Silica Glass Substrates Research Articles

Effect of deposition regime transition on the properties of Al:ZnO transparent conducting oxide layer by radio frequency magnetron sputtering system

High-quality zinc oxide thin films doped with aluminium adatoms have effectively been fabricated on pristine soda-lime silica glass substrates via radio frequency magnetron sputtering system. The deposition temperature was varied to explore the impact of deposition regime transition of as-deposited Al:ZnO thin films on their performance as transparent conducting oxide layers. In particular, the depositions were conducted at room temperature, 100 °C, 200 °C, and 300 °C, allowing for a comprehensive assessment of the resulting films. The Raman spectra depicted the modulation of Raman bands in correlation with the deposition regime transition, illustrating the impact of thermal induction on various properties of the as-deposited aluminium-doped zinc oxide thin films. Atomic force microscopy reveals the transformation from nearly spherical to elongated shape structure was obtained as the deposition process shifted from kinetic limited to thermodynamic limited regimes. The phase analysis and grazing incident of x-ray diffractometer disclose a single crystal orientation has been achieved at thermodynamic limited regime. However, two different crystal planes were predominant comparing between the surface and structural of as-deposited aluminium-doped zinc oxide thin films. It is also evident that a highly transparent with low lattice strain and better carrier concentrations of as-deposited aluminium-doped zinc oxide thin films were realized at thermodynamic limited regimes.

Comparative Analysis of Thermal Properties in Molybdenum Substrate to Silicon and Glass for a System-on-Foil Integration

Advanced electronics technology is moving towards smaller footprints and higher computational power. In order to achieve this, advanced packaging techniques are currently being considered, including organic, glass, and semiconductor-based substrates that allow for 2.5D or 3D integration of chips and devices. Metal-core substrates are a new alternative with similar properties to those of semiconductor-based substrates but with the added benefits of higher flexibility and metal ductility. This work comprehensively compares the thermal properties of a novel metal-based substrate, molybdenum, and silicon and fused silica glass substrates in the context of system-on-foil (SoF) integration. A simple electronic technique is used to simulate the heat generated by a typical CPU and to measure the heat dissipation properties of the substrates. The results indicate that molybdenum and silicon are able to effectively dissipate a continuous power density of 2.3 W/mm2 as the surface temperature only increases by ~15 °C. In contrast, the surface temperature of fused silica glass substrates increases by >140 °C for the same applied power. These simple techniques and measurements were validated with infrared camera measurements as well as through finite element analysis via COMSOL simulation. The results validate the use of molybdenum as an advanced packaging substrate and can be used to characterize new substrates and approaches for advanced packaging.

Extended-analysis for ZnO monolayers, (TiO2 & WO3)/ZnO bilayers, and WO3/TiO2/ZnO multilayers deposited on silica glass substrates by RF sputtering as promising cap layers in optoelectronic applications

This study employs radio frequency sputtering (RF) to fabricate a range of thin film structures on silica glass substrates. These structures encompass ZnO monolayers, (TiO2/ZnO and WO3/ZnO) bilayers, and (WO3/TiO2/ZnO) multilayers. Thorough investigations were conducted to analyze their structural evolution, surface morphology, and optical characteristics, affirming film crystallinity via X-ray diffraction. By Scherrer's formula, the crystallite size D is determined, the microstrain of films ε is extracted by the Williamson-Hall method, and then the dislocation density δ is computed. It is found that the crystallite size increases from 8.47 to 13.56 nm with increasing number of layers. FTIR spectra identified functional groups, while SEM provided cross-section views. The presence of a tungsten trioxide (WO3) cap layer significantly influences optical properties, particularly in multilayers, impacting key parameters such as optical bandgap and tail energy. As the number of layers increases, the bandgap decreases from 3.45 to 2.47 eV, while the tail energy increases from 0.48 to 0.96 eV. The optical dispersion parameters of the fabricated layers, including the single oscillator energy Eo (changing from 6.93 to 4.96 eV), dispersion energy Ed (ranging from 32 to 48 eV), and static refractive index no (varying from 2.36 to 3.26), are computed using the WWD (Wemple-Didomenico) model. As the number of layers rose, the sheet resistance (Rsh) of the films increased, accompanied by a decrease in coverage density (DC). Elevated sheet resistance contributes to enhanced electrical resistivity, potentially benefiting resistive devices. Simultaneously, reduced coverage density can improve transparency and promote coating uniformity, offering advantages in optoelectronic and display technologies. The study also assessed inter-band transition strength and examined energy loss functions, revealing improved optical properties with additional layers. These findings highlight the system's promising potential as a cap layer in optoelectronic applications.

