Search

Strain imaging is a critical aspect in the design and characterization of opto-electronics, microelectronics, flexible electronics, and on-chip photonics. However, strain mapping techniques are often material specific and strain measurements in amorphous materials remain a challenge. Here, we demonstrate strain mapping and optical characterization of an amorphous semiconductor using scanning reflectance anisotropy microscopy. Using reflection anisotropy spectroscopy and finite element simulations on evaporated amorphous germanium films, we showcase the strain sensitivity of the ellipsometric parameters. We demonstrate nondestructive mapping for simple and complex strain states in amorphous systems. The sub-degree phase and amplitude sensitivity of the microscope is able to determine strain states on the order of 10 − 3 . [ABSTRACT FROM AUTHOR]

In this study, we used Raman spectroscopy to compare the local structure of Ge2Sb2Te5 (GST) thin films with thicknesses of 90 nm and 271 nm that were crystallized through thermal annealing and laser radiation (laser annealing) during the recording of Raman spectra in situ. We found that for all crystallized films, the position of the main peaks in the Raman spectra was almost the same, and their structure corresponded to a hexagonal close packed state. It is noteworthy that the full width at half maximum (FWHM) of the main peaks varies considerably depending on the crystallization method used. [ABSTRACT FROM AUTHOR]

Boron nitride (BN) is a layered two-dimensional insulator with excellent chemical, thermal, mechanical, and optical properties. We present a comprehensive characterization of hBN as a dielectric thin film using a high impedance measurement system (100 T Ω) to reveal the AC conductivity and dielectric properties of reactively RF sputtered 200 nm thick films to 480 °C. The experimental results are analyzed with reference to various theoretical models proposed for electrical conduction in disordered or amorphous semiconductors. Electrical measurements indicate that the mechanism behind hBN AC conductivity is via correlated barrier hopping (CBH) and is assigned to localized states at the Fermi level, where N(EF) ∼ 1018 eV−1 cm−3. Our measurements also reveal a σ dc component, with resistance reducing from ∼1010 Ω (50 °C) to 3 × 108 Ω (480 °C). Single RC parallel circuit fits to Cole–Cole plots are achieved signifying a sole conduction path with capacitance values of ∼8 × 10−11 F. These findings may be of interest to material and device scientists and could open new pathways for hBN both as a dielectric material encapsulant and for semiconductor device applications including high-temperature operation. [ABSTRACT FROM AUTHOR]

The use of the multiple-trapping (MT) model to comprehend the transport of nonequilibrium charge carriers in amorphous semiconductors has proven highly effective. Under specific conditions, this model generates anomalous diffusion equations characterized by fractional time derivatives. This underscores the utility of the MT model in interpreting fractional transport equations, establishing initial and boundary conditions, and developing numerical methods for solving fractional kinetic equations. Also, this work provides a concise overview of applying fractional MT equations to address challenges in time-of-flight (TOF) experiments. Furthermore, it delves into the connection between the MT model and generalized fractional kinetic equations. In addition, the study introduces analytic approximate solutions of the fractional diffusion equation, incorporating MT phenomena and employing Laplace transforms. This approach is suitable for analyzing both the pre- and post-regimes of TOF transient current, applicable to amorphous semiconductors that display either nondispersive or dispersive transport characteristics. The effectiveness of this method is illustrated through numerical simulations of TOF transient current using the inverse Laplace transform technique with the Padé approximation. The practicality of the method is confronted with the experimental data obtained from thin films of amorphous selenium (a-Se), and the results of this confrontation are deemed satisfactory. The results of this study offer a new promising perspective for the two following reasons. First, employing fractional calculus to address the MT equations introduces a distinct approach compared to methodologies in the existing literature. This is substantiated by the inclusion of memory effects in fractional calculus, implying that the present solution is influenced by preceding time steps. Second, the numerical results demonstrate good agreement with experimental data. Consequently, the introduction of fractional calculus has the potential to offer fresh insights into the behavior of charge carriers in amorphous semiconductors. [ABSTRACT FROM AUTHOR]

Measurements of the dark conductivity and thermoelectric power in hydrogenated amorphous silicon–germanium alloys (a-Si1-xGex:H) reveal that charge transport is not well described by an Arrhenius expression. For alloys with concentrations of Ge below 20%, anomalous hopping conductivity is observed with a power-law exponent of 3/4, while the temperature dependence of the conductivity of alloys with higher Ge concentrations is best fit by a combination of anomalous hopping and a power-law temperature dependence. The latter has been attributed to charge transport via multi-phonon hopping. Corresponding measurements of the Seebeck coefficient reveal that the thermopower is n-type for the purely a-Si:H and a-Ge:H samples but that it exhibits a transition from negative to positive values as a function of the Ge content and temperature. These findings are interpreted in terms of conduction via hopping through either exponential band tail states or dangling bond defects, suggesting that the concept of a mobility edge, accepted for over five decades, may not be necessary to account for charge transport in amorphous semiconductors. [ABSTRACT FROM AUTHOR]

We report on investigating the structural and electronic properties of semiconducting and insulating layers produced in a process resembling percolation in a unique cold plasma fabrication method (plasma-enhanced chemical vapor deposition—PECVD). Amorphous carbon–tin films (Sn–C) produced from tetramethyl tin (TMT) with an acoustic-frequency glow discharge in a three-electrode reactor were investigated. The layers, after air exposure, oxidized to SnO2/Sn–C. Depending on the coupling capacitance applied to the plasma reactor, the films could be obtained in the form of an amorphous semiconductor or an amorphous insulator. We assume that the semiconductor consists of an internal network of channels auto-organized during deposition. The insulator does not demonstrate any internal structure features. An investigation on conductive filaments creating low-dimensional (LD) nanojunctions in the semiconductor and the location of energetic levels in the insulator was performed. The main parameters of the electronic band structure of the insulating film, such as the transport gap EG (5.2 eV), optical gap Eopt (3.1 eV), electron affinity Χ (2.1 eV), and ionization potential J (7.3 eV), were determined. We have demonstrated a simple approach for developing a catalyst candidate consisting of amorphous semiconductor–insulator nanojunctions for (photo)catalytic hydrogen evolution or CO2 reduction. [ABSTRACT FROM AUTHOR]

