Indium Oxide Films Research Articles

The effect of thickness on the optical and electrical properties of Hf doped indium oxide thin films

The doping of Hf has great potential to adjust the optical and electrical properties of In2O3 films, which has rarely been reported. In this paper, Hf-doped indium oxide films (IHFO) with excellent optical (average transmittance: 95.81%) and electrical properties (resistivity: 7.1 × 10−4 Ω cm) were deposited by RF sputtering on the glass substrate. X-ray photoelectronic spectra (XPS) showed that Hf4+ substituted In3+, resulting in an increase in carrier concentration and thus decreased resistivity. The X-ray diffraction (XRD) and Scanning electron microscopy (SEM) indicated that the change in the preferred orientation of IHFO film from (400) to (222) leads to different shape grains, which are associated with nuclei merging due to thickness increase. As the optical path of the visible light in film increase with film thickness, the film's visible light absorption is enhanced, resulting in the average transmittance of the films decreasing from 95.81% to 87.68%. Considering the effect of thickness on optical and electrical properties, the IHFO film at a thickness of 893 nm exhibits the highest FOM value of 2.85 × 10−2 Ω−1 with high average transmittance (89.84%) and low sheet resistance(12 Ω/sq). This result indicates that the IHFO film deposited with optimal thickness can be an alternative for high-performance TCO in various optoelectronic fields.

Enhancing the adhesion strength of ink-jet printed indium tin oxide films: The role of printing parameters

This study investigates the impact of printing parameters on the adhesion strength of ink-jet films, focusing on indium tin oxide (ITO) and indium oxide (In2O3) films deposited on ceramic substrates with varying printing speed and stack layers. The surface morphology of films with different printing parameters is characterized, and microscratch tests are conducted to calculate the adhesion energy of the films. The relationships between printing parameters, microstructures, and adhesion strength are emphasized, which could provide innovative insights into the mechanical properties of ink-jet printing films dependent on printing parameters. The results are also contributed to a new perspective on the design and repair of ink-jet printed indium tin oxide films.

Effect of the thickness and surface interface of In2O3 films on the transport and recombination of charges in a polymer solar cell

Indium oxide films were obtained by spin coating from a solution of indium nitrate in ethylene glycol followed by annealing at 300 °C. The influence of the thickness and surface interface of In2O3 films on the optical and photo-electrophysical properties of a polymer solar cell has been studied. It is shown that the surface roughness of the film gradually decreases with a decrease in the thickness of the film to 60 nm, and a further decrease in the thickness of the films leads to its increase. The absorption spectra of the films were measured. The values of the optical band gap width are determined. It was found that with a decrease in the thickness of the films, the width of the forbidden zone (Eg) also decreases. It was found that the parameters of the current-voltage characteristics (VAC) and electrophysical measurements also depend on the thickness and interface of the surface of the In2O3 films. It was found that with an In2O3 film thickness equal to 60 nm, a maximum efficiency value of 3.42 % is observed, at the same time, electrons in the photoactive layer have a maximum charge carrier lifetime and a low recombination rate

Sensitivity estimation of indium oxide thin film for gamma sensing

This article aims to study the modification in the structural, optical and electrical properties of indium oxide thin film after gamma irradiation and estimation of sensitivity for gamma sensing applications. The thin film of indium oxide was deposited on a 450 °C preheated glass substrate using the spray pyrolysis technique. The deposited thin film of molar concentration 0.15 M and thickness of around 600 nm was irradiated with different gamma doses (100 Gy, 200 Gy, 300 Gy and 400 Gy). The optical properties of the irradiated film are studied using UV–Visible spectroscopy. Transmittance increased after irradiation up to 200 Gy and beyond that, it decreased. Indium oxide is an n-type semiconductor which exhibits both direct and indirect transitions. Both direct and indirect bandgap energy are calculated using Tauc’s plot. Extinction coefficient and refractive index variation with irradiation were also estimated. Photoluminescence study confirmed the gamma-induced defect formation and annihilation for an irradiation dose of 400 Gy and 200 Gy, respectively. Resistivity also decreased up to 200 Gy and beyond that, it increased. The sensitivity of the deposited film was estimated from the electrical measurements, and it lies between 10.7 and 53.4 mA/cm2/Gy.Graphical abstract

An Efficient, Fast‐Responding, Low‐Loss Thermo‐Optic Phase Shifter Based on a Hydrogen‐Doped Indium Oxide Microheater

