Search Results (55)

Solution-processed metal oxide dielectrics often result in unstable thin-film transistor (TFT) performance, hindering the development of next-generation metal oxide electronics. In this study, we prepared fluorine (F)-doped zirconium oxide (ZrO₂) dielectric layers using a chemical solution method to construct TFTs. The characterization by X-ray photoelectron spectroscopy (XPS) revealed that appropriate fluoride doping significantly reduces oxygen vacancies and the concentration of hydroxyl groups, thereby suppressing polarization processes. Subsequently, the electrical properties of Al/F:ZrO₂/n⁺⁺Si capacitors were evaluated, demonstrating that the optimized 10% F:ZrO₂ dielectric exhibits a low leakage current density and stable capacitance across a wide frequency range. Indium zinc oxide (IZO) TFTs incorporating 10% F:ZrO₂ dielectric layers were then fabricated. These devices displayed reliable electrical characteristics, including high mobility over a broad frequency range, reduced dual-sweep hysteresis, and excellent stability under positive-bias stress (PBS) after three months of aging. These findings indicate that the use of the fluorine-doped ZrO₂ dielectric is a versatile strategy for achieving high-performance metal oxide thin-film electronics. Full article

The continuous growth of energy-efficient electronic devices and compact systems has motivated researchers to develop TFTs based on p-type semiconductors. This review examines the developments in p-type thin-film transistors (TFTs) processed using solution methods to achieve integration with complementary metal–oxide–semiconductor technology. Improving organic p-type materials is critical for achieving advanced mobility and stability characteristics with suitable process integration. Scientists study these materials for use in wearable devices which display mechanical strength when fitted onto a curve. This review presents an exclusive discussion about the wide spectrum of applications which involve flexible displays and sensors, together with upcoming technologies such as artificial skin and flexible integrated circuits. The article examines present material challenges, along with device reliability and large-scale production methods, to give a thorough analysis of solution-processed p-type TFTs toward their broad implementation in upcoming electronic devices. By summarizing the developments and most recent studies in the field, this review aims to provide useful information regarding current research into and future trends of p-type TFTs. Full article

Pixel circuits are key components of flat panel displays, including liquid crystal displays (LCDs), organic light-emitting diode displays (OLEDs), and micro light-emitting diode displays (micro-LEDs). Depending on the active layer material of the thin film transistor (TFT), pixel circuits are categorised into amorphous silicon (a-Si) technology, low-temperature polycrystalline silicon (LTPS) technology, metal oxide (MO) technology, and low-temperature polycrystalline silicon and oxide (LTPO) technology. In this review, we outline the fundamental display principles and four major TFT technologies, covering conventional single-gated TFTs to novel two-gated TFTs. We focus on novel pixel circuits for three glass-based display technologies with additional mention of pixel circuits for silicon-based OLED and silicon-based micro-LED. Full article

With the ongoing development of electronic devices, there is an increasing demand for new semiconductors beyond traditional silicon. A key element in electronic circuits, complementary metal-oxide semiconductor (CMOS), utilizes both n-type and p-type semiconductors. While the advancements in n-type semiconductors have been substantial, the development of high-mobility p-type semiconductors has lagged behind. Recently, tellurium (Te) has been recognized as a promising candidate due to its superior electrical properties and the capability for large-area deposition via vacuum processes. In this work, an innovative approach involving the addition of a metal-capping layer onto Te thin-film transistors (TFTs) is proposed, which significantly enhances their electrical characteristics. In particular, the application of an indium (In) metal-capping layer has led to a dramatic increase in the field-effect mobility of Te TFTs from 2.68 to 33.54 cm²/Vs. This improvement is primarily due to the oxygen scavenger effect, which effectively minimizes oxidation and eliminates oxygen from the Te layer, resulting in the production of high-quality Te thin films. This progress in high-mobility p-type semiconductors is promising for the advancement of high-performance electronic devices in various applications and industries. Full article