Amorphous semiconductors are widely applied to electronic and energy-conversion devices owing to their high performance and simple fabrication processes. The topological concept of the Berry curvature is generally ill-defined in amorphous solids, due to the absence of long-range crystalline order. Here, we demonstrate that the Berry curvature in the short-range crystalline order of kagome-lattice fragments effectively contributes to the anomalous electrical and magneto-thermoelectric properties in Fe–Sn amorphous films. The Fe–Sn films on glass substrates exhibit large anomalous Hall and Nernst effects comparable to those of the single crystals of topological semimetals Fe3Sn2 and Fe3Sn. With modelling, we reveal that the Berry curvature contribution in the amorphous state likely originates from randomly distributed kagome-lattice fragments. This microscopic interpretation sheds light on the topology of amorphous materials, which may lead to the realization of functional topological amorphous electronic devices. The topological character of solids is usually revealed by considering the Berry curvature of electronic bands in a periodic crystal. Here, authors demonstrate the influence of the Berry curvature on the electronic properties of an amorphous thin film. [ABSTRACT FROM AUTHOR]

High quality thin film p‐n junction diodes with high rectification ratios and low ideality factors have been fabricated from metal oxides, such as amorphous oxide semiconductors (AOSs), and characterized. Plasma treatment of interfaces has been demonstrated to improve devices made from AOSs, using current–voltage (I–V) measurements. However, capacitance–voltage (C–V) measurements of the devices have been scarcely reported in the literature. Therefore, the focus of this work is characterization of cuprous oxide (Cu2O)/amorphous zinc‐tin oxide (a‐ZTO) thin film heterojunction diodes using C–V analysis. Performance differences of plasma‐treated and untreated diodes that are difficult to observe in I–V analysis are more prominent in C–V analysis. Moreover, C–V analysis allows extraction of charge density profiles, which is a measure of the defect state density that led to intrinsic doping. The variation of doping densities of the untreated diode across the full range of applied reverse bias is shown to be up to 2 orders of magnitude, while those of the treated diodes are within a factor of 10 only. Junction charge profiles, interfacial charge depletion, and accumulation that are key features of rectifying diodes are shown to be clearly distinct between untreated, nitrogen‐treated, and oxygen‐treated diodes, thus explaining why oxygen‐treated diodes are superior. [ABSTRACT FROM AUTHOR]

The amorphous calcogenide semiconductor As0.63S2.70Sb1.37Te0.30 was synthesized and thin films based on it were obtained. XRD and optical images investigations showed the amorphous and homogeneous nature of the samples. The optical transmission spectrum in the UV-Vis range of As0.63S2.70Sb1.37Te0.30 thin films shows good transparency in the spectral range 0.7-3.5 µm with a single absorption threshold at 2.05 eV and with refractive index in infrared 2.3. The irradiation of films with light leads to a parallel shift of the transmission spectrum to the IR range. The materials with As0.63S2.70Sb1.37Te0.30 composition have high optical transparency have high optical transparency that make they promises for applications in holographic memory devices, optical amplitude and phase recorder, optical processing units and others. [ABSTRACT FROM AUTHOR]

Amorphous Cu–Sn–I is a promising p‐type transparent semiconductor. Therefore, herein, composition and structure of sputtered Cu–Sn–I thin films with varying thickness and Sn content are investigated by different electron microscopy techniques, energy‐dispersive X‐ray spectroscopy, and X‐ray absorption spectroscopy at the Cu, Sn, and I K‐edge. After exposure to air, the sputtered films are found to contain significant amounts of oxygen, leading to a complete phase separation of the resulting Cu–Sn–I–O films. Spatially‐resolved compositional analysis and high‐resolution transmission electron microscopy reveal that one phase consists of crystalline γ‐CuI while the other phase is composed of amorphous Cu–Sn–O, most likely a mixture of SnO2 and Cu2O/CuO. X‐ray absorption spectroscopy confirms that the local structural environment of the Sn and I atoms is similar to that in amorphous SnO2 and crystalline CuI, respectively. In contrast, the X‐ray absorption near edge structure and the extended X‐ray absorption fine structure of the Cu K‐edge both demonstrate that Cu atoms are not only bonded to I but also to O atoms. The incorporation of oxygen into the sputtered films thus completely alters the material and therefore clearly needs to be inhibited. [ABSTRACT FROM AUTHOR]

Amorphous mixed-anion semiconductors (AMASs) such as amorphous zinc oxynitride and amorphous zinc oxysulfide (a-ZnOS) have attracted attention as rare-metal-free amorphous semiconductors that exhibit electron mobility comparable to or greater than the electron mobilities of typical amorphous oxide semiconductors (AOSs), including amorphous In–Ga–Zn–O (a-IGZO). A characteristic feature of AMASs is that their conduction-band minimum (CBM) mainly consists of s-orbitals of the single cation, in contrast to conventional AOSs, whose CBM is composed of s-orbitals of multiple cations. This unique band structure suggests that the potential of carrier electrons in AMASs exhibits less spatial fluctuation than that of carrier electrons in AOSs. In this study, we analyzed the temperature dependence of the electron transport properties of a-ZnOS thin films using the random barrier model to evaluate the potential barrier height and its spatial variation. The analyses revealed that the barrier height of a-ZnOS is comparable to that of a-IGZO. This result was attributed to the large covalent nature of Zn–S bonds strongly influencing the potential at the CBM through the antibonding interaction. [ABSTRACT FROM AUTHOR]

