Comeback of epitaxial graphene for electronics: large-area growth of bilayer-free graphene on SiC

Abstract

We present a new fabrication method for epitaxial graphene on SiC which enables the growth of ultrasmooth defect-and bilayer-free graphene sheets with an unprecedented reproducibility, a necessary prerequisite for wafer-scale fabrication of high quality graphene-based electronic devices. The inherent but unfavorable formation of high SiC surface terrace steps during high temperature sublimation growth is suppressed by rapid formation of the graphene buffer layer which stabilizes the SiC surface. The enhanced nucleation is enforced by decomposition of polymer adsorbates which act as a carbon source. With most of the steps well below 0.75 nm pure monolayer graphene without bilayer inclusions is formed with lateral dimensions only limited by the size of the substrate. This makes the polymer assisted sublimation growth technique the most promising method for commercial wafer scale epitaxial graphene fabrication. The extraordinary electronic quality is evidenced by quantum resistance metrology at 4.2 K with until now unreached precision and high electron mobilities on mm scale devices. Main TextThe success of graphene as a basis for new applications depends crucially on the reliability of the available technologies to fabricate large areas of homogenous high quality graphene layers. Epitaxial growth on metals as well as on SiC substrates is employed with specific benefits and drawbacks.Single graphene layers epitaxially grown on SiC offer a high potential for electronic device applications. They combine excellent properties, e.g. high electron mobilities, with the opportunity for wafer-scale fabrication and direct processing on semi-insulating substrates without the need to transfer the graphene to a suitable substrate (Avouris & Dimitrakopoulos 2012). Some progress has been achieved during the recent years. In particular, high temperature sublimation growth under Ar atmosphere (Virojanadara et al. 2008),(Emtsev et al. 2009 or by confinement control (Heer et al. 2011), (Real et al. 2012) was a breakthrough for synthesizing large-area graphene on SiC substrates.The coverage of graphene bilayers could be reduced from wide stripes formed along the terraces to small micrometer-sized bilayer patches (Virojanadara et al. 2009). Further it was found that beyond pure sublimation growth from SiC graphene formation can be assisted by additional carbon supply from external sources (Al-Temimy et al. 2009;Moreau et al. 2010). In particular, by using propane in

Structure and electronic properties of closed-ring defects in epitaxial graphene

“…This is further substantiated by the electron doping characteristics revealed by the Raman spectroscopy results ( figure 1(d)). Moreover, the number of graphene layers has been clearly demonstrated to increase with increasing temperature [27,28,36] Therefore, the low graphitization temperature of 1300°C adopted for only 15 min ensures a bilayer configuration. We also note that the effective electron-donor doping of graphene is induced by the difference between the work functions of graphene and the SiC substrate, which drives electrons at the SiC/graphene interface from the SiC substrate into the graphene.…”

“…The wafers were subjected to a final high-temperature degassing stage by heating to 900°C and holding for 15 min and then heating to 1300°C and holding for 15 min to ensure the desorption of all Si atoms from the surface, yielding graphene layers on the surface of the SiC wafers. Other researchers have also obtained graphene films under degassing conditions of 1300°C to 2000°C [27,28]. Finally, the wafers were slowly annealed at decreasing temperature down to room temperature over a period of 4 h. The samples were transferred to the STM sample-stage and cooled to liquid nitrogen temperature (77 K) under ultra-high vacuum conditions (5×10 −10 Torr).…”

Транспортные свойства пленок графена, выращенных методом термодеструкции поверхности SiC (0001) в среде аргона

“…Процесс термодеструкции может осуществляться как в вакууме [2][3][4], так и в среде инертного газа [5][6][7][8]. На ранних этапах исследований структур графен/SiС нами использовалась технология получения графена в высоком вакууме [2,3].…”

“…2 представлена зависимость величины подвижности элек-тронов от концентрации носителей заряда в двумерном электронном газе в неинтеркалированном графене, выращенном в среде аргона на Si-грани. График построен с использованием данных измерений, полученных разными исследовательскими группами на графене, вы-ращенном при различных технологических условиях [5][6][7][8]. Четко прослеживается, что подвижность электронов в графене увеличива-ется с уменьшением концентрации носителей заряда в двумерном электронном газе.…”

Effect of Residual Gas Composition on Epitaxial Growth of Graphene on SiC

“…On the other hand, the carrier mobility has been observed to decrease with increasing argon pressure when time and temeperature are kept constant [12]. Other strategies to improve graphene quality involve thermal decomposition of deposited polymer adsorbate which acts as a carbon source [13]. The SiC step bunching, as another issue reducing graphene mobility on SiC, has been solved by amorphous carbon step pinning [14].…”