In2O3 Doping Research Articles

Metal-Organic Framework-Derived Au-Doped In2O3 Nanotubes for Monitoring CO at the ppb Level.

Achieving selective detection of ppb-level CO is important for air quality testing at industrial sites to ensure personal safety. Noble metal doping enhances charge transfer, which in turn reduces the detection limit of metal oxide gas sensors. In this work, metal-organic framework-derived Au-doped In2O3 nanotubes with high electrical conductivity are synthesized by pyrolysis of the Au-doped metal-organic framework (In-MIL-68) as a template. Gas-sensing experiments reveal that the detection limit of 0.2% Au-doped In2O3 nanotubes (0.2% Au, mass fraction) is as low as 750 ppb. Meanwhile, the sensing material shows a response value of 18.2 to 50 ppm of CO at 240 °C, which is about 2.8 times higher than that of pure In2O3. Meanwhile, the response and recovery times are short (37 s/86 s). The gas-sensing mechanism of CO is uncovered by in situ DRIFTS through the reaction intermediates. In addition, first-principles calculations suggest that Au doping of In2O3 significantly enhances its adsorption energy for CO and improves the electron transfer properties. This study reveals a novel synthesis pathway for Au-doped In2O3 nanotubular structures and their potential application in low concentration CO detection.

Effects of In2O3 doping on the microstructure and electrical properties of ZnO–V2O5–Nb2O5 varistor ceramics

To understand the effects of In2O3 on the microstructure, grain size dispersion, density and nonlinear electrical characteristics, ZnO–V2O5–Nb2O5 varistor ceramics with 0.02, 0.05 and 0.1 mol.% In2O3 were fabricated via sintering at 950–975 °C for 1 h. The sintered samples were evaluated by x-ray diffraction, scanning electron microscopy, density measurements and electrical measurements through a voltage source meter. In2O3 addition improves relative density to ≥99 % and acts as an efficient grain growth inhibitor, resulting in a narrower grain dispersion and finer ZnO grains due to the formation of In–V–O intergranular phases. The breakdown potential (E1mA) increases sharply to 7.49 ± 0.3 kV/cm (from 1.66 ± 0.1 kV/cm) as a result of grain size reduction to 2.1 ± 0.1 μm (from 3.89 ± 0.2 μm) with In concentration of 0.1 mol.% (from 0.02 mol.%). Doping of In2O3 improves the nonlinear exponent and reduces the leakage current density as a direct consequence of enhanced Schottky barrier height.

Investigations of In2O3 Added SiC Semiconductive Thin Films and Manufacture of a Heterojunction Diode

This study involved direct doping of In2O3 into silicon carbide (SiC) powder, resulting in 8.0 at% In-doped SiC powder. Subsequently, heating at 500 °C was performed to form a target, followed by the utilization of electron beam (e-beam) technology to deposit the In-doped SiC thin films with the thickness of approximately 189.8 nm. The first breakthrough of this research was the successful deposition of using e-beam technology. The second breakthrough involved utilizing various tools to analyze the physical and electrical properties of In-doped SiC thin films. Hall effect measurement was used to measure the resistivity, mobility, and carrier concentration and confirm its n-type semiconductor nature. The uniform dispersion of In ions in SiC was as confirmed by electron microscopy energy-dispersive spectroscopy and secondary ion mass spectrometry analyses. The Tauc Plot method was employed to determine the Eg values of pure SiC and In-doped SiC thin films. Semiconductor parameter analyzer was used to measure the conductivity and the I-V characteristics of devices in In-doped SiC thin films. Furthermore, the third finding demonstrated that In2O3-doped SiC thin films exhibited remarkable current density. X-ray photoelectron spectroscopy and Gaussian-resolved spectra further confirmed a significant relationship between conductivity and oxygen vacancy concentration. Lastly, depositing these In-doped SiC thin films onto p-type silicon substrates etched with buffered oxide etchant resulted in the formation of heterojunction p-n junction. This junction exhibited the rectifying characteristics of a diode, with sample current values in the vicinity of 102 mA, breakdown voltage at approximately −5.23 V, and open-circuit voltage around 1.56 V. This underscores the potential of In-doped SiC thin films for various semiconductor devices.

