Post-thermal Annealing Process Research Articles

Surface plasmon resonance synergistic coupling effects of gold nanoparticulates with silver grating in P3HT: PC61BM-based organic solar cell

A systematic study was carried out to observe possible boosts in the performance of poly-(3-hexyl thiophene):phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) based organic solar cell via synergistic coupling of plasmonic effects. Various volume concentration ratios of gold nanoparticles and nanorods ranging from 2%, 4%, 6%, and 8% were used to determine an optimum condition. An indicative 2% optimum condition led to synergistic tests. The synergistic coupling of gold nanorods with backcontact grating revealed a power conversion efficiency (PCE) of 4.88%. Since post-thermal annealing process results in optimum interfacial surface morphology and structural reorganization, a post-process hypothesis was performed to observe the behavior of the devices at RT with further comparisons at 40 °C. A further increase in the initial performance of the devices was observed with an optimum PCE of 5.43%. The behavior in the performances revealed stable measurements mostly attributed to conditions below the glass transition temperature of P3HT:PC61BM.

Effect of Post-thermal Annealing on the Structural, Morphological, and Optical Properties of RF-sputtered In2S3 Thin Films

Indium sulfide films were deposited by radio frequency magnetron sputtering technique on soda lime glass substrate. The deposition was conducted at the temperature of 150 °C and prepared films were then thermally annealed under argon atmosphere at 350 °C and 450 °C for 30 min. The impact of post-thermal annealing treatment on the properties of the films was investigated. From X-ray diffraction analysis, the formation of the stable tetragonal β-In2S3 crystal structure was substantiated and revealed that the thermal annealing treatment at 450 °C improved the crystallization of the films. The change in surface topographies and morphologies of the films depending on the post-thermal annealing process were examined by atomic force microscopy and scanning electron microscopy techniques, respectively. The stoichiometric ratio of constituent elements in the films was obtained by elemental analysis and it was seen that the films had slightly sulfur (S) deficit composition. It was found that the concentration of S slightly increased with the thermal annealing process. The room temperature photoluminescence spectra revealed that the films included vacancies of sulfur (VS: donor) and indium (In) (VIn: acceptor), indium interstitial (Ini: donor) and oxygen (O) in vacancy of sulfur (OVs: acceptor) defects with strong and broad emission bands at around 1.70, 2.20, and 2.71 eV.

Heterogeneous bimetallic oxysulfide nanostructure (Ni-Co) as hybrid bifunctional electrocatalyst for sustainable overall alkaline simulated seawater splitting

The design and development of high performance non-precious bifunctional electrocatalytic activity for oxygen/hydrogen evolution reaction (OER/HER) remains a significant challenge in overall seawater splitting process. Herein, we report the Co3S4/Co3O4 hybrid nanostructures catalyst with duel functions is successfully in-situ synthesized through self-templating strategy, whereas, Ninanostructure 3S2/NiO are grown on Ni foam using a facile hydrothermal reaction and post thermal annealing process. The designed self-standing Co3O4(Co3S4)/NiO(Ni3S2)/NF nanostructure (denoted as Co-Ni-S/NF) as a self-standing hybrid electrode demonstrates an excellent bifunctional electrocatalytic activity for OER and HER process in alkaline freshwater/alkaline simulated seawater as electrolyte. Taking advantage of the bimetallic synergistic effect and formation of an efficient interface layer of Ni3S2/NiO in a unique nanostructure, the resultant bifunctional electrocatalytic performance of Co-Ni-S/NF electrode for OER & HER processes are highly performed in both electrolyte conditions. Specifically, Co-Ni-S/NF hybrid electrode requires lower overpotentials of 270 mV (at 20 mV cm−2), 310 mV (at 50 mV cm−2) for OER and lower overpotentials of 239 mV (at 20 mV cm−2), 291 mV (at 50 mV cm−2) for HER in alkaline simulated seawater condition. For two-electrode based electrolyzer analyses, Co-Ni-S/NF electrode based electrolyzer demonstrates low cell voltage of 1.67 V to attain a current density of 10 mA cm−2 with stable activity of overall alkaline simulated seawater splitting process whereas hybrid electrode used as anode and cathode. Therefore, the proposed interface engineering strategy and rationally constructing electrocatalyst nanostructure via a self-templating route could be a promising opportunity to develop an active duel functional catalyst for direct seawater splitting applications.

