Annealing Of Films Research Articles

Controlling conduction band alignment and carrier concentration in gallium-doped magnesium zinc oxide by reactive cosputtering

Gallium-doped magnesium zinc oxide (GMZO) holds promise as a UV transparent conducting oxide with tunable bandgap and conductivity, though there has been relatively limited exploration of the broad compositional space available. Conductive GMZO films were deposited by reactive cosputtering at room temperature followed by annealing. The contributions of alloying and the Burstein–Moss effect to the optical bandgap were decoupled through comparisons of as-deposited and annealed films. Compositional analysis in conjunction with electrical characterization was used to quantify the activation of Ga doping in MZO. Combinatorial synthesis was used to explore the optoelectronic performance over a broad composition space. Reactive cosputtering can be used to tailor GMZO properties for optoelectronic applications over a wide range of bandgaps (3.3–4 eV) and resistivity (10−3–>100 Ω cm) through appropriate control of the Mg/Zn ratio and Ga content, respectively.

Rapid annealing of Au thin films by micron chevron-shaped laser beam scanning toward growth of single-grain crystal

A practicable solution to reduce the density of grain boundaries in metal thin films in order to improve their physical properties, and compatibility with nanoscale fabrications still remains a challenge for the thin film industry. We propose an alternative approach to the problem by using micron chevron-shaped laser beam (μCLB) annealing for rapid and selective growth of crystal grains in metal thin films. We investigate the laser annealing of various Au thin films and discuss the mechanisms of grain growth accounting for the microstructure of the Au films and interaction between the Au films and the substrate. The successful growth of single-grain crystal on a 50 nm Au film by μCLB annealing is also demonstrated and further optimization of the process is discussed.

Correlation of Bond Energy and Optical Band Energy of Annealed TiO2 Thin Films

We report on the correlation between bond energy and optical band energy of TiO2 thin films prepared through sol gel doctor-blade technique. The TiO2 films were deposited on doped fluorine tin IV oxide (SnO2:F) layer on glass substrates. UV-Vis-NIR spectroscopy was carried out on as-deposited and subsequent annealed films at different rates from room temperature up to 450°C. The average optical transmittance within the visible region was 73.5%, 73.4%, 70.5% and 69.9% for the as-deposited, 1-step annealed, 2°C/min, and 1°C/min films, respectively. FTIR spectroscopy confirmed presence of functional elements of Ti = O with a peak at 587.7 cm-1. Bond energy for the films was calculated using Madelung equation with inclusion of the second coordination sphere for crystalline state. The values of bond energies were found to be 3.99 eV, 4.02 eV, 4.12 eV and 4.16 eV for the as-deposited, 1-step annealed, 2°C/min, and 1°C/min films respectively. The analysis of the band gap was done using Tauc’s relation. Band gap energy ranged from 4.02 eV to 5.04 eV. A statistical correlation between bond energy and optical band energy was established. Films annealed at 1°C/min recorded the highest bond energy and lowest band gap energy. This is attributed to the process of nucleation and crystal growth which are governed by thermodynamic properties. Prolonged exposure to higher temperatures through low annealing rates led to formation of films with high bond energy and low band gap.

EFFECT OF ANNEALING ON THE STRUCTURE AND OPTICAL PROPERTIES OF LEAD SELENIDE AND CADMIUM SELENIDE THIN FILM PREPARED BY CHEMICAL BATH DEPOSITION

The effect of annealing on the structural and optical properties of lead selenide and cadmium selenide thin films prepared by chemical bath deposition has been studied. The films were annealed in air for a duration of 1 hour at temperatures of 673 K for CdSe and 573 K for PbSe. Both the as-deposited and annealed films were characterized by X-ray diffraction and optical absorption spectroscopy. The as–deposited CdSe films had the cubic structure with preferred orientation along (111) plane. However, after annealing there was a phase change from the cubic structure to the hexagonal structure with preferred orientation along the (002) plane. Both the as-deposited and annealed PbSe had the cubic structure with preferred orientation along the (200) plane. Other structural parameters such as the average crystallite size increased, whilst the dislocation density and strain decreased, suggesting a reduction in lattice imperfections after annealing. Optical absorbance of the films increased after annealing with a corresponding decrease in the direct band gap from 1.78 eV to 1.52 eV for CdSe, and 1.47 eV to 1.35 eV for PbSe. These results suggest an improvement in optical and structural properties after annealing.

