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A plasma-based undoped-HfO2 FeFET (ferroelectric FET) with non-volatile memory characteristics is demonstrated. Modifying the O2 plasma period in plasma-enhanced atomic layer deposition (PE-ALD) is an effective approach to enhance the remnant polarization ( $\text{P}_{\text {r}}$ ) up to 2P $_{\text {r}} = 25\,\,\mu \text{C}$ /cm2 for the MFM (metal/ferroelectric/metal) structure with ferroelectric undoped-HfO2 thin films, and successful integration is implemented for the FeFET. The appropriate O2 vacancies ( $\text{V}_{\text {o}}^{{2}+}$ ) benefit the formation of the ferroelectric phase since they play the role of dopants and help orthorhombic phase (o-phase) formation during post-metal annealing (PMA). The $\text{V}_{\text {o}}^{{2}+}$ -rich undoped-HfO2 FeFET exhibits a memory window (MW) of 0.5 V, ${5} \times {10}^{{4}}$ switching endurance cycles, and higher than $10^{{4}}$ sec of data retention with $\text{V}_{\text {P/E}} = \pm 5$ V.

A plasma-based ferroelectric undoped HfO x capacitor is fabricated using plasma-enhanced atomic layer deposition (PE-ALD), and the multilevel characteristics of synaptic behavior are investigated. A gradual ferroelectric phase transition in the material is confirmed by grazing incidence X-ray diffraction (GI-XRD) for different O2 plasma periods. The metal–ferroelectric–metal (MFM) capacitor presents excellent remnant polarization ( ${\text{P}}_{r}$ ) up to $13~\mu \text{C}$ /cm2 and a switching endurance of more than 108 cycles. Superior small potentiation/depression nonlinearity ( $\alpha _{p}/\alpha _{d} = -0.08$ /−1.66 for voltage modulation stimulation) for synaptic training and almost symmetry training curve ( $\vert \alpha _{p}$ - $\alpha _{d}\vert $ ) are obtained. High stability under multilevel operation with five consecutive cycles of alternating potentiation and depression is exhibited without significant polarization variation for each training step (pulse).

This letter reports the fabrication of polycrystalline silicon (poly-Si) tunneling field effect transistors (Tunneling FETs) using green nanosecond laser crystallization (GLC). During the GLC process, the Si is full-melted by laser scanning, hence the recrystallized poly-Si thin films with grain size as large as $1.2~\mu \text{m}$ are attained. This makes it possible to fabricate tunneling FET with high-quali ty poly-Si thin films. Compare with the tunneling FETs fabricated by solid phase crystallization (SPC), the ones via GLC show better subthreshold swing (S.S) of 418 mV/dec. and larger on/off ratio of $6.02 \times 10^{5}$ . Moreover, the activation energy curve is also presented to further demonstrate the con nection between device performance and crystallinity of poly-Si thin films.

The crystallinity of polycrystalline germanium (poly-Ge) films were demonstrated through continuous-wave laser crystallization (CLC) with Gaussian-distribution beam profile. The different grain sizes of CLC poly-Ge were observed in their three crystallization regions, which were 2 $\mu \text{m}$ , 680 nm, and 90 nm for the central, transition, and edge regions, respectively. Furthermore, the relation between crystallinity and carrier types in these three regions of counter-doped CLC poly-Ge films were investigated. In the central and transition regions, the CLC poly-Ge films with relatively low hole concentration were easily converted to n-type poly-Ge films through a counter-doping process. In contrast, the edge region with poor crystallinity exhibited p-type behavior due to high defect-generated hole concentration. According to these material properties of counter-doped CLC poly-Ge films, the corresponding transfer characteristics of p-channel poly-Ge thin-film transistor for three crystallization regions were further investigated. Subsequently, high-performance p-channel poly-Ge thin-film transistors in the central region exhibited a superior field-effect mobility of 792.2 cm2/V-s.

Resistive random access memory (RRAM) devices with analog resistive switching are expected to be beneficial for neuromorphic applications, and consecutive voltage sweeps or pulses can be applied to change the device conductance and behave synaptic characteristics. In this paper, RRAM devices with a reverse stacking order of 6-nm-thick HfO x and 2-nm-thick AlO x dielectric films were fabricated. The device with TiN/Ti/AlO x /HfO x /TiN stacked layers exhibited digital resistive switching, while the other device with TiN/Ti/HfO x /AlO x /TiN stacked layers could demonstrate synaptic characteristics that were analog set and reset processes under consecutive positive and negative voltage sweeps or a train of potentiation and depression pulses. Moreover, this device could also implement synaptic learning rules, spike-timing-dependent plasticity (STDP). Varying temperature measurements and linear fittings of the measured data were conducted to analyze current conduction mechanisms. As a result, the variation of resistive switching behavior between these two devices is attributed to the varying effectiveness of the oxygen scavenging ability of the Ti layer when put into contact with either AlO x or HfO x . Moreover, AlO x functioned as a diffusion limiting layer (DLL) in the device with TiN/Ti/HfO x /AlO x /TiN stacked layers, and gradual modulation of the production and annihilation of oxygen vacancies is the cause of synaptic characteristics.

Resistive random access memory (RRAM) devices with analog resistive switching are expected to be beneficial for neuromorphic applications, and consecutive voltage sweeps or pulses can be applied to change the device conductance and behave synaptic characteristics. In this paper, RRAM devices with a reverse stacking order of 6-nm-thick HfOx and 2-nm-thick AlOx dielectric films were fabricated. The device with TiN/Ti/AlOx/HfOx/TiN stacked layers exhibited digital resistive switching, while the other device with TiN/Ti/HfOx/AlOx/TiN stacked layers could demonstrate synaptic characteristics that were analog set and reset processes under consecutive positive and negative voltage sweeps or a train of potentiation and depression pulses. Moreover, this device could also implement synaptic learning rules, spike-timing-dependent plasticity (STDP). Varying temperature measurements and linear fittings of the measured data were conducted to analyze current conduction mechanisms. As a result, the variation of resistive switching behavior between these two devices is attributed to the varying effectiveness of the oxygen scavenging ability of the Ti layer when put into contact with either AlOx or HfOx. Moreover, AlOx functioned as a diffusion limiting layer (DLL) in the device with TiN/Ti/HfOx/AlOx/TiN stacked layers, and gradual modulation of the production and annihilation of oxygen vacancies is the cause of synaptic characteristics.

This letter reports of the fabrication of high-performance p-channel polycrystalline germanium (poly-Ge) thin-film transistors (TFTs) using continuous-wave laser crystallization (CLC). During the CLC process, the direction of crystallization matches the direction of laser scanning due to a strong temperature gradient in the melting region. This makes it possible to fabricate high-quality poly-Ge thin films with 1-D longitudinal grains as large as $2\,\,\mu \text{m}\,\,\times 20\,\,\mu \text{m}$ . We fabricated the proposed p-channel CLC Ge TFTs with channel width of $0.7~\mu \text{m}$ and a channel length each of $0.7~\mu \text{m}$ . Consequently, the proposed p-channel CLC Ge TFTs with single-crystal-like channel fabricated on a longitudinal grain with biaxial tensile strain achieved a superior field-effect mobility of 1014.9 cm2/V-s.