TY - JOUR
T1 - Graphene nucleation density on copper
T2 - Fundamental role of background pressure
AU - Vlassiouk, Ivan
AU - Smirnov, Sergei
AU - Regmi, Murari
AU - Surwade, Sumedh P.
AU - Srivastava, Nishtha
AU - Feenstra, Randall
AU - Eres, Gyula
AU - Parish, Chad
AU - Lavrik, Nick
AU - Datskos, Panos
AU - Dai, Sheng
AU - Fulvio, Pasquale
PY - 2013/9/19
Y1 - 2013/9/19
N2 - In this paper we discuss the effect of background pressure and synthesis temperature on the graphene crystal sizes in chemical vapor deposition (CVD) on copper catalyst. For the first time, we quantitatively demonstrate a fundamental role of the background pressure and provide the activation energy for graphene nucleation in atmospheric pressure CVD (9 eV), which is substantially higher than for the low pressure CVD (4 eV). We attribute the difference to a greater importance of copper sublimation in the low pressure CVD, where severe copper evaporation likely dictates the desorption rate of active carbon from the surface. At atmospheric pressure, where copper evaporation is suppressed, the activation energy is assigned to the desorption energy of carbon clusters instead. The highest possible temperature, close to the melting point of copper, should be used for large single crystal graphene synthesis. Using these conditions, we have synthesized graphene single crystals with sizes over 0.5 mm. Single crystal nature of synthesized graphene was confirmed by low-energy electron diffraction. We also demonstrate that CVD of graphene at temperatures below 1000 C shows higher nucleation density on (111) than on (100) and (101) copper surfaces, but there is no identifiable preference at higher temperatures.
AB - In this paper we discuss the effect of background pressure and synthesis temperature on the graphene crystal sizes in chemical vapor deposition (CVD) on copper catalyst. For the first time, we quantitatively demonstrate a fundamental role of the background pressure and provide the activation energy for graphene nucleation in atmospheric pressure CVD (9 eV), which is substantially higher than for the low pressure CVD (4 eV). We attribute the difference to a greater importance of copper sublimation in the low pressure CVD, where severe copper evaporation likely dictates the desorption rate of active carbon from the surface. At atmospheric pressure, where copper evaporation is suppressed, the activation energy is assigned to the desorption energy of carbon clusters instead. The highest possible temperature, close to the melting point of copper, should be used for large single crystal graphene synthesis. Using these conditions, we have synthesized graphene single crystals with sizes over 0.5 mm. Single crystal nature of synthesized graphene was confirmed by low-energy electron diffraction. We also demonstrate that CVD of graphene at temperatures below 1000 C shows higher nucleation density on (111) than on (100) and (101) copper surfaces, but there is no identifiable preference at higher temperatures.
UR - http://www.scopus.com/inward/record.url?scp=84884544379&partnerID=8YFLogxK
U2 - 10.1021/jp4047648
DO - 10.1021/jp4047648
M3 - Article
AN - SCOPUS:84884544379
SN - 1932-7447
VL - 117
SP - 18919
EP - 18926
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 37
ER -