Preliminary study on surface processing of silica glass by atmosphere inductively coupled plasma for direct bonding

The performance for some optical system strongly depends on bonding quality of multiple optic components. For heterogeneous integration of silica glass, the direct bonding contributes to a high-strength combination without contaminating the bonding interface, but the surface activation induced in vacuum leads to low efficiency and process complexity. Accordingly, surface processing by an atmosphere inductively coupled plasma (ICP) is proposed before direct bonding. The high-energy Ar-O2 ICP is generated to enhance the hydroxyl radical density and produce good surface hydrophilicity. With ICP irradiation for 10 seconds, the initial surface (contact angle of 41.8°) can be turned super hydrophilic (contact angle < 3°) which ensures high bonding strength. After ICP irradiation, the roughness and form accuracy of the silica glass substrate were well maintained. In addition, ICP irradiation can clean the surface to improve the bonding strength of samples. It is shown that ICP irradiation can improve the bond strength without degrading the surface characteristics. Therefore, direct bonding assisted by atmosphere ICP processing shows potential applicability for heterogeneous integration of high-performance optics.

The Influence of UV-Ozone, O2 Plasma, and CF4 Plasma Treatment on the Droplet-Based Deposition of Diamond Nanoparticles.

Surface treatment is critical for homogeneous coating over a large area and high-resolution patterning of nanodiamond (ND) particles. To optimize the interaction between the surface of a substrate and the colloid of ND particles, it is essential to remove hydrocarbon contamination by surface treatment and to increase the surface energy of the substrate, hence improving the diamond film homogeneity upon its deposition. However, the impact of substrate surface treatment on the properties of coatings and patterns is not fully understood. This study explores the impact of UV-ozone, O2 plasma, and CF4 plasma treatments on the wetting properties of the fused silica glass substrate surface. We identify the optimal time interval between the treatment and subsequent ND coating/patterning processes, which were conducted using inkjet printing and ultrasonic spray coating techniques. Our results showed that UV-ozone and O2 plasma resulted in hydrophilic surfaces, while CF4 plasma treatment resulted in hydrophobic surfaces. We demonstrate the use of CF4 plasma treatment before inkjet printing to generate high-resolution patterns with dots as small as 30 μm in diameter. Ultrasonic spray coating showed homogeneous coatings after using UV-ozone and O2 plasma treatment. The findings of this study provide valuable insights into the hydrocarbon airborne contamination on cleaned surfaces over time even in clean-room environments and have a notable impact on the performance of liquid coatings and patterns. We highlight the importance of timing between the surface treatment and printing in achieving high resolution or homogeneity.

Hydrothermally grown molybdenum doped ZnO nanorod arrays. The concept of novel ultrafast nanoscintillator

Molybdenum doped ZnO was hydrothermally grown as the arrays of nanorods deposited onto the fused silica glass substrate. The molybdenum doping level varied from 1 to 30 %. The influence of Mo on the electronic and crystalline structure as well as luminescence and defects in the ZnO nanorods is under study of the bundle of experimental techniques complemented with density functional theory calculations. The tendency of Mo to create energy states within the bandgap of ZnO and their influence on the energy levels of native defects as well as excitons were proven by the synergy of experiment and theory. The improvement of the timing characteristics of the exciton- and zinc vacancy-related emission bands upon Mo doping (1–10 %) was observed. This paves the way for the defect engineering strategy in the search of effective and ultrafast scintillator with the improved light yield as well as compared to other materials. The new concept is based on the combination of the exciton and the defect emission. It is expected to have the potential of application in the detection of gamma rays implemented in time-of-flight positron emission tomography (TOFPET). The 20 and 30 % Mo doping levels resulted in the zinc molybdates creation strongly outnumbering ZnO nanorods.