Resistive switching behaviors of cobalt oxide films with structural change by post-thermal annealing

We have studied the resistive switching behaviors of cobalt oxide films with structural changes by a post-thermal annealing process. During post-annealing at temperatures of 500–700 °C for the CoOx films deposited by ultra-high-vacuum RF magnetron sputtering, two structural phases of CoO and Co3O4 were modulated by selection of ambient N2 or O2 gases. As a device application of these films, the resistive random-access memory (ReRAM) structures of p+-Si/CoOx/Ti/Au were fabricated with CoO or Co3O4 films by post-annealing at 700 °C under N2 and O2 atmosphere, respectively. The resistive switching characteristics of the CoO device appeared much better than that of the Co3O4 device, also showing good uniformity from a cumulative probability distribution, long non-volatile retention characteristics of 104 s, good endurance of ∼100 cycles, and an excellent current ratio of 104. These results demonstrate the method to provide stable and good resistive switching properties of sputtered CoO films using the phase selection during post-thermal annealing.

Chromium-Rich Core-Shell Cr x Ir1-X O2 Nanotubes for Highly Efficient Oxygen Evolution Reaction in Alkaline Solution

Considering the growing attention to oxygen evolution reaction (OER) as a key role in clean energy through electrocatalytic water splitting, advanced materials for water oxidation are central to the area of renewable energy. In general, the OER process, involved four electron and four proton coupled electrochemical reaction, demands higher kinetics to overcome an overpotential than HER (hydrogen evolution reaction). For this aspect, significant research efforts have been devoted to developing efficient OER electrocatalyst with enhanced electrocatalytic kinetics and long-term durability.Here we present the synthetic processes and physical/electrochemical characterization of Cr x Ir1-x O2 nanotubes (NTs). Those NTs are synthesized through electrospinning, a simple way to facilitate 1D nanostructure, and post-thermal annealing process with different annealing speed (°C /min). As-prepared Cr x Ir1-x O2 NTs at the optimized conditions have shown outstanding OER electrocatalytic activity in alkaline media from the viewpoints of overpotential and Tafel slope as well as durability. The morphology and compositions of Cr x Ir1-x O2 were characterized by a field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The crystalline structures of the prepared Cr x Ir1-x O2 are investigated through high-resolution X-ray diffraction (XRD). Electrochemical activities for oxygen evolution reaction (OER) are studied with rotating disk electrode (RDE) voltammetry in N2-saturated 1.0 M KOH (aq); and compared with those of iridium single component oxides (IrOx and IrO2) and commercial iridium (cIr, counterparts in OER electrocatalysts).This work was financially supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT or by the Ministry of Education (NRF-2019R1F1A1059969, NRF-2018R1A6A1A03025340, NRF-2020R1A2B5B01001984, and NRF-2019R1F1A1062799).

Photocatalytic CO2 reduction and hydrogen production over Pt/Zn-embedded β-Ga2O3 nanorods

Gallium oxide has shown a potential catalyst application in energy and environment. Herein, β-Ga2O3 and Zn-embedded β-Ga2O3 nanorods were prepared by hydrothermal method and post-thermal annealing process. The physicochemical properties were examined by scanning electron microscopy, electron transmission microscopy (TEM), Auger elemental mapping, X-ray diffraction crystallography, UV–visible absorption, Raman, Fourier-transform infrared, and X-ray photoelectron spectroscopy. Photocatalytic CO2 reduction products over β-Ga2O3 nanorods in gaseous CO2/H2O atmosphere were found to be CO, CH4, and H2 with rates of 0.055, 0.058, and 14.8 μmol⋅g−1⋅h−1, respectively under UVC irradiation confirmed by gas chromatography. Upon 5 mol% Zn-embedding, the rates of CO, CH4, and H2 were observed to be 1.49, 0.24, and 0.19 μmol⋅g−1⋅h−1, respectively. The CO and CH4 yields were increased by 27 × and 4×, respectively. CH3OH was barely detected for Zn or Pt-only embedded β-Ga2O3, but significantly increased to 0.19 μmol⋅g−1⋅h−1 upon Pt/Zn(5 mol%)-cocatalyst embedding. The photocatalytic hydrogen production was increased by 3.6 × and 27.4 × upon Pt/Zn-cocatalyst embedding, compared with those of Zn-embedded and bare β-Ga2O3, respectively. The Pt/Zn-cocatalyst embedding was found to show 2.5 × higher rate than the Pt-only embedding. The rate reached to 404.5 μmol⋅g−1⋅h−1 for Pt(0.5 nm)/Zn(2 mol%)/β-Ga2O3. The unique demonstration tests provide precious information for the improvement of Ga2O3-based CO2 reduction and hydrogen production catalysts.

