Annealing Of Films Research Articles

Preparation of Sn doped In2O3 multilayer films on n-type Si with optoelectronics properties improved by using thin Al–Cu metals interlayer films

High-performance transparent conductive Sn doped In2O3/Al–Cu/Sn doped In2O3 (ITO/Al–Cu/ITO) multilayer films were prepared by radio frequency magnetron sputtering of ITO and direct current magnetron sputtering of aluminium Al and copper Cu on n-type Silicon (Si) substrate. The as-deposited and post annealed (400–600 °C) multilayer films microstructural, topological and morphological, optical and electrical properties were investigated. Structural analysis shows an amorphous structure for as-deposited film in spite of the inclusion of thin Al–Cu metals interlayer whereas cubic bixbyite polycrystalline structure was obtained by the annealed films. The films surface properties demonstrate an enhanced surface smoothness and grain size with increasing temperature. The films optimal optoelectronic properties were obtained at 600 °C, yielding a high optical transmittance of 89.2% at 480 nm wavelength, a good sheet resistance of 3.14 Ω/sq with a reduced electrical resistivity of 2.2 × 10−5 Ω-cm. According to the figure of merit (FOM), the film annealed at 600 °C exhibited a remarkable enhancement with a FOM value of 101.56 × 10−3 Ω−1. Current-voltage characteristics results showed an excellent n-Si/ITO/Al–Cu/ITO ohmic contact at 600 °C which can be a promising transparent conductive front window contact on silicon solar cells application.

Effects of thermal annealing on the characterization of p-NiO/n-GaAs heterojunctions produced by thermal evaporation

In this study, p-NiO/n-GaAs heterojunctions were fabricated using the thermal evaporation method that least affects the physical properties of the target sample. For the n-GaAs [100] crystal, all the cleaning process was carried out according to the conventional procedures. After making an ohmic contact with Au (99.9%) metal on the back mat face of the n-GaA single crystals, NiO was thermal evaporated on the front polished face of the crystal. Optical transmittance values of the NiO thin films were determined by a UV–Visible (UV–Vis) spectrophotometer. The optical band gaps of non-annealed and annealed NiO thin films were determined as 3.54 and 3.48 eV, respectively. XRD, SEM, EDX and AFM measurements were also performed to examine the effect of annealing in NiO thin films. Current–voltage (I-V) measurements of NiO/GaAs heterojunctions were made to determine photoelectric and electrical properties under illumination and in the dark. The energy dependence of interface states (Nss) were extracted from the I-V measurements by assuming the voltage dependence of the barrier height Фb and the ideality factor n. The NiO/GaAs contacts were found to have a good rectifier and photodiode properties from the I-V graphics.

High Mobility Reactive Sputtered CuxO Thin Film for Highly Efficient and Stable Perovskite Solar Cells

Copper oxide (CuxO) films are considered to be an attractive hole-transporting material (HTM) in the inverted planar heterojunction perovskite solar cells due to their unique optoelectronic properties, including intrinsic p-type conductivity, high mobility, low-thermal emittance, and energy band level matching with the perovskite (PS) material. In this study, the potential of reactive sputtered CuxO thin films with a thickness of around 100 nm has been extensively investigated as a promising HTM for effective and stable perovskite solar cells. The as-deposited and annealed films have been characterized by using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Photoluminescence (PL), UV-Vis spectroscopy, and Hall-effect measurement techniques. The significant change in structural and optoelectronic properties has been observed as an impact of the thermal annealing process. The phase conversion from Cu2O to CuO, including grain size increment, was observed upon thermal annealing. The transmittance and optical bandgap were found to vary with the films’ crystallographic transformation. The predominant p-type conductivity and optimum annealing time for higher mobility have been confirmed from the Hall measurement. Films’ optoelectrical properties were implemented in the complete perovskite solar cell for numerical analysis. The simulation results show that a 40 min annealed CuxO film yields the highest efficiency of 22.56% with a maximum open-circuit voltage of 1.06 V.

Link between Gas Phase Reaction Chemistry and the Electronic Conductivity of Atomic Layer Deposited Titanium Oxide Thin Films.

In situ monitoring of gas phase composition reveals the link between the changing gas phase chemistry during atomic layer deposition (ALD) half-cycle reactions and the electronic conductivity of ALD-TiO2 thin films. Dimethylamine ((CH3)2NH, DMA) is probed as the main product of both the TDMAT and water vapor half-reactions during the TDMAT/H2O ALD process. In-plane electronic transport characterization of the ALD grown films demonstrates that the presence of DMA, a reducing agent, in the ALD chamber throughout each half-cycle is correlated with both an increase in the films' electronic conductivity, and observation of titanium in the 3+ oxidation state by ex situ X-ray photoelectron spectroscopy analysis of the films. DMA annealing of as-grown TiO2 films in the ALD chamber produces a similar effect on their electronic characteristics, indicating the importance of DMA-induced oxygen deficiency of ALD-TiO2 in dictating the electronic conductivity of as-grown films.

