Search

We demonstrate that a ferroelectric can cause a differential amplification without needing such an external energy source. As the ferroelectric switches from one polarization state to the other, a transfer of energy takes place from the ferroelectric to the dielectric, determined by the ratio of their capacitances, which, in turn, leads to the differential amplification. This amplification is very different in nature from conventional inductor-capacitor based circuits where an oscillatory amplification can be observed. The demonstration of differential voltage amplification from completely passive capacitor elements only has fundamental ramifications for next generation electronics.

We experimentally demonstrate a monolithic 3D integrated complementary metal oxide semiconductor (CMOS) inverter using layered transition metal dichalcogenide semiconductor N-channel (NMOS) and P-channel (PMOS) MOSFETs, which are sequentially integrated on two levels. The two devices share a common gate. Molybdenum disulphide and tungsten diselenide are used as channel materials for NMOS and PMOS, respectively, with an ON-to-OFF current ratio (ION/IOFF) greater than 106 and electron and hole mobilities of 37 and 236 cm2/Vs, respectively. The voltage gain of the monolithic 3D inverter is about 45 V/V at a supply voltage of 1.5 V and a gate length of 1 μm. This is the highest reported gain at the smallest gate length and the lowest supply voltage for any 3D integrated CMOS inverter using any layered semiconductor.

In this work, we develop an ultrathin epitaxial h-AlN as an interfacial layer (IL) between HfO2 and monolayer WS2 channel by atomic layer deposition (ALD). The growth of ultrathin dielectrics using ALD has been challenging due to the dangling-bond-free surface of 2D materials. By utilizing sub-1 nm h-AlN as an IL and depositing HfO2 high-k dielectric, we were able to form a uniform and atomically flat gate dielectric without voids. The resulting structure exhibits an equivalent oxide thickness as low as 1 nm and ultra-low leakage currents of ∼10−6 A/cm2. The fabricated top-gate WS2 transistors demonstrate on-off ratios of around 106 and subthreshold swing as low as 93 mV/dec. Furthermore, we have verified the feasibility of using h-AlN IL for a gate-all-around structure. Our work presents a CMOS-compatible low-temperature ALD process for integrating gate dielectrics, offering excellent thickness scalability and uniform coverage around monolayer WS2 nanosheets. The combination of high-quality two-dimensional dielectrics and semiconductors will contribute to the development of future high-performance and low-power electronic devices. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) with only a few atoms thickness provide an excellent solution to scale down current semiconductor devices. Many studies have demonstrated that molybdenum disulfide (MoS2), a member of TMDs, is promising as a channel material to fabricate field-effect transistors (FETs). However, the carrier mobility in MoS2 FET is always far lower than the theoretical prediction. Although this poor performance can be attributed to the defects, it still lacks a quantitative analysis clarifying the correlation between carrier mobility and defect density. In this work, by using scanning tunneling microscopy, we directly counted the defects in MoS2 FETs with different carrier mobility. We found that vacancies and impurities equally contribute to carrier mobility and the total defect density induces a power-law decreasing tendency to the carrier mobility of MoS2 FET. Our current results directly prove that the reduction of point defects can exponentially improve the carrier mobility of FETs made by TMDs. [ABSTRACT FROM AUTHOR]

This paper presents an approach to enhance Hf0.5Zr0.5O2 (HZO) ferroelectric orthorhombic phase (O-phase) formation via in situ NH3 plasma treatment. High-resolution non-disruptive hard x-ray photoelectron spectroscopy confirmed that O-phase formation can be enhanced by suppressed interfacial diffusion between HZO and the top TiN electrode. Additional N-bonding facilitated by NH3 treatment was shown to suppress the interaction between TiN and HZO, thereby reducing the formation of oxygen vacancies within HZO. It was shown to improve the reliability and ferroelectric performance (examined by the leakage current and positive-up-negative-down measurements) of HZO devices. After cyclic operations, NH3-treated ferroelectric FETs (FeFETs) exhibited stable transfer characteristics and memory windows, whereas untreated devices presented unstable behaviors. Our results demonstrate the efficacy of the proposed in situ NH3-treatment scheme in enhancing the stability of HZO-based FeFETs. [ABSTRACT FROM AUTHOR]

A correction is presented to the article "Differential voltage amplification from ferroelectric negative capacitance" which was published in the perodical.