Properties investigation of crystalline silicon surface irradiated by nanosecond laser pulses in different background atmospheres

Black silicon materials were obtained by irradiation with ns laser pulses in different ambient atmospheres. The surface morphology, optical properties, and electrical properties of the black silicon were investigated after the ablation by ns laser pulses. Slab-like structures and boundaries were formed on the surface of black silicon fabricated in sulfur hexafluoride (SF6), argon (Ar), and vacuum. In addition, a micrometer-sized sphere was observed at the tip of the slab-like structure, which was not obvious for the black silicon prepared in oxygen (O2), nitrogen (N2), and air. The infrared absorption of all the black silicon materials was enhanced. For the two samples fabricated in SF6 and Ar, the infrared absorptance was approximately 50% at 1500 nm. A post-thermal annealing process decreased the infrared absorptance of all the black silicon materials except for that prepared in SF6. The sheet resistance of the black silicon was reduced by the ns laser irradiation process, and thermal annealing further decreased the sheet resistance of all the samples except for the one fabricated in SF6. After annealing at 875 K, the sheet carrier density of the black silicon fabricated in an Ar atmosphere and vacuum was approximately 1013 cm−2, which was approximately three orders of magnitude larger than that of the silicon substrate (1010 cm−2). The large difference in carrier density between the black silicon layer and substrate is beneficial for establishing contact junctions and for application in infrared photodetection.

Awakening n → π* electronic transition by breaking hydrogen bonds in graphitic carbon nitride for increased photocatalytic hydrogen generation

Achieving the excitation of lone pairs (n → π*) in graphitic carbon nitride (g-C3N4) can not only extend visible light absorption range, but also increase the amount of catalytically active π electrons, thereby leading to enhanced photocatalytic hydrogen (H2) generation. However, awakening n → π* electronic transition in g-C3N4 is highly challenging. Here we report on activating n → π* electronic transition by breaking hydrogen bonds in g-C3N4 through a post thermal annealing process. The g-C3N4 thus obtained shows greatly increased photocatalytic H2 generation under visible light irradiation. Under optimal conditions, the highest H2 generation rate reached 33.3 μmol·h−1, which is 25 times higher than that of pristine g-C3N4 without n → π* electronic transition (1.3 μmol·h−1). Moreover, the longest wavelength that can photoexcite g-C3N4 to generate H2 is 510 nm, nearly a 50 nm red shift to the absorption edge of pristine g-C3N4 (~460 nm). This work demonstrates a great potential of utilizing n → π* electronic transition to increase the photocatalytic performance of g-C3N4 via breaking hydrogen bonds.

From NiRh2O4 to RhNi Alloy: Preparation and Characterization of Nanofibers for Hydrogen Evolution in pH-Universal Media

Considering the growing attention to sustainable hydrogen production from water splitting, advanced materials for electrocatalytic water splitting are central to the area of renewable energy. Ideal water splitting catalysts should have not only low overpotential to produce hydrogen but also decent stability for a controlled period. While the previously reported water splitting catalysts have various compositions, the ones based on earth-abundant and non-precious metals are being studied extensively for hydrogen and oxygen production. However, noble metal oxides, in general, still exhibit superior electrocatalytic activity and enhanced stability under extreme environment compared with other cheap metals. Therefore, mixing non-precious transition metals (e.g. Ni, Co and Cu) with noble metals could be a possible strategy to utilize highly active but expensive noble metals providing economic feasibility.Here we present the synthetic processes and physical/electrochemical characterization of single-phase NiRh2O4 nanofibers (NFs) and their reduced form, RhNi NFs. Those NFs are synthesized through electrospinning, a simple way to facilitate 1D nanostructure, and post-thermal annealing process with and without hydrogen atmosphere. Under a certain optimized condition, single-phase NiRh2O4 NFs and single-phase alloy RhNi NFs are synthesized without and with hydrogen atmosphere, respectively. To find the proper synthetic conditions, NFs are electrospun with varying the precursor mixing ratios and calcined at different temperatures. The morphology and compositions of NiRh2O4 NFs and RhNi NFs were characterized by a field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The crystalline structure of the prepared NFs are investigated through high-resolution X-ray diffraction (XRD). Electrochemical activities of NiRh2O4 NFs and RhNi NFs for hydrogen evolution reaction (HER) are studied with rotating disk electrode (RDE) voltammetry in N2-saturated 1.0 M NaOH, 1.0 M PBS and 1.0 M HClO4 aqueous solutions; and compared with those of pure metallic Rh, Ni counterparts in addition to commercial Pt/C. This work was financially supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (NRF-2019R1F1A1059969 for CL) and Basic Science Research Program through the NRF funded by the Ministry of Education (NRF-2018R1A6A1A03025340 for YL and KMH).

