Annealing Of Films Research Articles

Large-Pore Ordered Mesoporous Turbostratic Carbon Films Prepared Using Rapid Thermal Annealing for High-Performance Micro-pseudocapacitors.

Carbonization by rapid thermal annealing (RTA) of precursor films structured by a brush block copolymer-mediated self-assembly enabled the preparation of large-pore (40 nm) ordered mesoporous carbon (MPC)-based micro-supercapacitors within minutes. The large pore size of the fabricated films facilitates both rapid electrolyte diffusion for carbon-based electric double-layer capacitors and conformal deposition of V2O5 without pore blockage for pseudocapacitors. The pores were templated using bottlebrush block copolymers (BBCPs) via cooperative assembly of phenol-formaldehyde resin to produce microphase-segregated carbon precursor films on a variety of substrates. Ultrafast RTA processing (∼50 °C/s) at elevated temperatures (up to 1000 °C) then generated stable, conductive, turbostratic MPC films, resolving a significant bottleneck in rapid fabrication. MPC prepared on stainless steel at 900 °C demonstrated exceptionally high areal and volumetric capacitances of 6.3 mF/cm2 and 126 F/cm3 (at 0.8 mA/cm2 using 6 M KOH as the electrolyte), respectively, and 91% capacitance retention after 10,000 galvanostatic charge/discharge cycles. Post-RTA conformal V2O5 deposition yielded pseudocapacitors with 10-fold increase in energy density (20 μW h cm-2 μm-1) without adversely affecting the high power density (450 μW cm-2 μm-1). The use of RTA coupled with BBCP templating opens avenues for scalable, rapid fabrication of high-performance carbon-based micro-pseudocapacitors.

Non-melt selective enhancement of crystalline structure in molybdenum thin films using femtosecond laser pulses

It is challenging to crystalize a thin film of higher melting temperature when deposited on a substrate with comparatively lower melting point. Trading such disparities in thermal properties between a thin film and its substrate can significantly impede material processing. We report a novel solid-state crystallization process for annealing of high melting point molybdenum thin films. A systematic investigation of laser induced annealing from single pulse to high pulse overlapping is reported upon scanning at fluences lower than the threshold required for the damage/ablation of molybdenum thin films. The approach allows better control of the grain size by changing the applied laser fluence. Atomic force microscopy surface morphology and x-ray diffraction (XRD) analysis reveal significant improvements in the average polycrystalline grain size after laser annealing; the sheet resistance was reduced by 19% of the initial value measured by a Four-point probe system. XRD confirms the enlargement of the single crystal grain size. No melting was evident, although a change in the close packing, shape and size of nanoscale polycrystalline grains is observed. Ultrashort laser induced crystallinity greatly enhances the electrical properties; Hall measurements reinforced that the overall carrier concentration increases after scanning at different laser fluences. The proposed method, based on the aggregation and subsequent growth of polycrystalline and single crystal-grains, leading to enhanced crystallization, has potential to be applicable in thin film processing industry for their wide applications.

Studying the linear and nonlinear optical properties of trifluoroethoxy-coated zinc phthalocyanine ((4TFEO) 4-ZnPc) thin films

Trifluoroethoxy-coated zinc phthalocyanine (4TFEO) 4-ZnPc thin films were prepared using the spin coating process. The crystal structure of powder and different temperature annealed thin films was examined using X-ray Diffraction (XRD), which confirmed the amorphous character for the powder, as-deposited and annealed films. Raman spectroscopy analysis revealed that samples exhibited comparable active modes. Due to the strong carbon-fluorine bond and fluorine's high electronegativity, spectrophotometric studies in the UV–Vis–NIR region indicated that annealing temperatures of 373 and 473K had no discernible influence on the optical gap and optical constants of (4TFEO) 4-ZnPc thin films. The oscillator energy Eo and the dispersion energy Ed were obeyed the usual dispersion area (λ > 850 nm). Dielectric constants were determined to calculate optoelectronic characteristics such as the high-frequency dielectric constant ε∞, lattice dielectric constant εL, ratio of carrier concentration to the effective mass (N/m∗), and plasma frequency ωP. The third-order nonlinear susceptibility χ(3), nonlinear refractive index n2 and two-photon absorption coefficient βc of the (4TFEO) 4-ZnPc thin films were measured for the (4TFEO) 4-ZnPc thin films, which showed a good correlation with linear refractive index WDD parameters and optical gap. These findings will be a lead step to understand deeper linear and nonlinear optical properties of (4TFEO) 4-ZnPc thin films as a probable candidate for optoelectronic devices applications.

