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The Tauc–Lorentz–Urbach (TLU) dispersion model allows us to build a dielectric function from only a few parameters. However, this dielectric function is non-analytic and presents some mathematical drawbacks. As a consequence of this issue, the model becomes inaccurate. In the present work, we will adopt a procedure to conveniently transform the TLU model into a self-consistent dispersion model. The transformation involves the integration of the original TLU imaginary dielectric function ϵ 2 by using a Lorentzian-type function of semi-width, Γ. This novel model is analytic and obeys the other necessary mathematical requirements of the optical constants of solid-state materials. The main difference with the non-analytic TLU model occurs at values of the photon energy near or lower than that of the bandgap energy (within the Urbach absorption region). In particular, this new model allows us to reliably extend the optical characterization of amorphous-semiconductor thin films within the limit to zero photon energy. To the best of our knowledge, this is the first time that the analytic TLU model has been successfully used to accurately determine the optical constants of unhydrogenated a-Si films using only their normal-incidence transmission spectra. [ABSTRACT FROM AUTHOR]

In this study, we propose tunable pH sensors based on the electric-double-layer transistor (EDLT) with time-dependent sensitivity characteristics. The EDLT is able to modulate the drain current by using the mobile ions inside the electrolytic gate dielectric. This property allows the implementation of a device with sensitivity characteristics that are simply adjusted according to the measurement time. An extended gate-type, ion-sensitive, field-effect transistor consisting of a chitosan/Ta2O5 hybrid dielectric EDLT transducer, and an SnO2 sensing membrane, were fabricated to evaluate the sensing behavior at different buffer pH levels. As a result, we were able to achieve tunable sensitivity by only adjusting the measurement time by using a single EDLT and without additional gate electrodes. In addition, to demonstrate the unique sensing behavior of the time-dependent tunable pH sensors based on organic–inorganic hybrid EDLT, comparative sensors consisting of a normal FET with a SiO2 gate dielectric were prepared. It was found that the proposed pH sensors exhibit repeatable and stable sensing operations with drain current deviations <1%. Therefore, pH sensors using a chitosan electrolytic EDLT are suitable for biosensor platforms, possessing tunable sensitivity and high-reliability characteristics. [ABSTRACT FROM AUTHOR]

We focused on the importance of solvent evaporation governed by the temperature of the pre-annealing stage (TS) in solution-processed zinc tin oxide (ZTO) thin-film transistors (TFTs). We controlled TS based on the boiling point (BP) of the solvent used. When TS reaches the BP, the field effect mobility is found to be about 1.03 cm2/V s, which is 10 times larger than the TS < Bp case (0.13 cm2/V s). The reason is presumed to be that residual organic defects are effectively removed as TS increases. In addition, when Ts is beyond Bp, the mobility is rather decreased due to structural defects such as pores and pinholes. Based on our results, it is noted that TS plays a significant role in the enhancement of electrical performance and stability of solution-processed ZTO TFTs. [ABSTRACT FROM AUTHOR]

In this work, we have proposed an extraction method for equivalent oxide thickness (EOT) of a thin high-dielectric-constant ($\kappa $) gate insulator (GI) through direct capacitance–voltage (${C}$ – ${V}$) measurements in amorphous indium tungsten oxide (a-IWO) nano-sheet (NS) junctionless (JL) transistors (a-IWO NS-JLTs). Without additional metal/insulator/Si-substrate (MIS) ${C}$ – ${V}$ measurements, the proposed extraction method can directly extract EOT (or equivalent $\kappa $ values) of a thin HfO2GI at different ON-state gate voltages (${V}_{G}$) in a-IWO NS-JLTs. Results of ${C}$ – ${V}$ measurements show that the extracted EOT varies with ON-state ${V}_{G}$ owing to the gate-controllable conductance of the amorphous oxide semiconductor (AOS) NS channel. Finally, the extracted EOT can be used to estimate the field-effect mobility ($\mu _{\text{FE}}$) of a-IWO NS-JLTs at different ON-state ${V}_{G}$. [ABSTRACT FROM AUTHOR]

This article discusses the advancements in device technology for integrated circuits (ICs) in the past decade. The main focus has been on developing higher-performance devices with lower power consumption and a smaller footprint. Three strategies have emerged: "more Moore" which introduces new structures to improve the performance of silicon-based transistors, using emerging semiconductors with high mobility, and developing novel devices based on new state variables. The article also highlights recent developments in the field and presents a collection of papers on emerging materials and transistors for ICs. [Extracted from the article]

This article discusses the potential of amorphous oxide semiconductor (AOS) for monolithic 3D dynamic random-access memory (DRAM). AOS, specifically indium gallium zinc oxide (IGZO), has properties that make it suitable for DRAM cell transistors, such as high carrier mobility and a large energy bandgap. The use of AOS in DRAM could enable monolithic 3D integration, increasing bandwidth, reducing access latency, and achieving high density. However, there are challenges to overcome, such as reducing interface resistance and controlling defects in the AOS film. If these challenges are addressed, AOS DRAM could revolutionize the field and find applications in emerging technologies like artificial intelligence and the Internet of Things. [Extracted from the article]