Monolithic Inorganic ZnO/GaN Semiconductors Heterojunction White Light-Emitting Diodes.

Monolithic light-emitting diodes (LEDs) that can generate white color at the one-chip level without the wavelength conversion through packaged phosphors or chip integration for photon recycling are of particular importance to produce compact, cost-competitive, and smart lighting sources. In this study, monolithic white LEDs were developed based on ZnO/GaN semiconductor heterojunctions. The electroluminescence (EL) wavelength of the ZnO/GaN heterojunction could be tuned by a post-thermal annealing process, causing the generation of an interfacial Ga2O3 layer. Ultraviolet, violet-bluish, and greenish-yellow broad bands were observed from n-ZnO/p-GaN without an interfacial layer, whereas a strong greenish-yellow band emission was the only one observed from that with an interfacial layer. By controlled integration of ZnO/GaN heterojunctions with different postannealing conditions, monolithic white LED was demonstrated with color coordinates in the range (0.3534, 0.3710)-(0.4197, 0.4080) and color temperatures of 4778-3349 K in the Commission Internationale de l'Eclairage 1931 chromaticity diagram. Furthermore, the monolithic white LED produced approximately 2.1 times higher optical output power than a conventional ZnO/GaN heterojunction due to the carrier confinement effect at the Ga2O3/n-ZnO interface.

Phase formation polycrystalline vanadium oxide via thermal annealing process under controlled nitrogen pressure

This article provides an approach to improve and control crystal phases of the sputtering vanadium oxide (VxOy) thin films by post-thermal annealing process. Usually, as-deposited VxOy thin films at room temperature are amorphous phase: post-thermal annealing processes (400 °C, 2 hrs) under the various nitrogen (N2) pressures are applied to improve and control the crystal phase of VxOy thin films. The crystallinity of VxOy thin films changes from amorphous to α-V2O5 phase or V9O17 polycrystalline, which depend on the pressure of N2 carrier during annealing process. Moreover, the electrical resistivity of the VxOy thin films decrease from 105 Ω cm (amorphous) to 6×10-1 Ω cm (V9O17). Base on the results, our study show a simply method to improve and control phase formation of VxOy thin films.

Synthesis of second-order nonlinearities in dielectric-semiconductor-dielectric metamaterials

We demonstrate a large effective second-order nonlinear optical susceptibility in electronic optical metamaterials based on sputtered dielectric-semiconductor-dielectric multilayers of silicon dioxide/amorphous silicon (a-Si)/aluminum oxide. The interfacial fixed charges (Qf) with opposite signs on either side of dielectric-semiconductor interfaces result in a non-zero built-in electric field within the a-Si layer, which couples to the large third-order nonlinear susceptibility tensor of a-Si and induces an effective second-order nonlinear susceptibility tensor χeff(2). The value of the largest components of the effective χeff(2) tensor, i.e., χ(2)zzz, is determined experimentally to be 2 pm/V for the as-fabricated metamaterials and increases to 8.5 pm/V after the post-thermal annealing process. The constituents and fabrication methods make these metamaterials CMOS compatible, enabling efficient nonlinear devices for chip-scale silicon photonic integrated circuits.

