High-Quality CVD-MoS2 Synthesized on Surface-Modified Al2O3 for High-Performance MoS2 Field-Effect Transistors

In this article, an effective way of chemical modification on the dielectric surface (Al
₂
O
₃
) is investigated to chemical vapor deposition (CVD)-grown high-quality monolayer MoS
₂
and the relevant back-gated FETs are fabricated without MoS
₂
transfer. As a result, the size of the triangle MoS
₂
is increased and its quality is improved as the surface of Al
₂
O
₃
is treated by H
₂
SO
₄
. Furthermore, as compared with the gate dielectrics of the SiO
₂
and as-deposited Al
₂
O
₃
, the fabricated transistor with the H
₂
SO
₄
-treated Al
₂
O
₃
as gate dielectric achieves better electrical properties: high carrier mobility of 12.9 cm
²
/Vs (~10 times higher than the untreated sample, ~5.2 times higher than the SiO
₂
gate-dielectric sample), small subthreshold swing of 110 mV/dec, and high ON/OFF ratio of 3 × 10
⁶
. The involved mechanisms are attributed to the fact that the H
₂
SO
₄
-treated Al
₂
O
₃
not only can increase its surface roughness to promote the nucleation and high-quality growth of MoS
₂
but also can improve the quality of the MoS
₂
/Al
₂
O
₃
interface. This simple chemical-modification treatment will open up an effective approach of combining the high-crystallinity CVD-MoS
₂
with the high-k dielectric without MoS
₂
transfer required.