Comparing the Effect of In2O3 and Eu2O3 Impurities on the Structural and Optical Properties of Cerium Oxide

This work compares the changes in optical and structural properties of cerium oxide (CeO2) when doped with different concentrations (3%,5%,7%, and 9%) of two oxides, In2O3 and Eu2O3. X-ray diffraction and spectrophotometry were employed in the visible, ultraviolet, and near-infrared regions. The findings demonstrated that CeO2 doped with In2O3 and Eu2O3 thin films were polycrystalline and had a cubic structure. The crystal size increased from 20.5 to 32.15 when Eu2O3 doping ratio increased from 0% to 7% and then decreased to 28.46 nm at 9%. While the crystal size showed an increase from 20.5 to 21.42 nm with the increase of the In2O3 doping ratio, while the lattice constant measured for cubic CeO2 changed opposite to that. The optical measurement showed that Eu2O3 and In2O3 doped CeO2 thin films have a direct band gap with allowed transition with 3.0 eV for the undoped CeO2. The band gap energy changed in a non-regular manner with the increase of the doping ratio of both oxides. The minimum band gap energy was 1.2 eV obtained for 7% Eu2O3 doped CeO2 thin film, and the minimum band gap energy was 1.4 eV obtained for 9% In2O3 doped CeO2. These results qualify them for use as absorbers in solar cell applications.

Fabrication and characterization of PEG-In2O3 modified PbO2 anode for electrochemical degradation of metronidazole

An In2O3-PbO2 anode with high electrocatalytic activity was prepared in our previous study. However, the service life of In2O3-PbO2 anode needed to be further improved. Thus, a typical stabilizer of polyethylene glycol (PEG) was used to modify the In2O3-PbO2 anode in this study. Theoretical and experimental results show that a small amount of PEG promoted the doping of In2O3 into β-PbO2 film, while excessive PEG reduced the doping of In2O3. Doping a moderate amount of PEG not only reduced the PbO2 crystal size, improved the density of electrode film, reduced the charge transfer resistance, increased the oxygen evolution potential, number of active sites and capacity of •OH generation of In2O3-PbO2 anode, but also prolonged the service life of In2O3-PbO2 anode from 96 to 137 h. In the process of electrochemical degradation of metronidazole, the PEG/In2O3-PbO2 anode exhibited superior electrocatalytic activity. The degradation rate constant at the PEG/In2O3-PbO2 anode was 1.682 times higher than that at In2O3-PbO2 anode. After 60 min of electrolysis, COD and TOC removals reached up to 80.92% and 78.52%, respectively, much higher than those of In2O3-PbO2 anode (69.24% and 55.83%, respectively). Additionally, a total of 13 intermediates generated in the degradation process were identified by LC-MS, and two possible degradation pathways were proposed accordingly. Overall, this study offers a promising approach for enhancing the electrocatalytic activity and stability of the PbO2 anode.

Effects of In2O3 doping on microstructure and electrical properties of ZnO low-voltage varistor

Effects of In2O3 doping on microstructure and electrical properties of ZnO low-voltage varistor

Microstructure and Electrical Properties of In2O3, La2O3 and Ga2O3 Doped ZnO-Bi2O3-MnO2-SiO2-TiO2 Varistor Ceramics

ZnO-Bi2O3-MnO2-SiO2-TiO2 varistor ceramics with addition of X2O3 (X = In, La, Ga) were manufactured through the conventional solid-state method and their phase transformation, microstructure, band gap, and electrical properties were investigated by X-ray diffractometer, Scanning electron microscopy, Fourier transform infrared spectroscopy, and solid UV absorption spectrometry, respectively. The results show that ZnO-Bi2O3-MnO2-SiO2-TiO2-0.15 mol% X2O3 ceramics can be successfully produced at a very low temperature of 875 °C. When X2O3, especially Ga2O3, is doped into ZnO varistors, the grain sizes of specimens are refined. The grain size of ZnO-based varistor ceramics with Ga2O3 doping decreases obviously from 4.31 to 3.10 μm, and the voltage gradient increases from 763.1 to 1047.5 V mm−1. The nonlinear coefficient of ZnO-based varistor ceramics with In2O3 doping increases from 26.5 to 36.7.

Optimizing the Electronic Structure of In2O3 through Mg Doping for NiO/In2O3 p-n Heterojunction Diodes.