In Situ Monitoring of Pulsed Laser Annealing of Eu-Doped Oxide Thin Films.

Eu3+-doped oxide thin films possess a great potential for several emerging applications in optics, optoelectronics, and sensors. The applications demand maximizing Eu3+ photoluminescence response. Eu-doped ZnO, TiO2, and Lu2O3 thin films were deposited by Pulsed Laser Deposition (PLD). Pulsed UV Laser Annealing (PLA) was utilized to modify the properties of the films. In situ monitoring of the evolution of optical properties (photoluminescence and transmittance) at PLA was realized to optimize efficiently PLA conditions. The changes in optical properties were related to structural, microstructural, and surface properties characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The substantial increase of Eu3+ emission was observed for all annealed materials. PLA induces crystallization of TiO2 and Lu2O3 amorphous matrix, while in the case of already nanocrystalline ZnO, rather surface smoothening0related grains’ coalescence was observed.

Effect of composition on L10 ordering, structural and magnetic properties of Fe100-xPtx alloy films prepared by controlled sputtering

Fe100-xPtx alloy films are fabricated by controlled ion beam sputtering. Composition of the films was tuned by varying the relative atomic percentage of iron and platinum via controlling the area exposed to the ion beam. Structural and magnetic properties of films are studied using x-ray reflectivity, x- ray fluorescence, x-ray diffraction and Magneto Optic Kerr Effect. Isochronal annealing of films was done at 500 °C for 1 hour. Evolution of L10 ordering upon thermal annealing is investigated and correlation with the relative atomic percentage has been observed and explained. The finding of the work is useful for the fabricating the future recording media material.

Effect of SiO2 Interlayer Thickness in Au/SiO2/Si Multilayer Systems on Si Sources and the Formation of Au‐Based Nanostructures

AbstractSi sources involved in the growth of Au–SiOx nanostructures are investigated through the rapid thermal annealing of gold thin films on SiO2/Si substrates with various SiO2 layer thicknesses (3, 25, 100, 500 nm) in a reducing atmosphere. This method reveals three Si sources whose involvement depends on the thickness of the SiO2 layers, i.e., Si diffusion from the substrate, and SiO from SiO2 decomposition and from Si active oxidation. Increasing thicknesses of the SiO2 layer hampers the Si diffusion and the decomposition of regions of the SiO2 layer, which decreases the concentrations of discovered regions weakening the Si active oxidation. These discovered regions appear in systems with a SiO2 layer of 25 or 100 nm, while they are absent for a 500 nm layer. Furthermore, Au–SiOx nanostructures of different shapes form in each system. Both behaviors indicate that the influence and transport mechanisms of the different Si sources are largely dependent on the thicknesses of the SiO2 layers and that they control the evolution of the Au–SiOx nanostructures. A clear understanding of the relationship between these thicknesses and the possible Si sources and their roles in the evolution of the nanostructures makes the tailored fabrication of nanostructures possible.

