Tin Oxide Thin Films Research Articles

Vortex harmonic generation in indium tin oxide thin film irradiated by a two-color field.

When a two-color Laguerre-Gaussian laser beam propagates through an indium tin oxide (ITO) material, the spatial distributions of odd- and even-order vortex harmonics carrying orbital angular momentum (OAM) are studied. The origin of vortex harmonics can be directly clarified by investigating their dependence on the incident laser field amplitude and frequency. In addition, it is shown that the spectral intensities of vortex harmonics are sensitive to the epsilon-near-zero nonlinear enhancing effects and the thickness of ITO materials. Thus the vortex harmonics can be conveniently tunable, which provides a wider potential application in optical communications based on high-order OAM coherent vortex beams.

Enhancing charge transport and photoluminescence characteristics via transition metals doping in ITO thin films

Abstract This study presents the synthesis and characterization of pristine and transition metal (Co, Fe, and Zr)-doped indium tin oxide (ITO) thin films fabricated via RF magnetron sputtering. The effect of transition metal doping on ITO thin films properties was comprehensively examined using numerous spectroscopic and microscopic methods such as XRD, FTIR, and SEM coupled with EDX, UV–visible and PL spectroscopy, and four-probe and J–V measurements. The cubic crystal structure of the materials was confirmed through XRD spectroscopy, while FTIR results validated the existence of chemical bonds, signified by sharp peaks at 608 cm−1 and 667 cm−1 in the fingerprint region. SEM imaging revealed a granular-like agglomerated structure, with EDX confirming the elemental composition of the samples. The incorporation of Co, Fe, and Zr ions into ITO is aimed at improving photoconductivity and the optical bandgap, with the ultimate objective of enhancing performance in photovoltaic applications. Our findings showed a significant decrease in optical transmission in the visible spectrum. The bandgap also experienced a minor decrease from 3.67 eV to 3.53 eV. Analysis of the photoluminescence spectra exhibited the majority of emission peaks in the UV region, ascribed to electronic transitions occurring via band-to-band and band-to-impurity interactions within the ITO. Electrical measurements indicated lower resistance, higher current flow, and increased carrier concentration in transition metals–doped ITO compared to the undoped ITO, with Zr-doped ITO exhibiting the highest conductivity and optimal charge flow among all dopants. These promising findings in terms of optical, structural, and electrical attributes signal the potential of these materials for photovoltaic system applications.

Examining the Effect of Thermal Treatment on the Surface Morphology and Structural Properties of Tin Dioxide Thin Films Grown Using an Economical Spray Deposition Method


 
 
 
 Tin oxide is a versatile material that is frequently used in temperature, gas, and photo-sensing applications. It is well-known for its beneficial physical and chemical properties. This work describes an economical fabrication technique that uses an airbrush to apply SnO2 to a glass substrate in ambient circumstances. Important variables were carefully controlled, such as a constant 30 cm distance from the head of the airbrush to the preheated substrates, a 0.5 ml/minute deposition rate, and a 200 °C deposition temperature. Following that, annealing procedures were conducted at 250 and 500 °C to investigate the effects on optical, morphological, and structural characteristics. X-ray diffraction (XRD) structural investigation revealed a significant increase in crystallinity at higher annealing temperatures, with each thin film consistently displaying the rutile phase (JCPDS No. 01-0657). The produced tin dioxide thin films appear homogeneous in the images taken by the scanning electron microscope (SEM). However, there were visible structural defects. Additionally, an increase in surface roughness with higher annealing temperatures was found by atomic force microscopy (AFM) examinations. Such result holds significant value in fields like gas sensing and photon absorption, where surface properties are critical to overall performance. Finally, extensive investigations combined with the economical fabrication approach present a potential path toward customizing tin oxide thin films for a range of applications. The material's advantage for practical applications is improved by the capacity to modify structural and morphological properties through annealing conditions, demonstrating its potential in emerging fields of technology.
 
 
 

Graded-Band-Gap Zinc-Tin Oxide Thin-Film Transistors with a Vertically Stacked Structure for Wavelength-Selective Photodetection.