Flow-based compact microfluidic electrochemical cell with Parafilm® channels

A planar interdigitated microelectrodes-based microfluidic electrochemical cell (P-μFEC) with channels made by Parafilm® sheets was conceptualized with the application as a sensor for detecting heavy metal ions. Herein, we first-timely proposed a new strategy for creating Parafilm® microchannels using a Plotter cutter and Hot bonding self-sealing method for solid Microfluidic devices (PPHM). For the prepared novel P-µFEC by the PPHM protocol, which operated in the laminar regime, its electrochemical performance was well-studied using the well-known electrochemical reporter potassium Ferri/Ferrocyanide (K3/K4[Fe(CN)6]). A reference electrode (RE) layer deposited at the top silica glass substrate was embedded within the device to minimize the ohmic drop (iRcell) between the working electrode (WE) and RE. The experimental and virtualized computational COMSOL results demonstrated: (i) The changes in the RE's placements had negligible influences on the P-µFEC's electrochemical performance. (ii) The laminar flow's influence on the P-µFEC's electrochemical performance was quite prominent, which was due to the changes in the mass transfer process from diffusion (stationary) to diffusion + convection (hydrodynamic). (iii) A direct virtualized demonstration of laminar flow's influences on the mass transfer process from diffusion (stationary) to diffusion + convection (hydrodynamic) was first timely validated by finite element analysis simulation using COMSOL Multiphysics. (iv) Finally, the proposed P-µFEC showed promise as a sensitive electrochemical sensor for different heavy metal ion substrate (model analytes) detection. The IUPAC detection limits for Cu2+, Pb2+, [Fe(CN)6]3- and Hg2+ is ∼318.6±3.55 μg/L, ∼191±5.4 4 μg/L, ∼113.5±9.9 μg/L, and 8.21±0.88 μg/L, respectively. Among them, the detection limit for Cu2+ and Hg2+ meets the US Environmental Protection Agency (EPA)'s water contamination level for Cu (1300 μg/L) and is close to the EPA level for Hg (2 μg/L), respectively. These findings demonstrate the potential of using the Parafilm® sheet as the microfluidic channel for a flow-based P-μFEC as a novel analytical tool.

Fine-tuned photochromic WO3-x thin films: A detailed study from structural analysis to UV photo-sensing application

The oxygen substoichiometry of as-prepared WO3 (tungsten trioxide) nano-powders (NPs) from a polyol process was tuned via peptization of the NPs in aqueous solutions of different Cr2O72− oxidizing concentrations. The as-synthesized materials have been characterized by X-ray scattering (XRD and PDF), transmission electron microscopy (TEM), X-ray photoelectron (XPS), and UV-VIS photochromic activity. The local atomic structure of WO3-X was investigated using total scattering atomic pair distribution function (PDF) analysis based on X-ray total scattering data collected on powder at ambient conditions. The PDF analysis confirms that the crystal structure of all studied samples can be described in terms of very small crystallites with a P21/n space-group monoclinic framework but with anomalous unit cell distortion parameters, indicating that small crystallite sizes resulted in a larger monoclinic distortion (as measured by the beta angle of the unit cell). The nanometer dimension of the crystallites combined as well as the oxygen-tungsten stoichiometric ratio control, are key features for optimized photochromic properties. Moreover, we present the fabrication of a WO3-x thin film based UV photosensor, which was carried out on silica glass substrates via the dip-coating method. The obtained films exhibited a UV photoresponse and photoelectric characteristics at 5 V bias voltages able to detect very low UV doses, inferior to 10 W/m2. The photo-detection measurements prove the usability of our device as a UV photodetector with a good responsivity of 0.37 A/W and external quantum efficiency of more than 100% even at a very low power density (9.2 W/m2) of UV illumination.

Fabrication and luminescence switching of Pt-loaded macro-porous Y2WO6:Eu3+ phosphor thin films for hydrogen-gas detection

A luminescence-switching phenomenon of Pt/Y2WO6:Eu3+ phosphor thin films was examined under redox conditions using hydrogen gas and air as a reductant and an oxidant, respectively. Macro-porous Y2WO6:Eu3+ thin films were initially synthesized by a Pechini-type sol–gel dip-coating method on silica glass substrates. Attempts were then made to load Pt nanoparticles (NPs) on the surface of the Y2WO6:Eu3+ thin films immersed in aqueous K2PtCl4 solutions through a method of self-regulated reduction of surfactants using a nonionic triblock copolymer (P-123). The amount of P-123, the concentration of the K2PtCl4 solutions, and the immersion duration were set as three parameters influencing the deposition of the Pt NPs. The number and size of the Pt NPs were found to be dependent on all the three parameters and their excessive deposition led to inevitable quenching of the Eu3+ emission from thin films. In contrast, the lightly loaded Pt NPs were effective to induce turn-off luminescence upon exposure of the thin films to hydrogen gas at a low temperature of 150 °C probably through their catalytic action. The recovery of luminescence was also possible simply by treating the reduced thin films at 200 °C in air. Thus the Pt/Y2WO6:Eu3+ phosphor thin films are promising as a facile hydrogen-gas detector.

