We report that highly crystalline graphene can be obtained from well-controlled surface morphology of the copper substrate. Flat copper surface was prepared by using a chemical mechanical polishing method. At early growth stage, the density of graphene nucleation seeds from polished Cu film was much lower and the domain sizes of graphene flakes were larger than those from unpolished Cu film. At later growth stage, these domains were stitched together to form monolayer graphene, where the orientation of each domain crystal was unexpectedly not much different from each other. We also found that grain boundaries and intentionally formed scratched area play an important role for nucleation seeds. Although the best monolayer graphene was grown from polished Cu with a low sheet resistance of 260 Ω/sq, a small portion of multilayers were also formed near the impurity particles or locally protruded parts.

We investigated the modulation of optical properties of single-walled carbon nanotubes (SWCNTs) by AuCl 3 doping. The van Hove singularity transitions (E 11 (S), E 22 (S), E 11 (M)) in absorption spectroscopy disappeared gradually with an increasing doping concentration and a new peak appeared at a high doping concentration. The work function was downshifted up to 0.42 eV by a strong charge transfer from the SWCNTs to AuCl 3 by a high level of p-doping. We propose that this large work function shift forces the Fermi level of the SWCNTs to be located deep in the valence band, i.e., highly degenerate, creating empty van Hove singularity states, and hence the work function shift invokes a new asymmetric transition in the absorption spectroscopy from a deeper level to newly generated empty states.

In spite of recent successful demonstrations of flexible and transparent graphene heaters, the underlying heat‐transfer mechanism is not understood due to the complexity of the heating system. Here, graphene/glass defoggers are fabricated and the dynamic response of the temperature as a function of input electrical power is measured. The graphene/glass defoggers reveal shorter response times than Cr/glass defoggers. Furthermore, the saturated temperature of the graphene/glass defoggers is higher than for Cr/glass defoggers at a given input electrical power. The observed dynamic response to temperature is well‐fitted to the power‐balance model. The response time of graphene/glass defogger is shorter by 44% than that of the Cr/glass defogger. The convective heat‐transfer coefficient of graphene is 12.4 × 10−4 W cm−2 °C−1, similar to that of glass (11.1 × 10−4 W cm−2 °C−1) but smaller than that of chromium (17.1 × 10−4 W cm−2 °C−1). The graphene‐based system reveals the lowest convective heat‐transfer coefficient due to its ideal flat surface compared to its counterparts of carbon nanotubes (CNTs) and reduced graphene oxide (RGO)‐based systems.

Despite recent progress in producing transparent and bendable thin-film transistors using graphene and carbon nanotubes, the development of stretchable devices remains limited either by fragile inorganic oxides or polymer dielectrics with high leakage current. Here we report the fabrication of highly stretchable and transparent field-effect transistors combining graphene/single-walled carbon nanotube (SWCNT) electrodes and a SWCNT-network channel with a geometrically wrinkled inorganic dielectric layer. The wrinkled Al2O3 layer contained effective built-in air gaps with a small gate leakage current of 10(-13) A. The resulting devices exhibited an excellent on/off ratio of ~10(5), a high mobility of ~40 cm(2) V(-1) s(-1) and a low operating voltage of less than 1 V. Importantly, because of the wrinkled dielectric layer, the transistors retained performance under strains as high as 20% without appreciable leakage current increases or physical degradation. No significant performance loss was observed after stretching and releasing the devices for over 1,000 times. The sustainability and performance advances demonstrated here are promising for the adoption of stretchable electronics in a wide variety of future applications.