Formation of RuO2 thin film using dopamine as a reducing, chelating, and adhesive agent simultaneously

We demonstrate a facile and seedless wet chemical process to deposit RuO2 thin film on a glass slide. The process entails the use of dopamine and its oxidized form, polydopamine (PDA), as the reducing and chelating agent, as well as the adhesive agent bonding the RuO2 and glass slide. The formula starts with the oxidation of K2RuCl5 to prepare RuO4 solution, followed by its reduction by dopamine to form chelated RuO2 colloids for the deposition of amorphous RuO2 thin film containing 26.5 at% hydrous RuO2 and 73.5 at% RuO2. After a mild Ar annealing, the RuO2 thin film exhibits a rutile phase with (110) preferred orientation. Elemental analysis indicates incomplete pyrolysis of PDA. Results from X-ray absorption spectroscopy confirm the presence of RuO4 and its transformation to RuO2. Electrochemical analysis of the adsorbed dopamine molecules on an ITO substrate validates the oxidative behavior of dopamine. The bonding strength of RuO2 thin film is determined by a tape-peeling test in which both the as-deposited and annealed RuO2 thin films show robust adhesion to the glass substrate.

Preparation and characterization of CuSbSe2 thin films deposited by pulsed laser deposition

CuSbSe2 has been a potential absorber layer for thin film solar cells by reason of its attractive photovoltaic properties and environmentally friendly constituent elements. In this work, high-quality CuSbSe2 thin film was prepared by pulsed laser deposition (PLD) and further in-situ annealing. Structural, morphological, compositional and optical properties of the unannealed and annealed films were characterized and compared separately. The results proved the existence of CuSbSe2, Sb2Se3 and Cu3SbSe3 in the unannealed film. With the rising of deposition temperature, the content of Sb2Se3 increased significantly. Moreover, in-situ annealing at 350 °C can effectively reduce the Sb2Se3 and Cu3SbSe3 in the film. The atomic ratio of Cu:Sb:Se in the annealed film is estimated to be 25.45:26.29:48.27, basically consistent with the stoichiometry ratio of CuSbSe2. Both annealed and unannealed CuSbSe2 films revealed a high absorption coefficient greater than 104 cm−1. The optical band gap of the annealed film was about 1.15eV, which meets the requirements for the absorber layer of solar cells.

Thickness effect on structural properties of post annealed barium hexaferrite films deposited by ion beam sputtering

Barium hexaferrite thin films were prepared by ion beam deposition on sapphire (102) single crystal substrates. The structural properties of the films were analyzed by means of X-ray diffraction, atomic force microscopy, magnetic force microscopy and scanning electron microscopy. The obtained results were interpreted as a presence of layered structure with different types of texture and its formation mechanism is proposed. The significant influence of BaFe12O19 thickness on its microstructure was observed. Films obtained under certain conditions are potentially fit for further growing of oriented hexaferrite with out-of-plane orientation of c-axis.

Spectroscopic Ellipsometry Characterization of As-Deposited and Annealed Non-Stoichiometric Indium Zinc Tin Oxide Thin Film.

A spectroscopic ellipsometry study on as-deposited and annealed non-stoichiometric indium zinc tin oxide thin films of four different compositions prepared by RF magnetron sputtering was conducted. Multi-sample analysis with two sets of samples sputtered onto glass slides and silicon wafers, together with the analysis of the samples onto each substrate separately, was utilized for as-deposited samples. Annealed samples onto the glass slides were also analyzed. Spectroscopic ellipsometry in a wide spectral range (0.2–6 eV) was used to determine optical constants (refractive index n and extinction coefficient k) of these films. Parameterized semiconductor oscillator function, together with Drude oscillator, was used as a model dielectric function. Geometrical parameters (layer thickness and surface roughness) and physical parameters (direct optical bandgap, free carrier concentration, mobility, and specific electrical resistivity) were determined from spectroscopic ellipsometry data modeling. Specific electrical resistivity determined from the Drude oscillator corresponds well with the results from electrical measurements. Change in the optical bandgap, visible especially for annealed samples, corresponds with the change of free carrier concentration (Moss–Burstein effect). Scanning electron microscope did not reveal any noticeable annealing-induced change in surface morphology.

