(Correspondent: Xiaoxuan Duan) ACS Nano(Impact Factor is 13.942),top international journal in field of materials, reportedUltrathin Piezotronic Transistors with 2 nm Channel Lengths,the latest research finding ofSchool of Advanced Materials and Nanotechnology, Xidian University and Beijing Institute of Nano-energy and Nano-system, Chinese Academy of Sciences. Under the joint guidance of Academician Wang Zhonglin, Honorary President of School of Advanced Materials and Nanotechnology and Prof. Qin Yong, the work was jointly completed by Dr. Wang Longfei and Liu Shuhai, a doctoral first-year graduate student. Wang Longfei and Liu Shuhai are the co-lead authors of the work.

Schematics of the Device

At present, it is very difficult to fabricate silicon-based field-effect transistors below 5 nm due to theshort-channel effects. When the channel decreases to several nanometers, CMOS devices cannot work due to their manufacturing process and basic physical principles (such as tunneling effect). In order to break through the size limit of transistors, researchers have explored and studied field-effect transistors of materials such as carbon nanotubes, semiconductor nanowires and two-dimensional transition metal compounds, but these devices still depends on the regulation mechanism of external gate voltage. If the bottleneck cannot be broke, this may mean the end of Moore's law.

In 2006, Academician Wang Zhonglin first proposed a new type of transistor, piezotronic transistor, which is completely different from the traditional CMOS devices. The piezotronic transistor uses piezoelectric polarization bound charge (it can generate piezoelectric potential) generated at the metal piezoelectric semiconductor interface as the "gate voltage" to regulate the transport characteristics of carrier in the transistor. This piezoelectric effect has been widely confirmed in Wurtzite piezoelectric semiconductor materials. It is possible to break the limitation of channel width by using interface control instead of traditional external channel control.

Ultra-thin Piezoelectric Transistor Based on Two Dimensional ZnO

In order to break through the limitation, under the joint guidance of Academician Wang Zhonglin,theHonorary President of School of Advanced Materials and Nanotechnology of Xidian University,theDirector of Beijing Institute of Nanoenergy and Nanosystem, Chinese Academy of Sciences, and Professor Qin Yong, Dr. Wang Longfei and Doctoral student Liu Shuhai have successfully fabricated a new type of ultra-thin ZnO piezoelectric transistor with a∼2 nm channel length by in-depth study of externalpiezoelectric properties oftwo dimensional ultra-thin ZnO surface. The piezoelectric effect is applied in two-dimensional ultra-thin non layered piezoelectric semiconductor for the first time.

Electrical Transport Characteristics of Ultra-thin ZnO Piezoelectric Transistor

In this work, the piezoelectric polarization charge generated at the metal semiconductor interface (i.e. the piezoelectric potential perpendicular to the plane) is used as the gate voltage to effectively regulate the carrier transport characteristics of the device, and a simple pressure control logic circuit is realized by connecting two ultra-thin piezoelectric transistors in series. This study confirmed the effectiveness of the "gating" effect of piezoelectric polarization charge in ultra-narrow channel. This design removes the need for external gate electrodes or other challenging patterned process design in nanoscale length. The results of this study also confirmed the effectiveness of piezoelectric effect in ultra-narrow channel for the first time, provided ideas for the research of new piezoelectric transistors, broadened the research field of piezoelectric electronics, and pioneered research on the piezoelectric properties of two-dimensional non layered piezoelectric materials. The research results also have great potential in applications in smart skin, human-machine interfacing and nano electromechanical system.

OR Logic Circuit by Pressure Control

Link to the paper:Ultrathin Piezotronic Transistors with 2 nm Channel Lengths (ACS Nano, 2