In2O3 is a wide bandgap oxide semiconductor, which has the potential to be used as an active material for transparent flexible electronics and UV photodetectors. However, the high concentration of unintentional background electrons existing in In2O3 makes it hard to be modulated by the electric field or form p-n heterojunctions with a sufficient band-bending width at the interface. In this work, we report the reduction of the background electrons in In2O3 by Mg doping (Mg-In2O3) and thereby improve the device performance of p-n diodes based on the NiO/Mg-In2O3 heterojunction. In particular, Mg doping compensates the free electrons in In2O3 and reduces the electron concentration from 1.7 × 1019 cm-3 without doping to 1.8 × 1017 cm-3 with 5% Mg doping. Transparent p-n heterojunction diodes were fabricated based on p-type NiO and n-type Mg-In2O3. The device performance was considerably enhanced by Mg doping with a high rectification ratio of 3 × 104 and a remarkable high breakdown voltage of >20 V. High-resolution X-ray photoelectron spectroscopy was used to investigate the interfacial electronic structure between NiO and Mg-In2O3, revealing a type II band alignment with a valence band offset of 1.35 eV and a conduction band offset of 2.15 eV. A large built-in potential of 0.98 eV was found for the undoped In2O3 but decreased to 0.51 eV for 5% Mg doping of In2O3. The NiO/Mg-In2O3 diodes with an improved rectification ratio and wider depletion region provide the possibility of achieving photodetectors with rapid photoresponse.

Improving ethanol sensing characteristics of indium oxide thin films by nitrogen incorporation

Incorporation of suitable dopants in semiconducting metal oxide (SMO) based gas sensors have been one proficient approach employed to improve their sensing characteristics. Indium oxide (In2O3), which is a n-type SMO, has been widely investigated for its ethanol sensing characteristics. For doping of In2O3, typically various metal based dopants have been considered, whereas non-metallic dopants have drawn only limited attention. In this work we have examined the impact of nitrogen incorporation on the ethanol sensing properties of In2O3 thin film. Using urea as a source, nitrogen has been doped at the interstitial site of In2O3 synthesised using sol-gel technique. Ethanol sensing properties of the nitrogen doped In2O3 thin film has been compared with pure In2O3 sensor over a wide range of temperature. Doping of nitrogen has been found to significantly enhance the ethanol sensing response of In2O3 (99.7 % at 250 °C), improves the stability of response under humid condition (change of response ∼ 4.5 % within relative humidity range 10–80 %) and offers very fast response time (1 s for 300 ppm ethanol). We discuss that modification of the electronic properties of In2O3 due to interstitial nitrogen incorporation leads to its superior sensing properties on exposure to ethanol vapour.

Microwave Hydrothermal Synthesis of In2O3-ZnO Nanocomposites and Their Enhanced Photoelectrochemical Properties

Indium oxide (In2O3) doped zinc oxide (ZnO) nanocomposites were successfully synthesized through a facile microwave hydrothermal method. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption isotherms (BET) and UV-Vis diffuse reflectance spectroscopy. The morphology of In2O3-ZnO composites was observed to be like flowers, and the diameter of particles constituting the porous petal was about 30 nm. The photoelectrocatalytic test results showed that the photoelectrocatalytic methylene blue (MB) degradation efficiency using In2O3-ZnO nanocomposites as photocatalysts under visible light irradiation and a certain voltage could reached above 95.3% after 60 min, much higher than that of In2O3 particles and ZnO particles. The enhanced photoelectrocatalytic activity was attributed to the doping of In2O3 and applied voltage, which beneficially reduced the recombination of electrons and holes in the photoelectrocatalytic process, therefore, it promoted the production of active species (•OH and •O−2).

Enhancement of CdS nanoparticles photocatalytic activity by Pt and In2O3 doping for the degradation of malachite green dye in water

A hydrothermal method was used to prepare CdS nanoparticles, and a photoassisted deposition method was used to prepare 0.5wt% In2O3/CdS, 0.5wt% Pt/CdS and 0.5wt% Pt, In2O3/CdS nanoparticles. Different techniques, such as UV–Vis, XPS, TEM, XRD, PL and BET surface area, were used to characterize the prepared materials. The results reveal that the doping of Pt, In2O3 on the surface of CdS nanoparticles plays an important role in the control electron-hole recombination rate. The photocatalytic performance of CdS, 0.5wt% In2O3/CdS, 0.5wt% Pt/CdS, and 0.5wt% Pt, In2O3/CdS nanoparticles was studied by measuring their photocatalytic oxidation of malachite green dye under visible light. Photocatalytic parameters such as the type of doped materials, photocatalyst dosage and photocatalytic stability were also studied. The photocatalytic activity of CdS is lower than that of doped cadmium sulphide nanoparticles. This can be attributed to the fact that the addition of Pt or In2O3 or both In2O3 and Pt to CdS nanoparticles decreases the electron-hole recombination rate or alternatively due to the transfer of electrons between the doped metal and CdS nanoparticles.

