Carrier doping effect of humidity for single-crystal graphene on SiC

Abstract

Carrier doping effects of water vapor and an adsorbed water layer on single-crystal graphene were evaluated. After annealing at 300 °C in nitrogen ambient, the sheet resistance of epitaxial graphene on a SiC substrate had a minimum value of 800 Ω/sq and the carrier density was estimated to be 1.2 × 10 13 cm-2 for an n-type dopant. The adsorbed water layer, which acted as a p-type dopant with a carrier density of-7.4 × 10 12 cm-2 , was formed by deionized (DI) water treatment. The sheet resistances of graphene samples increased with humidity, owing to the counter doping effect. The estimated p-type doping amounts of saturated water vapor were-2.5 × 10 12 cm-2 for DI-water-treated graphene and-3.5 × 10 12 cm-2 for annealed graphene.

High Stability of Epitaxial Graphene on a SiC Substrate

“…The electron mobility ( μ ) slightly increased from 920 to 1420 cm 2 V −1 s −1 , and the sheet electron density ( N s ) decreased from 1.18 × 10 13 to 2.76 × 10 12 cm −2 after five cycles of piranha treatment. Although this result shows that the epitaxial graphene film was positively doped after the piranha treatment, it can be considered that the washing process with DI water was the origin of this p‐doping effect . Figure b shows the sheet electron density versus electron mobility after each piranha treatment, and the dashed line shows a dependence of .…”

“…Figure b shows the sheet electron density versus electron mobility after each piranha treatment, and the dashed line shows a dependence of . The electron mobility values were almost proportional to the inverse of the square root of the sheet electron density , indicating that these changes were caused by doping effects without large scattering centers …”

Resistive-switching behavior in stacked graphene diode

“…High electron doping levels were the optimal condition for epitaxial graphene growth on SiC substrates. [23][24][25][26] This electron doping significantly lowered the metal contact resistance. 27) 2.2.…”

Vertically stacked graphene tunnel junction with structured water barrier

“…Before bonding, a thin water layer which acts as tunnel barrier is formed through deionized (DI) water treatment. 15) Through I-V measurement after fabricated, both direct tunneling (DT) and Fowler-Nordheim tunneling (FNT) phenomena are observed in the graphene/water barrier/graphene junction.…”

“…The estimated carrier density of sample A decreases owing to the p-type doping of 5.31 × 10 12 cm −2 caused by the DI water treatment. It is known that the structured water layer formed by the DI water treatment acts as a p-type dopant 15). Thus, the asymmetry in the I-V characteristics is attributed to the work function difference caused by the DI water treatment.…”