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Several studies on amorphous oxide semiconductor thin-film transistors (TFTs) applicable to next-generation display devices have been conducted. To improve the poor switching characteristics and gate bias stability of co-sputtered aluminum–indium–zinc oxide (AIZO) TFTs, we fabricate Al2O3/indium–zinc oxide (IZO) dual-active-layer TFTs. By varying the Al2O3 target power and oxygen partial pressure in the chamber during Al2O3 back-channel deposition, we optimize the electrical characteristics and gate bias stability of the Al2O3/IZO TFTs. The Al2O3/IZO TFTs, which are fabricated under 50 W Al2O3 target power and 13% oxygen partial pressure conditions, exhibit a high electron mobility of 23.34 cm2/V·s, a low threshold voltage of 0.96 V, an improved on–off current ratio of 6.8 × 107, and a subthreshold swing of 0.61 V/dec. Moreover, by increasing the oxygen partial pressure in the chamber, the positive and negative bias stress values improve to +0.32 V and −2.08 V, respectively. X-ray photoelectron spectroscopy is performed to reveal the cause of these improvements. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate biocompatible micromachined buckled membranes for the operation in liquids. The membranes feature diameters between 600 and 800 $\mu \text{m}$ as well as integrated piezoelectric thin film actuators, thus enabling switching between the bistable states. The membrane material is known to be not biocompatible, hence a hydrogenated amorphous silicon carbide (a-SiC:H) layer is deposited on the surface. For demonstration purposes, a 70 nm ±3 nm thin a-SiC:H coating with a specific silicon to carbon ratio was chosen, with a negligible impact on the overall switching performance of the bistable membranes. Furthermore, a relation between the membrane center velocity at the first characteristic resonance frequency and the switching ability of a membrane in different viscous fluids is shown. Based on a small signal analysis the switching behavior can be predicted. The membranes were successfully switched in liquids with a dynamic viscosity up to 286 mPa $\cdot \text{s}$. The biocompatibility of the membranes was examined by growing Caco-2 cells, a human carcinoma cell line, on a-SiC:H thin films, featuring different carbon contents and organic surface treatments. The proliferation and adhesion of the cells on the substrates are examined in an empirical cell growth and removal study. Only a-SiC:H surfaces pre-treated with an O2-plasma and coated with Collagen Type I indicated to provide an environment of improved cell adhesiveness compared to other surface treatments. The biological investigations resulted in good cell proliferation, that also depends on the altered hydrophilicity of the surface, as well as on the carbon content of the a-SiC:H thin films. This study reveals that a broad range of biocompatible a-SiC:H surfaces can be prepared, whereby the cell growth can be tailored in terms of proliferation and adhesion for different biomedical application scenarios. Finally, this paper reports on the mechanical features of bistable, buckled membranes and their suitability as a growth substrate for human cell cultures, due to the good biocompatibility of a-SiC:H thin films. We therefore suggest that it will be feasible to grow cells on bistable MEMS membranes, enabling cell experiments in liquid medical environments, with both mechanically excitable and biocompatible surfaces. [2022-0006] [ABSTRACT FROM AUTHOR]

The a-InGaZnO (a-IGZO) thin-film transistors (TFTs) in elevated-metal metal-oxide (EMMO) architecture was found to exhibit high stability against photo-bias stresses. In contrast to the common photo-enhanced degradation, an abnormal self-compensation effect of photo-bias instabilities was first observed for amorphous oxide semiconductor (AOS) TFTs. By analyzing the defect states and element distributions in both channel and source/drain (S/D) regions, the unique migration of thermally generated metal interstitials in a-IGZO S/D was clarified to be the origin. More specifically, the positive bias stress (PBS)-induced negative shift of threshold voltage (${V}_{\text{th}}$) originates from the ionization of positive metal ions near the backchannel, while these positively charged ions can be compensated by the illumination-excited electrons, resulting in photo-stable AOS TFTs. This also provides a flexible way to implement the electrically stable depletion-mode AOS TFTs. [ABSTRACT FROM AUTHOR]

The low–temperature poly–Si oxide (LTPO) backplane is realized by monolithically integrating low–temperature poly–Si (LTPS) and amorphous oxide semiconductor (AOS) thin–film transistors (TFTs) in the same display backplane. The LTPO–enabled dynamic refreshing rate can significantly reduce the display's power consumption. However, the essential hydrogenation of LTPS would seriously deteriorate AOS TFTs by increasing the population of channel defects and carriers. Hydrogen (H) diffusion barriers were comparatively investigated to reduce the H content in amorphous indium–gallium–zinc oxide (a–IGZO). Moreover, the intrinsic H–resistance of a–IGZO was impressively enhanced by plasma treatments, such as fluorine and nitrous oxide. Enabled by the suppressed H conflict, a novel AOS/LTPS integration structure was tested by directly stacking the H–resistant a–IGZO on poly–Si TFT, dubbed metal–oxide–on–Si (MOOS). The noticeably shrunken layout footprint could support much higher resolution and pixel density for next–generation displays, especially AR and VR displays. Compared to the conventional LTPO circuits, the more compact MOOS circuits exhibited similar characteristics. [ABSTRACT FROM AUTHOR]

In recent years, the downscaling of transistors has sparked considerable interest in the advancement of amorphous oxide semiconductors, particularly indium-hafnium-zinc oxide (IHZO) has remarkable potential in applications such as high-resolution displays and 3D NAND. For the first time, we propose the fabrication of IHZO thin film transistors (TFTs) via thermal atomic layer deposition (TH-ALD). The preparation, electrical properties, and stability of IHZO TFTs are investigated. The performance of TFT deposited at 250 °C and annealed in N 2 atmosphere at 300 °C exhibits a high field-effect mobility (μ) of 22.53 cm2/Vs, a high I on / I off of ∼107, a low threshold voltage (V th) of 0.15 V, and a minimum subthreshold swing (SS) of 0.24 V/decade. Furthermore, the threshold voltage shifts (Δ V th) in TFTs annealed in N 2 and O 2 are 0.31 and 0.16 V, respectively. These enhancements are attributed to the defects suppression and remaining ionized oxygen vacancies result in increased electron concentration in N 2 -annealed films. In comparison, O 2 annealing causes a reduction in field effect mobility but concurrently enhances stability due to the direct passivation of defects, which leads to fewer oxygen vacancies. Additionally, Hf content can also impact the performance of TFT devices, even a small addition of Hf also results in the effective reduction of the carrier concentration. These findings provide valuable insights into the device mechanism of IHZO TFTs, presenting a novel avenue for comprehending and augmenting their overall performance. • Hafnium suppresses trap density and reduces carrier concentration more effectively than Gallium. • Nitrogen-annealed InHfZnO thin film transistors can remain ionized oxygen vacancies increase electron concentration. • Oxygen-annealed InHfZnO thin film transistors directly passivate defects to enhance stability but reduce effect mobility. • 2-cycle deposition of Hafnium in Atomic Layer Deposition chamber forms defects to facilitate charge accumulation. [ABSTRACT FROM AUTHOR]