AbstractThermo‐optic (TO) phase shifters are very fundamental units in large‐scale active silicon photonic integrated circuits (PICs). However, due to the limitation of microheater materials with a trade‐off between heating efficiency and absorption loss, designs reported so far typically suffer from slow response time, high power consumption, low yields, and so on. Here, an energy‐efficient, fast‐responding, low‐loss TO phase shifter is demonstrated by introducing hydrogen‐doped indium oxide (IHO) films as the microheater, and the optimized electron concentration with enhanced mobility endows the IHO with high conductivity as well as high near‐infrared (NIR) transparency, which allow it to directly contact the silicon waveguide without any insulating layer for efficient tuning and fast response. The TO phase shifter achieves a sub‐microsecond response time (970 ns/980 ns) with a π phase shift power consumption of 9.6 mW, and the insertion loss introduced by the IHO microheater is ≈0.5 dB. The proposed IHO‐based microheaters with compatible processing technology illustrate the great potential of such material in the application of large‐scale silicon PICs.

Tungsten doped indium oxide (IWO) transparent electrode used in air-annealed perovskite solar cells

The common transparent electrode materials used in perovskite solar cells (PSCs), for example, the tin-doped indium oxide (ITO), usually have low carrier mobility and low transmittance in the near-infrared region which limits the short circuit current density (JSC). Accordingly, it is urgent to seek a novel transparent conductive material with high mobility and high transmittance. In this work, the tungsten doped indium oxide (IWO) film, composed of 0.5 wt% WO3 and 99.5 wt% In2O3, is employed in PSCs to act as the transparent electrode. The IWO-based PSCs exhibit superior performance as compared with the ITO-based counterparts mainly due to the excellent opto-electrical properties of IWO, such as high carrier mobility and infrared transmittance, fine surface morphology, etc. The performance of devices is further optimized by air-annealing treatment of the absorber layer. Air-annealing improves the crystallinity, decreases the defect states, and as a result, inhibits the non-radiative recombination. In summary, we fabricated the champion device based on IWO with the JSC of 26.2 mA/cm2 and its power conversion efficiency achieves 23.64%, the maximum record of IWO-based PSCs.

Multiple-State Nonvolatile Memory Based on Ultrathin Indium Oxide Film via Liquid Metal Printing.

In this work, the ultrathin two-dimensional (2D) indium oxide (InOx) with a large area of more than 100 μm2 and a high degree of uniformity was automatically peeled off from indium by the liquid-metal printing technique. Raman and optical measurements revealed that 2D-InOx has a polycrystalline cubic structure. By altering the printing temperature which affects the crystallinity of 2D-InOx, the mechanism of the existence and disappearance of memristive characteristics was established. The tunable characteristics of the 2D-InOx memristor with reproducible one-order switching was manifest from the electrical measurements. Further adjustable multistate characteristics of the 2D-InOx memristor and its resistance switching mechanism were evaluated. A detailed examination of the memristive process demonstrated the Ca2+ mimic dynamic in 2D-InOx memristors as well as the fundamental principles underlying biological and artificial synapses. These surveys allow us to comprehend a 2D-InOx memristor using the liquid-metal printing technique and could be applied to future neuromorphic applications and in the field of revolutionary 2D material exploration.

Transducer-Aware Hydroxy-Rich-Surface Indium Oxide Gas Sensor for Low-Power and High-Sensitivity NO2 Gas Sensing

Low-power metal oxide (MOX)-based gas sensors are widely applied in edge devices. To reduce power consumption, nanostructured MOX-based sensors that detect gas at low temperatures have been reported. However, the fabrication process of these sensors is difficult for mass production, and these sensors are lack uniformity and reliability. On the other hand, MOX film-based gas sensors have been commercialized but operate at high temperatures and exhibit low sensitivity. Herein, commercially advantageous highly sensitive, film-based indium oxide sensors operating at low temperatures are reported. Ar and O2 gases are simultaneously injected during the sputtering process to form a hydroxy-rich-surface In2O3 film. Conventional indium oxide (In2O3) films (A0) and hydroxy-rich indium oxide films (A1) are compared using several analytical techniques. A1 exhibits a work function of 4.92 eV, larger than that of A0 (4.42 eV). A1 exhibits a Debye length 3.7 times longer than that of A0. A1 is advantageous for gas sensing when using field effect transistors (FETs) and resistors as transducers. Because of the hydroxy groups present on the surface of A1, A1 can react with NO2 gas at a lower temperature (∼100 °C) than A0 (180 °C). Operando diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) shows that NO2 gas is adsorbed to A1 as nitrite (NO2-) at 100 °C and nitrite and nitrate (NO3-) at 200 °C. After NO2 is adsorbed as nitrate, the sensitivity of the A1 sensor decreases and its low-temperature operability is compromised. On the other hand, when NO2 is adsorbed only as nitrite, the performance of the sensor is maintained. The reliable hydroxy-rich FET-type gas sensor shows the best performance compared to that of the existing film-based NO2 gas sensors, with a 2460% response to 500 ppb NO2 gas at a power consumption of 1.03 mW.