Investigation of thermal annealing effects on MoO3 thin film by atomic layer deposition

Molybdenum oxide (MoO3) thin films have been obtained by plasma-enhanced atomic layer deposition using precursors of Mo(CO)6 and O2 plasma at a reactor temperature of 160 °C. The MoO3 thin films deposited on p-type silicon substrates with thermally grown 300 nm thick SiO2 layer with different numbers of ALD growth cycles. Spectroscopic ellipsometer is used to characterize as-grown film thickness and refractive index. The as-grown films are treated at annealing temperatures at 300–600 °C. The structural properties of as-grown and annealed thin films have been characterized by optical microscopy, µRaman spectra, and atomic force microscopy.

Фотофизические свойства тонких пленок перилена, модифицированного функциональными группами диангидрида и диимида тетракарбоновой кислоты

The morphology of organic semiconductor films of perylenetetracarboxylic acid dianhydride (PTCDA) and perylenetetracarboxylic acid dibenzyl-diimide (N, N`-DBPTCDI) formed by thermal vacuum deposition was studied by atomic force microscopy. It was shown that annealing of films at 420 K leads to rearrangement of their structure and crystallization. The optical absorption spectra of the films under study were used to estimate the optical band gap. The temperature dependence of the dark conductivity of PTCDA and N, N-DBPTCDI films before and after annealing (Т = 420 K) was established. The values of the activation energy of charge carrier traps are determined. The computer simulation of the density of localized states in the band gap of the films studied was carried out using the photoconductivity spectra in the constant photocurrent mode. Model photovoltaic cells based on PTCDA / СuPc and N, N-DBPTCDI / СuPc structures were formed. The kinetics of decay of the interfacial photo-voltage of the cells prepared was measured using pulsed light as an excitation source. On the basis of the performed measurements, the charge carrier mobility values in the investigated semiconductor materials were estimated.

LSPR based on-chip detection of dengue NS1 antigen in whole blood.

The development of a biosensor for rapid and quantitative detection of the dengue virus continues to remain a challenge. We report a lab-on-chip device that combines membrane-based blood plasma separation and a localized surface plasmon resonance (LSPR) based biosensor for on-chip detection of dengue NS1 antigen from a few drops of blood. The LSPR effect is realized by irradiating UV-NIR light having a spectral peak at 655 nm onto nanostructures fabricated via thermal annealing of a thin metal film. We study the effect of the resulting metal nanostructures on the LSPR performance in terms of sensitivity and limit of detection, by annealing silver films at temperatures ranging from 100 to 500 °C. The effect of annealing temperature on the nanostructure size and uniformity and the resulting optical characteristics are investigated. Further, the binding between non-targeted blood plasma proteins and NS1-antibody-functionalized nanostructures on the LSPR performance is studied by considering different blocking mechanisms. Using a nanostructure annealed at 200 °C and 2X-phosphate buffer saline with 0.05% Tween-20 as the blocking buffer, from 10 μL of whole blood, the device can detect NS1 antigen at a concentration as low as 0.047 μg mL−1 within 30 min. Finally, we demonstrate the detection of NS1 in the blood samples of dengue-infected patients and validate our results with those obtained from the gold-standard ELISA test.

Regular ordering of spherical microdomains in dewetted monolayer islands induced by thermal annealing of spin-coated ultrathin films of a triblock copolymer.

We report here spontaneous dewetting of a spin-coated, ultra-thin film of a sphere-forming block copolymer (BCP) upon thermal annealing, and that the dewetting resulted in the formation of plateau-shaped islands with a constant thickness consistent with the thickness of a monolayer, in which the spherical microdomains are regularly ordered two-dimensionally in a deformed hexagonal lattice. Thus, the spontaneous dewetting was ascribed to a mismatch between the initial spin-coated film thickness with respect to the monolayer thickness. Such dewetting of sphere-forming BCPs is considered to be deterministic compared to the cases of lamella- and cylinder-forming BCPs, as incommensuration in thickness is avoided by attaining perpendicular orientation without dewetting. We further quantitatively examined the ordering regularity of spherical microdomains in the dewetted monolayer islands to clarify the effect of confinement on sphere ordering. The degree of deformation of the hexagonal lattice was found to have an increasing tendency as a function of the degree of the deformation of the dewetted islands (the island shape), irrespective of the size of the island. Namely, islands with almost round shapes exhibit a well-ordered arrangement of the spherical microdomains in a perfect hexagonal lattice. Another notable finding is that the regular ordering of the spherical microdomains was found to be spoiled in the vicinity of the edge of the island. In other words, the spherical microdomains were well-ordered in a hexagonal lattice far from the edge of the island, while they were not regularly ordered in the vicinity of the edge, which may be due to mismatch between the curvature of the island's perimeter and the polygonal shape of ordered sphere grains.