The energy band dependent mobility in heterojunction amorphous oxide semiconductor thin‐film transistors (TFTs) is investigated. Results indicate that both of the energy band configurations with potential well (PW) and barrier (PB) formation could allow TFT with high‐mobility operation. Specifically, TFT with PW only exhibits high mobility when the gate electric field direction is consistent with that of build‐in electric field in PW, whereas TFT with PB could exhibit high mobility no matter what the electric field direction configuration is. [ABSTRACT FROM AUTHOR]

Structural inhomogeneities in the form of voids of nanometer sizes (nanovoids) have long been known to be present in hydrogenated amorphous semiconductors (Si, Ge). The physical and electrical properties of hydrogenated amorphous semiconductors can be pronouncedly influenced by thepresence and characteristics of such nanovoids. In this work, by measuring in situ the intrinsic stress developments during deposition of pure, amorphous and of hydrogenated amorphous semiconductor (Si, Ge) thin films, under the same conditions in ultrahigh vacuum and on a comparative basis, a major source of tensile stress development could be ascribed to the occurrence of nanovoids in a-Si:H and a-Ge:H. The measurements allowed a quantitative evaluation of the surface stress acting along the surface of the nanovoids: 1.1-1.9 N/m for a-Si:H and 0.9-1.9 N/m for a-Ge:H. [ABSTRACT FROM AUTHOR]

Hopping charge transport in amorphous semiconductors having spatially correlated exponential density of states has been considered. Average carrier velocity is exactly calculated for the quasi-equilibrium (nondispersive) transport regime. We suggest also a heuristic approach for the consideration of the carrier velocity for the non-equilibrium dispersive regime. [ABSTRACT FROM AUTHOR]

• Hybrid multilayer nanostructures were obtained by ion-beam sputtering method. • Multilayer nanostructures are formed from layers of superparamagnetic metal–insulator composite and ZnO semiconductor interlayers. • The structural, electrical, magnetic, magneto-optical properties and magnetoresistance of hybrid multilayer structures have been studied. • The magnetoresistance of hybrid multilayer nanostructures depends significantly on the thickness of ZnO interlayers. • An increase in the magnetoresistance of hybrid multilayer nanostructures in comparison with the reference metal–insulator composite has been experimentally discovered. The structural, electrical, magnetic, magneto-optical properties and magnetoresistance of {[(Co 40 Fe 40 B 20) 34 (SiO 2) 66 ]/[ZnO]} n multilayer structures, where n = 50 is the number of bilayers (Co 40 Fe 40 B 20) 34 (SiO 2) 66 nanocomposite and ZnO have been studied. The thicknesses of (Co 40 Fe 40 B 20) 34 (SiO 2) 66 nanocomposite layers as well as ZnO spacers were varied in a wide range. The samples were synthesized by ion-beam sputtering onto glass ceramic substrates. The (Co 40 Fe 40 B 20) 34 (SiO 2) 66 composite have an amorphous structure and the semiconductor ZnO interlayers have a hexagonal crystalline structure with the p63mc symmetry group. The nanocomposite layers containing a ferromagnetic component far from the percolation threshold are in a superparamagnetic state. The presented in the paper data of magnetization, magneto-optical transverse Kerr effect and magnetoresistance indicates that long-range ferromagnetic order does not form down to 77 K both for references ZnO films and studied multilayers with thin and thick ZnO interlayers. An increase in the magneto-optical signal in multilayers compared to references (Co 40 Fe 40 B 20) 34 (SiO 2) 66 composite films has been detected at 1.2 eV. The magnetoresistance of {[(Co 40 Fe 40 B 20) 34 (SiO 2) 66 ]/[ZnO]} n multilayers with thick (>32 nm) ZnO interlayers is lower than in reference (Co 40 Fe 40 B 20) 34 (SiO 2) 66 nanocomposite, while at thin ZnO interlayers magnetoresistance is significantly higher and reaches 12 % at temperatures of 77 К. Possible mechanisms of ferromagnetic and antiferromagnetic ordering, enhancement of the magneto-optical response and magnetoresistance in {[(Co 40 Fe 40 B 20) 34 (SiO 2) 66 ]/[ZnO]} n multilayer nanostructures are discussed. [ABSTRACT FROM AUTHOR]

Bi-layer thin film transistors (TFTs) have been fabricated with a channel structure comprising a dielectric layer, a semiconducting amorphous-Si-In-Zn-O (a-SIZO) layer, and a semiconducting amorphous-Si-Zn-Sn-O (a-SZTO) layer, aiming to improve field effect mobility and stability. These films were deposited using RF sputtering at room temperature. The TFTs with a bottom gate top contact, processed at 500 °C, exhibited high mobilities (> 32 cm 2 V−1 s−1) along with a current on/off ratio of approximately 10 8 and a subthreshold swing (SS) value below 0.5 V decade−1 primarily because of reduced trap density and presence of highly conducting ultrathin a-SIZO layer. Furthermore, the bi-layer TFTs demonstrated notable stability under negative and positive bias temperature stress conditions. [Display omitted] • Fabrication of bi-layer TFTs featuring a channel structure composed of a dielectric layer, semiconducting a-SIZO layer, and a semiconducting a-SZTO layer. • TFTs showcasing field effect mobilities exceeding 32 cm2 V−1 s−1, along with a current on/off ratio of approximately 108 and an SS value below 0.5 V decade−1. • Exceptional stability of the bi-layer TFTs demonstrated under temperature and bias stresses of ±20 V. [ABSTRACT FROM AUTHOR]

Amorphous oxide semiconductors are widely used in the backplane thin film transistors (TFTs) of displays and are extensively researched as materials for next-generation memory devices. However, they face reliability degradation due to stress factors such as thermal, bias, and light exposure. To mitigate these issues, extensive research is focused on improvements, including doping, enhancing crystallinity, and applying pre-and post-treatments. This study investigates the significantly improved reliability and electrical properties of amorphous indium gallium tin oxide (a-IGTO) TFTs by adopting a dual-channel configuration through simultaneous co-sputtering of HfO 2 and IGTO targets. The device fabrication involved co-sputtering HfO 2 and IGTO at the gate oxide interface, followed by depositing an IGTO-only layer, rather than doping the entire channel material. The effect of varying Hf concentration was evaluated by applying different HfO 2 sputtering powers. Optimal hafnium doping reduced the threshold voltage of the a-IGTO TFT from −0.85 V to 0.15 V compared to the pristine a-IGTO TFT, while enhancing the field-effect mobility (μ F E). Furthermore, the Hf-doped device exhibited improved stability, with a reduced threshold voltage shift (Δ V t h ) under positive (+15 V) and negative(-15 V) bias stress at 3000s, decreasing from 11.5 V to 4.8 V , and 4.7 V –1.1 V , respectively. This study proposes a novel device fabrication method to enhance the reliability of amorphous oxide semiconductor, addressing their inherent stress-related issues. [ABSTRACT FROM AUTHOR]