Mylar Interlayer-Mediated Performance Enhancement of a Flexible Triboelectric Nanogenerator for Self-Powered Pressure Sensing Application

A triboelectric nanogenerator (TENG) is a green energy harvester that transforms mechanical energy from the surroundings and body movements into useful electrical energy by the combined effect of triboelectrification and electrostatic induction. Here, we have developed a flexible organic–inorganic film-based contact separation mode TENG with polyvinyl butyral (PVB) and indium oxide (IO) films as contact materials. A biaxially oriented polyethylene terephthalate (BoPET) film (known as “Mylar”) has been used as the charge transition-blocking interlayer between the PVB triboelectric layer and the electrode, which prevents the recombination of generated charges with the interfacial charges on the electrode and thereby enhances the electrical output performance. The fabricated flexible PVB-IO TENG having a contact area of 4 cm2 and a separation gap of 5 mm generates an output voltage and a short-circuit current density of ∼700 V and ∼1.52 mA/m2, respectively. An enhancement of ∼85-fold in the peak power density is obtained for the PVB-IO TENG with the BoPET layer at a load resistance of 200 MΩ in comparison with the one without the BoPET interlayer. The as-fabricated device was used for capacitor charging and powering electronic gadgets such as digital thermometers, calculators, and LEDs. Also, the developed PVB-IO TENG has been demonstrated for the mechanical energy scavenging from human motions such as finger tapping, palm tapping, finger bending, and elbow bending. Moreover, the PVB-IO TENG was structurally modified into a self-powered pressure sensor by reducing its contact area and separation gap, which exhibits an excellent sensitivity of ∼4.38 V/kPa in the pressure range from 0.5 to 16 kPa.

High sensitivity of halide vapor phase epitaxy grown indium oxide films to ammonia

The effect of H2, NH3, CO and O2 on the electrically conductive properties of In2O3 films grown by halide vapor phase epitaxy has been studied. In the temperature range of 200-550oC, In2O3 films demonstrate gas sensitivity to all considered gases, a relatively high operation speed and repeatability of cycles. The greatest response to NH3 was obtained, which exceeded 33 arb. units at a temperature of 400oC and a gas concentration of 1000 ppm-1. A qualitative mechanism of gas sensitivity of In2O3 films is proposed. The obtained gas-sensitive characteristics are compared with known In2O3 sensors based on various materials. It is shown that the method of halide vapor phase epitaxy makes it possible to obtain indium oxide films with high gas sensitivity. Keywords: In2O3 films, halide vapor phase epitaxy, gas-sensitive properties, response.

Electrical Performance Enhancement and Low-Frequency Noise Estimation of In2O3-Based Thin Film Transistor Based on Doping Engineering

In this work, solution-derived InErO thin films were deposited to act as the channel layers of thin film transistors (TFTs). The effect of Er doping content on the morphology, oxygen defects, optical properties of indium oxide (In2O3) films, and electrical performance of InErO/Al2O3 TFTs was systematically investigated. Based on experimental results, it can be inferred that InErO-TFTs with 5% Er doping content has demonstrated improved electrical performance, including field effect mobility ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{\text {FE}}$ </tex-math></inline-formula> ) of 17.55 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{2}}\,\,\cdot \,\,\text{V}^{-{1}}\,\,\cdot \,\,\text{s}^{-{1}}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text{ON}}/{I} _{\text{OFF}}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.70\times 10^{{7}}$ </tex-math></inline-formula> , a subthreshold swing (SS) of 0.16 V/dec and threshold voltage shift of 0.10 and 0.09 V under positive bias stress (PBS) and negative bias stress (NBS) for 1800 s, respectively. The illumination NBS (NBIS) measurements have indicated the degraded device stability by reducing the light wavelength, which can be due to the ionization of oxygen vacancies. Low-frequency noise (LFN) characterizations on devices have shown that the interfacial density of states of In2O3-based TFTs decreases after Er doping. To demonstrate the potential applications of InErO-TFTs in logic circuits, a resistor-loaded unipolar inverter based on InErO/Al2O3 has been integrated, demonstrating good dynamic response behavior and high gain of 10. These results have indicated the great potential of solution-driven InErO-based TFTs for future applications in low-cost and high-performance electronics.