Modern Smart Street Light Monitoring Systems

Abstract: This study highlights the importance of Modern Street light control systems over traditional ones, with LED lamps emerging as the most suitable choice due to their advantagessuch as reduced heat production, lower electricity consumption, and extended lifespan. The main goal is to enhance system efficiency by minimizing unnecessary electricity loss during daylight and when lighting is not required. Automating street lights using LDR and PIR sensorsin conjunction with Arduino Uno offers a costeffective and secure solution, eliminating the drawbacks of manual switching and simplifying cost reduction and maintenance. Additionally,applying a ZnO coating to the street light casings provides effective protection against dust and moisture, resulting in efficient lighting. The process involves sol-gel deposition of ZnO nanoparticles on silica glass substrates, followed by preannealing and repeated dip coating. Annealing at temperatures between 450°C and 600°C further improves the results. The uniformand defect-free coatings are confirmed by SEM images, while transmission spectra reveal over80% penetration of visible light (400 nm to 900 nm). Lower precursor concentrations lead to better penetration of light below 300 nm wavelength.

Exploratory study of potential usefulness of cost-effective composites thin films for energy device

In this study, we synthesized neat and loaded lead phosphate glass (PbO–P2O5) with the inclusion of Cr, Co, Ni, and Zn using an inexpensive sol–gel technique. These composites were then deposited on silica glass substrates. Our objective was to investigate the influence of these fillers on the properties of the glass. The concentrations of the fillers were varied from 0 to 16 wt%, and the resulting thin films were characterized by measuring the absorption coefficient and estimating the optical band gap at room temperature. Additionally, we measured the electrical resistivity of the semiconducting thin films as a function of filler concentrations and temperature. To assess the overall performance of the films, we calculated the figure of merit using the Iles and Soclof approach, considering the DC resistance versus free carrier concentration and absorption coefficient. Interestingly, our results revealed a significant improvement in the figure of merit at specific filler concentrations. The obtained results are comprehensive and provide detailed insights. They indicate that the thin films produced in this study have the potential to be useful in energy devices, particularly in applications involving P–N junctions and similar structures.

Nonequilibrium Casimir–Polder Interaction between Nanoparticles and Substrates Coated with Gapped Graphene

The out-of-thermal-equilibrium Casimir–Polder force between nanoparticles and dielectric substrates coated with gapped graphene is considered in the framework of the Dirac model using the formalism of the polarization tensor. This is an example of physical phenomena violating the time-reversal symmetry. After presenting the main points of the used formalism, we calculate two contributions to the Casimir–Polder force acting on a nanoparticle on the source side of a fused silica glass substrate coated with gapped graphene, which is either cooler or hotter than the environment. The total nonequilibrium force magnitudes are computed as a function of separation for different values of the energy gap and compared with those from an uncoated plate and with the equilibrium force in the presence of graphene coating. According to our results, the presence of a substrate increases the magnitude of the nonequlibrium force. The force magnitude becomes larger with higher and smaller with lower temperature of the graphene-coated substrate as compared to the equilibrium force at the environmental temperature. It is shown that, with increasing energy gap, the magnitude of the nonequilibrium force becomes smaller, and the graphene coating makes a lesser impact on the force acting on a nanoparticle from the uncoated substrate. Possible applications of the obtained results are discussed.

Enhanced Adhesion of Copper Films on Fused Silica Glass Substrate by Plasma Pre-Treatment.