The bulk form of Se 78 In (22- x) Bi x (x = 0, 4, 8, and 12 at.%) was produced with melt-quench technology. Subsequently, thin films of these compositions were produced through the thermal evaporation method under vacuum conditions. Analysis via diffraction of X-rays confirmed the disordered character of the resulting films. The refractive index (n) and extinction coefficient (k) were computed using optical transmission T (λ) and reflection R (λ) data. Analysis of optical constants revealed that the optical energy gap E g o p t decreases while the Urbach tail E u augments as the Bi content increases. Other related constants were determined and investigated in relation to variations in Bi content. The outcomes of our study were compared with those published previously. Non-linear parameters were calculated and discussed for the investigated films. [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]

• 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]

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 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]

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]

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]

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]

The present paper investigated the influence of Bi concentration on the structural, linear, and non‐linear optical properties of thermally evaporated BixIn35‐xSe65 (x = 0, 5, 7, 10, 15 at %) thin films. The structural analysis by the XRD measurements showed the crystalline nature at 7 and 15% Bi while the other concentrations showed amorphous nature. The corresponding bonding change was analyzed by Raman spectroscopy. The optical study by UV‐Vis spectroscopy showed the decrease in transmittance and an increase in absorbance property. The linear optical parameters such as absorption coefficient, extinction coefficient, optical density increased while skin depth decreased with Bi additives. The direct, as well as the indirect optical bandgap, decreased along with the decrease in the Tauc parameter. The variation is well explained on the basis of density of defect states by the Mott and Davis model. The non‐linear refractive index and non‐linear susceptibility increased significantly with Bi % which is good for non‐linear optical applications. The static linear refractive index as calculated by the Dimirov and Sakha empirical relation showed an incremental behavior with Bi% concentration and satisfied Moss's rule. The surface structure and elemental concentration were analyzed by FESEM and EDX analysis. The result of the above investigation suggests that these materials can be used as an absorbing layer for several optoelectronic and photonic applications. [ABSTRACT FROM AUTHOR]

We investigated the optical properties of amorphous and crystalline antimony (Sb)-doped tin dioxide (SnO2) thin films grown using the co-sputtering deposition method at room temperature. We used undoped and Sb-doped (8?wt. %) SnO2 targets. Varying the relative power ratio of the two targets, we controlled the Sb-composition of the SnO2 :Sb thin films up to 2.3 at. % of Sb contents. Through annealing, the as-grown amorphous SnO2 :Sb thin films were transformed to crystalline thin films. Dielectric functions were obtained from the measured ellipsometry angles, Ψ and Δ, using the Drude and parametric optical constant models. We determined the absorption coefficients and optical gap energies of the SnO2 :Sb thin films from the dielectric functions. We found increasing optical gap energy with increasing Sb composition. Increases in the Drude tail amplitudes, a signature of free carrier concentrations, were found in annealed, crystalline thin films with increasing Sb composition. The increase in the optical gap energy with increasing Sb composition was mainly attributed to the Burstein-Moss effect. Using Hall effect measurements, we obtained Hall carrier concentrations (NHall) and electron Hall mobilities (μHall). The carrier concentrations and mobilities increased from 2.6?×?1019?cm-3 and 1.0?cm2/(V s) to 2.0?×?1020?cm-1 and 7.2?cm2/(V s), respectively, with increasing Sb contents. This result suggests that the nominally undoped SnO2 films are unintentionally n-type doped. Assuming that the NHall and optical carrier concentrations (Nopt) were the same, we obtained the effective masses of the SnO2 :Sb thin films with increasing Sb compositions. The effective masses of the SnO2 :Sb thin films increased from 0.245 m0 to 0.4 m0 with increasing Sb doping contents, and the nonparabolicity of the conduction band was estimated. We discussed the relation between the optical (μopt) and Hall (μHall) mobilities as a function of Sb contents and grain sizes. [ABSTRACT FROM AUTHOR]

We present a compact model based on surface potential for amorphous-InGaZnO thin-film transistors, built using multiple trapping and detrapping theory. Using this model, the surface potential can be calculated analytically, so it can be used to rapidly determine the transistor characteristics during circuit simulation. We verified the proposed model using both numerical simulation and experiment, showing that the model is accurate over a wide range of operation regions. The model also provides a physics-based consistent description of DC and AC device characteristics and enables accurate design of amorphous InGaZnO thin-film transistor circuits. [ABSTRACT FROM AUTHOR]

As the gate size continues to decrease in nanoscale transistors, having metal gates with amorphous or near amorphous structures can potentially reduce grain-induced work function variation. Furthermore, amorphous materials are known to have superior diffusion barrier properties, which can help prevent work function change due to the diffusion of metals in contact with the gate. In this work we show that with the addition of cobalt, thin films of polycrystalline TiN become more amorphous with a smaller grain size. Cox(TiN)1-x films, where x=60-80%, appear to consist of nanocrystals embedded in an amorphous matrix, and are thermally stable with no significant crystallization up to an annealing temperature of at least 600 °C. Reducing the nitrogen gas flow ratio during sputter deposition from 9% to 2.5% further decreases the films' crystallinity, which is apparent by more sparse and even smaller nanocrystals. In addition to being partially amorphous, these CoTiN films also exhibit good thermal stability, low resistivity, low roughness, and have the potential for atomic layer deposition compatibility. Even though these materials are not completely amorphous, their small crystal size and amorphous matrix can potentially reduce work function variation and improve their diffusion barrier property. These properties make CoTiN a good candidate as a gate material for future nanoelectronic devices and technology. [ABSTRACT FROM AUTHOR]