• The effect of Ga on the optical properties of Se 80 Sn 20 films were studied for the first time for this percentage of Se and Sn. • Amorphous thin films of different thicknesses of Se 80 Sn 20- x Ga x (x = 0, 5, 10 and 15) have prepared. • Linear and nonlinear optical properties are calculated and analysed. • Comparative study is considered with the data of other authors for nearly compositions. The glassy compositions of Se 80 Sn 20- x Ga x (x = 0, 5, 10 and 15) were synthesized in a bulk and thin film forms by melt quenching and thermal evaporation techniques respectively. X-ray diffraction patterns (XRD) indicate that the investigated film compositions are in amorphous state. The transmittance spectra T (λ) of films in the thickness range (119–727 nm) were measured in the range of wavelengths (350–2500 nm). Swanepoel's method was used to calculate the optical parameters (refractive index n and absorption index k) from T (λ) data. Value of Urbach energy (E e) was found to decrease from 0.126 eV to 0.106 eV with increasing Ga content. Values of indirect allowed optical energy gap E g opt increases from 1.231 eV to 1.818 eV with the increase Ga concentration. The optical conductivity σ opt. increases with increasing the incident photon energy (h ν). Other parameters are calculated and analyzed as a function of the change in Ga concentration. The linear dispersion parameters are used to calculate the nonlinear optical susceptibility χ (3) and the nonlinear refractive index n 2. The shifts in the optical parameters values by adding Ga suggest that the prepared films may use for potential photonic devices. [ABSTRACT FROM AUTHOR]

• The ZnSnO thin-film transistors by atomic layer depositon need annealing over 500 °C. • Implementation of ZnSnO TFT with excellent performance at low temperature. • The process temperature was lowered by adopting a multilayered ZnO/SnO 2 structure. • ZnSnO thin-films are applicable to flexible substrates by lowering process temperature to 350 °C. The performance of conventional ZnSnO (ZTO) amorphous oxide semiconductor thin-film transistors deposited by atomic layer deposition was optimized at annealing temperatures greater than 500 °C, which is higher than the application temperature of flexible substrates (400 °C). Therefore, we deposited a ZTO thin film as a multilayered ZnO/SnO 2 structure to lower the process temperature to below 400 °C. To optimize the performance of the device with a multilayered structure, we examined the effects of cycles and growth temperatures. Finally, after performing 6 supercycles with 10 cycles of ZnO and 20 cycles of SnO 2 , at a growth temperature of 180 °C and annealing at 350 °C for 1 h, the device achieved a saturation carrier mobility of 8.09 cm2/V·s, threshold voltage of 1.6 V, subthreshold swing of 0.58 V/dec, and on–off current ratio of 2.63 × 107. The optimized multilayer-structured device performed better than the ZTO device annealed at 350 °C for 1 h, and even outperformed the device annealed at 500 °C for 1 h. X-ray photoelectron spectroscopy analysis was also conducted to analyze the properties of conventional ZTO and multilayered ZnO/SnO 2 thin films. [ABSTRACT FROM AUTHOR]

Low-temperature process compatibility is a key factor in successfully constructing additional functional circuits on top of pre-existing circuitry without corrupting characteristics thereof, a technique that typically requires die-to-die (wafer-to-wafer) stacking and interconnecting. And against thermal annealing, which is mandatory and is possible only globally for activating amorphous oxide semiconductors, the selective control of electrical characteristics of the oxide thin-films for integrated circuit applications is challenging. Here, a low-temperature process that enables n-type doping of the designed region of insulating In2O3 thin-film is demonstrated. A short hydrogen plasma treatment followed by low-temperature annealing is used to increase interstitial and substitutional hydrogen associated bond states creating shallow donor levels in the insulating In2O3 surface to transform the thin-film into an n-type semiconductor. As a result, an In2O3 thin-film transistor with a high on/off current ratio (>108), a field-effect mobility of 3.8 cm2 Vâˆ'1 sâˆ'1, and a threshold voltage of ∼3.0 V has been developed. Compared to performing just thermal annealing, the H-plasma assisted annealing process resulted in an n-type In2O3 thin-film transistor showing similar characteristics, while the processing time was reduced by ∼1/3 and the plasma-untreated area still remained insulating. With further development, the hydrogen plasma doping process may make possible a monolithic planar process technology for amorphous oxide semiconductors. [ABSTRACT FROM AUTHOR]

In this study, the effect of radiation on an amorphous semiconductor InWZnO (IWZO) thin film has been investigated. From the x-ray photoelectron spectroscopy in-depth analysis, most of the oxygen vacancies in pristine IWZO films are located at the bottom of the film. As the radiation dose increases, the proportion of oxygen vacancies at the bottom of the film increases. However, the top of the IWZO film is hardly affected by the radiation dose. In addition, the resistive switching behavior of an IWZO memristor under irradiation has also been investigated. A forming process and a bipolar I–V curve of the IWZO memristor vary with the radiation dose. The high resistance state of the memristor is significantly degraded at a radiation dose of 1000 krad, which is due to the more defects in the IWZO film. The retention time of the IWZO memristor is up to 104 s at 85 °C with 100 krad. The damaged site in the IWZO film is observed and fabricated into memristors under radiation. The IWZO film as the resistive switching layer exhibits great potential in harsh environments such as polar regions, space technology, nuclear military, and medical imaging. [ABSTRACT FROM AUTHOR]