Construction of CuO/Cu2O@CoO core shell nanowire arrays for high-performance supercapacitors

Abstract In this paper, we reported construction of CuO/Cu 2 O@CoO core-shell nanowire arrays by combining a chemical deposition method and post-thermal annealing process on Cu foil without any binders and conductive additives. The nanowire arrays were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDX) techniques. The determination results indicate that the nanowire arrays are distinct CuO/Cu 2 O nanowire core decorated with branched CoO nanosheet shells. In addition, the as-obtained nanowire arrays demonstrate outstanding areal capacitance of 280 mF cm − 2 at a current density of 1 mA cm − 2 as well as superior cycling stability which remains 90.7% of initial capacitance after 3000 cycles. The facile and cost-effective synthesis integrated with the robust electrochemical performances suggests that the CuO/Cu 2 O@CoO core-shell nanowire arrays are expected to be promising candidate electrodes for high-performance supercapacitor and other energy storage applications.

Bottom-gate coplanar graphene transistors with enhanced graphene adhesion on atomic layer deposition Al2O3

A graphene transistor with a bottom-gate coplanar structure and an atomic layer deposition (ALD) aluminum oxide (Al2O3) gate dielectric is demonstrated. Wetting properties of ALD Al2O3 under different deposition conditions are investigated by measuring the surface contact angle. It is observed that the relatively hydrophobic surface is suitable for adhesion between graphene and ALD Al2O3. To achieve hydrophobic surface of ALD Al2O3, a methyl group (CH3)-terminated deposition method has been developed and compared with a hydroxyl group (OH)-terminated deposition. Based on this approach, bottom-gate coplanar graphene field-effect transistors are fabricated and characterized. A post-thermal annealing process improves the performance of the transistors by enhancing the contacts between the source/drain metal and graphene. The fabricated transistor shows an Ion/Ioff ratio, maximum transconductance, and field-effect mobility of 4.04, 20.1 μS at VD = 0.1 V, and 249.5 cm2/V·s, respectively.

Nitrogen-doped carbon nanoparticles derived from acrylonitrile plasma for electrochemical oxygen reduction.

Nitrogen-doped carbon nanoparticles were synthesized via a solution plasma process, with acrylonitrile as a single-source precursor, followed by a post-thermal annealing process. The nitrogen-bonding states can be tuned by varying the annealing temperature. The best electrocatalytic activity for oxygen reduction reaction (ORR) in terms of both onset potential and limiting current density can be achieved for the catalyst annealed at an optimal temperature of 800 °C because of the high content of graphitic-N catalytic sites and a large specific surface area.

Reliability of hydrogen sensing based on bimetallic Ni–Pd/graphene composites

Graphene-supported nickel–palladium (Ni–Pd) bimetallic nanoparticles (Ni–Pd/Gr) were synthesized using a simple chemical method, followed by a post-thermal annealing process. The characteristics of resistivity-type hydrogen (H2) sensors composed of Pd–Gr composites (with small amounts of Ni added to the Pd nanoparticles (Pd NPs)) were investigated in detail. Pd NPs with various amounts of Ni embedded into the Pd lattice were synthesized by varying the molar ratios of the Ni/Pd precursors. The results from this work indicate that the addition of Ni not only enhances performance, but also reduces the hysteresis behavior of the Pd–Gr composite based H2 sensors. H2 was detectable from 1 to 1000 ppm based on a rapid recovery response with suitable Ni/Pd percentages. At the optimal Ni/Pd percentage of 7% (Ni/Pd ∼7%), sensors showed a small enhancement of sensitivity, fast recovery, and minimum hysteresis effect. From our experiment, the addition of Ni to Pd NPs results in a reduction of the hysteresis effect and reliability on H2 sensors based on Pd–Gr composites.

Growth and Characterization of High-Quality Dielectric Sputtered Zinc Oxide Films from the First Principle

