Effect of epoxy exposure on the electronic properties of graphene

Investigation of carrier density and mobility variations in graphene caused by surface adsorbates

“…6). The idea was to surface dope the normally p-type graphene so strongly n-type that it is transformed to an n-type graphene, which offers the opportunity to the study of the electrical parameter variations and their inter-correlations, as a function of time, as the transformation happens [10]. The graphene sample (transferred to a Si/SiO2 substrate like other discussed above) was exposed to C9H22N2 vapor by putting a drop in its close proximity, which was followed by measurement of conductivity, mobility and carrier concentration as a function of time approximately 10 mins after exposure.…”

“…Although numerous reports on graphene's excellent sensing behavior exist, there are many instances where the sensing mechanism is not completely understood [9]. For example, while many sensing applications are based on the change in conductivity or Dirac point in graphene, measured in various device configurations (resistor, FET, Schottky diode), and/or with functionalization layers (Pd, Pt, Au), those simple measurements are not sufficient to provide a detailed understanding of the sensing mechanisms in graphene [10][11][12][13]. This is because conductivity is proportional to the product of two basic charge carrier properties, mobility and concentration, so information regarding the change in conductivity (due to molecular adsorption) does not offer insight into their individual changes.…”

“…One way to independently determine the variation in mobility and conductivity caused by molecular adsorption is by fabricating a graphene based field effect transistor in a back-gated configuration [10,14]. This allows one to extract the conductance (σ) and transconductance (gm) from the Id -Vd and the Id -Vg plots, respectively, which can then be used to find the field effect mobility and the carrier concentration (please refer to appropriate formulas and discussion below).…”

Direct measurement of K+ ion efflux from neuronal cells using a graphene-based ion sensitive field effect transistor

“…Graphene was synthesized using a home-built semi-automated CVD system on a copper foil (Alfa Aesar, 99.999% purity) at 1035 C using CH 4 , H 2 , and Ar gases, following standard synthesis process developed in our lab. 6,7,10 Following synthesis, a 1.5 Â 3 mm graphene-on-copper foil was cut out of the large area sample to transfer the graphene onto a target SiO 2 /Si substrate. A solution based transfer process was followed using an initial PMMA coating on the graphene followed by treatment with ammonium persulfate to etch out the copper substrate.…”

“…This issue can be addressed by fabricating graphene-based ISFETs (GISFETs), which uses impervious graphene as the ion sensing layer, which is typically coated with an ion selective membrane (that prevents damage to the graphene layer itself). Due to its high carrier mobility and atomically thin nature, graphene has demonstrated excellent ionic sensitivity, [6][7][8][9] making it very well suited for ion efflux measurements.…”