The reliability of amorphous oxide semiconductor thin-film transistors (AOS-TFTs) is vital for high-definition displays and functional electronic devices. However, drain current drop (DCD) degradation has been commonly observed in the output characteristics of thin-film transistors (TFTs) with channel lengths of ${L} < 10 \mu \text{m}$. Here, we show that DCD is a reversible process that is closely related to reduced metal-oxygen bonds. Based on device theory and simulations, we propose that the DCD effect is mainly caused by hot carriers, whose velocities are inversely proportional to the drain depletion width. Therefore, DCD failure could be alleviated simply by using the drain-offset structure. Experiments show that drain-offset TFTs improve DCD critical voltages (by ~130%) without sacrificing the ON-/ OFF-ratio. These studies provide theoretical and experimental approaches to effectively suppress DCD. [ABSTRACT FROM AUTHOR]

The tellurium (Te)‐doped Ag60‐xSe40Tex (x = 0%, 5%, 10%, 15%) thin films of thickness ∼800 nm were prepared from the bulk sample by thermal evaporation method on a glass substrate. The X‐ray diffraction study revealed the amorphous nature of the films whereas the change in vibrational modes was noticed from the Raman spectroscopy. The composition of the films was verified by energy dispersive X‐ray analysis and the surface morphology pictures were taken by field emission scanning electron microscopy and atomic force microscope. The changes in optical properties (linear and non‐linear) with Te addition were studied from UV‐Visible spectroscopy data and related empirical formulas. The addition of Te reduced the bandgap values significantly and the reduction in transmission resulted in the increase of the linear refractive index. The decrease in optical bandgap is due to an increase in disorder while the width of the tail in the gap increased with Te%. The optical density, dispersion energy, extinction coefficient, carrier concentration, dielectric constant, oscillator wavelength increased while the oscillator energy, oscillator strength, optical electronegativity decreased with Te content. The electrical susceptibility increased with Te content. The non‐linear susceptibilities and the non‐linear refractive index increased which is good for the nonlinear photonic devices. [ABSTRACT FROM AUTHOR]

To provide a unique opportunity for on‐chip scaled bioelectronics, a symmetrically gated metal‐oxide electric double layer transistor (EDLT) with ion‐gel (IG) gate dielectric and simple in‐plane Corbino electrode architecture is proposed. Using amorphous indium‐gallium‐zinc oxide (a‐IGZO) semiconductor and IG dielectric layers, low‐voltage driven EDLTs with high ionotronic effects can be realized. More importantly, in contrast to the conventional asymmetric rectangular EDLTs which can cause non‐uniform potential variation in the active channel layer and eventually degrade the sensing performance, the new symmetrical in‐plane type EDLTs achieve high and spatially uniform ion responsive behaviors. The symmetrically gated a‐IGZO EDLTs exhibited a responsivity of 129.4% to 5 ppm mercury (Hg2+) ions which are approximately three times higher than that with conventional electrode structure (responsivity of 38.5%). To confirm the viability of the new device architectures and the findings, the detailed mechanism of the symmetric gating effects in the in‐plane EDLTs with a variety of electrical characterization and 3D fine element analysis simulations is also discussed. [ABSTRACT FROM AUTHOR]

Electrical characteristics of self-aligned top-gate (SATG) amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with 4 nm-thick atomic-layer-deposited (ALD) AlOx gate insulator (GI) are investigated. It is demonstrated that the SATG a-IGZO TFTs present high-performance metrics including a near-ideal subthreshold swing (SS) of 60.9 mV/dec, a low off-state current below 10−12 A, a positive ${V}_{\text{th}}$ of 0.1 V, and a decent mobility of 14.1 cm2/ $\text{V}\,\cdot $ s. In addition, the TFTs exhibit negligible ${V}_{\text{th}}$ shifts less than 0.02 V against electrical bias stresses. Both high performance and excellent stability are thus simultaneously achieved for the ultrathin GI of amorphous oxide semiconductor (AOS) TFTs. [ABSTRACT FROM AUTHOR]

Thin-film transistors (TFTs) based on amorphous Indium-Gallium-Zinc Oxide (a-IGZO) can be used to drive the quantum-dot light-emitting diodes (QLEDs) for active-matrix (AM) displays. To reduce the fabrication complexity, Al reaction-induced conductive a-IGZO is developed as a common electrode, which simultaneously serves as a drain electrode for the TFT and as a bottom electrode for the QLED. The obtained a-IGZO electrode exhibits a low sheet resistance of 120 $\Omega $ / and a high transmittance of 92.1% at a thickness of 100 nm. With the proposed a-IGZO electrode, QLED demonstrates a high external quantum efficiency of 26%. Moreover, because both TFT and QLED share the same a-IGZO electrode, at least two patterning processes can be reduced in making a AM display. Our results suggest that Al reaction-induced conductive a-IGZO could be a promising pixel electrode for AMQLED displays. [ABSTRACT FROM AUTHOR]

To utilize continuous ultralow intensity signals from oxide synaptic transistors as artificial synapses that mimic human visual perception, we propose strategic oxide channels that optimally utilize their advantageous functions by stacking two oxide semiconductors with different conductivities. The bottom amorphous indium–gallium–zinc oxide (a-IGZO) layer with a relatively low conductivity was designed for an extremely low initial postsynaptic current (PSCi) by achieving full depletion at a low negative gate voltage, and the stacked top amorphous indium–zinc oxide (a-IZO) layer improved the amplitude of the synaptic current and memory retention owing to the enhancement in the persistent photoconductivity characteristics. We demonstrated an excellent photonic synapse thin-film transistor (TFT) with a precise synaptic weight change even in the range of ultralow light intensity by adapting this stacking IGZO/IZO channel. The proposed device exhibited distinct ∆PSC values of 3.1 and 18.1 nA under ultralow ultraviolet light (350 nm, 50 ms) of 1.6 and 8.0 μW/cm2. In addition, while the lowest light input exhibited short-term plasticity characteristics similar to the "volatile-like" behavior of the human brain with a current recovery close to the initial value, the increase in light intensity caused long-term plasticity characteristics, thus achieving synaptic memory transition in the IGZO/IZO TFTs. [ABSTRACT FROM AUTHOR]

