No abstract

No abstract

The development of organic thin-film transistors (OTFTs) with low power consumption and high gain will advance many flexible electronics. Here, by combining solution-processed monolayer organic crystal, ferroelectric HfZrOx gating and van der Waals fabrication, we realize flexible OTFTs that simultaneously deliver high transconductance and sub-60 mV/dec switching, under one-volt operating voltage. The overall optimization of transconductance, subthreshold swing and output resistance leads to transistor intrinsic gain and amplifier voltage gain over 5.3 × 104 and 1.1 × 104, respectively, which outperform existing technologies using organics, oxides and low-dimensional nanomaterials. We further demonstrate battery-powered, integrated wearable electrocardiogram (ECG) and pulse sensors that can amplify human physiological signal by 900 times with high fidelity. The sensors are capable of detecting weak ECG waves (undetectable even by clinical equipment) and diagnosing arrhythmia and atrial fibrillation. Our sub-thermionic OTFT is promising for battery/wireless powered yet performance demanding applications such as electronic skins and radio-frequency identification tags, among many others.

No abstract

The development of organic thin-film transistors (OTFTs) with low power consumption and high gain will advance many flexible electronics applications. Here, by combining solution-processed monolayer organic crystal, ferroelectric HfZrOx gating and van der Waals device fabrication, we realize flexible OTFTs that simultaneously deliver high transconductance and sub-60mV/dec switching, under one-volt operating voltage. The overall optimization of transconductance, subthreshold swing and output resistance leads to transistor intrinsic gain and amplifier voltage gain over 5.3×104 and 1.1×104, respectively, which outperform existing technologies using organics, oxides and low-dimensional nanomaterials. We further demonstrate battery-powered, integrated wearable electrocardiogram (ECG) and pulse sensors that can amplify human physiological signal by 900 times with high fidelity. The sensors are capable of detecting extremely weak ECG waves (undetectable even by clinical equipment) and diagnosing arrhythmia and atrial fibrillation. Our sub-thermionic OTFT is promising for battery/wireless powered yet performance demanding applications such as electronic skins, radio-frequency identification tags, among many others.

The growing demand for high-performance logic transistors has driven the exponential rise in chip integration, while the transistors have been rapidly scaling down to sub-10 nm. The increasing leakage current and subthreshold slope (SS) induced by short channel effect (SCE) result in extra heat dissipation during device operation. The performance of electronic devices based on two-dimensional (2D) semiconductors such as the transition metal dichalcogenides (TMDC) can significantly reduce power consumption, benefiting from atomically thin thickness. Here, we discuss the progress of dielectric integration of 2D metal–oxide–semiconductor field effect transistors (MOSFETs) and 2D negative capacitance field effect transistors (NCFETs), outlining their potential in low-power applications as a technological option beyond scaled logic switches. Above all, we show our perspective at 2D low-power logic transistors, including the ultra-thin equivalent oxide thickness (EOT), reducing density of interface trap, reliability, operation speed etc. of 2D MOSFETs and NCFETs.

As complementary metal-oxide-semiconductor (CMOS) scaling down to sub-10 nm node, emerging technology to reduce power consumption enforced by shortchannel effects is actively pursued. [1] At single transistor level, the most effective way is to reduce operating voltage (V DD ) and subthreshold slope (SS). [2] However, SS in metal-oxide-semiconductor fieldeffect transistors (MOSFETs) is limited to 60 mV dec −1 at room temperature due to thermionic emission of carriers in the Boltzmann tail. To this end, novel concepts are proposed to design steep-slope transistors, including tunnel FET (TFET), [3] impact ionization MOS (IMOS), [4] and nanoelectromechanical FET (NEM-FET). [5] While achieving steep slope, these new device concepts sacrifice other aspects. TFETs utilize the band-to-band tunneling current and suffer from low on-state current. The IMOS needs very large bias voltage to drive impact ionization and has stability issues. For NEM-FET, speed is limited to MHz due to the moving of heavy mass. Recently, negative capacitance (NC) effect in an FE/dielectric gate stack is proposed as a possible solution to break the 60 mV dec −1 limitation. [6][7][8][9][10][11][12] HfO 2 -based FE materials are particularly attractive because of: 1) excellent CMOS-compatibility by atomic layer deposition (ALD), [13,14] 2) scalability to ultrathin thickness, [15] 3) no sacrifice of I on , [8] and 4) potential GHz operation. [16] In the original Landau-Ginzburg-Devonshire (LGD) theory, a ferroelectric below its Curie temperature is described by a doublewell free energy landscape. The two degenerate energy minima define two stable spontaneous polarization states, which can be programmed by the application of electric field. The minima of energy states are separated by a metastable region where the second-order differential of energy versus polarization is negative, defining a region of negative capacitance. [6] It has been proposed to stabilize the metastable negative capacitance region by serially adding a dielectric (DE) with parabolic energy landscape, the so-called capacitance matching. [17,18] The Landau-Khalatnikov (L-K) model shows that such quasistatic NC can theoretically give rise to sub-60 mV dec −1 switching without hysteresis in logic devices. [19] However, so far, the experimental observation of negative capacitance still cannot be fully explained by L-K model. The negative capacitance (NC) effect in ferroelectric materials provides a possible solution to break the Boltzmann tyranny and realize steep-slope field-effect transistors (FETs) with sub-60 mV dec −1 subthreshold slope (SS). HfO 2 -based ferroelectrics (FE) have attracted great attention as dielectric candidates for NCFETs due to their excellent scalability and compatibility with complementary metal-oxide-semiconductor technology. However, understanding of the ferroelectric properties of HfO 2 -based FEs, especially at reduced thickness, is still at an early stage. The quasistatic polarization relaxation behavior of ferroelectric Hf x Zr 1−x O 2 (HZO) thin fil...

No abstract