Filter-free wavelength-selective photodetectors have garnered significant attention due to the growing demand for smart sensors, artificial intelligence, the Internet of Everything, and so forth. However, the challenges associated with large-scale preparation and compatibility with complementary metal-oxide-semiconductor (CMOS) technology limit their wide-ranging applications. In this work, we address the challenges by constructing vertically stacked graded-band-gap zinc-tin oxide (ZTO) thin-film transistors (TFTs) specifically designed for wavelength-selective photodetection. The ZTO thin films with various band gaps are fabricated via atomic layer deposition (ALD) by varying the ALD cycle ratios of zinc oxide (ZnO) and SnO2. The ZTO film with a small Sn ratio exhibits a decreased band gap, and the resultant TFT shows a degraded performance, which can be attributed to the Sn4+ dopant introducing a series of deep-state energy levels in the ZnO band gap. As the ratio of Sn increases further, the band gap of the ZTO also increases, and the mobility of the ZTO TFT increases up to 30 cm2/V s, with a positive shift of the threshold voltage. The photodetectors employing ZTO thin films with distinct band gaps show different spectral responsivities. Then, vertically stacked ZTO (S-ZTO) thin films, with gradient band gaps increasing from the bottom to the top, have been successfully deposited using consecutive ALD technology. The S-ZTO TFT shows decent performance with a mobility of 18.4 cm2/V s, a threshold voltage of 0.5 V, an on-off current ratio higher than 107, and excellent stability under ambient conditions. The resultant S-ZTO TFT also exhibits obviously distinct photoresponses to light at different wavelength ranges. Furthermore, a device array of S-ZTO TFTs demonstrates color imaging by precisely reconstructing patterned illuminations with different wavelengths. Therefore, this work provides CMOS-compatible and structure-compact wavelength-selective photodetectors for advanced and integrable optoelectronic applications.

Enhancing electronic properties by suppressing nucleation delay for low-temperature processed atomic-layer-deposited amorphous zinc–tin-oxide thin films

Atomic-layer-deposited (ALD) zinc-tin-oxide (ZTO) thin films offer promising electronic properties for many applications, but their development has been limited by their tendency to experience significant nucleation delay—which tends to introduce impurity—during deposition. This study utilized in-situ quartz crystal microbalance (QCM) analysis combined with ex-situ compositional analysis to examine the nucleation-delay characteristics of ZTO ALD and their dependence upon the oxidant-precursor settings. The results indicated that nucleation delay occurred solely during the ZnO-on-SnO2 deposition step as a result of persisting ethyl ligands of the organozinc precursor, diethylzinc, which could be mitigated by using H2O2 instead of H2O as the oxidant precursor and introducing a discrete-feeding or exposure procedure for the H2O2 half cycle to increase the effective oxidant dose. The effects of nucleation delay on the electronic properties of ALD ZTO films was examined with thin-film transistor (TFT) devices, where suppression of nucleation delay yielded substantial improvement in the device performance, achieving a high field-effect mobility of 21.5 cm2/V s, low sub-threshold swing of 0.16, high on/off ratio of 2 × 108, and enhance-mode operation without needing elevated-temperature post-processing. The findings present valuable improvements over the state of the art and provide insights useful for the development of other types of ALD multi-component films.

Atomic layer etching of indium tin oxide

This work presents the atomic layer etching (ALE) process for sputtered indium tin oxide (ITO) thin films using thermal surface modification with BCl3 and modified surface removal by low ion energy Ar plasma. In this approach, an elevated temperature is required for high synergy ALE due to the low volatility of indium chlorides, and 150°C is proved to be suitable. An etch per cycle (EPC) of 1.1 Å and ALE synergy of 82% was achieved. Both surface modification and modified surface removal steps exhibited self-limited EPC. The ALE process was developed in a conventional reactive ion etching tool and retains the thin film absolute uniformity on the wafer. ITO was photolithographically patterned on whole wafers using photoresist as an etch mask for the ALE, and clear smoothing of the unmasked areas is observed, which is a characteristic of an ideal ALE process. This confirms that the developed ALE process can be utilized to pattern ITO using conventional photolithography. The demonstrated ITO ALE can be used to fabricate, for example, thin channel or recessed channel transistors, with self-smoothened channels for reduced surface scattering.