We present a new method to obtain topological insulator Bi2Se3 thin films with a centimeter large lateral length. To produce amorphous Bi2Se3 thin films, we have used a sequential flashevaporation method at room temperature. Transmission electron microscopy has been used to verify that the prepared samples are in a pure amorphous state. During annealing, the samples transform into the rhombohedral Bi2Se3 crystalline structure which was confirmed using X-ray diffraction and Raman spectroscopy. Resistance measurements of the amorphous films show the expected Mott variable range hopping conduction process with a high specific resistance compared to the one obtained in the crystalline phase (metallic behavior). We have measured the magnetoresistance and the Hall effect at different temperatures between 2K and 275 K. At temperatures T ⩽50K and fields B ⩽ 1 T, we observe weak anti-localization in the MR; the Hall measurements confirm the n-type character of the samples. All experimental results of our films are in quantitative agreement with results from samples prepared using more sophisticated methods. [ABSTRACT FROM AUTHOR]

The electrical performance of thin-film transistors that use an amorphous oxide semiconductor (AOS) is significantly improved by incorporating metal cations as carrier suppressors. However, the effect of these elements on the performance of AOS-based photodetectors (PDs) is still unknown. This study uses a precursor containing lithium (Li) element and a sol-gel process to produce a Li-doped amorphous ZnSnO (a-ZTO) thin-film for UV PD applications. The results of x-ray photoelectron spectroscopy analysis show that the number of oxygen vacancies (Vo) in a-ZTO thin-films decreases significantly from ∼32.1% to ∼14.4% after Li-doping (3 at%). The dark current decreases and the photocurrent increases in the ZTO-based PD so an ultra-high photo-to-dark current ratio (PDCR) of 1185 is achieved. The significant increase in PDCR means that solution-processed a-ZTO are eminently suited to use in UV PDs that use In-free AOSs. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) is one of the best transparent conducting oxide (TCO) materials with a wide bandgap and good electrical and optical properties. Its low cost, nontoxicity and transparency in the optical region of the electromagnetic spectrum make it very promising candidate for solar cell applications. In this work, zinc acetate precursor was used to grow a ZnO thin film by using sol-gel spin-coating technique. The surface morphological study using scanning electron microscope (SEM) was carried out to confirm the growth pattern and crystal distribution. The optical properties, transmission (T), reflection (R), optical bandgap (Eg), refractive index (n), and extinction coefficient (k) were extracted and investigated to be used in the simulation of ZnO/Cu2O heterostructure solar cell, where ZnO thin film plays a double role: as the TCO window, as well as the emitter of the n-p junction. However, the solar cell showed weak external quantum efficiency (EQE) compared to those prepared by using zinc nitrate and diethyl zinc precursors. TCAD numerical simulation was used to clarify the origin of this weak EQE by taking into account two parameters. The first studied parameter is the root-mean-square interface roughness, RMS, in Haze modeling approach, H, which describes how much of incident light is scattered at the interface. The second studied parameter is the density of defects in the ZnO bulk with continuous distribution of states in its bandgap similar to an amorphous semiconductor made of tail bands and Gaussian distribution deep level bands. Consequently, and by adjusting and investigating the effect of the σRMS and the constituents of the bandgap states, we were able to obtain a good agreement between simulated and measured EQE characteristics of the solar cell. [ABSTRACT FROM AUTHOR]

We investigated the electrical properties and operational stability of amorphous indium-tin-zinc-oxide (a-ITZO) thin-film transistors (TFTs). We fabricated the a-ITZO TFTs using deposition by radio frequency sputtering at room temperature followed by a rapid thermal annealing (RTA) process at different temperatures and oxygen pressure (PO2). This is a more practical annealing route compared to a conventional furnace. Based on film densification and oxygen vacancy optimization, the a-ITZO TFTs exhibited 9.8 cm2 Vs−1, 0.82 V/decade and 1.39 V, for saturation mobility, sub-threshold swing and threshold voltage, respectively. Operation stability tests and hysteresis behavior of a-ITZO TFTs suggest that oxygen vacancy concentration of a-ITZO thin films gradually decreases under higher PO2, consequently affecting the threshold voltage and the shift seen after a gate bias stress test. This observation suggests that gate bias stress and hysteresis stability of an a-ITZO device is due to the effect of oxygen-controlled pressure in the RTA process. This a-ITZO TFTs electrical characterization qualitatively coincides with x-ray photoelectron spectroscopic analyses of oxygen vacancy concentration in a-ITZO thin films. Thus, our systematic a-ITZO thin film optimization using the oxygen-ambient RTA process is a practical basis for high-performance amorphous oxide semiconductor TFT post-annealing methods. [ABSTRACT FROM AUTHOR]

Photochemistry has emerged in the last few years as a powerful tool for the low‐temperature processing of metal oxide thin films prepared by solution methods. Today, its implementation into the fabrication procedure makes possible the integration of amorphous semiconductors or functional crystalline oxides into flexible electronic systems at temperatures below 350 °C. In this review, the effects of UV irradiation at the different stages of the chemical solution deposition of metal oxide thin films are presented. These stages include from the synthesis of the precursor solution to the formation of the amorphous metal‐oxygen network in the film and its subsequent crystallization into the oxide phase. Photochemical reactions that can be induced in both the solution deposited layer and the irradiation atmosphere are first described, highlighting the role of the potential reactive chemical species formed in the system under irradiation, such as free radicals or oxidizing compounds. Then, the photochemical effects of continuous UV light on the film are shown, focusing on the decomposition of the metal precursors, the condensation and densification of the metal‐oxygen network, and the nucleation and growth of the crystalline oxide. All these processes are demonstrated to advance the formation and crystallization of the metal oxide thin film to an earlier stage, which is ultimately translated into a lower temperature range of fabrication. The reduced energy consumption of the process upon decreasing the processing temperature, and the prospect of using light instead of heat in the synthesis of inorganic materials, make photochemistry as a promising technique for a sustainable future ever more needed in our life. [ABSTRACT FROM AUTHOR]

