He TIAN

In order to further break the bottleneck of gate length transistors below 1 nm, He Tian (Affiliated to Professor Tian-Ling Ren's group) developed vertical MoS(2) transistors with sub-1-nm gate lengths. Under the control of ultra-short sub-1 nm physical gate length, the transistor can be turned on and off effectively. Its off current is in the order of pA, the switching ratio can reach 10(5), and the subthreshold swing is 117mv / Dec.

Tian skillfully used the ultra-thin monatomic layer thickness and excellent conductivity of graphene film as the gate and controls the switching of vertical MoS2 channel through graphene lateral electric field, so as to realize the physical gate length of 0.34nm.

The vertical electric field of graphene is screened by depositing metal aluminum on the surface of graphene followed by aluminum natural oxidation. Then hafnium dioxide deposited by atomic layer is used as gate medium and single-layer molybdenum disulfide film deposited by chemical vapor deposition is used as channel.

This work promotes the further development of Moore's law down to the sub-1 nanometer level and provides a reference basis for the application of two-dimensional thin films in future integrated circuits.

Tian was also engaged in the study of biomimetic synaptic devices of two-dimensional materials, and realized two-dimensional black-phosphorus anisotropic synapses, black-phosphorus field-controlled band-gap transistors. Moreover, he also participated in the scientific research cooperation with Professor Ahmed H. Zewail of California Institute of Technology (1999 Nobel Prize winner, father of femtosecond chemistry), to observe the diffusion of photogenerated carriers in real time at the picosecond Level in SEM.

At present, Tian is committed to wearable real-time monitoring of human pulse. He and his team are developing an ultra-sensitive graphene pressure sensor which can sense small pressure of 0.1 Pa and measure human pulse accurately when applied to wrist. This method can achieve the accuracy and portability of the wrist blood pressure monitor, which is a new generation of potential technology.