In this article, we investigate the effect of thermal treatment on a piezoelectric material, zinc oxide, which has found numerous applications in sensors and actuators. Even though the exact mechanisms rendering electrical properties are less known, we suspect that the thermal treatments are responsible for improvement of electrical characteristics of the deposited thin films. We establish that the thermal agitation is responsible for improvement of orders of magnitude in electrical characteristics of sputtered ZnO thin films. The surface quality of the thin films deposited is process dependent. ZnO films were deposited using a dielectric sputtering method, on oxidized silicon 100 n-type wafers. Further, these films were thermally annealed in oxygen ambient at 600 °C in a tube furnace with 2 mL/min pressure. It is observed that, after thermal annealing, the quality of the films is improved by orders of magnitude. The luminance, crystalline quality, and surface morphology of these thin films was measured with atomic force microscopy, scanning electron microscopy with BSD detector (BSD-SEM), and Fourier transform infrared spectroscopy (FTIR). The results infer that the film’s surface is very smooth and dense. The surface roughness is improved by 1.3149 nm from 7.882 nm prior to thermal annealing to post-annealing surface roughness with 6.5671 nm. Post-thermal annealing process reveals average grain size was 50 nanometers; the surface roughness is reduced to 6.5671 nm. A significant improvement in electrical current-voltage characteristics was recorded with I-V curve. It is suspected to be due to substantial enhancement in electrical conductivity as a result of thermal treatment and improved spectral response recorded a FTIR peak shift of 1 wave number in total. The FTIR peak shift is suspected to be due to evaporation and reduction in oxygen vacancies due to thermal annealing process. The post-annealed ZnO films will be used for actuation in the future.

Wide-spectrum Mg and Ga co-doped ZnO–TCO thin films with introduced hydrogen grown by magnetron sputtering at room temperature

• The introduction of H 2 gas improved the properties of ZnO thin films. • The formation of Mg O bond widened the band-gap of ZnO. • H atoms function as donor in the ZnO thin films. • The optical energy band gap of 3.74 eV was obtained. • The mobility of ZnO thin films can be enhanced after vacuum annealing. Transparent conductive hydrogenated Mg and Ga co-doped ZnO (HMGZO) thin films were deposited on glass substrates at room temperature by pulsed direct current magnetron sputtering, with hydrogen being introduced at various flow rates. X-ray diffraction results showed that these HMGZO thin films are polycrystalline, with a preferred (0 0 2) crystal-plane orientation. Hydrogen donors are responsible for the increase of carrier concentration and the lowest resistivity of 4.4 × 10 −3 Ω cm, with a carrier concentration of 1.92 × 10 20 cm −3 and a mobility of 7.3 cm 2 /V s, was obtained at an H 2 flow rate of 9.0 sccm. The average transmittance of the HMGZO thin films exceeded 88.6% for wavelengths of 330–1100 nm. The optical band gap ( E g ) increased from 3.41 to 3.74 eV with increasing the H 2 flow rate from 0 to 16.0 sccm. The widening of E g could be attributed both to Burstein–Moss band-filling and to incorporation of Mg atoms. The electrical stability of HMGZO thin films with post thermal annealing process was also investigated.

Effect of thermal treatment on the optical and the structural properties of In0.5Ga0.5As quantum dots

The optical and the structural properties of a 3-stacked In0.5Ga0.5As quantum dot (QD)/GaAs structure subjected to a post thermal annealing process have been investigated. Photoluminescence (PL) and time-resolved PL spectroscopy have been performed to examine the optical properties of the as-grown and thermally-treated QD structures. Thermal annealing of the QD structure at temperatures up to 700 °C leads to enhancements of the PL intensity and the carrier decay time without any PL peak shifts. The increases in the PL intensity and the carrier lifetime can be attributed to a reduction in the number of crystal defects in the QDs and in the GaAs layer near the QDs. The structural properties of the In0.5Ga0.5As QDs/GaAs heterointerface have been further examined with a transmission electron microscope analysis.

Fabrication and characterization of iron and fluorine co-doped BST thin films for microwave applications

The effects of fluorine co-doping by means of a post-thermal annealing process of iron-doped BST thin films in a fluorine-containing atmosphere have been investigated. XPS and ToF-SIMS sputter depth profiling verified a homogeneous fluorine distribution in the thin films. By employing EPR, it was shown that singly charged ( $$ {\text{Fe}}_{\text{Ti}}^{\prime } $$ – $$ {\text{V}}_{\text{O}}^{ \cdot \cdot } $$ )· defect complexes, as well as ‘isolated’ $$ {\text{Fe}}_{\text{Ti}}^{\prime } $$ centres with a distribution of $$ {\text{F}}_{\text{O}}^{ \cdot } $$ sites in remote coordination spheres exist in the fluorinated films. Tunability enhancement due to fluorine co-doping as well as a Q-factor enhancement due to iron doping is demonstrated.