Influence of synthesis parameters and thermal annealing on grain size of polycrystalline aluminum thin film

The thin polycrystalline aluminium films were synthesized on monocrystalline silicon substrates by ion-plasma sputtering. The synthesis was carried out at temperatures of 80 and 160°C and deposition rate of 10 and 110 nm/min. As-deposited films were annealed for 15 h at 550°C. The morphology of aluminium films before and after annealing was obtained using SEM images. The surfaces of as-deposited Al thin films, synthesized at high temperature, were uneven, while for low temperature films they were smooth enough with Al hillocks on the top of the film. After thermal annealing, morphology of the films was changed slightly. XRD patterns were obtained to calculate the average Al grain size of as-deposited and annealed films. The XRD analysis showed that an increase in the synthesis temperature leads to an increase in the average grain size from 50 to 84 nm and that increase in the rate of Al film synthesis leads to an increase in the average grain size from 50 to 63 nm. As the result of annealing, the average grain size increased for all samples and the final meaning was from 78 to 140 nm.

Hollow cathode gun for electron beam annealing

An electron gun with a hollow cathode was tuned to be used in electron beam annealing. Electron beams with an energy of 1 keV and a current of 100 mA were obtained. It is shown that the diameter of the electron beam varies in the range from 7 to 5 mm, while the specific power is from 2·105 to 2·104 W/m2. Such electron beams have a soft, non-destructive effect on the surface and are suitable for electron beam annealing of various films.

High refractive index (Dy) doped (GeTe)80(InTe)20 thin films for sub-THz and millimeter-wave applications

Chalcogenide materials are ideal for IR applications because of their wide transmission window, variable bandgap, and high nonlinearity. In this regard, optical characteristics of ( Dy ) doped ( GeTe 2 ) 80 ( In 2 Te 3 ) 20 thin films have been measured and investigated. The influence of annealing on the optical characteristics of thin films has been reported. The reflectance and transmittance spectra were used to calculate the refractive index ( n ) and extinction coefficient ( k ) of thin films. With the annealing of as-prepared film, the penetration depth (Δ) measured at a wavelength of 1.1 μm and bandgap ( E g ) decrease. The relaxation process has been realized using electric modulus ( M ) determination, and the dielectric loss has been estimated in terms of loss tangent (tan δ). Wemple Di-Domenico (WDD) model has been employed to calculate dispersion energy ( E d ) and average energy gap ( E 0 ). Using the values of E 0 and E d , the static refractive index ( n 0 ) and the moments ( M -1 , M -3 ) of the optical spectra have been determined. Sellmeier oscillator parameter ( λ 0 ) increases while S o decreases with a rise in the annealing temperature.

End-Capping π-Conjugated Naphthodithiophene Diimide (NDTI)-Based Triads with Noncovalent Intramolecular S···O Interactions: A Route towards High-Performance Solution-Processable Air-Stable n-Type Semiconductors

Introducing noncovalent intramolecular interactions into functional π-conjugated organic molecules or polymers is a useful method to improve the performance of organic semiconducting devices. In this study, two small molecules based on naphthodithiophene diimide (NDTI), NDTI-BTIC1 and NDTI-BTIC2, were successfully designed and synthesized by covalently connecting an electron-deficient NDTI-core and two 3-(dicyanomethylidene)-indan-1-one (IC) groups with thiophene substituted by an alkoxy chain or alkyl chain, respectively. Density functional theory (DFT) calculations on the optimized geometries of the triads predict that the existence of noncovalent intramolecular S (thiophene)···O (alkoxy) interactions is possible in NDTI-BTIC1. The molecular orbital distributions of NDTI-BTIC1 and NDTI-BTIC2 show that the lowest unoccupied molecular orbitals (LUMOs) are delocalized in the whole molecule, implying the possibility to show n-type transport characteristics. The two molecules further demonstrated LUMOs at a low altitude of −4.37 to −4.45 eV, low enough for the stable transmission of electrons in the atmosphere. The solution-processing method was used to prepare transistors based on the two molecules’ bottom-gate top-contact (BGTC), which exhibited unipolar n-type field-effect transistor (FET) characteristics in the air. The FET performance of NDTI-BTIC1 is higher than that of NDTI-BTIC2 in both the as-spun and thermal annealed films, possibly attributed to the existence of noncovalent intramolecular S···O interactions in NDTI-BTIC1. Moreover, the maximum electron mobility of NDTI-BTIC1 obtained at 150 °C thermal annealing is improved by one order of magnitude compared to that of NDTI-BTIC2, being 0.17 and 0.085 cm2 V–1 s–1, respectively. The transport difference of the two molecules was proved by film morphology analysis. The results show that constructing noncovalent intramolecular S···O conformational locks between the TIC unit and NDTI can improve the organic field-effect transistor (OFET) devices’ performance through reasonable molecular design strategies.

