Electrospinning‐Driven Binary Oxide Nanofiber Networks with Tunable Amorphous Microstructure for Booming Transistors and Circuits Operation

One long-standing goal in the emerging field of flexible and transparent electronic devices is to meet the demand of key markets, such as enhanced output performance for metal oxide semiconductor thin film transistors (TFTs) prepared by a solution process. While solution-based fabrication techniques are cost-effective and ensure large-area coverage at low temperature, their utilization has the disadvantage of introducing large trap states into TFTs. Such states, the formation of which is induced by intrinsic defects initially produced during preparation, have a significant impact on electrical performance. Therefore, the ability to enhance the electrical characteristics of solution-processed TFTs, along with attaining a firm understanding of their physical nature, remains a key step towards extending their use. In this study, measurements of low-frequency noise and random telegraph signal noise are employed as generic alternative tools to examine the origins of enhanced output performance for solution-processed ZnO TFTs through the control of defect sites by Al evaporation.

The measurement of low frequency noise can be considered as an important part in optimization of sensor noise-signal ratio. But sometimes, the intrinsic low frequency noise is affected by contact noise, which can be generated by geometrical defect of thin film. Thus, the measured noise level could not reveal material properties. We report different low frequency noise measurement methods in a general geometry sample of thin film. A detailed analysis of noise measurement has been described by relative equations. Finally, a discussion has been investigated in systematic measurements of low frequency noise at room temperature in La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (LSMO) thin films and noise measurements are presented by noise spectral densities as function of frequency.

A hybrid-excitation technique was applied to nitrify amorphous silicon (a-Si:H) film surface using ammonia (NH3) gas and to deposit silicon nitride (SiNx) film using disilane (Si2H6) and NH3 gases for an a-Si:H thin-film transistor (TFT) at 280°C. With the use of this SiNx film as a gate insulator, a coplanar a-Si:H TFT with high field-effect electron mobility (5.3 cm2/(V·s)) was fabricated. This high electron mobility is considered to be due to three features as follows: (1) a good SiNx/a-Si:H interface created by the hybrid-excited nitrification of the a-Si:H film surface, (2) an ion-bombardment-free nitrogen-rich SiNx film fabricated by hybrid-excitation chemical vapor deposition (CVD) and (3) an a-Si:H film with less ion-bombardment damage. This hybrid-excited nitrification and the CVD effects on electrical properties of SiNx/(100)Si interface are also discussed.

Low-frequency noise in low temperature unhydrogenated polysilicon thin film transistors

Interface state densities, low frequency noise and electron mobility in surface channel In 0.53Ga 0.47As n-MOSFETs with a ZrO 2 gate dielectric

Robust, versatile, direct low-frequency noise characterization method for material/process quality control using cross-shaped 4-terminal devices

Thin-film transistors, fabricated on polycrystalline silicon films prepared by combined solid phase crystallization of amorphous silicon and excimer laser annealing processes, have been investigated by electrical and low frequency noise measurements in relation to the active layer thickness and the laser energy density. The device performance is improved with increasing the laser energy density until a critical value where the film is completely melted. By decreasing the active layer thickness from 50 to 25 nm, although the subthreshold characteristics are improved, the electron mobility and the threshold voltage are degraded. The noise data indicate that the degradation is related to electron trapping in both gate and substrate oxide interface traps.

