Monolayer MoS_(2)-based transistors with low contact resistance by inserting ultrathin Al_(2)O_(3)interfacial layer

Transition metal dichalcogenides(TMDCs)are promising high performance electronic materials due to their interesting semiconductor properties.However,it is acknowledged that the effective electrical contact between TMDCs-layered materials and metals remains one of the major challenges.In this work,the homogeneous monolayer MoS_(2)films with high crystalline quality were prepared by chemical vapor deposition method on SiO2/Si substrates.The back-gate field-effect transistors(FETs)were fabricated by inserting an ultrathin Al_(2)O_(3)interlayer between the metal electrodes and MoS_(2)nanosheets.With the addition of an ultrathin 0.8 nm Al_(2)O_(3)interlayer,the contact resistance decreased dramatically from 59.9 to 1.3 kΩμm and the Schottky barrier height(SBH)dropped from 102 to 27 meV compared with devices without the Al_(2)O_(3)interlayer.At the same time,the switching ratio increased from~106to~108,and both the on-current and field-effect mobility were greatly improved.We find that the ultrathin Al_(2)O_(3)interlayer can not only reduce the SBH to alleviate the Fermi level pinning phenomenon at the interface,but also protect the channel materials from the influence of air and moisture as a covering layer.In addition,the lattice and band structures of Al_(2)O_(3)/MoS_(2)film were calculated and analyzed by first-principles calculation.It is found that the total density of states of the Al_(2)O_(3)/MoS_(2)film exhibits interfacial polarized metals property,which proves the higher carrier transport characteristics.FETs with Al_(2)O_(3)interlayers have excellent stability and repeatability,which can provide effective references for future low power and high performance electronic devices.