Metal oxide semiconductors, such as indium gallium zinc oxide (IGZO), have attracted significant attention from researchers in the fields of liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs) for decades. This interest is driven by their high electron mobility of over ~10 cm²/V·s and excellent transmittance of more than ~80%. Amorphous IGZO (a-IGZO) offers additional advantages, including compatibility with various processes and flexibility making it suitable for applications in flexible and wearable devices. Furthermore, IGZO-based thin-film transistors (TFTs) exhibit high uniformity and high-speed switching behavior, resulting in low power consumption due to their low leakage current. These advantages position IGZO not only as a key material in display technologies but also as a candidate for various next-generation electronic devices. This review paper provides a comprehensive overview of IGZO-based electronics, including applications in gas sensors, biosensors, and photosensors. Additionally, it emphasizes the potential of IGZO for implementing logic gates. Finally, the paper discusses IGZO-based neuromorphic devices and their promise in overcoming the limitations of the conventional von Neumann computing architecture. Full article

High-k metal oxides are gradually replacing the traditional SiO₂ dielectric layer in the new generation of electronic devices. In this paper, we report the production of five-element high entropy metal oxides (HEMOs) dielectric films by solution method and analyzed the role of each metal oxide in the system by characterizing the film properties. On this basis, we found optimal combination of (AlGaTiYZr)O_x with the best dielectric properties, exhibiting a low leakage current of 1.2 × 10⁻⁸ A/cm² @1 MV/cm and a high dielectric constant, while the film’s visible transmittance is more than 90%. Based on the results of factor analysis, we increased the dielectric constant up to 52.74 by increasing the proportion of TiO₂ in the HEMOs and maintained a large optical bandgap (>5 eV). We prepared thin film transistors (TFTs) based on an (AlGaTiYZr)O_x dielectric layer and an InGaZnO_x (IGZO) active layer, and the devices exhibit a mobility of 18.2 cm²/Vs, a threshold voltage (V_th) of −0.203 V, and an subthreshold swing (SS) of 0.288 V/dec, along with a minimal hysteresis, which suggests a good prospect of applying HEMOs to TFTs. It can be seen that the HEMOs dielectric films prepared based on the solution method can combine the advantages of various high-k dielectrics to obtain better film properties. Moreover, HEMOs dielectric films have the advantages of simple processing, low-temperature preparation, and low cost, which are expected to be widely used as dielectric layers in new flexible, transparent, and high-performance electronic devices in the future. Full article

The control of the performance of single-walled carbon nanotube (SWCNT) random network-based transistors is of critical importance for their applications in electronic devices, such as complementary metal oxide semiconducting (CMOS)-based logics. In ambient conditions, SWCNTs are heavily p-doped by the H₂O/O₂ redox couple, and most doping processes have to counteract this effect, which usually leads to broadened hysteresis and poor stability. In this work, we coated an SWCNT network with various common polymers and compared their thin-film transistors’ (TFTs’) performance in a nitrogen-filled glove box. It was found that all polymer coatings will decrease the hysteresis of these transistors due to the partial removal of charge trapping sites and also provide the stable control of the doping level of the SWCNT network. Counter-intuitively, polymers with electron-withdrawing functional groups lead to a dramatically enhanced n-branch in their transfer curve. Specifically, SWCNT TFTs with poly (vinylidene fluoride) coating show an n-type mobility up to 61 cm²/Vs, with a decent on/off ratio and small hysteresis. The inverters constructed by connecting two ambipolar TFTs demonstrate high gain but with certain voltage loss. P-type or n-type doping from polymer coating layers could suppress unnecessary n- or p-branches, shift the threshold voltage and optimize the performance of these inverters to realize rail-to-rail switching. Similar devices also demonstrate interesting antiambipolar performance with tunable on and off voltage when tested in a different configuration. Full article

Metal-oxide (MOx) thin-film transistors (TFTs) require complex circuit structures to cope with their depletion mode characteristics, making them applicable only to large-area active matrix (AM) displays despite their low manufacturing cost and decent performance. In this paper, we report a simple MOx 10T-2C scan driver circuit that overcomes the depletion mode characteristics using a series-connected two transistor (STT) configuration and clock signals with two kinds of low-voltage levels. The proposed circuit has a wide operating range of TFT characteristics, i.e., −2.8 V ≤ V_TH ≤ +3.0 V. Through the measurement results of the manufactured sample, it was confirmed that the performance and area of our circuit are suitable for high-resolution mobile displays. Full article