Plasmon-enhanced photoluminescence from TiO2 and TeO2 thin films doped by Eu3+ for optoelectronic applications.

In this work we study the luminescence properties of europium-doped titanium dioxide and tellurium oxide thin films enhanced by gold plasmonic nanostructures. We propose a new type of plasmon structure with an ultrathin dielectric film between plasmonic platform and luminescent material. Plasmonic platforms were manufactured through thermal annealing of the gold thin film. Thermal dewetting of gold film results in spherical gold nanostructures with average dimensions of 50 nm. Both, luminescent TiO2:Eu and TeO2:Eu films were deposited by RF magnetron sputtering from mosaic targets. The morphology of the gold nanostructures was investigated by SEM and TEM, while the composition of oxides film was analyzed by XPS. Luminescence properties were studied on the basis of excitation and emission spectra. The experiments show that the additional dielectric layer enhances the luminescence intensity. Such structures could be potential candidates as phosphors in white LEDs.

Optical constants, dispersion parameters and energy loss functions of crystal violet as a potential absorber thin film for solar energy conversion and storage applications

Highly homogenous crystal violet (CV) thin films are grown by spin coating technique. X-ray diffraction (XRD) measurements have been carried out to identify the dominant orientation of the films. The XRD pattern of as-deposited film showed an amorphous structure which turns into nanocrystalline by thermal annealing at 150 °C for 1 h. The spectroscopic characterization of as-deposited and annealed CV films was estimated via spectrophotometric measurements of transmission and reflection in the spectral range 190–2000 nm. Optical constants of CV films were determined. Wemple-DiDomenico model was applied to the normal dispersion region of refractive index spectrum and from which, many dispersion parameters were calculated. The type of most probable transitions and values of optical energy gaps for CV films were estimated by Tauc plot. The dissipation energy and volume & surface loss functions were estimated. The influence of annealing temperature on the spectroscopic properties, dispersion parameters and energy loss functions were investigated which revealed an improvement in the optical properties and decreased values of energy loss functions for the annealed CV films. The obtained results of optical features for CV films reveals that CV films are an excellent potential absorbing material in solar energy conversion and storage devices.

Thermal oxidation impact on the optoelectronic and hydrogen sensing properties of p-type copper oxide thin films

The paper presents the results of the investigation of the post-process annealing effect on selected properties of copper oxide thin films deposited by magnetron sputtering. It was found that the prepared thin films were nanocrystalline with the crystallite size smaller than 20 nm. Annealing at temperatures of 200 °C, 300 °C and 350 °C caused metallic copper oxidation to copper(I) oxide and then to copper(II) oxide. As-deposited and annealed at 200 °C thin films were composed of Cu and Cu2O. Copper(I) oxide transformation into CuO started at 300 °C, while the thin film annealed at 350 °C consisted of a single CuO phase. Scanning electron microscopy imaging revealed that annealing of the as-deposited thin films caused gradual formation of cupric oxide nanowires. Optimum annealing temperature for nanowires growth was 350 °C. X-ray photoelectron spectroscopy showed that the surface of the as-deposited thin films was oxidized to Cu2O and CuO, while in the case of annealed films it was completely oxidized to CuO. Thermal treatment also contributed to the increase in coating transparency in the infrared range. The transmission coefficient at 1500 nm of the thin film annealed at 350 °C was equal to 68. The resistivity of the as-deposited copper oxide thin film was equal to 1.9•10−3 Ωcm, while the highest resistivity of the annealed thin films was equal to 32 Ωcm for the coating annealed at 200 °C. A further increase in the annealing temperature resulted in a slight decrease in the resistivity value. Based on Seebeck coefficient measurements, it was found that all coatings were characterized by p-type conductivity. Additionally, sensing properties toward hydrogen were examined. The best sensor response exceeding 13 was observed for the thin film annealed at 200 °C.