Nanosecond near resonant excitation in As50S50 thin films leads to strong nonlinear optical response, i.e. nonlinear absorption coefficient up to 4 × 106 cm GW−1 and nonlinear refractive index of 8.5 cm2 GW−1, both of which are the strongest ever reported in amorphous semiconductors. We propose a three-level energy band model to explain this effect, which indicates that the nonlinear process is reverse saturable absorption in nature, mediated by excited-state absorption from slow interband transition between the conduction and valence band. On the other hand, observation of negative nonlinear refractive index reveals the occurrence of self-defocusing effect. Finally, benefitting from the strong nonlinear response, we demonstrate a promising application of As50S50 thin films as an optical limiter for optoelectronic sensors. [ABSTRACT FROM AUTHOR]

In this article, we have developed an amorphous CuNiSnO (a-CNTO), which is a p-type amorphous oxide semiconductor (AOS). The a-CNTO thin films were deposited by the pulsed laser deposition method, having high amorphous quality with a rather smooth surface. The a-CNTO films grown at 100 °C exhibited the smoothest surface (root-mean-square roughness of 0.25 nm), highest visible transparency (~85%), and most favorable p-type conductivity (hole concentration of ~1015 cm−3), which are very suitable for electronic device fabrication. Thus, the obtained p-type a-CNTO thin-film transistors (TFTs) have an ON-to- OFF current ratio of ~ 1.2 × 105, the threshold voltage of −2.3 V, the field-effect mobility of 1.37 cm2/Vs, and subthreshold swing of 0.70 V/decade. As a new kind of p-type AOS, the achievement of the p-type a-CNTO TFTs and the low-temperature processes may open the door for practical applications in transparent and flexible electronics. [ABSTRACT FROM AUTHOR]

The object of our current investigation is Cu-As2Se3 thin film structures. The impact of corona discharge on photoinduced modifications of the transmission spectra of both asdeposited and exposured with actinic light of the Cu-As2Se3 structures have been studied. Two cases have been investigated. First normal irradiation of the film structures without charging, and another one, when exposure was switched on, 7 kV corona charge at different polarity was applied. As a result, in the region of the weak absorption in the transmission spectra the photobleaching effect was observed and in the region of the strong absorption the photodarkening phenomena was manifested. In the region o weak absorption higher values of photobleaching was observed during exposure in the field of positive corona discharge. The obtained results are qualitatively analyzed taking into account the photodarkening of the semiconductor during it doping with Cu ions as well as transmission increases of the structure during photodiffusion of the cupper in the amorphous semiconductor. [ABSTRACT FROM AUTHOR]

Amorphous indium gallium zinc oxide is a popular semiconductor candidate for amorphous oxide semiconductor thin-film transistors in the field of flat-panel display. However, the existence of gallium component restricts the enhancement of mobility dramatically. In this study, we report a new praseodymium (Pr) dopant as a stabilizer in amorphous indium zinc oxide semiconductor (IZO) with high mobility and stability. Meanwhile, the PrIZO TFTs were fabricated to investigate the effects of Pr on electrical properties, stability and aging effect. The optimal PrIZO TFT exhibited a desired performance with a saturation mobility (μsat) of 25.8/32.6 cm2 V−1 s−1, an Ion/Ioff ratio of 3.5 × 107/5.4 × 107, a subthreshold swing value of 0.14/0.13 V dec−1 and a threshold voltage (Vth) of 2.9/2.1 V, respectively, before and after an air environment storage period of 90 days without passivation layer, which exhibits lower sensitivity of the channel region to oxygen/moisture from the atmosphere than IZO TFT. XRD analysis revealed that the Pr dopant had no effect on the amorphous state of IZO thin film with annealing up to 400 °C. XPS analyses suggested that the fraction of oxygen vacancy subpeak decreased significantly with Pr incorporated into IZO. The μ-PCD decay analyzation and the subgap density of states indicate that acceptor-like trap states induced by Pr ions lead to the suppression of ambient-induced excess carrier in conduction band. This work is anticipated to provide a kind of reliable stabilizer for amorphous oxide semiconductor without deteriorating mobility significantly. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous carbon (a-C:H) and nitrogen-incorporated a-C:H (a-C:N:H) thin films were deposited using radio frequency-plasma-enhanced chemical vapor deposition technique and studied for their electrical, optical, and nano-mechanical properties. Introduction of nitrogen and increase of self bias enhanced the conductivity of a-C:H and a-C:N:H films, whereas current-voltage measurement reveals heterojunction formation due to their rectifying behavior. The bandgap of these films was changed over wide range from 1.9 eV to 3.45 eV by varying self bias and the nitrogen incorporation. Further, activation energy was correlated with the electronic structure of a-C:H and a-C:N:H films, and conductivity was discussed as a function of bandgap. Moreover, a-C:N:H films exhibited high hardness and elastic modulus, with maximum values as 42 GPa and 430 GPa, respectively, at -100 V. Observed fascinating electrical, optical, and nano-mechanical properties made it a material of great utility in the development of optoelectronic devices, such as solar cells. In addition, we also performed simulation study for an a-Si:H solar cell, considering a-C:H and C:N:H as window layers, and compared their performance with the a-Si:H solar cell having a-SiC:H as window layer. We also proposed several structures for the development of a near full-spectrum solar cell. Moreover, due to high hardness, a-C:N:H films can be used as a protective and encapsulate layer on solar cells, especially in n-i-p configuration on metal substrate. Nevertheless, a-C:H and a-C:N:H as a window layer can avoid the use of additional hard and protective coating and, hence, minimize the cost of the product. [ABSTRACT FROM AUTHOR]