In this study, a KrF excimer laser with a high-absorption coefficient in metal oxide films and a wavelength of 248 nm was selected for the post-processing of a film and metal oxide thin film transistor (MOTFT). Due to the poor negative bias illumination stress (NBIS) stability of indium gallium zinc oxide thin film transistor (IGZO-TFT) devices, terbium-doped Tb:In₂O₃ material was selected as the target of this study. The XPS test revealed the presence of both Tb³⁺ and Tb⁴⁺ ions in the Tb:In₂O₃ film. It was hypothesized that the peak of the laser thermal effect was reduced and the action time was prolonged by the f-f jump of Tb³⁺ ions and the C-T jump of Tb⁴⁺ ions during the laser treatment. Studies related to the treatment of Tb:In₂O₃ films with different laser energy densities have been carried out. It is shown that as the laser energy density increases, the film density increases, the thickness decreases, the carrier concentration increases, and the optical band gap widens. Terbium has a low electronegativity (1.1 eV) and a high Tb-O dissociation energy (707 kJ/mol), which brings about a large lattice distortion. The Tb:In₂O₃ films did not show significant crystallization even under laser energy density treatment of up to 250 mJ/cm². Compared with pure In₂O₃-TFT, the doping of Tb ions effectively reduces the off-state current (1.16 × 10⁻¹¹ A vs. 1.66 × 10⁻¹² A), improves the switching current ratio (1.63 × 10⁶ vs. 1.34 × 10⁷) and improves the NBIS stability (ΔV_ON = −10.4 V vs. 6.4 V) and positive bias illumination stress (PBIS) stability (ΔV_ON = 8 V vs. 1.6 V). Full article

Defect annihilation of the IGZO/SiO₂ layer is of great importance to enhancing the bias stress stabilities of bottom-gate coplanar thin-film transistors (TFTs). The effects of annealing temperatures (T_a) on the structure of the IGZO/SiO₂ layer and the stabilities of coplanar IGZO TFTs were investigated in this work. An atomic depth profile showed that the IGZO/SiO₂ layer included an IGZO layer, an IGZO/SiO₂ interfacial mixing layer, and a SiO₂ layer. Higher T_a had only one effect on the IGZO layer and SiO₂ layer (i.e., strengthening chemical bonds), while it had complex effects on the interfacial mixing layer—including weakening M-O bonds (M: metallic elements in IGZO), strengthening damaged Si-O bonds, and increasing O-related defects (e.g., H₂O). At higher T_a, IGZO TFTs exhibited enhanced positive bias temperature stress (PBTS) stabilities but decreased negative bias temperature stress (NBTS) stabilities. The enhanced PBTS stabilities were correlated with decreased electron traps due to the stronger Si-O bonds near the interfacial layer. The decreased NBTS stabilities were related to increased electron de-trapping from donor-like defects (e.g., weak M-O bonds and H₂O) in the interfacial layer. Our results suggest that although higher T_a annihilated the structural damage at the interface from ion bombardment, it introduced undesirable defects. Therefore, to comprehensively improve electrical stabilities, controlling defect generation (e.g., by using a mild sputtering condition of source/drain electrodes and oxides) was more important than enhancing defect annihilation (e.g., through increasing T_a). Full article

We applied excimer laser annealing (ELA) on indium-zinc oxide (IZO) and IZO/indium-gallium-zinc oxide (IGZO) heterojunction thin-film transistors (TFTs) to improve their electrical characteristics. The IZO and IZO/IGZO heterojunction thin films were prepared by the physical vapor deposition method without any other annealing process. The crystalline state and composition of the as-deposited film and the excimer-laser-annealed films were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy. In order to further enhance the electrical performance of TFT, we constructed a dual-heterojunction TFT structure. The results showed that the field-effect mobility could be improved to 9.8 cm²/V·s. Surprisingly, the device also possessed good optical stability. The electron accumulation at the a-IZO/HfO, HfO/a-IGZO, and a-IGZO/gate insulator (GI) interfaces confirmed the a-IGZO-channel conduction. The dual-heterojunction TFT with IZO/HfO/a-IGZO-assisted ELA provides a guideline for overcoming the trade-off between high mobility (μ) and positive V_Th control for stable enhancement mode operation with increased I_D. Full article