Effect of annealing temperature on the structural and optical properties of Ge15Se75Zn10 thin films

Ge15Se75Zn10 thin films were deposited onto cleaned glass substrates by the vacuum thermal evaporation technique. The as-deposited and annealed thin films were characterized by scanning electron microscopy, X-ray diffraction and optical spectroscopy. The average particle sizes of the crystallized GeSe and ZnSe phases increase with increasing annealing temperature. Some optical parameters of the as-deposited and annealed Ge15Se75Zn10 thin films were studied using both transmittance T(?) and reflectance R(?) measurements. The analysis of T(?) and R(?) data revealed the existence of direct optical band gap (EG) and the corresponding values were calculated to be 2.913, 2.802 and 2.692 eV for the as-deposited and annealed thin films at 373 and 423 K, respectively. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple-Didomenico (WD) model. The width of band tails of localized states (Ee), the single oscillator energy (E0), the dispersion energy (Ed), the high frequency dielectric constant (?L) and the steepness parameter (S) were estimated.

Effect of annealing temperature on the electrical and photoluminascence properties of tin oxide thin films prepared by sol-gel spin coating technique

Tin oxide thin films were sucessfully synthesized by sol–gel spin coating technique using SnCl2·2H2O and Ethanol as precurser. The prepared films were post annealed at different temperatures such as 300, 400, 500, 600 and 700 °C. The room temperature electrical conductivities of the as prepared and post annealed tin oxide thin films at different temperatures were ranging from 0.0820 × 103 Ω−1 m−1–0.5766 × 103 Ω−1 m−1. The Figure of merit values were calculated and are ranging from 4.3336 × 10−6 Ω−1 –25.0907 × 10−6 Ω−1. PL study shows that an intense and broad blue asymmetric emission band centered at 389 nm.

Effect of Mo monoatomic interlayer on magnetic properties of in-plane anisotropic Nd-Fe-B/Mo/FeCo nanocomposite multilayered films

The Nd-Fe-B/Mo/Fe-Co multilayered films on MgO(001) were fabricated by UHV sputtering method. The as-deposited films showed soft magnetic properties with weak perpendicular magnetic anisotropy, and after annealing above 650°C, these films showed in-plane magnetic anisotropy, good squareness, and hard magnetic properties with high coercivity of about 8 kOe. The (220) peak of Nd2Fe14B was identified in the XRD pattern after annealing of the film, which means that the c-axis, which is the easy axis of magnetization, points in the plane of the film, consistent with the measurement of the magnetization curve. The positive peak of ΔM plot of in-plane direction of the film annealed at 800°C was shown. This result suggests existence of exchange coupling between the Nd-Fe-B and Fe-Co layers in the in-plane anisotropic multilayered film with monoatomic Mo interlayer.

Synthesis and Characterization of Zinc Tin Sulphide (ZTS) Thin Films via Chemical Bath Deposition Route

Zinc Tin Sulphide (ZTS) thin films were deposited on glass substrates by Chemical Bath Deposition (CBD) technique. The CBD was obtained by preparing 20 ml of 0.5M of Zinc chloride solution, 20ml of 0.5M stannum chloride (SnCl2) with 3ml of Triethanolamine (TEA) (N(CH2CH2OH)3) and 25ml of 0.5M of Thiourea as complexants. The grain size of ZTS from the SEM micrographs was spherically-shaped without visible defects like crack or peel. The SEM micrograph of the annealed ZTS thin films, however, showed a dense sponge-like structure. ZTS thin films reflectance curve exhibited average reflectance below 30% for all films. Annealed ZTS thin films (at 200 0 C) exhibited the greatest reflectance of about 30% than all other films. Both as-deposited and annealed ZTS films exhibited transmittance above 40% for wavelength around 780 nm and above. The extrapolated band gaps energy values for ZTS for as-deposited and annealed thin films varied from the range of 3.30 to 3.40 eV. The resistivity increased with an increase in heat treatment and it ranged between, 1.83 × 10-1 Ωm to 9.71 × 10-2 Ωm.

