Evaluating Au and Pd contacts in mono and multilayer MoS2 transistors

The search of a p-type metal contact on MoS
2
has remained inconclusive, with high work-function metals such as Au, Ni and Pt showing n-type behavior [1] and mixed reports of n as well as p-type behavior for Pd. In this work we report for the first time, quantitative band alignment of Pd and Au-MoS
2
interfaces using low temperature and scanning photocurrent measurements on MoS
2
transistors with varying metal contacts (Au-Au, Pd-Pd and Au-Pd). Our results indicate n-type behavior for Pd contacts on multilayer as well as monolayer MoS
2
transistors and a barrier height (Ф
b
) of nearly 0.5 eV, four times that for Au contacts indicating that the MoS
2
Fermi-level is pinned in the upper half of MoS
2
bandgap.