Высокая чувствительность пленок оксида индия, полученных методом хлоридной газофазной эпитаксии, к аммиаку

The effect of H2, NH3, CO and O2 on the electrically conductive properties of In2O3 films grown by halide vapor phase epitaxy has been studied. In the temperature range of 200−550°C, In2O3 films demonstrate gas sensitivity to all considered gases, a relatively high operation speed and repeatability of cycles. The greatest response to NH3 was obtained, which exceeded 33 arb.units at a temperature of 400°C and a gas concentration of 1000 ppm. A qualitative mechanism of gas sensitivity of In2O3 films is proposed. The obtained gas-sensitive characteristics are compared with known NH3 sensors based on various materials. It is shown that the method of halide vapor phase epitaxy makes it possible to obtain indium oxide films with high gas sensitivity

Conductive Polyaniline-Indium Oxide Composite Films Prepared by Sequential Infiltration Synthesis for Electrochemical Energy Storage.

Composites of conductive polymers (CP) and metal oxides (MO) have attracted continued interest in the past decade for diverse application fields because the synergistic effects of CP and MO enable the realization of unusual electronic, electrochemical, catalytic, and mechanical properties of the composites. Herein, we present a novel method for the sequential infiltration synthesis of composite films of polyaniline (PANI) and indium oxide (InO x ) with high electrical conductivities (4-9 S/cm). The synthesized composite films were composed of two phases of graded concentration: InO x with oxygen vacancies and PANI with partially protonated molecular units. The PANI-InO x composite films displayed enhanced electrochemical activity with a pair of well-defined redox peaks. The open interfacial regions between the InO x and PANI phases may provide efficient pathways for ion diffusion and active sites for improved charge transfer.

Low-temperature crystallization of indium oxide thin films with a photoactivable additive

In this study, we report a simple route to the low-temperature crystallization of solution-processed indium oxide thin films by introducing ammonium nitrate in the sol–gel metal oxide precursor solution as photoactivable additive and applying deep ultraviolet (DUV) irradiation onto the as-spun oxide films in an inert atmosphere. Thermal and structural analyses revealed that the initial temperatures for condensation and crystallization were reduced down to 130 and 200 °C, respectively, by the in situ generation of reactive chemical species enabled by DUV-assisted nitrate photolysis. Furthermore, transmission electron microscopy confirmed that the degree of indium oxide film crystallinity was gradually enhanced as the amount of nitrate in the precursor solution was increased. Finally, electrical characterizations showed that carrier mobility, threshold voltage, subthreshold swing, and threshold voltage shift under the positive bias stress of sol–gel indium oxide thin-film transistors were improved from 0.21 to 5.03 cm2/V s, from 4.18 to 1.64 V, from 1.33 to 0.72 V/dec, and from 6.44 to 4.04 V, respectively, by combining ammonium nitrate and DUV photoactivation.

Investigation of Effect of ClO4- Ions on the Growth of Indium Oxide Films on In Electrode in Dilute Na2B4O7 Solution by Potentiometric Technique

Investigation of Effect of ClO4- Ions on the Growth of Indium Oxide Films on In Electrode in Dilute Na2B4O7 Solution by Potentiometric Technique

Macroscopic analysis and design of Si HFGFET gas sensor for sensitive gas detection

In this study, we investigate gas sensing performance of horizontal floating-gate field-effect transistor (HFGFET) gas sensors having different FET channel width and length, and the number and length of FG fingers using both technology computer-aided design (TCAD) device simulation and actual gas sensing measurement. The HFGFET gas sensors have a control-gate (CG) and a FG, which are horizontally interdigitated. An indium oxide (In2O3) film is locally deposited between the CG and FG to be used as a sensing layer. Utilizing a simplified equivalent circuit and electrical characteristics of the HFGFET gas sensors, we define a new parameter G, which represents a magnitude of gas sensitivity. The effect of channel width and length, and the number and length of FG fingers of the HFGFET gas sensors on gas sensitivity is first investigated by TCAD device simulation, and then verified by NO2 and H2S gas sensing measurement.

Relation between disorder and homogeneity in an amorphous metal

Disorder and homogeneity are two concepts that refer to spatial variation of the system potential. In condensed-matter systems disorder is typically divided into two types; those with local parameters varying from site to site (diagonal disorder) and those characterized by random transfer-integral values (off-diagonal disorder). Amorphous systems in particular exhibit off-diagonal disorder due to random positions of their constituents. In real systems diagonal and off-diagonal disorder may be interconnected. The formal depiction of disorder as local deviations from a common value focuses attention on the short-range components of the potential-landscape. However, long range potential fluctuation are quite common in real systems. In this work we seek to find a correlation between disorder and homogeneity using amorphous indium-oxide films with different carrier-concentrations and with different degree of disorder. Thermal treatment is used as a means of fine tuning the system disorder. In this process the resistance of the sample decreases while its amorphous structure and chemical composition is preserved. The reduced resistivity affects the Ioffe-Regel parameter that is taken as a relative measure of disorder in a given sample. The homogeneity of the system was monitored using inelastic light-scattering. This is based on collecting the Raman signal from micron-size spots across the sample. The statistics of these low-energy data are compared with the sample disorder independently estimated from transport measurements. The analysis establishes that heterogeneity and disorder are correlated.