In amorphous InAlZnO (a-IAZO), the addition of the third cation of Al further slows the crystallization kinetics of In2O3 and enhances amorphous phase stability, compared to the binary cation system of InZnO. In addition, substantially high carrier mobilities of a-IAZO are obtained, in its unannealed state: Hall mobility of 30–50 cm2/Vs at a high carrier density regime (>~1018/cm3) and thin film transistor (TFT) field effect mobility of ~8–15 cm2/Vs at a low carrier density regime (<~1016/cm3). Gate bias stress stability of IAZO TFTs is investigated with positive and negative gate biases over time. Because of the channel depletion of n-type IAZO when negative gate bias is applied, no performance instabilities were identified. However, with positive gate bias stress (PBS) conditions (30 V), the threshold voltage (VT) shifts towards higher voltages during the initial 100 s and then no significant changes in VT are observed during the remaining time, over 105 s of the dependent measurements. The TFT field effect mobility shows a similar trend: increases from 7.64 cm2/Vs to 11.74 cm2/Vs within the first 100 s and then is saturated. It is identified that the PBS-induced device parameter variations are attributed to an increase and saturation of trap density at the channel/dielectric interface. [ABSTRACT FROM AUTHOR]

Summary: The roles of amorphous phases in photochemical water splitting of semiconductors are still in debate, as the effects of the amorphous phase are largely irregular even in a single material. We presumed that the photochemistry of crystal‐amorphous mixed semiconductor systems would be governed by the interface characteristics, and conducted a systematic study to understand the origins of the largely varying photochemical reaction of semiconductors having an amorphous phase. First‐principles calculations on crystalline anatase and amorphous TiO2 showed that the coexistence of crystalline and amorphous TiO2 and the exposure of the phase boundary are advantageous due to the accelerated charge separation by interface dipole moment and the parallelizable oxygen evolution reaction at the boundary. Our computation‐based strategies were demonstrated in our experiments: only the TiO2 nanoparticle and nanotube having partial amorphization on surfaces have highly enhanced photocatalytic water splitting performances (approximately 700%) compared to the pristine and completely amorphized TiO2 systems. [ABSTRACT FROM AUTHOR]

We aim to derive a phenomenological approach to link the theories of anomalous transport governed by fractional calculus and stochastic theory with the conductivity behavior governed by the semi-empirical conductivity formalism involving Debye, Cole–Cole, Cole–Davidson, and Havriliak–Negami type conductivity equations. We want to determine the anomalous transport processes in the amorphous semiconductors and insulators by developing a theoretical approach over some mathematical instruments and methods. In this paper, we obtain an analytical expression for the average behavior of conductivity in complex or disordered media via the fractional-stochastic differential equation, the Fourier–Laplace transform, some natural boundary initial conditions, and familiar physical relations. We start with the stochastic equation of motion called the Langevin equation, develop its equivalent master equation called the Klein–Kramers or Fokker–Planck equation, and consider the time-fractional generalization of the master equation. Once we derive the fractional master equation, we then determine the expressions for the mean value of the variables or observables through some calculations and conditions. Finally, we use these expressions in the current density relation to obtain the average conductivity behavior. [ABSTRACT FROM AUTHOR]

In solution-processed oxide thin-film transistors, postdeposition thermal processing significantly changes the film’s transport properties and is essential for high-performance devices. The mobility, bias stability, and trapping–detrapping related hysteresis are improved with higher processing temperatures, which is generally attributed to decreased concentrations of localized states that act as electron traps. Fabricating and characterizing 29 devices, we provide further experimental evidence that postdeposition processing, indeed, leads to enhanced channel electron mobility in sol–gel indium–zinc oxide TFTs, and on the basis of a simple model, we extract physical parameters that yield a quantitative assessment of the changes in the densities and the properties of the localized trap states. The data are obtained for sol–gel indium–zinc oxide thin films and TFTs subjected to thermal postdeposition processing from 300 °C to 500 °C. The extracted parameters indicate that the trap state densities in the bulk semiconductor and at the interface decrease by factors of 5 and 3, respectively. Furthermore, the localized states become shallower, and the band mobility increases with higher processing temperatures. [ABSTRACT FROM AUTHOR]

In this study, we present programming speed enhancement in amorphous oxide semiconductor memory thin-film transistor (TFT). We developed a nonvolatile memory transistor based on InZnSnO back-channel-etch TFT with InGaZnO charge storage layer inserted between gate insulators. We proposed double-gate (DG) and body-contacted (BC) memory structure to improve memory erase speed, which is the most important issue in oxide memory TFTs. DG memory did not show sufficient improvement due to large voltage drop in second gate insulator. BC memory, which can control back-channel potential directly, showed significant improvement on memory program/erase speed. [ABSTRACT FROM AUTHOR]

In this work, amorphous praseodymium-doped In-Sn-Zn-O (ITZO-Pr) thin-film transistors (TFTs) were fabricated with improved negative-bias illumination stress (NBIS) stability under different radio frequency (RF) magnetron sputtering powers. The optimized ITZO-Pr TFTs presented field effect mobility ($\boldsymbol {\mu }_{\text{FE}}$) of 20.9 cm $^{2}\cdot {}\text{V}^{-1}\cdot {}\text{s}$ −1, steep subthreshold (SS) of 0.27 V/dec, and small threshold voltage shift (${\Delta } {V}_{\text{th}} = -2.12$ V) under NBIS (−20 V, 3600 s). All Pr-doped devices exhibited a reduction in light responsivity of more than one order of magnitude compared with ITZO TFTs. Moreover, after Pr doping, relaxation processes of photoelectrons changed and then the activation energy (${E}_{\text{a}}$) of light-induced electrons relaxation decreased, which enhanced the NBIS stability of ITZO TFTs effectively. [ABSTRACT FROM AUTHOR]

The dynamic self-heating (SH) degradation was investigated on a-InGaZnO (a-IGZO) thin-film transistors (TFTs) under constant drain bias and varied gate pulses. Besides the negative shift of threshold voltage (${V}_{{\mathrm {th}}}$), similar with that under DC SH stress, the asymmetric degradations near drain and source revealed the concomitant hot-carrier (HC) effect. The HC-induced local barrier near drain could compensate certain SH-induced ${V}_{{\mathrm {th}}}$ shift, while a drastic SH effect would in turn enhance the HC barrier to high enough to cause hard breakdown. For a-IGZO TFTs under dynamic SH stresses, the interactions between SH and HC effects dominate the degradation behaviors and can be sensitively tuned by the falling time of gate pulse, suggesting a feasible method of lessening the dynamic instability. [ABSTRACT FROM AUTHOR]

