEO and PE. The resistivity versus temperature characteristic of a metal microparticle-fi lled polymer is determined largely by the thermal behavior of the polymer. As shown in Table 1 , amorphous ...

One-dimensional defects in graphene have a strong influence on its physical properties, such as electrical charge transport and mechanical strength. With enhanced chemical reactivity, such defects may also allow us to selectively functionalize the material and systematically tune the properties of graphene. Here we demonstrate the selective deposition of metal at chemical vapour deposited graphene's line defects, notably grain boundaries, by atomic layer deposition. Atomic layer deposition allows us to deposit Pt predominantly on graphene's grain boundaries, folds and cracks due to the enhanced chemical reactivity of these line defects, which is directly confirmed by transmission electron microscopy imaging. The selective functionalization of graphene defect sites, together with the nanowire morphology of deposited Pt, yields a superior platform for sensing applications. Using Pt-graphene hybrid structures, we demonstrate high-performance hydrogen gas sensors at room temperature and show its advantages over other evaporative Pt deposition methods, in which Pt decorates the graphene surface non-selectively.

2D materials are layered crystalline materials and are the most attractive nanomaterials due to their potentials in next-generation electronics. Because most 2D materials are atomically thin, a suitable fabrication process without degradation of the original properties of the material is required to realize 2D-material-based devices. Atomic layer deposition (ALD) is an ideal technique for adding materials with atomic scaling precision to nanomaterials. Due to the surface-sensitive reactions of ALD, growth on 2D materials is strongly affected by the surface properties of the 2D materials. In this Perspective, ALD growth on 2D materials is reviewed and discussed with previously reported results to provide insights to readers who are investigating 2D materials and relevant topics.

Achieving complete absorption of visible light with a minimal amount of material is highly desirable for many applications, including solar energy conversion to fuel and electricity, where benefits in conversion efficiency and economy can be obtained. On a fundamental level, it is of great interest to explore whether the ultimate limits in light absorption per unit volume can be achieved by capitalizing on the advances in metamaterial science and nanosynthesis. Here, we combine block copolymer lithography and atomic layer deposition to tune the effective optical properties of a plasmonic array at the atomic scale. Critical coupling to the resulting nanocomposite layer is accomplished through guidance by a simple analytical model and measurements by spectroscopic ellipsometry. Thereby, a maximized absorption of light exceeding 99% is accomplished, of which up to about 93% occurs in a volume-equivalent thickness of gold of only 1.6 nm. This corresponds to a record effective absorption coefficient of 1.7 × 10(7) cm(-1) in the visible region, far exceeding those of solid metals, graphene, dye monolayers, and thin film solar cell materials. It is more than a factor of 2 higher than that previously obtained using a critically coupled dye J-aggregate, with a peak width exceeding the latter by 1 order of magnitude. These results thereby substantially push the limits for light harvesting in ultrathin, nanoengineered systems.

High-quality Co films with low resistivity ͑10 ⍀ cm͒ were deposited by plasma-enhanced atomic layer deposition ͑PE-ALD͒ from metallorganic precursors and NH 3 plasma. The deposition characteristics and film properties were investigated. Especially, we compared the results using two cyclopentadienyl Co precursors, CoCp͑CO͒ 2 and CoCp 2 . While low resistivity Co films were deposited by both precursors, much better self-limiting behavior was observed for CoCp 2 . Rutherford backscattering and X-ray photoelectron spectroscopy analysis have shown that the impurity contents in PE-ALD Co film were very low. CoSi 2 formation by post deposition annealing with Ti capping layer was studied by synchrotron X-ray diffraction.The contact resistance increase with decreasing line width for the source/drain contact using TiSi 2 as a contact material poses a serious problem with device scaling. 1 CoSi 2 has been studied as an alternative due to its immunity to the shrinkage of line width, low resistivity, and thermal stability. 2,3 In other words, the sheet resistance of CoSi 2 remains almost constant with scaling down while that of TiSi 2 steeply increases. The effect is routinely mentioned as a fine line effect. 4 Sputtering has been a standard deposition technique for Co, which is annealed to form CoSi 2 contact through self-aligned silicide process. In current dynamic random access memory ͑DRAM͒ technology, stacked capacitor structure has benefits over trench capacitor for abiding by the scaling down of the memory devices. 5 For stacked capacitor structure, however, the capacitor-over-bitline ͑COB͒ requires that the contact material should be formed in deep contact holes with high aspect ratio. Thus, inherent poor step coverage of sputtering is becoming more problematic for sub-50 nm technology node high density DRAM fabricaiton. 6,7 Atomic layer deposition ͑ALD͒ is a promising deposition technique in the nanoscale regime due to its excellent conformality and thickness controllability at atomic scale. However, ALD of Co has rarely been reported except for recent reports using laboratorysynthesized acetamidinate precursor, without detailed film properties. 8,9 The ALD of high-quality Co using commercially available Co precursors is important for the implementation of Co ALD for nanoscale device contact fabrication. In this study, we developed a plasma-enhanced ALD ͑PE-ALD͒ process using metallorganic ͑MO͒ precursors and NH 3 plasma. High purity Co thin films with low resistivity, close to the bulk value, were successfully deposited using various metallorganic Co precursors, including biscyclopentadienyl Co ͑CoCp 2 ͒ and cyclopentadienyl dicarbonyl Co ͑CoCp͑CO͒ 2 ͒. We compared the growth characteristics and film properties of PE-ALD from these two cyclopentadienyl Co precursors.A remote plasma-enhanced ALD system was built and used in this study. A detailed configuration of the chamber can be found in our previous report. 10 To produce adequate vapor pressure, the temperature of the bubbler containing CoCp 2 ͑solid͒ was maintai...

The formation of Pt nanowires (NWs) by atomic layer deposition on highly ordered pyrolytic graphite (HOPG) is investigated. Pt is deposited only at the step edges of HOPG and not on the basal planes, leading to the formation of laterally aligned Pt NWs. A growth model involving a morphological transition from 0-D to 1-D structures via coalescence is presented. The width of the NWs grows at a rate greater than twice the vertical growth rate. This asymmetry is ascribed to the wetting properties of Pt on HOPG as influenced by the formation of graphene oxide. A difference in Pt growth kinetics based on crystallographic orientation may also contribute.