Thin HfO2 films were grown by atomic layer deposition
on chemical vapor-deposited large-area graphene. The graphene was
transferred, prior to the deposition of the HfO2 overlayer,
to the HfO2 bottom dielectric layer pregrown on the Si/TiN
substrate. Either HfCl4 or Hf[N(CH3)(C2H5)]4 was used as the metal precursor for the
bottom layer. The O2 plasma-assisted process was applied
for growing HfO2 from Hf[N(CH3)(C2H5)]4 also on the top of graphene. To improve
graphene transfer, the effects of the surface pretreatments of the
as-grown and aged Si/TiN/HfO2 substrates were studied and
compared. The graphene layer retained its integrity after the plasma
processes. Studies on resistive switching on HfO2-graphene-HfO2 nanostructures revealed that the operational voltage ranges
in the graphene-HfO2 stacks were modified together with
the ratios between high- and low-resistance states.
The use of thin layers of amorphous hafnium oxide has been shown to be suitable for the manufacture of Resistive Random-Access memories (RRAM). These memories are of great interest because of their simple structure and non-volatile character. They are particularly appealing as they are good candidates for substituting flash memories. In this work, the performance of the MIM structure that takes part of a 4 kbit memory array based on 1-transistor-1-resistance (1T1R) cells was studied in terms of control of intermediate states and cycle durability. DC and small signal experiments were carried out in order to fully characterize the devices, which presented excellent multilevel capabilities and resistive-switching behavior.
In the attempt to understand the behavior of HfO2-based resistive switching devices at low temperatures, TiN/Ti/HfO2/W metal–insulator–metal devices were fabricated; the atomic layer deposition technique was used to grow the high-k layer. After performing an electroforming process at room temperature, the device was cooled in a cryostat to carry out 100 current–voltage cycles at several temperatures ranging from the “liquid nitrogen temperature” to 350 K. The measurements showed a semiconducting behavior in high and low resistance states. In the low resistance state, a hopping conduction mechanism was obtained. The set and reset voltages increased when temperature decreased because the thermal energies for oxygen vacancies and ions were reduced. However, the temperature did not influence the power absorbed in the reset transition, indicating the local temperature in the filament controls the transition. The set transition turned from gradual to abrupt when decreasing the temperature, due to a positive feedback between the current increase and the Joule heating at low temperatures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.