Low density carbon nanotube forest as an index-matched and near perfect absorption coating

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98687/1/ApplPhysLett_99_211103.pd

Case studies of electrical characterisation of graphene by terahertz time-domain spectroscopy

Graphene metrology needs to keep up with the fast pace of developments in graphene growth and transfer. Terahertz time-domain spectroscopy (THz-TDS) is a non-contact, fast, and non-destructive characterization technique for mapping the electrical properties of graphene. Here we show several case studies of graphene characterization on a range of different substrates that highlight the versatility of THz-TDS measurements and its relevance for process optimization in graphene production scenarios

The Effect of Ethanol on Abnormal Grain Growth in Copper Foils

Single-crystal Cu not only has high electrical and thermal conductivity, but can also be used as a promising platform for the epitaxial growth of two-dimensional materials. Preparing large-area single-crystal Cu foils from polycrystalline foils has emerged as the most promising technique in terms of its simplicity and effectiveness. However, the studies on transforming polycrystalline foil into large-area single-crystal foil mainly focus on the influence of annealing temperature and strain energy on the recrystallization process of copper foil, while studies on the effect of annealing atmosphere on abnormal grain growth behavior are relatively rare. It is necessary to carry out more studies on the effect of annealing atmosphere on grain growth behavior to understand the recrystallization mechanism of metal. Here, we found that introduction of ethanol in pure argon annealing atmosphere will cause the abnormal grain growth of copper foil. Moreover, the number of abnormally grown grains can be controlled by the concentration of ethanol in the annealing atmosphere. Using this technology, the number of abnormally grown grains on the copper foil can be controlled to single one. This abnormally grown grain will grow rapidly to decimeter-size by consuming the surrounding small grains. This work provides a new perspective for the understanding of the recrystallization of metals, and a new method for the preparation of large-area single-crystal copper foils

Room temperature broadband terahertz gains in graphene heterostructures based on inter-layer radiative transitions

We exploit inter-layer radiative transitions to provide gains to amplify terahertz waves in graphene heterostructures. This is achieved by properly doping graphene sheets and aligning their energy bands so that the processes of stimulated emissions can overwhelm absorptions. We derive an expression for the gain estimation and show the gain is insensitive to temperature variation. Moreover, the gain is broadband and can be strong enough to compensate the free carrier loss, indicating graphene based room temperature terahertz lasers are feasible

Gas-particle partitioning process contributes more to nitrate dominated air pollution than oxidation process in northern China

Nitrate has been recognized as a key aerosol component in regional haze formation in China. However, reducing nitrate aerosol concentration remains a major challenge. Generally, the formation of particulate nitrate (NO3-) is mainly affected by two processes: oxidation (to generate gaseous HNO3 or particulate NO3-) and gas-particle partitioning (HNO3-NO3- partition). Here, we proposed a new method to explore the contributions of above two processes (CobsOxi (%) and CobsG/P (%)) to nitrate formation based on field observation, and combined theoretical calculation and modeling to verify it. Quantitative results showed that gas-particle partitioning process (average CobsG/P (%) was 64.90%) always contributed more than oxidation process (average CobsOxi (%) was 35.10%) for particulate nitrate formation under different pollution scenarios in the ambient environment. We argued that this phenomenon was mainly caused by high aerosol pH (&gt;4.5). Nevertheless, as pollution level rose, the CobsOxi (%) will also increase (contributing to 32%, 38%, 40% and 41% under clean, light, medium and heavy pollution levels) which may be attributed to the increased HNO3 production rate and relatively enhanced heterogeneous reaction pathway. The results indicate future strategies for prevention and control of nitrate pollution should both consider reducing precursors emission and regulating aerosol acidity, in order to increase the effectiveness of reducing nitrate dominated pollution.</p

Direct visualisation of focal depth modulation in plasmonic slits with stepped corrugations

Abstract not available