Plasma enhanced hot filament CVD growth of thick carbon nanowall layers

Carbon nanowalls are carbon nanostructures consisting of arrays of graphitic carbon plates which are mainly positioned perpendicularly to the growth surface. Carbon nanowalls have received considerable interest in recent years, since they are closely related to graphene from the structural point of view, while maintaining an open honeycomb lattice on the nanoscale. They are thus believed to be an interesting electrode material for many applications since they offer high chemical resistance, low electrical resistance and high surface area. In this paper we are presenting a method that allows the growth of thick layers of carbon nanowalls onto flat and porous substrates, both carbon and refractory metal based. Such methods are promising for making electrodes for use in electrochemical devices

Fast growth of polycrystalline graphene by chemical vapor deposition of ethanol on copper

High conductive graphene films can be grown on metal foils by chemical vapor deposition (CVD). We here analyzed the use of ethanol, an economic precursor, which results also safer than commonly-used methane. A comprehensive range of process parameters were explored in order to obtain graphene films with optimal characteristics in view of their use in optoelectronics and photovoltaics. Commercially-available and electro-polished copper foils were used as substrates. By finely tuning the CVD conditions, we obtained few-layer (2-4) graphene films with good conductivity (-500 Ohm/sq) and optical transmittance around 92-94% at 550 nm on unpolished copper foils. The growth on electro-polished copper provides instead predominantly mono-layer films with lower conductivity (>1000 Ohm/sq) and with a transmittance of 97.4% at 550 nm. As for the device properties, graphene with optimal properties as transparent conductive film were produced by CVD on standard copper with specific process conditions

Nitrogen-doped graphene films from chemical vapor deposition of pyridine: influence of process parameters on the electrical and optical properties

Graphene films were produced by chemical vapor deposition (CVD) of pyridine on copper substrates. Pyridine-CVD is expected to lead to doped graphene by the insertion of nitrogen atoms in the growing sp2 carbon lattice, possibly improving the properties of graphene as a transparent conductive film. We here report on the influence that the CVD parameters (i.e., temperature and gas flow) have on the morphology, transmittance, and electrical conductivity of the graphene films grown with pyridine. A temperature range between 930 and 1070 °C was explored and the results were compared to those of pristine graphene grown by ethanol-CVD under the same process conditions. The films were characterized by atomic force microscopy, Raman and X-ray photoemission spectroscopy. The optical transmittance and electrical conductivity of the films were measured to evaluate their performance as transparent conductive electrodes. Graphene films grown by pyridine reached an electrical conductivity of 14.3 × 105 S/m. Such a high conductivity seems to be associated with the electronic doping induced by substitutional nitrogen atoms. In particular, at 930 °C the nitrogen/carbon ratio of pyridine-grown graphene reaches 3%, and its electrical conductivity is 40% higher than that of pristine graphene grown from ethanol-CVD

Contamination-free graphene by chemical vapor deposition in quartz furnaces

Abstract Although the growth of graphene by chemical vapor deposition is a production technique that guarantees high crystallinity and superior electronic properties on large areas, it is still a challenge for manufacturers to efficiently scale up the production to the industrial scale. In this context, issues related to the purity and reproducibility of the graphene batches exist and need to be tackled. When graphene is grown in quartz furnaces, in particular, it is common to end up with samples contaminated by heterogeneous particles, which alter the growth mechanism and affect graphene’s properties. In this paper, we fully unveil the source of such contaminations and explain how they create during the growth process. We further propose a modification of the widely used quartz furnace configuration to fully suppress the sample contamination and obtain identical and clean graphene batches on large areas

Single layer graphene film by ethanol chemical vapor deposition: Highly efficient growth and clean transfer method

The choice of ethanol (C2H5OH) as carbon source in the Chemical Vapor Deposition (CVD)\ud of graphene on copper foils can be considered as an attractive alternative among the\ud commonly used hydrocarbons, such as methane (CH4) [1]. Ethanol, a safe, low cost and easy\ud handling liquid precursor, offers fast and efficient growth kinetics with the synthesis of fullyformed\ud graphene films in just few seconds [2]. In previous studies of graphene growth from\ud ethanol, various research groups explored temperature ranges lower than 1000 °C, usually\ud reported for methane-assisted CVD. In particular, the 650–850 °C and 900 °C ranges were\ud investigated, respectively for 5 and 30 min growth time [3, 4]. Recently, our group reported\ud the growth of highly-crystalline, few-layer graphene by ethanol-CVD in hydrogen flow (1–\ud 100 sccm) at high temperatures (1000–1070 °C) using growth times typical of CH4-assisted\ud synthesis (10–30 min) [5]. Furthermore, a synthesis time between 20 and 60 s in the same\ud conditions was explored too. In such fast growth we demonstrated that fully-formed graphene\ud films can be grown by exposing copper foils to a low partial pressure of ethanol (up to 2 Pa)\ud in just 20 s [6] and we proposed that the rapid growth is related to an increase of the Cu\ud catalyst efficiency due weak oxidizing nature of ethanol. Thus, the employment of such liquid\ud precursor, in small concentrations, together with a reduced time of growth and very low\ud pressure leads to highly efficient graphene synthesis. By this way, the complete coverage of a\ud copper catalyst surface with high spatial uniformity can be obtained in a considerably lower\ud time than when using methane

Rapid and highly efficient growth of graphene on copper by chemical vapor deposition of ethanol

The growth of graphene by chemical vapor deposition on metal foils is a promising technique to deliver large-area films with high electron mobility. Nowadays, the chemical vapor deposition of hydrocarbons on copper is the most investigated synthesis method, although many other carbon precursors and metal substrates are used too. Among these, ethanol is a safe and inexpensive precursor that seems to offer favorable synthesis kinetics. We explored the growth of graphene on copper from ethanol, focusing on processes of short duration (up to one min). We investigated the produced films by electron microscopy, Raman and X-ray photoemission spectroscopy. A graphene film with high crystalline quality was found to cover the entire copper catalyst substrate in just 20 s, making ethanol appear as a more efficient carbon feedstock than methane and other commonly used precursors