We report on the specific contact resistance of interfaces between thin amorphous semiconducting IZO channel layers and IZO source/drain metallization in amorphous oxide thin film transistors (TFTs). As-deposited, low carrier density amorphous IZO layers are difficult to produce and consequently very thin (10-30 nm) channel layers are required for IZO TFT device applications in order to achieve adequately low off-state current. In this article, the transmission line model (TLM) and structures that also serve as IZO gate-down TFTs were used to examine IZO/IZO homojunctions with thin (10 nm) and thick (100 nm) channel layers. Thin, 10 nm, IZO channel devices with IZO source/drain contacts show a threshold voltage of -3.9 V and a very high specific contact resistance (ρC) that varies with gate voltage (VG) in the range 0-10 V from 460 to 130 Ω cm2. Annealing in air at 200 °C resulted in a tenfold improvement in ρC (34 Ω cm2) and corresponds to an increase in carrier density in the channel. Thicker IZO films (100 nm) were too conducting to function as TFTs, but, at zero bias, effective specific contact resistance measured using TLM was 17 Ω cm2 in the as-deposited state and 0.13 Ω cm2 in the annealed state. Corresponding channel resistivity obtained from TLM at VG = 0 V decreased after annealing from 8.2 Ω cm (as-deposited) to 0.3 Ω cm (annealed). The effect of both annealing and positive gate bias is shown to be an increase in carrier density and a corresponding decrease in specific contact resistance. [ABSTRACT FROM AUTHOR]

We discuss in this paper the evolution of both the density of states (DOS) located between the band-tail states and the DOS around the Fermi level N(EF) in amorphous carbon nitride films (a-CNx) as a function of the total nitrogen partial pressure ratio in the Ar/N2 plasma mixture. The films were deposited by three different deposition techniques and their microstructure was characterized using a combination of infrared and Raman spectroscopy and optical transmission experiments, completed with electrical conductivity measurements, as a function of temperature. The observed changes in the optoelectronic properties are attributed to the modification in the atomic bonding structures, which were induced by N incorporation, accompanied by an increase in the sp2 carbon bonding configurations and their relative disorder. The electrical conductivity variation was interpreted in terms of local effects on the nature and energy distribution of π and π* states. [ABSTRACT FROM AUTHOR]

Thick films of polycrystalline silicon for solar cells can be made by crystallization of amorphous silicon. Due to the high internal stress of amorphous silicon films, deposition of such thick films is challenging. In this paper, we investigate the failure behavior of thick amorphous silicon films. Depending on the deposition method of amorphous silicon films, they can be cracked or delaminated. While nonhydrogenated amorphous silicon films deposited by an evaporator are cracked when the accumulated strain in thick films reaches a critical point, hydrogenated amorphous silicon films deposited by plasma enhanced chemical vapor deposition are delaminated from the substrate. Critical cracking/delamination thicknesses of amorphous silicon films are theoretically derived and excellent agreement with experimental results is shown. [ABSTRACT FROM AUTHOR]

Simultaneous and locally resolved determination of the mechanical stress variation and the free hole concentration using Raman spectroscopy is demonstrated in laser crystallized amorphous silicon layers. Such layers are often used for the fabrication of thin film solar cells, e.g., on borosilicate glass substrates. The combined effects of stress and doping on the Raman signal can be separated based on the use of three wavelengths in the visible. The results show that the free hole concentration in the samples investigated varies between 1×1018 and 1.3×1019 cm-3. Stress as well as the free hole concentration vary substantially within the sample. The stress level varies between 575 and 850 MPa (±12 MPa). Cross-sectional transmission electron microscopy images show the presence of extended lattice defects such as dislocations and grain boundaries in the crystallized Si layer which could account for the lateral stress variations detected by Raman spectroscopy. The impact of film inhomogeneity in terms of stress and doping on the performance of a solar cell will be discussed. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous Si thin films were prepared by plasma-enhanced chemical vapor deposition technique. As-deposited samples were thermally annealed at various temperatures to obtain nanocrystalline Si. The microstructures and carrier transport behaviors were evaluated during the transition process from amorphous to nanocrystalline structures. Raman scattering spectroscopy and Fourier-transform infrared spectroscopy were used to characterize the changes in microstructures and bonding configurations. It is found that hydrogen is completely effused from the film at the annealing temperature of 600 °C, while crystallization occurs at around 700 °C. The carrier transport characteristics in nanocrystallized films are different from those in the amorphous Si films. The carrier transport in the amorphous silicon films is strongly influenced by the defect states resulting from the effusion of hydrogen. The dual activation energies are found in temperature-dependent conductivity results which can be attributed to the two different conduction paths in the samples. In the case of the nanocrystallized Si films obtained by high temperature annealing, the transport process is accounted for in the framework of a three-phase model comprised of amorphous and nanocrystalline phases and the grain boundary in the films. [ABSTRACT FROM AUTHOR]

