Indium Tin Oxynitride Research Articles

Enhancement on carrier mobility in amorphous indium tin oxynitride (ITON) thin films

Indium tin oxynitride (ITON) thin films were deposited by reactive DC magnetron sputtering technique. The samples were deposited onto glass and silicon (100) substrates at room temperature. For this purpose, the sputtering reactive atmosphere was composed of different argon and nitrogen concentrations, to modify the structural, optical and electrical properties of obtained ITON thin films. Energy dispersive spectroscopy (EDS) was used in order to know the chemical composition of the different deposited samples, the nitrogen incorporation in the indium tin oxide structure was verified in all ITON analyzed samples. Additionally, through an infrared absorption spectroscopy study of the deposited films, it was possible to confirm the nitrogen incorporation in the ITO structure for the samples deposited under nitrogen presence. Several absorption bands corresponding to In–N, N–N, In–O, and Sn–O bonds were detected. As the effect of nitrogen incorporation, both crystalline structure and surface morphology are widely affected. On the other hand, the nitrogen presence in the structure leads to increase the carrier mobility reaching a value above 1100 cm2/Vs for the sample deposited in a higher nitrogen flux concentration, this result of high mobility raises ITON thin films a promising candidate to be used as an active layer in thin film transistors. The band gap values were calculated using the Tauc parabolic band model from the absorption spectra and it resulted in values near to 4.0 eV. Finally, the obtained transmission values were in the order of 75–80% in the visible region.

ITO:SiC Ceramic Matrix Composite Thermocouples for Engine Components

Surface temperature measurements of ceramic matrix composite (CMC) based engine components within the hot section of a gas turbine engines are needed to verify engine designs and cooling requirements. Traditional temperature sensors cannot be applied to silicon carbide (SiC) based CMC's for this purpose, since they cannot be welded or embedded in the material. For these reasons, a novel thermocouple was developed for surface temperature measurement of p-type SiC-SiC CMC's. This novel thermocouple uses the p-type SiC-SiC CMC itself as one of the thermoelements and indium-tin-oxide (ITO) as the other thermoelement. Since both thermoelements are wide bandgap semiconductors, this thermocouple has exceptional thermoelectric output. A thermoelectric output of 272 μV/°K was observed for this ITO:SiC CMC thermocouple, which is an order of magnitude larger than that of type-K thermocouples. A drift rate of 3.28 °C/h was measured for this ITO:SiC CMC thermocouple. In addition, indium tin oxynitride (ITON) protective coatings deposited via reactive sputtering enabled these thermocouples to operate at 1000 °C. The ITON coating served as an oxygen diffusion barrier to prevent oxidation at the ITO:SiC CMC junction. Nitrogen and air anneals at 550 and 1000 °C, respectively, were used to improve the high temperature stability of the ITO and ITON coatings. Performance, fabrication details, and challenges using these ITO:SiC CMC thermocouple are discussed within.

Effect of sputtering deposition process of indium tin oxynitride on surface damage of gallium nitride film

The indium tin oxynitride (ITON) thin film was deposited on the gallium nitride (GaN) film/c-plane sapphire substrate using the magnetron sputtering method. The effects of ITON film sputtering deposition process on the surface damages of GaN film, i.e. the surface morphology, structure and component of GaN films, are investigated systematically. The surface root-mean-square roughness of the GaN film increases after direct current sputtering deposition process (DC-SDP), while that decreases after radio frequency sputtering deposition process (RF-SDP). The photoluminescence intensity ratios of GaN films related with DC-SDP and RF-SDP versus the raw GaN film are 0.46 and 0.98, respectively. It indicates that the raw GaN film surface is damaged seriously after DC-SDP, but almost has no damages after RF-SDP. The atomic concentration ratio of N and Ga in the raw GaN film reduces from 0.97 to 0.87 after DC-SDP, and from 0.97 to 0.96 after RF-SDP. It suggests that RF-SDP can compensate more N atoms to the GaN film than that of DC-SDP. From the high resolution transmission electron microscopy images, we can see that the nitrogen vacancy density at the ITON/GaN interface after RF-SDP is smaller than that after DC-SDP. The forward turn-on voltages (corresponding to the operating current 20 mA) of light emitting diode (LED) fabricated with the GaN films after RF-SDP and that after DC-SDP are 2.6 and 3.0 V, respectively. It can be concluded that the technology of RF-SDP is useful to reduce the surface structural damages of the GaN films and the forward turn-on voltage of the device, and improves the performance of GaN-based LEDs.

