Identification of a strong contamination source for graphene in vacuum systems

Abstract

To minimize parasitic doping effects caused by uncontrolled material adsorption, graphene is often investigated under vacuum. Here we report an entirely unexpected phenomenon occurring in vacuum systems, namely strong n-doping of graphene due to chemical species generated by common ion high-vacuum gauges. The effect-reversible upon exposing graphene to air-is significant, as doping rates can largely exceed 10(12) cm(-2) h(-1), depending on pressure and the relative position of the gauge and the graphene device. It is important to be aware of this phenomenon, as its basic manifestation can be mistakenly interpreted as vacuum-induced desorption of p-dopants.

Graphene Field‐Effect Transistors for the Sensitive and Selective Detection of Escherichia coli Using Pyrene‐Tagged DNA Aptamer

“…Second, more wrinkles and vestiges are possible on the graphene channel with large w / l ratios, which deteriorate the carrier mobility of the G‐FETs. Besides, more contamination can be introduced to the graphene sample with large size . Both w / l ratio and V ds were kept as constants for the real‐time electrical monitoring in this study and the carrier mobility µ was chosen as the most important parameter to assess the sensing performance.…”

Organic Covalent Patterning of Nanostructured Graphene with Selectivity at the Atomic Level

“…These facts confirm the selective covalent patterning of gr/Ru(0001) through treatment with CH 3 CN beyond reasonable doubt. Given the relatively inert nature of CH 3 CN, and knowing that under high-vacuum (10 −6 Torr) conditions ion gauges produce and emit active chemical species through ionization of the residual gases in the vacuum chamber, which can be adsorbed onto graphene, 45 we reasoned the same process may take place during the exposure of the graphene surface to the acetonitrile molecules in UHV, since we use an ion gauge to measure the partial 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 pressure of the acetonitrile gas. In order to gather experimental evidence of the molecular fragments that can be produced in the ion gauge during the CH 3 CN exposition, we introduced in the UHV chamber the same partial pressure (1×10 -6 Torr) of acetonitrile used during the graphene exposure and recorded the mass spectrum of the gas utilizing a quadrupole mass spectrometer (QMS) (see Supporting Information D for details).…”

Steady-state photoconductivity and multi-particle interactions in high-mobility organic semiconductors

“…Previously, it was observed that high-vacuum gauges generate electrically neutral free radicals that land at the exposed surfaces of molecular crystals or other samples placed in high-vacuum chambers, thus creating surface traps that lead to a noticeable decrease of the charge carrier mobility at the surface and an increase of the threshold voltage in vacuum-gap OFETs, as measured in the dark 17 . Furthermore, it was shown more recently that gauge effect also takes place in graphene 18 . Here, we show that in addition to having an influence on the dark surface transport, high-vacuum gauges also drastically reduce photoconductivity of rubrene crystals ( Fig.…”