Amorphous erbium-doped silicon oxide (SiyO1-y:Er, y≥1/3) thin films are currently under investigation as a luminescent material system for complementary metal-oxide semiconductor compatible light emitters. We have grown films with y≈1/3 and investigated their properties using both positron annihilation and photoluminescence (PL) spectroscopies. Films were characterized “as deposited,” following irradiation with 1 MeV Si+ ions and after isochronal annealing. The PL yield from both Er3+ ions and sensitizing defects is reduced by irradiation, depending strongly on the irradiation fluence and reaching saturation at ∼4×1013 Si+/cm2. Higher implantation fluences result in an open-volume defect structure in the film that persists after annealing. This annealing behavior is similar to that of an unrecoverable quenching effect on Er3+-related PL near 1540 nm, and we suggest that these open-volume defects may cause a decoupling of the Er3+ ions from sensitizing oxide point defects that form as a result of the film deposition process. [ABSTRACT FROM AUTHOR]

Amorphous silicon (a-Si) based thin film solar cell grown on flexible stainless steel substrate is one of the most promising energy conversion devices in the future. This type of solar cell uses a transparent conductive oxide (TCO) film as top electrode. It has been a widely accepted opinion that the radio frequency sputtering deposition of the TCO film produces a higher yield than direct current sputtering, and the reason is not clear. Here we show that the damage to the solar cell during the sputtering process is caused by a reverse bias applied to the n-i-p junction. This reverse bias is related to the characteristics of plasma discharge. The mechanism we reveal may significantly affect the solar cell process. [ABSTRACT FROM AUTHOR]

Fe–Ni based amorphous thin films were prepared by thermal evaporation. These films were irradiated by 108 MeV Ag8+ ions at room temperature with fluences ranging from 1×1012 to 3×1013 ions/cm2 using a 15 UD Pelletron accelerator. Glancing angle x-ray diffraction studies showed that the irradiated films retain their amorphous nature. The topographical evolution of the films under swift heavy ion (SHI) bombardment was probed using atomic force microscope and it was noticed that surface roughening was taking place with ion beam irradiation. Magnetic measurements using a vibrating sample magnetometer showed that the coercivity of the films increases with an increase in the ion fluence. The observed coercivity changes are correlated with topographical evolution of the films under SHI irradiation. The ability to modify the magnetic properties via SHI irradiation could be utilized for applications in thin film magnetism. [ABSTRACT FROM AUTHOR]

An amorphous chalcogenide Ge2Sb2Te5 film is most commonly used for phase-change data storage, in which its small volume is switched between amorphous and crystalline states by local heating with short laser or current pulses. A speed of amorphous-to-crystalline phase transformation in Ge2Sb2Te5 and Ag0.1(Ge2Sb2Te5)0.9 films has been evaluated on a nanosecond time scale using a 658-nm laser beam. The focused laser beam with a diameter <10 μm was illuminated in the power (P) and pulse duration (t) ranges of 1–17 mW and 10–460 ns, respectively, with subsequent detection of the response signals reflected from the film surface. We also evaluated the material characteristics, such as optical absorption and energy gap, crystalline phases, and sheet resistance of as-deposited and annealed films. The experiments showed that the crystallization speed of the Ge2Sb2Te5 film is largely improved by adding Ag. For example, the threshold pulse durations (tT) for Ge2Sb2Te5 and Ag0.1(Ge2Sb2Te5)0.9 films are approximately 70 and 30 ns for P=7 mW. In addition, the sheet resistance in the amorphous state of the Ag0.1(Ge2Sb2Te5)0.9 film is approximately ten times that of the Ge2Sb2Te5 film. This improvement can lead to a low programming current in electronic operation. To understand the ultrafast crystallization in the amorphous Ag0.1(Ge2Sb2Te5)0.9 film, we suggest heat confinement by electron hopping. [ABSTRACT FROM AUTHOR]

Atomic scale computer simulations on structures and photoinduced volume changes of flatly and obliquely deposited amorphous selenium (a-Se) films have been carried out in order to understand how the properties of chalcogenide glasses are influenced by their preparation method. Obliquely deposited a-Se thin films contain more coordination defects and larger voids than the flatly deposited ones. To model the photoinduced volume changes the electron excitation and hole creation were treated independently within the framework of tight-binding formalism. Covalent and interchain bond breakings and formations were found. The obliquely deposited samples containing voids showed a wide spectrum of photoinduced structural changes in the microscopic level and volume changes in the macroscopic level. [ABSTRACT FROM AUTHOR]

A room-temperature photoluminescence (PL) study of amorphous nonstoichiometric silicon nitride (SiNX) films prepared under low temperature is reported. PL peak position can be tuned from 1.90 to 2.90 eV by adjusting the film composition. The luminescence lifetime is within the nanosecond range. The dependence of the PL lifetime on the emission energy suggests that band tail states are involved in the thermalization and recombination of photon-generated carriers. This is further supported by the correlation between the optical band gap, the PL peak energy, and the width of the PL spectrum. We propose that optical transitions among band tail states are the main light emission mechanisms. [ABSTRACT FROM AUTHOR]

Amorphous Si films of 60 and 10 nm thick on glass substrates were irradiated by a linearly polarized Nd:YAG pulse laser with the wavelength λ=532 nm at the incident angle θi=0. The surface of the irradiated 60-nm-thick film had both periodic ridges perpendicular to the electric field vector E and aperiodic ridges roughly parallel to E, where the spatial period of the periodic ridges was almost λ. From the continuous 10-nm-thick film, the separate rectangular Si islands were formed with a periodic distance of λ, with the edges parallel or perpendicular to E. When θi was increased from normal incidence of the s-polarized beam for a 60-nm-thick film, the aperiodic ridges were reduced while the periodic ridges were still formed. For a 10-nm-thick film, the Si stripes were formed perpendicular to E, using the s-polarized beam at θi=12°. In order to investigate the mechanisms of the surface modifications of, in particular, aperiodic ridges, islands, and stripes, we improved the previous theoretical model of the periodic distribution of the beam energy density (periodic E-D) generated by irradiation of the linearly polarized laser beam, taking account of the multireflection effect in the Si film which is semitransparent for λ. Further, the calculated E-D was corrected with respect to the thermal diffusion in the irradiated Si film. The calculation results show that the two-dimensional E-D consists of a constant or a dc term and a sinusoidal or an ac term which contains various spatial periods. The multireflection effect strongly influences the amplitude and phase of every ac term, which means that the amplitude and phase depend on the film thickness. The thermal diffusion during the heating of the irradiated film greatly reduces the amplitudes of the ac terms with periods below the thermal diffusion length. The theoretical calculation showed that, by increasing θi, the temperature distribution in the irradiated Si film was changed from two-dimensional toward one-dimensional, which can explain the above experimental results reasonably. [ABSTRACT FROM AUTHOR]