Investigation of structural and photoluminescence properties of nanocrystalline tin oxide thin films grown by ultrasonic spray pyrolysis method

Investigation of structural and photoluminescence properties of nanocrystalline tin oxide thin films grown by ultrasonic spray pyrolysis method

Characterization and Performance Evaluation of Ni-Doped SnO2 Thin Films for Optoelectronic Applications: Structural, Optical, and Electrical Insights

Undoped and Ni-doped tin oxide (SnO2) thin films were synthesized using the spray pyrolysis technique on ordinary glass substrates. The study aimed to investigate the physico-chemical properties of these thin films using various characterization techniques. X-ray diffraction (XRD) analysis revealed a polycrystalline behavior with a tetragonal structure and a preferential orientation along the [110] direction for both undoped and Ni-doped SnO2 films. Raman spectroscopy confirm the tetragonal rutile structure and shows a slight enhancement of crystallinity for 4% Ni doped SnO2 thin films. Optical measurements showed a decrease in transmittance with increasing dopant ratio, indicating reduced transparency, and a decrease in band gap with Ni insertion. Electrical measurements, conducted through I-V curve analysis, confirmed Ohm’s law compliance and indicated a decrease in resistivity with Ni doping, suggesting improved electrical conductivity. Additionally, the study explored the performance of thin-film solar cells utilizing SnO2 as a transparent conducting layer through numerical simulations using SCAPS-1D software. The effects of Ni doping on the solar cell performance were examined, suggesting potential enhancements or modifications in efficiency and functionality. Overall, the findings provide valuable insights into the structural, optical, and electrical properties of undoped and Ni-doped SnO2 thin films, offering promising avenues for their application in optoelectronic devices.

Indium tin oxide thin film preparation and property relationship for humidity sensing: A review

AbstractThis review aims to present a critical overview of indium tin oxide (ITO) thin film preparation methods, structure–property relationship, and its humidity sensing. A range of passive and active humidity sensors with thin films (based on metal oxides) detects humidity. ITO thin film has advantageous properties, such as low resistivity and high stability, making it highly suitable for humidity sensing applications. ITO thin film has shown the efficient level of humidity sensing, and a compatible size of humidity sensor can monitor the interface conditions humidity. So far, the application of ITO thin film for humidity measurement has yet to be explored at commercial scale, specifically in the detection of lower environmental humidity range (below 5% relative humidity (RH)). The research reveals a gap in improving the ITO thin film properties with an optimal range of preparation conditions. The research opportunities in the preparation, properties, characteristics, and efficient humidity sensitivity of ITO thin film are reviewed in this work.

Large second-order susceptibility from a quantized indium tin oxide monolayer.

Due to their high optical transparency and electrical conductivity, indium tin oxide thin films are a promising material for photonic circuit design and applications. However, their weak optical nonlinearity has been a substantial barrier to nonlinear signal processing applications. In this study, we show that an atomically thin (~1.5 nm) indium tin oxide film in the form of an air/indium tin oxide/SiO2 quantum well exhibits a second-order susceptibility χ2 of ~1,800 pm V-1. First-principles calculations and quantum electrostatic modelling point to an electronic interband transition resonance in the asymmetric potential energy of the quantum well as the reason for this large χ2 value. As the χ2 value is more than 20 times higher than that of the traditional nonlinear LiNbO3 crystal, our indium tin oxide quantum well design can be an important step towards nonlinear photonic circuit applications.

Tunable properties of SnOx sputter-deposited by RGPP and GLAD techniques: A potential candidate for photosensing and all-oxide solar cells

In this work, optical and electrical properties of tin-oxide (SnOx) thin-films were investigated for broadband photosensing and photovoltaic applications. The GLancing Angle Deposition (GLAD) and Reactive Gas Pulsing Process (RGPP) techniques were used to study the effects of the oxygen ratio variation and deposition angle on the film optoelectronic and photovoltaic properties. The deposition angle of the particle flux was kept at 80° and the injected oxygen gas concentration was tuned by changing the oxygen pulsing time from 0 to 20 s. It is found that the material band gap increases from 0.9 eV to 3.56 eV when the oxygen content increases. The deposited SnOx films exhibited improved and tuned optoelectronic properties, demonstrating their potential applications for developing alternative broadband photosensing layers and eco-friendly all-oxide solar cells. In this regard, SnOx-based photosensor and all-oxide SnOx solar cell structures were developed using the deposited thin-films. It is revealed that the prepared SnOx photosensor shows the highest responsivity of 32.7 mA/W and improved ION/IOFF ratio of 48 dB. Moreover, the optimized all-oxide SnOx solar cell demonstrates a high efficiency of 3.41 %, a short-circuit current of 14.53 mA/cm2 and an open circuit voltage of 0.49 V. These interesting results make the proposed elaboration process based on combined RGPP and GLAD techniques highly suitable for the development of high-performance optoelectronic and photovoltaic devices based on cost-effective metal oxide materials.