Effect of nitrogen incorporation on the structural, optical and dielectric properties of reactive sputter grown ITO films

Abstract The changes in the optical, microstructural and electrical properties, following the nitrogen incorporation into indium tin oxide thin films are investigated. The films are formed by r.f. sputtering from an indium-tin-oxide (80% In2O3–20% SnO2) target in a mixture of Ar and N2 plasma (75% N2–25% Ar and 100% N2 respectively) on fused silica glass substrate. The impact of rapid thermal annealing (up to 500 °C, in N2 ambient) on the properties of indium tin oxynitride (ITON) thin films is also reported. The UV–vis–NIR ellipsometry (SE) characterization of ITON films was performed assuming several realistic approaches based on various oscillator models, using a chemical composition gradient depth profiling, in agreement with the X-ray photoelectron spectroscopy measurements. The Hall measurements show that the ITON films prepared by r.f. sputtering in 75% N2 and annealed at 500 °C behave as degenerate semiconductors. X-ray diffraction analysis proved that ITON thin films retain an amorphous structure even after RTA at 500 °C in N2 ambient and atomic force microscopy showed the formation of continuous and smooth ITON thin films, with a morphology consisting in quasispherical nanometric particles.

Metallic and Ceramic Thin Film Thermocouples for Gas Turbine Engines

Temperatures of hot section components in today's gas turbine engines reach as high as 1,500 °C, making in situ monitoring of the severe temperature gradients within the engine rather difficult. Therefore, there is a need to develop instrumentation (i.e., thermocouples and strain gauges) for these turbine engines that can survive these harsh environments. Refractory metal and ceramic thin film thermocouples are well suited for this task since they have excellent chemical and electrical stability at high temperatures in oxidizing atmospheres, they are compatible with thermal barrier coatings commonly employed in today's engines, they have greater sensitivity than conventional wire thermocouples, and they are non-invasive to combustion aerodynamics in the engine. Thin film thermocouples based on platinum:palladium and indium oxynitride:indium tin oxynitride as well as their oxide counterparts have been developed for this purpose and have proven to be more stable than conventional type-S and type-K thin film thermocouples. The metallic and ceramic thin film thermocouples described within this paper exhibited remarkable stability and drift rates similar to bulk (wire) thermocouples.

Effect of Annealing on the Properties of Indium−Tin−Oxynitride Films as Ohmic Contacts for GaN-Based Optoelectronic Devices

Indium-tin-oxynitride (ITON) films have been fabricated by rf sputtering from an indium-tin-oxide target in nitrogen plasma. The influence of postdeposition annealing up to 800 degrees C is analyzed by electrical, optical, and surface characterization of the films in comparison to indium-tin-oxide (ITO) films fabricated in argon plasma. High-temperature annealing resulted in ITO(N) films with similar carrier concentrations. However, the resistivity and optical transmittance of the ITON films were higher than those of the ITO films. Photoelectron spectroscopy revealed that nitrogen is incorporated into the ITON structure in an unbound state as well as through the formation of metal-nitrogen and oxynitride bonds that decorate oxygen vacancies. When the core level electron spectra of ITO and ITON films are compared, a correlation between carrier concentration and the incorporated nitrogen is found. Changes in ITON electrical properties are mainly induced by the release of nitrogen at temperatures above 550 degrees C. In this context, ohmic contact behavior was achieved for ITON on p-type GaN after annealing at 600 degrees C, while no ohmic contact could be realized using ITO.

Derivation of the complex refractive index of ITO and ITON films in the infrared region of the spectrum by the analysis of optical measurements

We use the Newton–Raphson method to analyze the optical spectra of indium–tin-oxide and indium–tin–oxynitride films, by deriving the complex refractive index and, thereby, the plasma wavelength and the relaxation time. Reflectance and transmittance as well as partial derivatives of them, necessary for the application of the method, are introduced in analytical form reducing complexity and improving speed. The films we have investigated were deposited on glass by sputtering at different RF power levels. After deposition, they were subjected to annealing at 600 °C and were measured prior to and after that treatment. The results obtained are physically meaningful and lead to useful inferences about the quality of the material in the two different types of the investigated films.

