A method is presented that allows for the first time the preparation of highly defined polymer brush coatings on the wafer-scale under ambient conditions (room temperature, exposure to air) from a broad variety of monomers. The discovered high oxygen-tolerance of the surface-initiated Cu(0)-mediated controlled radical polymerization (SI-CuCRP) yields entire wafers homogeneously covered by a polymer brush of linear, high molar mass polymers with narrow dispersities (Đ = 1.1) at extremely high grafting densities (≈1 chain per nm 2 ). The low-tech and air tolerant method requires only ≲4 mL reaction solution containing a monomer and a ligand between two facing substrates. Thus, the SI-CuCRP is scalable to any surface area with minimal costs and minimal equipment. Despite the simplicity of the method, the high endgroup fidelity of SI-CuCRP is demonstrated by the preparation of a tetrablock copolymer brush which is the first example of a higher order block copolymer brush prepared by any surface-initiated polymerization. Finally, we present a new facile lithographic technique, the copper plate proximity printing (CP 3 ), which relies on the proximity of the bulk copper surface to the initiator-bearing substrate. The CP 3 is resist-and development-free and transfers the copper plate profile (of a copper coin) directly into an image composed of a 3D polymer brush. † Electronic supplementary information (ESI) available. See

The search for ways to synthesize single wall carbon nanotubes (SWCNT) of a given electronic type in a controlled manner persists despite great challenges because the potential rewards are huge, in particular as a material beyond silicon. In this work we take a systematic look at three primary aspects of semiconducting enriched SWCNT grown by chemical vapor deposition. The role of catalyst choice, substrate, and feedstock mixture are investigated. In terms of semiconducting yield enhancement, little influence is found from either the binary catalyst or substrate choice. However, a very clear enrichment is found as one adds nominal amounts of methanol to an ethanol feedstock. Yields of up to 97% semiconducting SWCNT are obtained. These changes are attributed to two known etchant processes. In the first, metal SWCNT are preferentially etched. In the second, we reveal etchants also preferentially etch small diameter tubes because they are more reactive. The etchants are confirmed to have a dual role, to preferentially etch metallic tubes and narrow diameter tubes (both metallic and semiconducting) which results in a narrowing of the SWCNT diameter distribution. ■ INTRODUCTIONWithin the search for materials suitable for electronic devices beyond silicon, single-walled carbon nanotubes (SWCNT) are regarded as a leading candidate due to their outstanding electrical and physical properties, i.e. high mobility and high current-carrying capacities. 1−4 More interestingly, closely packed arrays of parallel aligned SWCNT, as the active channel material, 5,6 are attractive for the scalable fabrication of highly integrated circuits. 2,7 Such SWCNT circuits will provide obvious improvements to the on-driving current, charge carrier mobility, cutoff frequency, and device-to-device consistency, as well as offer compatibility with existing Si fabrication technology. 1,3 In order to realize this goal, the SWCNT should possess the following essential characteristics; be in highdensity and be well-aligned with a controlled orientation and, ideally, all be high-purity semiconducting nanotubes of a controlled conductivity type, ultimately of a single chirality. 3,7,8 While dense SWCNT arrays can carry higher currents in thin film transistors (TFT) and are more robust for integrated circuits, it is semiconducting-rich SWCNT arrays that guarantee high on/off ratios enabling efficient switching. 3,5,7,8 Therefore, the reproducible fabrication of type-selected, semiconducting (sc-) SWCNT on different substrates is crucial. 4,8 The current bottleneck is that most current SWCNT synthesis routes yield a mix of both metallic (m-) and semiconducting (sc-) SWCNT. 2,4,7 This negatively affects the performance of devices based on mixed metallic and semiconducting tubes. 7−9 Currently, there are two main competing approaches for the preparation of semiconducting-rich SWCNT; in the first, preselected semiconducting nanotubes are deposited on the target substrate from solution. 10,11 This strategy has had success regarding separation of the nanotube...

The interface between a carbon nanotube (CNT) and its environment can dramatically affect the electrical properties of CNT-based field-effect transistors (FETs). For such devices, the channel environment plays a significant role inducing doping or charge traps giving rise to hysteresis in the transistor characteristics. Thereby the fabrication process strongly determines the extent of those effects and the final device performance. In CNT-based devices obtained from dispersions, a proper individualization of the nanotubes is mandatory. This is generally realized by an ultrasonic treatment combined with surfactant molecules, which enwrap nanotubes forming micelle aggregates. To minimize impact on device performance, it is of vital importance to consider post-deposition treatments for removal of surfactant molecules and other impurities. In this context, we investigated the effect of several wet chemical cleaning and thermal post treatments on the electrical characteristics as well as physical properties of more than 600 devices fabricated only by wafer-level compatible technologies. We observed that nitric acid and water treatments improved the maximum-current of devices. Additionally, we found that the ethanol treatment successfully lowered hysteresis in the transfer characteristics. The effect of the chemical cleaning procedures was found to be more significant on CNT-metal contacts than for the FET channels. Moreover, we investigated the effect of an additional thermal cleaning step under vacuum after the chemical cleaning, which had an exceptional impact on the hysteresis behavior including hysteresis reversal. The presence of surfactant molecules on CNT was evidenced by X-ray photoelectron and Raman spectroscopies. By identifying the role of surfactant molecules and assessing the enhancement of device performance as a direct consequence of several cleaning procedures, these results are important for the development of CNT-based electronics at the wafer-level.

Single-walled carbon nanotubes (SWCNTs) were decorated with metal nanoparticles. Using a complementary analysis with spatially resolved micro-Raman spectroscopy, high resolution transmission electron microscopy, electron diffraction, and tip-enhanced Raman spectroscopy, we show that the SWCNTs form bundles in which smaller diameter SWCNTs are the ones preferentially affected by the presence of Au and Ag nanoparticles. This result is exploited to evaluate the structural organization of SWCNTs with mixed chiralities in bundles, leading us to postulate that smaller diameter SWCNTs surround larger ones. We found that this effect occurs for very distinct scenarios including SWCNTs both in nanometer thin films and in field effect transistor configurations at the wafer-level, suggesting a universal phenomenon for SWCNTs deposited from dispersions.