Enhanced stability and mobility of solution-processed oxide thin-film transistors with bilayer terbium-incorporated indium oxide channel

The trade-off between mobility and stability in oxide thin-film transistors (TFTs) hinders further advances of an active-matrix flat panel display. Herein, a solution-processed bilayer active channel is designed to improve the stability and mobility simultaneously. The optical bandgap and work function of Tb:In2O3 films are modulated by tuning the film thickness and Tb concentration of Tb-doped indium oxide (Tb:In2O3) films. Large conduction band offset is achieved in a Tb:In2O3 bilayer channel, which induces accumulation of abundant electrons at the interface. The mobility is significantly improved to 38.2 cm2/V s, and the photoinduced stability of bilayer Tb:In2O3 TFTs is improved with low threshold voltage shift of 0.26 and −0.38 V under negative-bias illumination stress and negative-bias temperature illumination stress, respectively.

Achievement of 25.54% power conversion efficiency by optimization of current losses at the front side of silicon heterojunction solar cells

AbstractParasitic absorption in the front window layers of transparent conductive oxide (TCO) films and carrier selective collection layers and the optical shading losses from the metallic finger grid mainly limit the current generation in silicon heterojunction (SHJ) solar cells. In this work, we demonstrate an improved short‐circuit current density (Jsc) of 40.24 mA/cm2 through a combination of novel window layers composed of transition metal doped indium oxide (IMO) and hydrogenated nanocrystalline silicon oxide (nc‐SiOx:H) films and Cu plating for SHJ solar cells. By introducing water vapor during direct current (DC) magnetron sputtering deposition process, IMO films show a large optical band gap (Eg) of about 3.88 eV and high mobility up to 83.2 cm2/V·s, while maintaining a low carrier concentration, which leads to high transparency and low near‐infrared (NIR) free carrier absorption (FCA). In addition to its high deposition rate and crystalline volume fraction, we found that nc‐SiOx:H films deposited by very high frequency (VHF) excited plasma‐enhanced chemical vapor deposition (PECVD) show an excellent surface passivation quality, which not only improves the open circuit voltage (Voc) of SHJ cells but also increases the Jsc through improved carrier selective collection. The quantified Jsc breakdown analysis was performed to identify the room for improvement, and it showed that the front shading loss (about 1.32 mA/cm2) is the largest portion. By combining the benefits of these window layer enhancements with the further use of fine line width and conductivity of Cu plating, SHJ solar cells, with a Jsc improvement of 0.57 mA/cm2 and a certified efficiency of 25.54%, were achieved on a total area of 274.5 cm2 using in‐house pilot production line equipment.

High-performance multiple-doped In2O3 transparent conductive oxide films in near-infrared light region

High-quality W, Mo, Ti, Zr, and Ga-doped indium oxide (multiple-doped In2O3) films are deposited at room temperature by direct current magnetron sputtering process under different oxygen proportion, with 200 °C annealing. A maximum Hall mobility of 71.6 cm2 V−1 s−1 is obtained at a middle oxygen proportion of 2%, thanks to the reduction of impurity scattering center, which is nearly three times higher than an ITO film of 23.6 cm2 V−1 s−1. The multiple-doped In2O3 films showed a remarkable 30% improvement of the optical transmittance (&amp;gt;80%) in the near-infrared (NIR) region compared to the ITO film (about 60%), which is mainly attributed to the decrement of free carrier absorption due to low carrier concentration (&amp;lt;2 × 1020 cm−3), an order magnitude lower than the ITO film (1.56 × 1021 cm−3). Additionally, x-ray diffraction results confirm that the films have a polycrystalline structure with preferential orientation growth in the &amp;lt;100&amp;gt; direction. In the NIR region, the multiple-doped In2O3 films have a superior figure of merit of 5.02 × 10−3 Ω−1, which is an order magnitude higher than the ITO film (5.31 × 10−4 Ω−1). This work reports a new In2O3-based material with both high electrical and optical performance, which is suitable for the application of advanced optoelectronic devices.