Noncatalytic chemical vapor deposition of graphene on high-temperature substrates for transparent electrodes

Abstract

A noncatalytic chemical vapor deposition mechanism is proposed, where high precursor concentration, long deposition time, high temperature, and flat substrate are needed to grow large-area nanocrystalline graphene using hydrocarbon pyrolysis. The graphene is scalable, uniform, and with controlled thickness. It can be deposited on virtually any nonmetallic substrate that withstands ∼1000 o C. For typical examples, graphene grown directly on quartz and sapphire shows transmittance and conductivity similar to exfoliated or metalcatalyzed graphene, as evidenced by transmission spectroscopy and transport measurements. Raman spectroscopy confirms the sp 2 -C structure. The model and results demonstrate a promising transfer-free technique for transparent electrode production.Graphene, a monolayer of sp 2 carbon atoms, has received much attention. The use of graphene in transparent electronics is one of its most promising applications. 1 Apart from its high transparency/conductivity, the flexibility and ease of integration on a variety of substrates are obvious advantages. 30-inch graphene has been demonstrated by virtue of the recent advances in chemical vapor deposition (CVD), 2 which is compatible with the existing semiconductor technology. 3 Nevertheless, the necessity of etching the metal catalyst and transfer of graphene to foreign substrates hampers wide industrialization. Thus, efforts are put into the metal-free growth of graphene on materials including SiO 2 , 4-6 Al 2 O 3 , 7 MgO, 8 etc. To date, however, the graphitization process on dielectrics is poorly understood while the experiments are largely experience based. Recently, we have shown that large-area uniform graphene can be grown on virtually any hightemperature substrates, on Si 3 N 4 or HfO 2 , for instance. 9 In this letter, we provide a broader and deeper insight, discussing in detail the growth mechanism of graphene directly on insulators. As an example, we show our results on graphene on quartz and sapphire, hinting at the future prospects of the transfer-free graphene for transparent electrodes.Bulk graphite is usually made at >3000 o C and catalysis is needed to lower the temperature. 10 However, nanoscale graphene flakes form without any catalysts at merely ∼1000 o C. For example, carbon black which is produced massively by natural gas pyrolysis 11-14 is nothing else but chaotically connected graphene flakes. 11 Although widely used in industry, this process has so far been overlooked for making large-area graphene. Here, we show that macroscopically amorphous carbon black can be turned into textured graphene thin films when a) Electronic mail: jiesu@chalmers.se. the carbon precursor concentration and growth temperature are high, also requiring a relatively long deposition time and flat substrate. Fig. 1(a) illustrates the CVD reactor used in this work. The middle region is heated to 1000 o C while the left and right sides are <600 o C. There is no material deposition in the right zone because of the reduced CH 4 decomposition efficiency at lo...

Metal-free plasma-enhanced chemical vapor deposition of large area nanocrystalline graphene

“…Nevertheless, there is still scope for research in direct deposition of graphene and nanocrystalline graphene (NCG) layer onto insulator substrates [7]. There has been some research into metal-free deposition of graphene to achieve this goal, such as molecular beam epitaxy (MBE) [8,9], CVD [7,10,11] and various plasma-enhanced methods based on partially modified tools [12][13][14]. Although these films have typically a higher defect rate compared to graphene obtained by exfoliation or CVD, they can be suitable for applications such as saturable absorber in mode-locked lasers [15].…”

Direct Growth of Graphene on Insulator Using Liquid Precursor Via an Intermediate Nanostructured State Carbon Nanotube

“…Another way is to grow graphene directly on dielectric insulators without using any metal catalyst, which is a much-needed technique for its electronic application. Recently, many research groups have pursued the direct growth of graphene on various dielectric substrates including hexagonal boron nitride (h-BN) [7, 8], glass [9–11], quartz [12], sapphire [13, 14], Si 3 N 4 [15–17], SiO 2 [18–21], and high-k dielectrics such as MgO [22, 23], ZrO 2 [23], and TiO 2 [24], using CVD without using metal catalysts. However, the as-grown graphene on above substrates exhibits poor quality, which is comparable neither with that of graphene grown on metal substrates such as Ni [1] and Cu [3] nor with epitaxial graphene on SiC [25].…”

A highly sensitive, large area, and self-powered UV photodetector based on coalesced gallium nitride nanorods/graphene/silicon (111) heterostructure

“…20 Its remarkable characteristics, including its high carrier mobility, 21 broad spectral absorption wavelength, and fast carrier transport, have attracted numerous researchers interested in building hybrid devices. [22][23][24] Prior researchers have used graphene as a transparent contact with GaN NRs due to its high conductivity and low optical absorbance (approximately 2.3%) for light in a wavelength range of 300 nm to the nearinfrared, 25 and produced around 25 A/W responsivity as a result. 26 Others have compared photocurrent production and responsivity in GaN PDs with and without graphene, determining that a GaN PD with graphene produces 35Â more photocurrent and higher responsivity than it does without graphene.…”