Reverse degradation of nickel graphene junction by hydrogen annealing

Abstract

Metal contacts are fundamental building components for graphene based electronic devices and their properties are greatly influenced by interface quality during device fabrication, leading to resistance variation. Here we show that nickel graphene junction degrades after air exposure, due to interfacial oxidation, thus creating a tunneling barrier. Most importantly, we demonstrate that hydrogen annealing at moderate temperature (300 0C) is an effective technique to reverse the degradation.

Influence of Humidity on Contact Resistance in Graphene Devices

“…Also, Zhang et al hint at the long-term degradation of contact resistance after exposure to air which can be reversed by hydrogen annealing in case of nickel graphene contacts. 34 The steep slope, that is, the abnormal sheet resistance, of device 4 indicates possible defects or contamination of the graphene sheet. Therefore, this device was not considered in the averaging.…”

“…Our values of the sheet resistance are in line with previous literature studying graphene on SiO 2 . , Our measured contact resistances are 1.6 to 2.4 times higher than previously reported values by Passi et al and Russo et al for devices without additional treatment to reduce their contact resistance (1518 and 800 Ω μm, respectively). , This discrepancy might be due to a difference in contact design because we place the graphene on top of the metallization rather than below, as in those cases. Also, Zhang et al hint at the long-term degradation of contact resistance after exposure to air which can be reversed by hydrogen annealing in case of nickel graphene contacts . The steep slope, that is, the abnormal sheet resistance, of device 4 indicates possible defects or contamination of the graphene sheet.…”

“…However, it should be noted that many of these metals form insulating oxides at their surfaces, which degrade the contact resistance and hence makes the usage of these metals more challenging. 34 It is feasible to deposit inert gold as metallization on the top metal interconnect layer of CMOS circuits. 48 , 49 This approach emphasizes the suitability of integrating bottom-contacted graphene at the back end of the line.…”

“…This includes materials such as aluminum, titanium, and nickel which are utilized in metal interconnect layers of conventional complementary metal–oxide–semiconductor (CMOS) integrated circuits. However, it should be noted that many of these metals form insulating oxides at their surfaces, which degrade the contact resistance and hence makes the usage of these metals more challenging . It is feasible to deposit inert gold as metallization on the top metal interconnect layer of CMOS circuits. , This approach emphasizes the suitability of integrating bottom-contacted graphene at the back end of the line.…”