The active-matrix technology incorporates a transistor to exert precise control over each pixel within a pixel array, eliminating the issue of crosstalk between neighboring pixels that is prevalent in the passive-matrix approach. Consequently, the active-matrix method facilitates the realization of high-resolution arrays, and this inherent advantage has propelled its widespread adoption, not only in display applications but also in diverse sensor arrays from lab to industry. In this comprehensive review, we delve into instances of active-matrix arrays utilizing thin-film transistors (TFTs) that leverage emerging materials such as organic semiconductors, metal oxide semiconductors, two-dimensional materials, and carbon nanotubes (CNTs). Our examination encompasses a broad classification of active-matrix research into two main categories: (i) displays and (ii) sensors. We not only assess the performance of TFTs based on emerging materials within the active-matrix framework, but also explore the evolving trends and directions in active-matrix-based displays and sensors. Full article

We studied the impact of NF₃ plasma treatment on the HfO₂ gate insulator of amorphous tin oxide (a-SnO_x) thin-film transistors (TFTs). The plasma treatment was for 0, 10, or 30 s. The HfO₂ insulator demonstrated a slightly higher breakdown voltage, whereas the capacitance value remained almost constant (~150 nF/cm²). The linear mobility slightly increased from ~30 to ~35 cm²/Vs when the treatment time increased from 0 to 10 s, whereas a 30 s-treated TFT demonstrated a decreased mobility of ~15 cm²/Vs. The subthreshold swing and the threshold voltage remained in the 100–120 mV/dec. range and near 0 V, respectively. The hysteresis dramatically decreased from ~0.5 V to 0 V when a 10 s treatment was applied, and the 10 s-treated TFT demonstrated the best stability under high current stress (HCS) of 100 μA. The analysis of the tin oxide thin film crystallinity and oxygen environment demonstrated that the a-SnO_x remained amorphous, whereas more metal–oxygen bonds were formed with a 10 s NF₃ plasma treatment. We also demonstrate that the density of states (DOS) significantly decreased in the 10 s-treated TFT compared to the other conditions. The stability under HCS was attributed to the HfO₂/a-SnO_x interface quality. Full article

In contrast to lift-off and shadow mask processes, the back-channel wet etching (BCWE) process is suitable for industrial-scale metallization processes for the large-area and mass production of oxide thin-film transistors (TFTs). However, chemical attacks caused by the corrosive metal etchants used in the BCWE process cause unintended performance degradation of oxide semiconductors, making it difficult to implement oxide TFT circuits through industrial-scale metallization processes. Herein, we propose composition engineering of oxide semiconductors to enhance the chemical durability and electrical stability of oxide semiconductors. The chemical durability of InZnO against Al etchants can be improved by increasing the content of indium oxide, which has a higher chemical resistance than zinc oxide. As a result, A damage-free BCWE-based metallization process was successfully demonstrated for oxide TFTs using In-rich InZnO semiconductors. Furthermore, In-rich InZnO TFTs with wet-etched Al electrodes exhibited electrical performance comparable to that of lift-off Al electrodes, without chemical attack issues. Full article

Metal-oxide-semiconductor (MOS)-based thin-film transistors (TFTs) are gaining significant attention in the field of flexible electronics due to their desirable electrical properties, such as high field-effect mobility (μ_FE), lower I_OFF, and excellent stability under bias stress. TFTs have widespread applications, such as printed electronics, flexible displays, smart cards, image sensors, virtual reality (VR) and augmented reality (AR), and the Internet of Things (IoT) devices. In this study, we approach using a low-temperature solution-processed hafnium zirconium oxide (HfZrOx) gate insulator (GI) to improve the performance of lanthanum zinc oxide (LaZnO) TFTs. For the optimization of HfZrO GI, HfZrO films were annealed at 200, 250, and 300 °C. The optimized HfZrO-250 °C GI-based LaZnO TFT shows the μ_FE of 19.06 cm²V⁻¹s⁻¹, threshold voltage (V_TH) of 1.98 V, hysteresis voltage (V_H) of 0 V, subthreshold swing (SS) of 256 mV/dec, and I_ON/I_OFF of ~10⁸. The flexible LaZnO TFT with HfZrO-250 °C GI exhibits negligible ΔV_TH of 0.25 V under positive-bias-temperature stress (PBTS). The flexible hysteresis-free LaZnO TFTs with HfZrO-250 °C can be widely used for flexible electronics. These enhancements were attributed to the smooth surface morphology and reduced defect density achieved with the HfZrO gate insulator. Therefore, the HfZrO/LaZnO approach holds great promise for next-generation MOS TFTs for flexible electronics. Full article