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Titanium oxynitride (TiON) thin films were deposited on glass substrates by reactive sputtering of a Ti target under a flow of O2 and N2 gases. When the total number of O and N atoms bonded to Ti was small, the TiON films took on a nano-crystalline fcc structure primarily oriented toward the (200) direction. As the TiON films became more oxidized and/or nitrided, they gradually transformed into an amorphous state with their carrier concentration being between 1018 and 1019 cm−3. The efficiency of oxidization was six times higher than that of nitridation. The optical transmittance of TiON films deposited at RT under sufficient O2 and N2 flow rates reached 100% at wavelengths longer than 1000 nm. However, complete termination of Ti with N atoms failed to occur at low O2 flow rates even when the N2 flow rate was increased. The carrier concentration (n) of the TiON films could be varied in a wide range between 1018 and 3 × 1021 cm−3. The n (×10−19 cm−3) versus Hall mobility (μ) (cm2 V−1 s−1) plot scaled as log μ = 1.23 − 0.38⋅log n between 1 × 1018 and 1 × 1020 cm−3. The Hall mobility reached 20–50 cm2 V−1 s−1 at n = 1018 cm−3, which means this film is promising as an amorphous semiconductor. The log–log plot of resistivity (ρ) (mΩ cm) against n scaled as log ρ = 1.74 − 0.87⋅log n. [ABSTRACT FROM AUTHOR]

Selective doping is a key technology for integrated circuit (IC) fabrication since it enables ultrahigh density transistors with various electrical characteristics to be integrated on a single substrate. Also, for vertical IC integration, low-processing temperature compatibility is an essential feature since the annealing of additional ICs fabricated on top should not compromise the characteristics of underlying ICs. For amorphous oxide semiconductor (AOS) thin-films, which are actively being pursued for vertical integration, a selective doping process combined with a low temperature activation thermal annealing process has not been demonstrated. In this Letter, we demonstrate a low-temperature selective doping process that enables selective multi-level n-type doping of insulating amorphous In2O3 (a-In2O3) thin-films. By applying multiple H plasma processes on lithographically defined areas, a monolithic planar In2O3 inverter circuit was demonstrated. Also, the doping process was used to fabricate and demonstrate the operation of an In2O3 thin-film transistor with a 30 nm spaced channel, showing that our process may be used for back-end-of-line vertical integration of AOS devices. [ABSTRACT FROM AUTHOR]

Chalcogenide glasses have been widely adopted as a material platform for achieving reconfigurable metamaterials and metasurfaces, primarily through exploiting nonvolatile phase transitions inherent to these semiconductors. In such devices, the atomic lattice of the nanostructured medium reversibly changes between amorphous and crystalline phases, invoked through an energy‐intensive melt/quench process that can reduce device endurance due to chemical and geometrical drift. Metal‐doped amorphous chalcogenide semiconductors (MdACs) exhibit a directional photoinduced movement of their constituent metal‐ions when exposed to light with a photon energy equivalent or higher than the bandgap of the host chalcogenide glass. This "photoionic" movement results in nonvolatile changes of refractive index and conductivity at the nanoscale enabling a nonvolatile, nonbinary dynamic modulation of light removing the need for a phase transition. It is shown here that this photoionic movement in silver‐doped amorphous germanium selenide metasurfaces enables reversible optical switching. Understanding and integrating the photoionic mechanism within various optoelectronic device platforms presents significant potential for realizing a range of nonvolatile optically reconfigurable nanophotonic devices for emerging display, data storage, and signal processing applications. [ABSTRACT FROM AUTHOR]

In the family of amorphous semiconductors, non-oxide chalcogenide glasses (ChGs) are in the spotlight because of their widespread applications in various scientific and industrial fields. In this paper, we have studied thermally activated A.C. conduction in multi-component Se-Te-Sn-Ge (STSG) glassy alloys in bulk form at different audio frequencies. The activation energy of A.C. conductivity and other electrical parameters have also been calculated to explore the material's conduction mechanism. The A.C. conductivity σac is found proportional to ωs where ω is the angular frequency. The frequency exponent s is found to decrease with increasing temperature, which is in agreement with the correlation barrier hopping (CBH) model. The variation of the A.C. conduction with temperature and frequency of the glasses has been studied. Their microstructure has also been studied using the XRD characterisation technique to explore their electrical transport properties. XRD patterns confirm the glassy nature of the as-prepared samples. The change in behaviour of various electrical parameters after 2 atomic weight percentages of Ge indicates the occurrence of a stiffness transition followed by a self-organisation of the corner-sharing and the edge-sharing arrangements of the GeSe4 phase. [ABSTRACT FROM AUTHOR]

The DC and RF electronic behaviors of GeTe-based phase change material switches as a function of temperature, from 25K to 375 K, have been examined. In its polycrystalline (ON) state, GeTe behaved as a degenerate p-type semiconductor, exhibiting metal-like temperature dependence in the DC regime. This was consistent with the polycrystalline (ON) state RF performance of the switch, which exhibited low resistance S-parameter characteristics. In its amorphous (OFF) state, the GeTe presented significantly greater DC resistance that varied considerably with bias and temperature. At low biases (<1V) and temperatures (<200 K), the amorphous GeTe low-field resistance dramatically increased, resulting in exceptionally high amorphous-polycrystalline (OFF-ON) resistance ratios, exceeding 109 at cryogenic temperatures. At higher biases and temperatures, the amorphous GeTe exhibited nonlinear current-voltage characteristics that were best fit by a space-charge limited conduction model that incorporates the effect of a defect band. The observed conduction behavior suggests the presence of two regions of localized traps within the bandgap of the amorphous GeTe, located at approximately 0.26-0.27 eV and 0.56-0.57 eV from the valence band. Unlike the polycrystalline state, the high resistance DC behavior of amorphous GeTe does not translate to the RF switch performance; instead, a parasitic capacitance associated with the RF switch geometry dominates OFF state RF transmission. [ABSTRACT FROM AUTHOR]