Molecular Dynamics Simulation of Laser Induced Heating of Silicon Dioxide Thin Films

The full-atomistic classical molecular dynamics simulation of the laser heating of silicon dioxide thin films is performed. Both dense isotropic films and porous anisotropic films are investigated. It is assumed that heating occurs due to nodal structural defects, which are currently considered one of the possible causes of laser induced damage. It is revealed that heating to a temperature of 1000 K insignificantly affects the structure of the films and the concentration of point defects responsible for the radiation absorption. An increase in the heating temperature to 2000 K leads to the growth of the concentration of these defects. For “as deposited” films, this growth is greater in the case of a porous film deposited at a high deposition angle. Annealing of film reduces the difference in the concentration of laser induced defects in dense and porous films. The possible influence of optical active defects arising due to heating on the laser induced damage threshold is discussed.

Enhanced photodetection performance of sputtered cupric oxide thin film through annealing process

This study demonstrates an improvement in the photodetection response of a Cupric Oxide (CuO) thin film through the annealing process. The CuO thin film was deposited on silicon substrate using DC magnetron sputtering system. Annealing of the as-deposited film was carried out in a muffle furnace at 400 and 500 °C for two hours. X-ray diffraction patterns revealed the formation of a single phase CuO film whose crystallinity was improved with increase of the annealing temperature. The field emission scanning electron microscopy indicated a compact and fine granular structure of the as-deposited film whereas the segregation and agglomeration of grains was observed after the film’s annealing. The photodetection performance of CuO film with Al contacts was investigated under the exposure of visible light. The current–voltage graphs of as-deposited and annealed films displayed Schottky contact between the metal and semiconductor, owing to a lower work function of Al than that of the CuO. The photo-to-dark current ratio of the device was significantly enhanced after the film’s annealing. The increase in photocurrent became more pronounced upon increasing the light intensity from 58 to 511 µW/cm2. The maximum current gain and sensitivity values were found to be 66 and 6500% respectively at 10 V bias for the film annealed at 500 °C. The rise and fall time of the Al/CuO/Al photodetector was decreased after the film’s annealing.

Rapid thermal annealing induced engineering of surface and photoluminescence properties of (K,Na)NbO3 thin films for optoelectronic applications

The present study is focused on understanding the mechanism of luminescence behavior and how it gets affected with post annealing temperature via rapid thermal annealing of (K,Na)NbO3 thin films. The crystalline KNN perovskite structure with preferred (001)-orientation is observed upon annealing at 750 and 800 °C. After annealing, the evolution kinetics of surface features is resulted from the simultaneous evaporation-recondensation and volume diffusion of particles. The volatilization of alkali species after annealing and, in contrast, the lattice oxygen and Nb5+ chemical state of niobium related to KNN is enhanced. Narrowing of optical band gap after annealing is attributed to the generation of shallow defects deep below the conduction band owing to order–disorder and/or distortion in NbO6 octahedra. Photoluminescence (PL) quenching behavior is observed after RTA with 290 nm excitation wavelength. A strong blue emission is observed at 800 °C after exciting with 266 nm wavelength. The kinetics of decay lifetime from time-resolved PL results revealed the enhancement of transitions more likely via radiative states. The RTA induced results specify that KNN can be one of the promising candidates for use in LEDs, smart glass windows, optical switches/sensors, and optoelectronic devices.

