Work Function Modulation and Thermal Stability of Reduced Graphene Oxide Gate Electrodes in MOS Devices

Abstract

Work function (WF) tuning of the contact electrodes is a key requirement in several device technologies, including organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), and complementary metal oxide semiconductor (CMOS) transistors. Here, we demonstrate that the WF of the gate electrode in an MOS structure can be modulated from 4.35 eV (n-type metal) to 5.28 eV (p-type metal) by sandwiching different thicknesses of reduced graphene oxide (rGO) layers between top contact metals and gate dielectric SiO2. The WF of the gate electrode shows strong dependence on the rGO thickness and is seen to be nearly independent of the contact metals used. The observed WF modulation is attributed to the different amounts of oxygen concentrations in different thicknesses of rGO layers. Importantly, this oxygen concentration can also be varied by the reduction extent of the graphene oxide as experimentally demonstrated. The results are verified by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses. The obtained WF values are thermally stable up to 800 °C. At further high temperatures, diffusion of metal through the rGO sheets is the main cause for WF instability, as confirmed by cross-sectional high-resolution transmission electron microscopy analysis. These findings are not limited to MOS devices, and the WF modulation technique has the potential for applications in other technologies such as OLEDs and OPVs involving graphene as conducting electrodes.

Tuning the work function of graphene toward application as anode and cathode

“…The WF of graphene is about 4.6 eV (in the range of graphite), for which its application as a cathode must be decreased, while use as an anode requires a high WF (to increase the hole injection efficiency) [11]. Therefore, using graphene in two different electronic parts demands some modifications in its electronic behavior [6,[12][13][14][15][16].…”

Work Functions of Pristine and Heteroatom-Doped Graphenes under Different External Electric Fields: Anab InitioDFT Study

“…7 Graphene can be selected as a work function tuning material for the contact electrodes in these electronic devices. 8 Because the work function is closely related to electronegativity and ionization energy, it is also important for the chemical reactivity of a graphene nanosheet. Therefore, it is necessary to conduct a comprehensive research on graphene work functions.…”

On the Effect of Native SiO2 on Si over the SPR‐mediated Photocatalytic Activities of Au and Ag Nanoparticles

“…Specifically, if less hot electrons are transferred to Si, they can become more availablef or transfer to adsorbed O 2 molecules that subsequently participate in the PATP oxidation. On the contrary,f or Ag, the work functiono fw hich is smallerr elativet oS i, [51,52] its energy band bends towards lower energy values.W hen the hot electrons reach the interface between Ag and Si, part of the SPR-excited hot electrons will transfer back to the Ag as presented in Figure S3b. This allows the formation of aq uantum barrier that can drive hot electrons to the conduction band of Si when as they pass through the interface during SPR excitation (SupportingI nformation Figure S3a).…”