Surface composition and electronic properties of indium tin oxide and oxynitride films

The surface properties of indium tin oxynitride films prepared by rf-sputtering in nitrogen atmosphere were investigated by X-ray and ultraviolet photoelectron spectroscopy as well as electron energy loss spectroscopy and Auger electron spectroscopy depth profiling. The results are compared to reference measurements on conventional rf-sputtered indium tin oxide films. The incorporated nitrogen is present in different chemical environments. Employing these different spectroscopic techniques, it was found that desorption of nitrogen from the ITON structure upon annealing is the origin of the observed drastical changes in the surface composition and electronic structure. The formation of oxygen vacancies and Sn surface segregation upon annealing is linked to improvements in the physical properties (larger spectral range of transmittance and higher conductivity) of the films.

Optical emission spectroscopy during fabrication of indium-tin-oxynitride films by RF-sputtering

Indium-tin-oxide (ITO) and indium-tin-oxynitride (ITON) films have been deposited on glass by rf-sputtering from an ITO target, using Ar plasma and N 2 plasma, respectively, and different rf-power. Optical emission spectroscopy (OES) was employed to identify the species present in the plasma and to correlate them with the properties of the ITO and ITON thin films. Emission lines of ionic In could only be detected in N 2 plasma, whereas in the Ar plasma additional lines corresponding to atomic In and InO, were detected. The deposition rate of thin films was correlated with the In species, rather than the nitrogen species, emission intensity in the plasma. The higher resistivity and lower carrier concentration of the ITON films, as compared to the respective properties of the ITO films, were attributed to the incorporation of nitrogen, instead of oxygen, in the ITON structure.

ITON Schottky contacts for GaN based UV photodetectors

Lateral Schottky ultraviolet detectors were fabricated in GaN using indium-tin-oxynitride (ITON) as a contact metal. The GaN semiconductor material was grown on 2 in. sapphire substrate by metal–organic chemical vapor deposition (MOCVD). The Schottky contact has been realized using ITON that has been deposited using sputter techniques. I– V characteristics have been measured with and without UV illumination. The device shows photo-to-dark current ratios of 10 3 at −1 V bias. The spectral responsivity of the UV detectors has been determined. The high spectral responsivity of more than 30 A/W at 240 nm is explained by a high internal gain caused by generation–recombination centers at the ITON/GaN interface. Persistent photocurrent effect has been observed in UV light (on–off) switching operation, time constant and electron capture coefficient of the transition has been determined.

Optical characterization of indium-tin-oxynitride fabricated by RF-sputtering

Indium-tin-oxynitride (ITON) and indium-tin-oxide (ITO) thin films have been fabricated by r.f. sputtering from an indium-tin-oxide target in a plasma containing N 2 and Ar gases, respectively. The properties of films grown at two different plasma pressures were examined just after deposition and after annealing. Although the electrical properties of these films were improved after annealing, the properties of the ITON films were still inferior to those of the ITO films. The resistivity of the ITON films after annealing was reduced by a factor of two for the film at the higher plasma pressure, but the carrier concentration was almost the same. The ITON films fabricated at low pressure exhibited a significant blue shift in transmittance, which was not related to the increase carrier concentration after annealing.

Properties of rf-sputtered indium–tin-oxynitride thin films

Indium–tin-oxide (ITO) and indium–tin-oxynitride (ITON) thin films have been fabricated by rf-sputtering in plasma containing Ar or a mixture of Ar and N2, respectively. The structural, electrical and optical properties of ITON films were examined and compared with those of ITO films. The microstructure of ITON films was found to be dependent on the nitrogen concentration in the plasma. Increasing the amount of nitrogen in the plasma increased the resistivity and reduced the carrier concentration and mobility of the films. The electrical properties of the ITON films improved after annealing. The absorption edge of the ITON films deposited in pure N2 plasma was shifted towards higher energies and showed reduced infrared reflectance compared to the respective properties of ITO films. The potential of indium–tin-oxynitride films for use as a transparent conductive material for optoelectronic devices is addressed.