A non-thermal atmospheric jet plasma pre-treatment technique was introduced to help the growth of extremely sticky copper films on fused silica glass substrates. A tape test was utilized to assess the bonding quality between copper films and fused silica glass substrates. AFM was used to characterize the sample surface roughness and XPS for chemical bonding characterization. The Owens-Wendt method and a Theta Lite Optical Tensiometer were used to analyze the contact angle and surface energy. The results showed that the surface energy greatly increased from 34.6 ± 0.3 mJ·m-2 to 55.9 ± 0.4 mJ·m-2 after 25 s plasma pre-treatment due to the increasing Si-O and Si-N concentrations, which brought about the electrostatic force increasing at the copper/glass interface. After 25 s plasma pre-treatment, the average surface roughness (Sa) grew from 0.8 ± 0.1 nm to 2.4 ± 0.3 nm. With higher surface roughness, there were more spaces and vacancies for the copper atoms to make contact on the bonded surfaces and increase the mechanical bite force. The electrostatic force and the mechanical bite force on the interface helped to form an atomic diffusion connection layer and improved the interactions between the copper film and the glass substrate. The findings in the SEM supported the conclusions stated above. Therefore, the adhesion between copper films and fused silica glass substrates increased by about 20% by 25 s plasma pre-treatment compared with the untreated glass substrate.

Praseodymium-dopant effect on bismuth-substituted yttrium iron garnet films on fused silica glass substrate at the 1310 and 1550-nm wavelengths

The optical and magneto-optic (MO) properties of the praseodymium (Pr)-dopant effect on bismuth-substituted yttrium iron garnet (Bi:YIG) films coated on fused silica glass substrates by using the metal-organic-decomposition (MOD) method with chemical solutions were investigated at the 1310 and 1550-nm wavelength regions. The maximum Faraday rotation angle of the Pr-codoped Bi:YIG (Pr,By:YIG) film was observed to be 0.09 and 0.046 deg/μm at the wavelengths of 1310 and 1550 nm, respectively, when the film was annealed at a temperature of 750 °C, while those of the plain Bi:YIG film were 0.059 and 0.039 deg/μm. More than 50% improvement in the Faraday rotation value of the Pr,Bi:YIG film was observed compared to that of the Bi:YIG film at the 1310 nm wavelength. The absorption coefficient of the Pr,Bi:YIG film was comparable to that of the Bi:YIG film. Therefore, the Pr,Bi:YIG film prepared with the MOD method is potentially useful for MO applications such as optical isolators and circulators.

Annealing temperature dependence of mechanical and structural properties of chromium-gold films on the silica glass substrate

Efficient mechanical properties of thin gold films on dielectric substrates are essential in micro-electro-mechanical systems applications. Hence, the film performance should be optimized via thermal treatment. In this paper, gold films with a nominal thickness of 100 nm and a chromium adhesion layer of 10 nm are deposited on the fused glass substrate. Annealing temperature dependency of the mechanical and structural properties of chromium-gold films is carefully investigated. The surface, cross-sectional morphology, hardness, Young's modulus, adhesion, stress, and conductivity of the chromium-gold bilayer film are explored for the annealing temperature range from 100 °C to 700 °C. The results show that the transition point temperature varies for different properties. The transition point at 200 °C for the adhesion and resistivity can be attributed to the improvement of the crystalline state caused by annealing. When the annealing temperature reaches 300 °C, Young's modulus, and the hardness are reduced, and the residual stress is minimized. Significant diffusion of chromium atoms into the gold layer is observed for the annealing temperature of 400 °C, which alters the initial structure of the bilayer films and modifies film properties. Moreover, resistivity reaches a maximum value, and the internal stress starts to increase, which is caused by the diffusion of the chromium film. Consequently, the definite annealing temperature needs to be selected for the required film properties.

Structural and morphological characterizations of glass based composites in thin films form

By using a low-cost sol gel method, neat and loaded phosphate glass containing Cr, Co, Ni, and Zn was synthesized and then placed on a silica glass substrate. Cr, Ni, Co, and Zn loading amounts were diluted inside the matrix using rates varying from 0 wt% to 16 wt% in order to study the impact of loading elements on glass characteristics. By using XRD and SEM, it was determined how loading factors affected the structural and morphological characteristics of glass thin layers. When the annealing temperature was maintained at 250 °C, X-ray diffractograms revealed that the deposited glass films had an amorphous nature, whilst also X-ray pattern results revealed that the loaded films had a low crystalline nature. Morphology studies indicated the homogeneity and the edge of crystallinity of the obtained thin films. All results were described in detail and they indicated that the films prepared in this study can be used in many nanotechnology applications.