Structural Characterization and Electrical Conductivity of Mechanically Alloyed 10mol% In2O3–Doped CeO2 Nanoparticles

Method: Nanocrystalline powder of 10 mol% indium oxide doped ceria is synthesized by mechanically alloying the stiochiometric powder mixture of CeO2 and In2O3 within 5 h of milling in open air. Further milling up to 8 h confirms the stable cubic structure of the compound with increase in milling time. Objective: Detailed structure and microstructure of the compound have been characterized by Rietveld powder structure and microstructure refinement method using XRD data and analyzing HRTEM images. Effect of In2O3 doping on electrical conductivity of nanocrystalline CeO2 is studied by measuring the electrical conductivity of the compound in the temperature range 300°C-600°C. The DC conductivity of doped ceria (σdc ~ 3x10-4 S/cm at 540°C for doped ceria) has been enhanced to ~100 times in comparison to that of the undoped ceria (σdc ~ 4x10-6 S/cm at 540°C) nanoparticles has been found. Conclusion: This significant increment in electrical conductivity has been interpreted through the microstructure characterization of the doped compound. Keywords: Oxides, milling, defects, x-ray diffraction, microstructure, electrical conductivity.

Low indium content In–Zn–O system towards transparent conductive films: structure, properties and comparison with AZO and GZO

In this work, low content indium doped zinc oxide (IZO) thin films were deposited on glass substrates by RF magnetron sputtering using IZO ceramic targets with the In2O3 doping content of 2, 6, and 10 wt%, respectively. The influences of In2O3 doping content and substrate temperature on the structure and morphology, electrical and optical properties, and environmental stability of IZO thin films were investigated. It was found that the 6 wt% doped IZO thin film deposited at 150 °C exhibited the best crystal quality and the lowest resistivity of 9.87 × 10−4 Ω cm. The corresponding Hall mobility and carrier densities were 9.20 cm2 V−1 s−1 and 6.90 × 1020 cm−3, respectively. Compared with 2 wt% Al2O3 doped ZnO and 5 wt% Ga2O3 doped ZnO thin films, IZO thin film with the In2O3 doping content of 6 wt% featured the lowest surface roughness of 1.3 nm. It also showed the smallest degradation with the sheet resistance increased only about 4.4% at a temperature of 121 °C, a relative humidity of 97% for 30 h. IZO thin film with 6 wt% In2O3 doping also showed the smallest deterioration with the sheet resistance increased only about 2.8 times after heating at 500 °C for 30 min in air. The results suggested that low indium content doped ZnO thin films might meet practical requirement in environmental stability needed optoelectronic devices.

Synthesis and study of solid solutions based on indium oxide in the In2O3–ZrO2(HfO2) systems as a material for fuel cell interconnectors

Nanocrystalline (8–10 nm) solid solutions on the basis of indium oxide in the systems In2O3–ZrO2 and In2O3–HfO2 are synthesized by hydroxide coprecipitation. It is established that the use of polyvinyl alcohol decreases the degree of agglomeration of precipitates and increases the dispersity of the synthesized powders. The optimal conditions for the consolidation of powders on the basis of In2O3 are selected. It is shown that In2O3 doping with zirconium and hafnium dioxides significantly increases the electrical conductivity of solid solutions compared to pure indium oxide. The influence of temperature and oxygen partial pressure on the conductivity of solid solutions on the basis of In2O3 was investigated.

Influence of dopant species and concentration on grain boundary scattering in degenerately doped In2O3 thin films

The influence of dopant species and concentration on the grain boundary scattering of differently doped In2O3 thin films is studied by means of room temperature and temperature dependent Hall effect measurements. Barrier heights at grain boundaries EB are evaluated from temperature dependent carrier mobility taking the theoretically calculated temperature dependence of intragrain mobility into account. It is thereby shown that also samples with a negative temperature coefficient of mobility exhibit significant grain boundary barrier heights and that EB is usually underestimated when evaluated based on Seto's model. It is also shown that the most commonly used Sn doping of In2O3 with a dopant concentration >2wt.% SnO2 leads to significantly enhanced grain boundary scattering compared to nominally undoped, Zr-doped and H-doped films. An effect of grain boundary scattering is even observed for carrier concentrations ~1021cm−3 if the films exhibit a pronounced (100) texture. The poor grain boundary properties of highly Sn-doped In2O3 are attributed to segregation of the Sn dopants, which is also indicated by measurements of surface Sn concentration.

