Van der Waals integration of high-κ perovskite oxides and two-dimensional semiconductors

Abstract

Two-dimensional semiconductors can be used to build next-generation electronic devices with ultrascaled channel lengths. However, semiconductors need to be integrated with high-quality dielectrics—which are challenging to deposit. Here we show that single-crystal strontium titanate—a high-κ perovskite oxide—can be integrated with two-dimensional semiconductors using van der Waals forces. Strontium titanate thin films are grown on a sacrificial layer, lifted off and then transferred onto molybdenum disulfide and tungsten diselenide to make n-type and p-type transistors, respectively. The molybdenum disulfide transistors exhibit an on/off current ratio of 108 at a supply voltage of 1 V and a minimum subthreshold swing of 66 mV dec−1. We also show that the devices can be used to create low-power complementary metal–oxide–semiconductor inverter circuits.

Combining Freestanding Ferroelectric Perovskite Oxides with Two-Dimensional Semiconductors for High Performance Transistors

“…The integration of these freestanding complex oxides with 2D materials, however, was not reported until very recently by two research groups in parallel with preparation of our work. In these two recent works , SrTiO 3 (STO) thin layers are isolated freestanding and used as high-κ dielectrics for field-effect transistors based on 2D materials. Yang et al show that in devices utilizing a freestanding layer of STO, ON/OFF ratios of 10 8 and subthreshold swings of 66 mV/dec can be achieved .…”

“…In these two recent works , SrTiO 3 (STO) thin layers are isolated freestanding and used as high-κ dielectrics for field-effect transistors based on 2D materials. Yang et al show that in devices utilizing a freestanding layer of STO, ON/OFF ratios of 10 8 and subthreshold swings of 66 mV/dec can be achieved . Huang et al.…”

“…This polarization influences the electronic properties of the 2D material-oxide interface, and its switchable character provides an additional tuning parameter for device operation. Memristive properties have, in this way, been added to 2D-based field effect transistors and tunnel junctions. − As already achieved with the dielectric STO, , any step forward in facilitating the stackable aspect of these ferroelectric components would immediately expand their potential applications, using the van der Waals integration strategy to fabricate novel hybrid 2D heterostructures.…”

“…Yang et al show that in devices utilizing a freestanding layer of STO, ON/OFF ratios of 10 8 and subthreshold swings of 66 mV/dec can be achieved. 30 Huang et al show that the STO layer is exceptional for use as a dielectric layer because it possesses a subone-nanometer capacitance equivalent thickness with a low leakage current (less than 10 −2 A•cm −2 at 2.5 MV•cm −1 ). 29 Prior to the isolation of freestanding layers of complex oxides, 2D materials were already integrated with complex oxide dielectrics epitaxially grown onto 3D oxide substrates to improve and add new functionalities to 2D-based devices.…”

“…This adds an additional characteristic beyond exceptional device properties when compared with recent results utilizing STO. 29,30 This hysteretic behavior can be used to fabricate low energy consumption transistors or memory storage devices. We compare the performance of the fabricated BTO-based devices with that obtained in MoS 2 transistors fabricated with hexagonal boron nitride (hBN) flakes of similar thickness finding comparable mobility values, indicating that the ultrahigh dielectric constant of BTO effectively screens out the charge impurities.…”