Role of Postdeposition Thermal Annealing on Intracrystallite and Intercrystallite Structuring and Charge Transport in Poly(3-hexylthiophene)

The performance of electronic devices comprising conjugated polymers as the active layer depends not only on the intrinsic characteristics of the materials but also on the details of the extrinsic processing conditions. In this study, we examine the effect of postdeposition thermal treatments on the microstructure of poly(3-hexylthiophene) (P3HT) thin films and its impact on their electrical properties. Unsurprisingly, we find thermal annealing of P3HT thin films to generally increase their crystallinity and crystallite coherence length while retaining the same crystal structure. Despite such favorable structural improvements of the polymer active layers, however, thermal annealing at high temperatures can lead to a net reduction in the mobility of transistors, implicating structural changes in the intercrystallite amorphous regions of these semicrystalline active layers take place on annealing, and the simplistic picture that crystallinity governs charge transport is not always valid. Our results instead suggest tie-chain pullout, which occurs during crystal growth and perfection upon thermal annealing to govern charge transport, particularly in low-molecular-weight systems in which the tie-chain fraction is low. By demonstrating the interplay between intracrystallite and intercrystallite structuring in determining the macroscopic charge transport, we shed light on how structural evolution and charge-transport properties of nominally the same polymer can vary depending on the details of processing.

Reversal of charge transfer direction at gold/copper phthalocyanine film interface on post deposition annealing: A vibrational spectroscopic study

Charge transfer interaction at the gold (Au)/copper phthalocyanine (CuPc) interface, with Au on CuPc film, was investigated using vibrational techniques - Fourier Transform Infra Red and Raman spectroscopy, in combination with X- ray photoelectron spectroscopy. The charge transfer direction at this interface was found to be changing after annealing of the CuPc film, as compared to that before annealing. Molecule to metal charge transfer at the Au/CuPc interface observed for the as deposited film was found to be reversing to metal to molecule charge transfer for the annealed film. This reversal of charge transfer direction in the latter was attributed to the modified electronic structure/work function of the CuPc film and the varying orientation of CuPc molecules at the interface, brought about by the increased surface roughness, change in morphology, etc. The reversal in charge transfer direction was suggested to be supporting the reduction in parasitic contact resistance at the Au/CuPc interface for a top contact OFET with the annealed CuPc film, as compared to that with the as deposited film. This study demonstrates the influence of morphology of the organic semiconductor film on the charge transfer behaviour at the metal/organic semiconductor interface.

МОБІЛЬНИЙ СЕНСОР АЦЕТОНУ

The aim of this work is to develop mobile sensors for acetone based on metal oxide for their subsequent use in the development of devices for monitoring health status. The following research methods were used in the work: measuring the sensitivity of sensor samples on the film thickness and annealing temperature; removal of dependences of sensitivity, selectivity and detection limits on operating temperature; studying the morphology of sensor samples using X-ray diffractometry and field emission scanning electron microscopy. An acetone sensor was developed on the basis of nanostructured thin zinc oxide films, its sensitivity was determined at various temperatures, as a result of which the optimal operating temperature of the sensor was about 400 ° C. The sensitivity value of the ZnO gas sensor was more than 26.5% at 1000 ppm, 65% at 500 ppm and 5% at 300 ppm acetone. Possible future directions of development are the development of multisensor VOC sensor systems for implementation in wireless intelligent systems for monitoring the health of the population.

Investigation of the phase composition and photoluminescence of CVD (YxGdyEuz)2O3 films on Si substrates after annealing in the air

• (Y x Gd y Eu z ) oxide-silicate films were obtained by annealing of the oxide films on Si. • The oxide-silicate films exceeded the oxide films in the integral PL intensity. • An order of the cation positions filling was set up by comparing the PL spectra. • The Ln-O binding energy affects the red-orange shift of PL chromaticity to a greater extent. • The composition (xyz), optimal in efficiency and chromaticity of PL was set up.