Pb doping of In2O3 and their conversion to highly conductive PbS/In2S3−3xO3x nanowires with infra red emission

We have grown Pb doped In2O3 nanowires at 800°C which have the cubic bixbyite crystal structure of In2O3 and contain orthorhombic α-PbO. These had resistances up to ≈10Ω and exhibited photoluminescence at 2.5eV but we observed the gradual emergence of infra red emission from 0.8μm to 1.2μm after processing under H2S between 200°C and 400°C. The resultant PbS/In2S3−3xO3x nanowires had similar resistances and consist of stacked crystals with sizes that depend on the Pb content. We discuss the potential of Pb for doping metal oxide semiconductors and the importance of PbS/In2O3 p–n tunnel junctions for solar cells.

In2O3:Ga and In2O3:P-based one-electrode gas sensors: Comparative study

Gas sensing characteristics of one-electrode sensors based on the In2O3 ceramics doped by gallium and phosphorus have been discussed. In2O3-based ceramic was prepared by sol–gel technology. Ozone, CO, CH4 and H2 were used as tested gases. The doping concentration effect on the sensor parameters such as magnitude of response, operating temperature, response and recovery times, sensitivity to the air humidity, and selectivity have been analyzed. It was shown that In2O3 doping by Ga and P could be used for the sensor performance optimization. It was assumed that the appearance of the second phase (InPO4 and Ga2O3) and the change of structural parameters, taking place during doping process, were the main factors controlling the change of operating characteristics in In2O3:P and In2O3:Ga-based sensors.

Indium oxide—a transparent, wide-band gap semiconductor for (opto)electronic applications

The present review takes a semiconductor physics perspective to summarize the state-of-the art of In2O3 in relation to applications. After discussing conventional and novel applications, the crystal structure, synthesis of single-crystalline material, band-structure and optical transparency are briefly introduced before focussing on the charge carrier transport properties. The issues of unintentional n-type conductivity and its likely causes, the surface electron accumulation, and the lack of p-type conductivity will be presented. Intentional doping will be demonstrated to control the electron concentration and resistivity over a wide range, but is also subject to compensation. The control of the surface accumulation in relation to Schottky and ohmic contacts will be demonstrated. In the context of scattering mechanisms, the electron mobility and its limits will be discussed. Finally, the Seebeck coefficient and its significance will be shown, and ferromagnetic doping of In2O3 will be critically discussed. With this overview most if not all ingredients for the use of In2O3 as semiconductor material in novel or improved conventional devices will be given.

Promoting Effects of In2O3on Co3O4for CO Oxidation: Tuning O2Activation and CO Adsorption Strength Simultaneously

The doping of In2O3 significantly promoted the catalytic performance of Co3O4 for CO oxidation. The activities of In2O3–Co3O4 increased with an increase in In2O3 content, in the form of a volcano curve. Twenty-five wt % In2O3–Co3O4 (25 InCo) showed the highest CO oxidation activity, which could completely convert CO to CO2 at a temperature as low as −105 °C, whereas it was only −40 °C over pure Co3O4. The doping of In2O3 induced the expansion of the unit cell and structural distortion of Co3O4, which was confirmed by the slight elongation of the Co–O bond obtained from EXAFS data. The red shift of the UV–vis absorption illustrated that the electron transfer from O2– to Co3+/Co2+ became easier and implied that the bond strength of Co–O was weakened, which promoted the activation of oxygen. Low-temperature H2-TPR and O2-TPD results also revealed that In2O3–Co3O4 behaved with excellent redox ability. The XANES, XPS, XPS valence band, and FT-IR data exhibited that the CO adsorption strength became weaker due to the downshift of the d-band center, which correspondingly weakened the adsorption of CO2 and obviously inhibited the accumulation of surface carbonate species. In short, the doping of In2O3 induced the structural defects, modified the surface electronic structure, and promoted the redox ability of Co3O4, which tuned the adsorption strength of CO and oxygen activation simultaneously.

Mg acceptor doping of In2O3 and overcompensation by oxygen vacancies

Mg-doped indium oxide (In2O3) thin films were grown by plasma-assisted molecular beam epitaxy with Mg-concentrations ranging from 1017 to 6×1020 cm−3. In this concentration range Mg was incorporated into In2O3 without discernable impediment nor formation of secondary phases. Despite the role of Mg as acceptor, the films were n-type conductive in the as-grown state or after annealing in vacuum. For Mg-concentrations well in excess of the unintentional donor concentration annealing in oxygen resulted in semi-insulating films without detectable p-type conductivity. These results strongly suggest oxygen vacancies to act as shallow donors in In2O3 that can overcompensate the Mg acceptors.