In-memory computing featuring a radical departure from the von Neumann architecture is promising to substantially reduce the energy and time consumption for data-intensive computation. With the increasing challenges facing silicon complementary metal-oxide-semiconductor (CMOS) technology, developing in-memory computing hardware would require a different platform to deliver significantly enhanced functionalities at the material and device level. Here, we explore a dual-gate two-dimensional ferroelectric field-effect transistor (2D FeFET) as a basic device to form both nonvolatile logic gates and artificial synapses, addressing in-memory computing simultaneously in digital and analog spaces. Through diversifying the electrostatic behaviors in 2D transistors with the dual-ferroelectric-coupling effect, rich logic functionalities including linear (AND, OR) and nonlinear (XNOR) gates were obtained in unipolar (MoS2) and ambipolar (MoTe2) FeFETs. Combining both types of 2D FeFETs in a heterogeneous platform, an important computation circuit, i.e., a half-adder, was successfully constructed with an area-efficient two-transistor structure. Furthermore, with the same device structure, several key synaptic functions are shown at the device level, and an artificial neural network is simulated at the system level, manifesting its potential for neuromorphic computing. These findings highlight the prospects of dual-gate 2D FeFETs for the development of multifunctional in-memory computing hardware capable of both digital and analog computation.

Ferroelectric field effect transistor (FeFET) emerges as an intriguing non-volatile memory technology due to its promising operating speed and endurance. However, flipping the polarization requires a high voltage compared with that of reading, impinging the power consumption of writing a cell. Here, we report a CMOS compatible FeFET cell with low operating voltage. We engineer the ferroelectric Hf 1-x Zr x O 2 (HZO) thin film to form negative capacitance (NC) gate dielectrics, which generates a counterclock hysteresis loop of polarization domain in the fewlayered molybdenum disulfide (MoS 2) FeFET. The unstabilized negative capacitor inherently supports subthermionic swing rate and thus enables switching the ferroelectric polarization with the hysteresis window much less than half of the operating voltage. The FeFET shows a high on/off current ratio of more than 10 7 and a counterclockwise memory window (MW) of 0.1 V at a miminum program (P)/erase (E) voltage of 3 V. Robust endurance (10 3 cycles) and retention (10 4 s) properties are also demonstrated. Our results demonstrate that the HZO/MoS 2 ferroelectric memory transistor can achieve new opportunities in size-and voltage-scalable non-volatile memory applications.

Here we report the ZrOx-based negative capacitance (NC) FETs with 45.06 mV/decade subthreshold swing (SS) under ± 1 V VGS range, which can achieve new opportunities in future voltage-scalable NCFET applications. The ferroelectric-like behavior of the Ge/ZrOx/TaN capacitors is proposed to be originated from the oxygen vacancy dipoles. The NC effect of the amorphous HfO2 and ZrOx films devices can be proved by the sudden drop of gate leakage, the negative differential resistance (NDR) phenomenon, the enhancement of IDS and sub-60 subthreshold swing. 5 nm ZrOx-based NCFETs achieve a clockwise hysteresis of 0.24 V, lower than 60 mV/decade SS and an 12% IDS enhancement compared to the control device without ZrOx. The suppressed NC effect of Al2O3/HfO2 NCFET compared with ZrOx NCFET is related to the partial switching of oxygen vacancy dipoles in the forward sweeping due to negative interfacial dipoles at the Al2O3/HfO2 interface.

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In this paper, we design the uniaxially and biaxially strained black phosphorus (BP) photodetectors. Different strains applied in the zigzag or armchair direction can effectively tune the direct band gap of 5-layer of BP. The optical field intensity is modeled to determine the absorption for the BP layer. The strain effect on the band structure of BP is investigated using first-principles method based on density functional theory. The cut-off wavelength of strained 5-layer of BP pin photodetector is extended to middle infrared range with a high responsivity of 66.29 A/W, which means that the strained black phosphorus photodetector provides a new approach for the middle-infrared range optoelectronic devices.