The structural, optical, and transport properties of hydrogenated amorphous carbon films deposited on the grounded electrode under different dilutions (pure CH4, CH4+H2, and CH4+Ar) in radio frequency powered plasma enhanced chemical vapor deposition process have been studied. Though all the samples deposited were observed to be polymer-like carbon, they have different optical and transport properties. While some of the samples were highly conductive under dark (∼10-1 S cm-1 at room temperature), others exhibited very low (<10-12 S cm-1) dark conductivity and were photoconductive (∼10-9–10-10 S cm-1) only under ultraviolet (UV) light (wavelength λ<250 nm). There appears to be a close link between the transport properties and optical absorption. Based on optical absorption, we propose two possible models for the distribution of the density of states involving the π and σ states. The evolution of these states and of the deep defect absorption has a profound impact on the transport properties and particularly on the UV photoconductivity. Comparing the two models, it seems more probable that the UV photoconductivity (for photon energy >4.96 eV) is rather linked to transitions involving the σ-σ* states. [ABSTRACT FROM AUTHOR]

We have fabricated hydrogenated amorphous silicon (a-Si:H)/crystalline silicon (c-Si) heterojunction solar cells with different a-Si:H layer thicknesses, in order to determine effects of a-Si:H layer thicknesses on the performance of a-Si:H/c-Si solar cells. The thicknesses of a-Si:H p-i layers formed on a n-type c-Si substrate were controlled accurately on the atomic scale by applying real-time spectroscopic ellipsometry during the a-Si:H growth. With increasing a-Si:H p-i layer thicknesses, the open-circuit voltage (Voc) and fill factor increase drastically up to 40 Å (i layer) and 30 Å (p layer), whereas the short-circuit current density (Jsc) reduces gradually. By using optimum a-Si:H layer thicknesses (i/p=40/30 Å), we obtained a solar cell efficiency of 16.1% without incorporating surface texture and a back-surface field structure. Quite interestingly, the optimum a-Si:H i-layer thickness (40 Å) shows good correlation with a SiH2-rich interface structure formed at the a-Si:H/c-Si heterointerface, suggesting that the optimum i-layer thickness is governed by the interface properties of the a-Si:H/c-Si. Quantum efficiency measurements further revealed that the influence of a-Si:H layer thickness on the solar cell is quite different between a-Si:H p and i layers. Based on results obtained from this study, we discuss the roles of a-Si:H p-i layers incorporated in a-Si:H/c-Si heterojunction solar cells. [ABSTRACT FROM AUTHOR]

We use postdeposition atomic force microscopy and in situ spectroscopic ellipsometry to analyze the roughening of hydrogenated amorphous silicon films deposited by hot-wire chemical vapor deposition at 150 °C. From the atomic force microscopy data, the root-mean-squared roughness w increases with deposition time t as w∝tβ with β=0.37±0.02, and the correlation length ξ increases as ξ∝t1/z with 1/z=0.31±0.02. From the height-difference correlation function, we obtain a roughness exponent α=0.87±0.04 and a root-mean-squared local slope δ, which increases as δ∝tκ with κ=0.17±0.03. These measurements are indicative of anomalous growth, which we attribute to geometric shadowing. However, the roughening behavior we observe using atomic force microscopy is not reproduced in the spectroscopic ellipsometry data. This contradicts previous reports which found a linear relationship between the thickness of the optical roughness layer and the root-mean-squared roughness. We discuss the discrepancy between the two techniques in terms of short-range roughness and vector perturbation theory. [ABSTRACT FROM AUTHOR]

Plasma treatment with fluoro-containing gases is widely studied to improve the electrical performance of amorphous oxide semiconductor-based thin-film transistors (TFTs). However, given its research solely focuses on improving electrical performance, its practical use faces limitations due to an insufficient comprehension of its influence on device reliability – a pivotal factor for optimal, long-term device operation. Herein, improvements in the electrical performance and reliability of highly transparent amorphous indium-gallium-tin-oxide (a-IGTO) TFTs through SF 6 plasma treatment, a facile and straightforward approach with high applicability, are thoroughly investigated. Furthermore, the addition of oxygen gas, a widely used supplementary gas in plasma treatment, is analyzed. The diffusion of S and F by SF 6 plasma treatment breaks the weak bonds between the metal ions and oxygen atoms and reduces the number of oxygen vacancies in a-IGTO thin films. Despite the decrease in the oxygen vacancies, the carrier concentration is increased, as F acts as a donor-like defect. This diffused S and F effect increased the field-effect mobility (μ, 19.4 cm2/V·s) by a factor of about two and also greatly reduced the threshold voltage (V th) shifts under various bias stress tests. The high performance and reliability of SF 6 plasma-treated a-IGTO TFTs demonstrate the feasibility of transparent TFT-based next-generation transparent electronics. [ABSTRACT FROM AUTHOR]