We demonstrate a metal sandwiched Al-doped zinc tin oxide (AZTO) thin-film device to exhibit a characteristic evolution process from Schottky junction diode to resistive-switching random access memory (RRAM) applications. The proposed TiN/Ti/AZTO/Pt device can initially show good rectifying characteristics and high forward-bias current for Schottky diodes. After applying with an electrically triggered forming process, the transition of electrical behavior occurs and evolves from the diode to RRAM characteristics. The RRAM device exhibits the coexistence of bipolar and unipolar resistive-switching modes through the positive-bias forming and reversed-bias forming process, respectively. In addition, the RRAM device with bipolar mode can perform the functionality of multilevel cell storage, while the one with unipolar mode shows stable resistive-switching performance. Furthermore, one-transistor and one-resistor (1T1R) architecture with an RRAM cell connected with a thin-film transistor (TFT) device is developed in this paper. The TFT device using AZTO film as an active channel layer performs good electrical characteristics for a driver in the 1T1R operation scheme. The integration of AZTO-based electronic devices has great potential for increasing the application diversity of metal oxide AZTO thin film as well as the flexibility of circuit design in the emerging optoelectronic technologies.

ABSTRACTLarge‐area, high‐resolution organic light‐emitting diode (OLED) displays require high‐performance oxide thin‐film transistors (TFTs) with excellent mobility and stability, as well as little threshold voltage shift, especially for G8.5+ OLED production lines. Our previous work demonstrated rare‐earth doped oxides are ideal channel layer materials for TFTs due to their superior mobility and stability. However, scaling up TFT production from pilot lines to mass manufacturing poses significant challenges, largely because of the complexity of multi‐element composite materials and intricate processes. In this study, an end‐to‐end graph convolutional network (GCN) model is employed to optimize TFT production processes. By encoding process parameters as graph nodes and features, the GCN effectively predicts critical drain current–gate voltage (I–V) characteristics, enabling precise calculation of electron mobility, subthreshold slope, and threshold voltage. The model achieves a mean absolute percentage error of 19.9% on validation data. Based on the optimized parameters, a TFT device with properties including a mobility of 37.8 cm2/Vs, a threshold voltage of 0.9 V, and a subthreshold slope of 0.62 V/dec was successfully produced. These results highlight the potential of GCN‐based models to address the complexities of TFT mass production, providing a powerful tool for process optimization and performance enhancement.

High-dielectric constant (k) materials have attracted a lot of attention for use as gate insulators (GIs) that enable low-voltage operation of thin film transistors (TFTs). However, high-k GIs also induce severe degradation in TFT characteristics, such as effective mobility (μeff). Therefore, in this study, a stacked GI structure of ZrO2 and SiO2 was investigated. The mechanism by which the properties of the high-k GI influence TFT operating characteristics was revealed. Based on this mechanism, an optimized stacked GI structure that exhibited a low subthreshold swing and high μeff was found and used to achieve low-voltage operation in a TFT device.

Amorphous oxide semiconductors (AOSs) exhibiting high mobility in the range of 10–30 cm2/Vs have received significant attention for their application in flexible and transparent electronics such as next-generation displays. Here, we report on how the oxygen volume fraction (vol.%) in the O2/Ar sputter gas affects both the electrical properties of sputtered amorphous In-Zn-O (a-IZO) and the threshold voltage of a-IZO thin film transistor (TFT) devices. As the oxygen fraction increases during sputter deposition, the carrier density in a-IZO is adjusted from the heavily-doped regime of >1020/cm3 to the semiconducting regime of <1017/cm3. A series of bottom-gated TFT devices were fabricated through depositing the channel a-IZO films as a function of O2 vol.%. All the TFTs manufactured operate in depletion mode and the threshold voltage is found to shift positively with the increasing presence of O2 in the sputter gas. These results are attributed to both a decrease in oxygen vacancy defects, which donate two free carriers per vacancy, and a subsequent reduction in the a-IZO channel’s carrier density.