Exploring the interplay of the water–methanol solvent admixture on the optoelectronic properties of spray pyrolyzed fluorine-doped tin oxide thin films and their potential use in solar cell fabrication

A FTO thin film, M90, prepared using 90 vol% CH3OH, exhibits the highest FOM, indicating its potential use in photovoltaics and other applications.

Aluminum Capping-Induced Enhancement of Electrical Performance and Stability in Zinc Tin Oxide Thin-Film Transistors via a Low-Resistance Electron Pathway

Aluminum Capping-Induced Enhancement of Electrical Performance and Stability in Zinc Tin Oxide Thin-Film Transistors via a Low-Resistance Electron Pathway

Modification of the Physical Properties of SnO2 Thin Films for Optoelectronic Applications Combining Rapid Atmospheric Pressure Chemical Vapor Deposition Technique and Heat Treatment

Herein, the influence of the postannealing process on tin oxide thin films deposited by chemical vapor deposition in the atmospheric pressure technique is investigated. The as‐deposited films are heat treated under different environments, including ambient air, oxygen, nitrogen, and vacuum. The postannealing process is performed at 600 ºC for 60 min. It is worth mentioning that no sign of damage or destruction has been observed in samples after the annealing process. The structural characterization of the thin films is studied using X‐ray diffraction analysis, which reveals an increase in the peak intensities after annealing. Field‐emission scanning electron microscope surface morphology shows that heat‐treated tin oxide thin films have larger grain sizes than as‐deposited ones. Hall effect analysis shows a significant reduction in sheet resistance and a substantial increase in mobility after postannealing. The ultraviolet–visible–near‐infrared transmittance spectra in the 300–3000 nm range exhibit near 80% transparency in the visible region after annealing. Furthermore, the estimated bandgap values increase from 2.95 to 3.08 eV as the carrier concentration increases after the heat treatment. The results suggest the superiority of the oxygen‐annealed sample over the other annealing environments.

Rapid laser fabrication of indium tin oxide and polymer-derived ceramic composite thin films for high-temperature sensors

Thin-film sensors are essential for real-time monitoring of components in high-temperature environments. Traditional fabrication methods often involve complicated fabrication steps or require prolonged high-temperature annealing, limiting their practical applicability. Here, we present an approach using direct ink writing and laser scanning (DIW-LS) to fabricate high-temperature functional thin films. An indium tin oxide (ITO)/preceramic polymer (PP) ink suitable for DIW was developed. Under LS, the ITO/PP thin film shrank in volume. Meanwhile, the rapid pyrolysis of PP into amorphous precursor-derived ceramic (PDC) facilitated the faster sintering of ITO nanoparticles and improved the densification of the thin film. This process realized the formation of a conductive network of interconnected ITO nanoparticles. The results show that the ITO/PDC thin film exhibits excellent stability, with a drift rate of 4.7 % at 1000 °C for 25 h, and withstands temperatures up to 1250 °C in the ambient atmosphere. It is also sensitive to strain, with a maximum gauge factor of −6.0. As a proof of concept, we have used DIW-LS technology to fabricate a thin-film heat flux sensor on the surface of the turbine blade, capable of measuring heat flux densities over 1 MW/m2. This DIW-LS process provides a viable approach for the integrated, rapid, and flexible fabrication of thin film sensors for harsh environments.