We report first-principles investigations of crystalline and amorphous boron and M1xM2yXzB14-z (M1, M2=Al, Mg, Li, Na, Y; X=Ti, C, Si) phases (so-called "BAM" materials). Phase stability is analyzed in terms of formation energy and dynamical stability. The atomic configurations as well as the electronic and phonon density states of these phases are compared. Amorphous boron consists of distorted icosahedra, icosahedron fragments, and dioctahedra, connected by an amorphous network. The presence of metal atoms in amorphous BAM materials precludes the formation of icosahedra. For all the amorphous structures considered here, the Fermi level is located in the mobility gap independent of the number of valence electrons. The intra-icosahedral vibrations are localized in the range of 800 cm-1, whereas the inter-icosahedral vibrations appear at higher wavenumbers. The amorphization leads to an enhancement of the vibrations in the range of 1100-1250 cm-1. The mechanical properties of BAM materials are investigated at equilibrium and under shear and tensile strain. The anisotropy of the ideal shear and tensile strengths is explained in terms of a layered structure of the B12 units. The strength of amorphous BAM materials is lower than that of the crystalline counterparts because of the partial fragmentation of the boron icosahedra in amorphous structures. The strength enhancement found experimentally for amorphous boron-based films is very likely related to an increase in film density, and the presence of oxygen impurities. For crystalline BAM materials, the icosahedra are preserved during elongation upon tension as well as upon shear in the (010)[100] slip system. [ABSTRACT FROM AUTHOR]

The redistribution of hydrogen during solid phase epitaxial regrowth (SPER) of preamorphized silicon has been experimentally investigated, modeled, and simulated for different H concentrations and temperatures. H was introduced by H implantation and/or infiltration from the sample surface during partial thermal anneals in air in the 520-620 °C temperature range. We characterized the time evolution of the H redistribution by secondary ion mass spectrometry and time resolved reflectivity. The good agreement between all experimental data and the simulations by means of full rate equation numerical calculations allows the quantitative assessment of all the phenomena involved: in-diffusion from annealing atmosphere and the H effect on the SPER rate. We describe the temperature dependence of microscopic segregation of H at the amorphous/crystal (a-c) interface. Only a fraction of H atoms pushed by the a-c interface can be incorporated into the crystal bulk. We propose an energetic scheme of H redistribution in amorphous Si. The segregation of H at the a-c interface is also considered for (110) and (111) orientated substrates. Our description can also be applied to other material systems in which redistribution of impurities during a solid-solid phase transition occurs. [ABSTRACT FROM AUTHOR]

We formed Si-rich W silicide films composed of Sin clusters, each of which encapsulates a W atom (WSin clusters with 8 < n ≤~12), by using a gas-phase reaction between WF6 and SiH4 in a hot-wall reactor. The hydrogenated WSinHx clusters with reduced F concentration were synthesized in a heated gas phase and subsequently deposited on a substrate heated to 350-420 °C, where they dehydrogenated and coalesced into the film. Under a gas pressure of SiH4 high enough for the WSinHx reactant to collide a sufficient number of times with SiH4 molecules before reaching the substrate, the resulting film was composed of WSin clusters with a uniform n, which was determined by the gas temperature. The formed films were amorphous semiconductors with an optical gap of ~0.8-1.5 eV and an electrical mobility gap of ~0.05-0.12 eV, both of which increased as n increased from 8 to 12. We attribute this dependence to the reduction of randomness in the Si network as n increased, which decreased the densities of band tail states and localized states. [ABSTRACT FROM AUTHOR]

We formed Si-rich W silicide films composed of Sin clusters, each of which encapsulates a W atom (WSin clusters with 8 < n ≤~12), by using a gas-phase reaction between WF6 and SiH4 in a hot-wall reactor. The hydrogenated WSinHx clusters with reduced F concentration were synthesized in a heated gas phase and subsequently deposited on a substrate heated to 350-420 °C, where they dehydrogenated and coalesced into the film. Under a gas pressure of SiH4 high enough for the WSinHx reactant to collide a sufficient number of times with SiH4 molecules before reaching the substrate, the resulting film was composed of WSin clusters with a uniform n, which was determined by the gas temperature. The formed films were amorphous semiconductors with an optical gap of ~0.8-1.5 eV and an electrical mobility gap of ~0.05-0.12 eV, both of which increased as n increased from 8 to 12. We attribute this dependence to the reduction of randomness in the Si network as n increased, which decreased the densities of band tail states and localized states. [ABSTRACT FROM AUTHOR]

Charge carriers that execute multi-phonon hopping generally interact strongly enough with phonons to form polarons. A polaron's sluggish motion is linked to slowly shifting atomic displacements that severely reduce the intrinsic width of its transport band. Here a means to estimate hopping polarons' bandwidths from Seebeck-coefficient measurements is described. The magnitudes of semiconductors' Seebeck coefficients are usually quite large (>k/|q| = 86 µV/K) near room temperature. However, in accord with the third law of thermodynamics, Seebeck coefficients must vanish at absolute zero. Here, the transition of the Seebeck coefficient of hopping polarons to its low-temperature regime is investigated. The temperature and sharpness of this transition depend on the concentration of carriers and on the width of their transport band. This feature provides a means of estimating the width of a polaron's transport band. Since the intrinsic broadening of polaron bands is very small, less than the characteristic phonon energy, the net widths of polaron transport bands in disordered semiconductors approach the energetic disorder experienced by their hopping carriers, their disorder energy. [ABSTRACT FROM AUTHOR]

The temperature dependence of the dark conductivity of hydrogenated amorphous silicon (a-Si:H) thin films and a-Si:H films containing germanium or silicon nanocrystalline inclusions are examined. Analysis using the reduced activation energy provides clear evidence that conduction is non-Arrhenius, and is more accurately described by an anomalous hopping expression σ(T) = σ1 exp[-(T0/T)K] where the exponent is K~0.75±0.05. This observed temperature dependence is discussed in terms of alternative models for electronic transport in amorphous semiconductors. [ABSTRACT FROM AUTHOR]