&#x0D; &#x0D; &#x0D; A major unsolved issue with chemical fertilizers is the low nutrient use efficiency. It has been reported that an excessive amount of up to 70% of the nitrogen applied to plants with traditional fertilizers is lost to the surrounding. Hence, the drastic pollution effects of chemical fertilizer usage. Slow-release fertilizers aim to reduce such losses via slow and sustained release of nutrients to the plant. In this study, we report the successful fabrication and characterization of a novel and biodegradable cellulose acetate (CA) electrospun nanofiber (NF) mat loaded with nitrogen, phosphorus and potassium plant nutrients of urea, hydroxyapatite nanoparticles (HANPs) and MOP respectively to be used as a slow-release fertilizer (SRF). It was envisaged that the unique properties of the electrospun NFs could overcome the shortcomings of traditional slow-release fertilizers (SRFs). The fabrication of the NFs was done with 8.5% w/v CA polymer dissolved in a 6 mL solvent system of acetone to dimethylformamide in a 2:1 volume ratio along with the addition of the aforementioned nutrients at 10% of the polymer weight. Electrospinning parameters were set after parameter optimization. The high-voltage supply was set at 16 kV, the spinneret to collector distance was 13cm and the flow rate was 1.5 ml/h. The solutions were electrospun only when the relative humidity was approximately between 65 to 70%. The HANPs incorporated were synthesized by the wet chemical precipitation method. The successful synthesis of the HANPs was confirmed via Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD) analysis. The successful loading of the nutrients onto the electrospun NF mat was evident from FTIR, Raman and EDX analysis. Furthermore, the scanning electron microscopy images of the nutrient loaded NFs depicted a reduced average diameter with respect to those of the neat NF mat. The total nitrogen percentage of the nutrient loaded NF mat was determined to be 2.60% from Kjeldahl analysis. The initial nutrient release studies in water depicted a biphasic release model for orthophosphate and potassium nutrients while only a burst release profile was observed for nitrogen. It can be concluded that the electrospun NF mats display a potential application with regards to SRFs. However, several modifications to the NF mat fabrication such as the usage of coaxial electrospinning will have to be made in order to better optimize the nutrient loading and enhance its slow-release properties.&#x0D; Keywords: Electrospinning, Nanofiber mat, Slow-release, Hydroxyapatite nanoparticles&#x0D; &#x0D; &#x0D;

Solution-processed ytterbium oxide dielectrics for low-voltage thin-film transistors and inverters

Oxide semiconductors are increasingly becoming the material of choice in the emerging printed and flexible electronics domain. While they have attracted tremendous research attention in the area of solution processed/printed electronics, the vacuum deposited amorphous oxide semiconductor TFTs have also achieved serious commercial success in the transparent and curved display industries. Nonetheless, it may be noted that although the n-type oxides demonstrate excellent electronic transport, the performance of the hole conducting p-type oxides are still unsatisfactory and thus it affects the fabrication of all oxide complementary metal oxide semiconductor (CMOS) circuits. In order to resolve the issue, unipolar depletion-load type pseudo-CMOS inverters have recently been proposed. In this regard, here, we demonstrate a co-continuous mesoporous indium oxide based thin film transistor (TFT) technology with edge-FET architecture and near vertical transport. At the next step, high performance, unipolar depletion-load type inverters have been fabricated using these edge-FET TFTs. The fabricated TFTs have shown average ON-current of 1.95 mA alongside excellent On/Off ratio (>10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> ). On the other hand, the depletion-load type inverters have demonstrated sharp voltage transfer characteristics (VTC) with a maximum signal gain of 58 at VDD= 2 V, supply voltage.

Poly-Si thin-film transistor (TFT) is the key building element for high-density 3D NAND Flash memory. Random grain boundary (GB) location and interface traps (Dit) density have been shown as the major root cause of variability [1]. However, with CNL pinned at midgap our previous model cannot adequately address experimental results - especially the cause of very low Vt TFT devices. In this work we point out that to accurately model the TFT device, CNL should not be restricted at the mid-gap only, as in the conventional assumption for Si/SiO2 interface trap, but should be randomly distributed inside the bandgap for GB trap. This makes donor-type Dit active besides the acceptor-type Dit. Simulation including the random CNL can well explain the very low-Vt devices and gives better TFT variability model. Furthermore, GB trap CNL plays an important role in governing the device subthreshold behavior during PE cycling for 3D NAND Flash.