Study of flashlamp annealing to promote crystallization of indium tin oxide thin films

The use of flashlamp annealing as a low-temperature alternative or supplement to thermal annealing is investigated. Flashlamp annealing and thermal annealing were conducted on 100 nm thick indium tin oxide (ITO) films deposited on glass to compare the properties of films under different annealing methods. The ITO samples had an average initial sheet resistance of 50 Ω/sq. After flashlamp annealing, the sheet resistance was reduced to 33 Ω/sq only, while by thermal annealing at 210 °C for 30 min, a sheet resistance of 29 Ω/sq was achieved. Using a combination of flashlamp annealing and thermal annealing at 155 °C for 5 min, a sheet resistance of 29 Ω/sq was achieved. X-ray diffraction analysis confirmed that flashlamp annealing can be used to crystallize ITO. Flashlamp annealing allows for low-temperature crystallization of ITO on a time scale of 1–3 min. Through electrical and optical characterizations, it was determined that flashlamp annealing can achieve similar electrical and optical properties as thermal annealing. Flashlamp offers the method of low-temperature annealing, which is particularly suitable for temperature sensitive substrates.

Studies on physical properties of tin oxide films

This paper reports the study of some physical properties of thin films of tin oxide, such as the structural properties, surface morphology and optical transmission and reflection. The thin films of tin oxide were deposited by the method of thermal evaporation under vacuum. Transmission electron microscopy (TEM) was used to study the structural properties and the atomic force microscopy (AFM) method was used to study the surface morphology of thin films of tin oxide. The absorption and extinction coefficients of the investigated thin layers were determined from the transmittance and reflectance spectra recorded in the range of wavelengths between 190 and 1100 nm.

Q-switched erbium-doped fiber lasers with ITO thin film saturable absorbers: A comprehensive cavity configuration study

This study presents the utilization of an indium tin oxide (ITO) thin film as a saturable absorber (SA) in various cavity configurations to illustrate a Q-switched erbium-doped fiber laser (EDFL). The system is designed in three distinct configurations, including linear, single-ring, and Figure-8 cavities, by integrating ITO in the setup, which has a modulation depth of 48.04 %. The research findings highlight that the single-ring cavity design has better performance over linear and Figure-8 designs in terms of Q-switched EDFL performance. The advantage of the single-ring cavity design is demonstrated by the higher values of the repetition rate and signal-to-noise ratio, which are 37.60 kHz and 57.45 dB, respectively. Subsequently, this single-ring cavity can be employed in applications of tunable, switchable dual-wavelength systems and optical fiber sensing.

Bi2O3 doped indium tin oxide thin films fabricated via liquid metal printing

Indium tin oxide (ITO) is a classical transparent conducting oxide (TCO), which is widely used in semiconductor industry. Reducing the cost of preparing ITO films and further improving its optoelectronic properties are urgent technological challenges to be solved. Here, we proposed to tackle this issue through doping elements in ITO films via liquid metals printing process. Conceptual experiments demonstrate the synthesis of Bi2O3 doped ITO at the centimeter scale using low-temperature fabrication techniques, which display the advantages of high uniformity, strong visible light transmission and low resistivity. The band gap decreases from 3.88 eV to 3.07 eV with increasing doping of Bi2O3 and demonstrates n-type semiconductor nature. The Schottky diodes based on doped ITO films show typical Ohmic contact. The best output current of doped ITO Schottky diodes can reach 1261.7 μA at 10 V, which is about 41 times the output current of the undoped ITO Schottky diodes. Additionally, the nanofilm resistance decreased linearly with increasing Bi mass fraction in ITO film. Moreover, Schottky diodes have good stability in the atmosphere within half a year and multilayer printing can enhance output current. The process as established here offers significant opportunities for future synthesis and fabrication processes in the electronics industries.

Quantitative study of the thickness-dependent stress in indium tin oxide thin films

A quantitative analysis of stress in indium tin oxide (ITO) films with varying thicknesses was conducted using high-precision stylus profilometry. The experimental results revealed a transition of the stress type from tensile to compressive as the ITO film thickness increased. Further investigation of the surface morphology of the ITO films indicated that the tensile stress originated from the impingement and coalescence of newly deposited equiaxed grains, while the observed compressive stress was attributed to the incorporation of excess material in the boundaries of columnar grains. The ability to monitor stress evolution in sputtered ITO films on glass substrates provides valuable insights for process control in ITO device manufacturing.