Carbon content in PEALD-In2O3 thin films impact to its electrical and structural properties

In this paper, indium oxide (In 2 O 3 ) thin films are prepared by plasma-enhanced atomic layer deposition (PEALD) using cyclopentadienylindium(I) (InCp) as the metal precursor and O 2 plasma as the oxidant. The mechanism and effects of annealing temperature under the air atmosphere on optical, structural, and electrical properties of the films are investigated. The experimental results show that both of the as-deposited and annealed films are polycrystalline bixbyite-cubic structure. No significant influences on the optical properties are observed when the annealing temperature increases from 300 to 600 °C. However, it is confirmed the filling of oxygen vacancy defects by the in-diffused oxygen atoms from the annealing ambient. The carbon impurities resulting from the incompletely reacted InCp are found to be at the interstitial sites in the In 2 O 3 lattice, which can be greatly removed by the annealing treatment. As a consequence, the electrical resistivity increases with increasing annealing temperature mainly related to the reduced carrier concentration. This paper is helpful for PEALD In 2 O 3 films to be applied to optoelectronic devices where the suppression of the oxygen defects, carrier concentration, and carbon impurities are required. • PEALD In 2 O 3 thin films with low carbon content were obtained by the air annealing. • Effects of various annealing temperatures and its mechanisms are studied. • Removal of carbon impurities as annealing affects the film properties.

The influence of Ge substitution and H2S annealing on Cu2ZnSnS4 thin films

Cu2Zn(Sn1-xGex)S4 thin films (where x = 0, 0.25, 0.50, 0.75, and 1) were deposited by spin coating technique and annealed under 30 and 40 ccm H2S:Ar (1:9) flows to understand the influence of Ge atom content ratio and H2S flow rate during the annealing of thin films on morphological, structural and optical properties of Cu2Zn(Sn1-x Gex)S4 thin films. It was seen that the Ge content has a strong influence on the structural and optical properties of the films. The crystal size of the films decreased sharply for Cu2Zn(Sn0.75Ge0.25)S4 thin film and started to increase slowly owing to the formation of high dislocation density and strain in the structures. The Raman spectra show the formation of kesterite thin films and blue Raman shift with Ge substitution to the content. The films obtained under 40 ccm H2S:Ar (1:9) flows have weak secondary peaks associated with ZnS formation. The UV–Vis data showed the increase of optical bandgap from 1.52 to 2.05 eV with a rise in Ge ratio in the structures.

Influence of plasmon resonance on the luminescence of titanium dioxide thin films doped with rare earth ions

In this work the study of the optical properties of europium doped titanium dioxide thin films (TiO2:Eu) enhanced by gold plasmonic nanostructures are presented. Plasmonic platforms were manufactured by thermal annealing of thin film of Au, deposited on a Corning glass substrate. As a result of thermal treatment, gold spherical nanostructures with average dimensions of 50 nm were obtained. Luminescent TiO2:Eu film was deposited by RF magnetron sputtering method, from mosaic target. Morphology of gold nanostructures was investigated by SEM and TEM microscopes, while composition of oxides film was analysed by XPS methods. Luminescence properties were studied on the basis of excitation and emission spectra. Experiments have shown that such structures exhibit interesting luminescent properties and could be potential candidates for optoelectronics applications.

Optical properties of GeO[SiO] and GeO[SiO2] solid alloy layers grown at low temperature

The optical properties of GeO[SiO] and GeO[SiO2] solid alloy films grown on Si(001) substrates were studied using Raman, Fourier transform infrared absorption (FTIR) and photoluminescence (PL) spectroscopies. A PL signal was observed in the infrared region both for as-deposited and annealed germanium silicate suboxide films. Furnace annealing led to an increase of the PL signal and to a redshift of the PL maximum. The PL at ∼1100 nm is most probably due to defect-induced radiative transitions while the PL at ∼1500 nm may be rather caused by amorphous Ge nanoclusters and Ge nanocrystals. Finally, the temperature dependence of the PL was studied. Anomalous quenching of the PL signal is observed which does not follow the classical Arrhenius law. The temperature dependence of the PL intensity is well explained by using a Berthelot model.