2D Materials with Charge-Density-Wave Effects: From Physics to Applications

A.A. Balandin
University of California, Riverside,
United States

Keywords: graphene, 2D materials, CDW

Summary:

The charge density wave (CDW) phase is a quantum state consisting of a periodic modulation of the electronic charge density accompanied by a periodic distortion of the atomic lattice. Several two-dimensional (2D) materials, which belong to the group of layered transition metal dichalcogenides (TMDs), exhibit unusually high transition temperatures to different CDW symmetry-reducing phases. Crystals of 1T-TaS2 have the transition between the nearly-commensurate (NC-CDW) and the incommensurate (I-CDW) phases at temperature of 350 K. This transition can also be triggered by an applied voltage in a wide temperature range. It is accompanied by an abrupt change in the current and a robust hysteresis, which can be used for practical applications. In this presentation, I will describe how the integration of three different 2D materials, such as 1T-TaS2, graphene and h-BN, in a way that exploited the unique properties of each, yielded a simple, miniaturized, voltage-controlled oscillator (VCO) suitable for a variety of applications [1]. We investigated the total ionizing dose (TID) effect on 1T-TaS2 CDW devices by examining the current-voltage characteristics under X-ray irradiation at doses up to 1 Mrad (SiO2). It was found that devices made with 2D CDW materials are surprisingly radiation hard [2]. The hardness against X-rays was attributed to the high carrier concentration and absence of the gate dielectric in the device structure. We have also demonstrated how such 2D CDW devices can be used for implementing an oscillatory neural network for memory and logic applications [3-4]. This work was supported, in part, by NSF EFRI 2-DARE project: Novel Switching Phenomena in Atomic MX2 Heterostructures for Multifunctional Applications; and UC-National Laboratory Collaborative Research and Training Program. [1] G. Liu, B. Debnath, T. R. Pope, R. K. Lake, T. T. Salguero and A. A. Balandin, "A charge-density-wave oscillator based on an integrated TaS2-BN-graphene device operating at room temperature" Nature Nanotechnology, 11, 845 (2016). [2] G. Liu, E. Zhang, C. Liang, M. Bloodgood, T. Salguero, D. Fleetwood, A. Balandin, "Total-Ionizing-Dose Effects on Threshold Switching in 1T-TaS2 Charge Density Wave Devices." IEEE Electron Device Lett., 38, 1724 (2017). [3] A. Khitun, G. Liu, and A. A. Balandin, "Two-Dimensional Oscillatory Neural Network Based on Room-Temperature Charge-Density-Wave Devices," IEEE Trans. Nanotechnology, 16, 860 (2017). [4] More details can be found on the web-site: http://balandingroup.ucr.edu/