Mechanically transferred large-area Ga$_2$O$_3$ passivates graphene and suppresses interfacial phonon scattering

TL;DR

This study introduces a large-area Ga$_2$O$_3$ passivation layer for graphene, which preserves high mobility, reduces resistivity at low temperatures, and offers protection against further processing, enhancing graphene's applicability.

Contribution

It presents a novel mechanical transfer method for large-area amorphous Ga$_2$O$_3$ passivation that improves graphene's electrical stability and protection.

Findings

Passivated graphene maintains high field effect mobility.

Resistivity is reduced below 220 K due to phonon screening.

Ga$_2$O$_3$ passivation protects graphene during further processing.

Abstract

We demonstrate a large-area passivation layer for graphene by mechanical transfer of ultrathin amorphous Ga$_2$O$_3$ synthesized on liquid Ga metal. A comparison of temperature-dependent electrical measurements of millimetre-scale passivated and bare graphene on SiO$_2$/Si indicate that the passivated graphene maintains its high field effect mobility desirable for applications. Surprisingly, the temperature-dependent resistivity is reduced in passivated graphene over a range of temperatures below 220 K, due to the interplay of screening of the surface optical phonon modes of the SiO$_2$ by high-dielectric-constant Ga$_2$O$_3$, and the relatively high characteristic phonon frequencies of Ga$_2$O$_3$. Raman spectroscopy and electrical measurements indicate that Ga$_2$O$_3$ passivation also protects graphene from further processing such as plasma-enhanced atomic layer deposition of Al$_2$O$_3$.