外部压电极化电荷对二维半导体输运的动态调制

The discovery of piezotronic effect in two-dimensional semiconductors has made it have important application prospect in the fields of human-computer interaction and flexible electronics. The effect mainly utilizes the piezoelectric polarization charges inside the materials to turn the transport process of carriers, while the piezoelectric coefficient of semiconductors is generally not high, and its modulation effect is limited. Therefore, we consider designing the composite piezoelectric devices, for example，coupling ferroelectric materials (such as PZT) with larger piezoelectric coefficients and two-dimensional semiconductors (such as MoS2) to achieve multi-functional coupling by using their respective advantages. The typical application of this combination is the ferroelectric field effect transistor, which mainly uses the remanent polarization states of ferroelectric materials to control the on-off of semiconductor channel，and then achieves memory function. But the modulation mode is static. The polarized ferroelectric materials also have piezoelectric properties. The change of their surface piezoelectric polarization charges under strain also could modulate the carrier transport process in semiconductors. In this research proposal, we will couple the ferroelectric materials and the two-dimensional semiconductors on the flexible substrates to realize the dynamic modulation of the semiconductor transport by the piezoelectric polarization charges of ferroelectric materials under strain, thus preparing the novel composite piezoelectric devices. Meanwhile, we will systematically study the dynamic modulation process and mechanism of external piezoelectric polarization charge on two-dimensional semiconductors. This research has certain reference significance for the design of new flexible electronic devices.

二维半导体中压电电子学效应的发现使它在人机交互和柔性电子学等领域有着重要应用。该效应主要利用材料内部的压电极化电荷调节载流子的输运过程，而半导体材料的压电系数普遍不高，因此其调制效果有限。所以我们考虑设计复合压电器件，如将压电系数较大的铁电材料（如PZT）和二维半导体（如MoS2）复合，利用各自材料的优势实现多功能耦合。这种结合典型的应用就是铁电晶体管，它主要利用铁电材料的剩余极化状态控制半导体沟道的开关进而实现存储的。然而这种调制方式是静态的，而极化后的铁电材料还具有压电性，应变下其表面压电极化电荷的变化同样可以调节半导体内载流子的输运。本项目研究内容是在柔性衬底上将铁电材料和二维半导体耦合，利用应变下铁电材料压电极化电荷的变化实现对半导体输运的动态调制，制备出新型复合压电器件；同时系统研究外部压电极化电荷对二维半导体的动态调制过程和机理。该研究对新型柔性电子器件的设计具有一定借鉴意义。

由于压电半导体中压电系数较低，压电电子学效应较弱，因此外部应变对载流子输运调制的效果不高。本项目通过将半导体与压电系数较高的铁电材料复合，制备出复合压电电子学器件，系统研究了外加应变对半导体材料内部载流子输运的调制。研究以MoS2和PMNPT等材料为研究载体，研究铁电材料在外加应变作用下的变形机制、压电极化以及界面耦合等特点，及其对半导体材料内部载流子输运的调制机制。优化了器件结构，研究了复合压电器件中外部应变对器件输出电流的调制效果和调制机理，在此基础上制备出了高灵敏的应变传感器件。研究结果表明，在外加0.08%的微小应变时，复合压电器件的输出电流变化可达100倍以上，高于传统的压电电子学器件和传统应变传感器件，实现了外部压电极化电荷对半导体载流子输运的有效调制。该复合压电器件结构简单，易于制备，灵敏度高，这种优势使它在高分辨传感成为可能。该器件在人机交互、智能传感和微机电系统（MEMS）等领域有着重要应用前景。