Glass Additive and Subtractive Manufacturing of a Fiber Optic Rotary Encoder for Downhole Pressure Sensing

This article presents a fiber optic rotary encoder-based pressure sensor for downhole applications. The rotary encoder, which is composed of an encoding pad and an all-glass optical fiber sensing head, converts the rotation angles of a pressure transducer to digital codes. The optical fiber only serves as the telemetry channel to directly transmit the data in digital format such that the environmental temperature influence and the long-time drift are minimized. The glass additive and subtractive manufacturing (ASM) techniques are used to embed the multichannel optical fibers into a bulk-fused silica glass substrate. Because the fused silica glass shares a similar material property to the optical fiber (e.g., thermal expansion coefficient), the optical fiber sensing head is well sealed and fixed even at an elevated temperature. The picosecond laser blackening technique is used to fabricate the high reflectivity contrast encoding pad with high accuracy. The proposed pressure sensor was manufactured and experimentally verified to have a signal-to-noise ratio (SNR) of 23 dB and a linear pressure response with a root-mean-square error (RMSE) of 0.37. During the 400-h 250 °C long-term stability test, there was no digital code variation. In addition, a mathematical model to study the relationships between the sensor’s performances and design parameters was established. According to the model, a 12-bit encoder (0.02% pressure sensitivity) can be achieved with a radius of 20 mm.

Effect of UV Irradiation on the Growth of ZnO:Er Nanorods and Their Intrinsic Defects

Nanorods of erbium-doped zinc oxide (ZnO:Er) were fabricated using a hydrothermal method. One batch was prepared with and another one without constant ultraviolet (UV) irradiation applied during the growth. The nanorods were free-standing (FS) as well as deposited onto a fused silica glass substrate (GS). The goal was to study the atomistic aspects influencing the charge transport of ZnO nanoparticles, especially considering the differences between the FS and GS samples. We focused on the excitons; the intrinsic defects, such as zinc interstitials, zinc vacancies, and related shallow donors; and the conduction electrons. UV irradiation was applied for the first time during the ZnO:Er nanorod growth. This led to almost total exciton and zinc vacancy luminescence reduction, and the number of shallow donors was strongly suppressed in the GS samples. The effect was much less pronounced in the FS rods. Moreover, the exciton emission remained unchanged there. At the same time, the Er3+ content was decreased in the FS particles grown under constant UV irradiation while Er3+ was not detected in the GS particles at all. These phenomena are explained.

Evaluation of the helium hermeticity reliability of copper through-glass vias

This work aims to understand and assess the helium hermeticity reliability of metallized copper (Cu) through-glass vias (TGVs) made in Corning® HPFS® Fused Silica glass substrate. To assess this, the Cu TGV wafers were subjected to numerous stringent environmental reliability tests that includes high temperature storage (HTS) at 125 °C, highly accelerated stress testing (HAST), 130 °C/85 % RH and thermal shock (−40 °C/125 °C). Using a helium leak rate of >1.0 × 10−8 atm·cm3/s as the failure criteria, it was found that all the Cu TGV wafers used in this study significantly outperformed specification requirements, irrespective of the harsh environmental conditions that they were subjected to. This finding clearly attests to the robustness and suitability of Cu TGV wafers used in this study for stringent helium hermeticity requirement applications. At the completion of the tests, no failures were found for all samples subjected to thermal shock and HTS even after 9000 cycles and 4600 h respectively. For HAST samples that failed after exposure times of 400 h and 1500 h, it was found that the root cause for their failure was due to the erosion of Cu at the titanium (Ti)–Cu interface, caused by the formation of CuO and/or Cu2O. This led to sidewall debonding of the Ti–Cu interface, resulting in helium leak rates > 1.0 × 10−8 atm·cm3/s. Additionally, higher HAST exposure time was found to lead to increased degradation of the Ti–Cu interface.

Effect of vacuum annealing on the optical properties of tungsten oxide films

• Annealing of WO 3– x films in vacuum initiates their coloration in blue. • Colored film absorption band is adequately described by the Breit-Wigner distribution. • Annealing temperature rise nonlinearly increases the absorption band intensity. • Decrease in the spectral line width is saturated when annealing temperature increases. • Asymptote of refractive index dispersion decreases in proportion to the temperature. In this work, the thermochromic properties of tungsten oxide films are studied. The goal of this work is to study the influence of vacuum annealing on optical properties of amorphous WO 3– x films deposited on silica glass substrates. These dependences of the absorption index were approximated using the Breit-Wigner distribution. An increase in the annealing temperature led to an increase in the intensity and a decrease in the width of the absorption band in the near infrared range of the film transmission spectrum. This changed the dispersion of absorption and refractive indices.