Investigation of amorphous-crystalline transformation induced optical and electronic properties change in annealed As50Se50 thin films

The present work reports the amorphous-crystalline phase transformation in thermally evaporated As50Se50 thin films upon annealing at below Tg (423 K) and above Tg (523 K). The structural transition was probed by XRD, Raman and X-ray photoelectron spectroscopy. The composition and surface morphology were probed by EDS and FESEM techniques. The transmittance and reflectance spectra over the wavelength range 500 nm–1200 nm were used to deduce the optical parameters. The various optical parameters of the as-prepared and annealed As50Se50 thin films were estimated and discussed in terms of density of defect states and disorders. The indirect optical energy gap decreased for the 423 K annealed film and abruptly increased for 523 K annealed film as compared to the as-prepared film. The Swanepoel envelope method, WDD model, and Sellemeire postulates were employed for the analysis of refractive index, static refractive index, oscillator energy, dispersion energy, oscillator wavelength and dielectric constant. The changes in the linear and nonlinear properties showed opposite behavior for the two annealed films. The non-linear refractive index and 3rd order susceptibility were found to be increased for 423 K annealed film and decreased for the 523 K annealed film. The optical as well as the electrical conductivity changed with annealing and the electrical susceptibility increased for 523 K annealed film. The tunable optical properties can be applied for several optoelectronic applications. The amorphous to crystalline structural transformation occurred at annealing above Tg. The 3rd order susceptibility was found to be more at 423 K annealing and less at 523 K annealing.

Investigations of crystallization kinetics and phase transformation of 1000 nm of Ge20Sb20Te60 thin film from electrical measurements

In this work we will focus first on obtain the sheet resistance, Rs of thin film whose surface thickness is equal to 1000 nm for the chalcogine Ge20Sb20Te60 at different heating rates , this is done against temperature in the range from 70 to 370 °C. The sheet resistance curve and through derivation of sheet resistance as a function of temperature there was clearly evidence of two crystallization regions for the studied sample. Second, the thermal data we obtained was used to complete the thermal calculations and then the electrical calculations thereafter. The activation energies of crystallization were evaluated by kinetic criteria. The activation energy, Ec , and Avrami index, n, were obtained by analyzing the data via JMA methods. The results indicated that the transformation from amorphous to crystalline phases. The crystalline phases for the as-deposited and annealed film were identified via x-ray diffraction (XRD).

Investigation and characterization of the annealing effects on the ferroelectric behavior of PLD BaTiO3

This work investigates the ferroelectric behavior of barium titanate (BaTiO3) with and without annealing of the deposited film. 105.7 nm of BaTiO3 was deposited via pulsed laser deposition on a niobium-doped strontium titanate substrate. 50 nm of tungsten was sputtered and patterned into contact pads, and the film was subjected to electrical and material characterization. Annealing times greater than 30 min decreased the leakage current by 2–3 orders of magnitude. We demonstrate multiple, distinct, repeatable polarization states of BaTiO3 as a function of the film annealing time, and the forming and hysteresis sweep pulse lengths and amplitudes.

Investigations of structure development, electrical and thermal properties of polyvinylidene fluoride-expanded graphite nanocomposites

From natural graphite, expanded graphite (ExGr) has been synthesized using perchloric acid. Polyvinylidene fluoride (PVDF)–ExGr nanocomposites have been synthesized through non-solvent precipitation method followed by melt crystallization at 200°C and quenching in water at room temperature. The electrical percolation threshold has been found to be above 4 wt% ExGr in PVDF. With the addition of 0.5 wt% sonicated ExGr in PVDF-7 wt% graphite, the electrical conductivity is enhanced to two orders when compared to that of PVDF-7 wt% graphite. Thermogravimetric analysis proves very good dispersion of graphite nanosheets, as there exists at least 20°C enhancement in the onset temperature of thermal degradation with the addition of 3 wt% ExGr in PVDF. Structure development in PVDF due to the incorporation of ExGr particles has been understood through lattice mismatch theory. The impedance decreases with increase in the concentration of ExGr in PVDF at room temperature due to the formation of conducting channels. In another set of experiment, annealing of solution-casted films at 120°C for 5 h results in the formation of electroactive γ-phase, as confirmed through Fourier transform infrared and X-ray diffraction (XRD) analyses of representative samples. The composites are characterized by XRD, scanning electron microscopy and transmission electron microscopy.

Optimization of linear and nonlinear optical parameters of As40Se50Te10 thin films by thermal annealing

The present study reports the linear and nonlinear optical properties of as-prepared and annealed As40Se50Te10 thin films prepared on glass substrate by thermal evaporation method. The modifications in different properties after annealing were studied by XRD, EDAX, Raman spectroscopy, FESEM and UV–Vis-NIR and XPS spectroscopy. The study reports the decrease in optical band gap due to increase in disorder while the width of the tail in the gap increased with annealing temperature. The linear refractive index, optical as well as electrical conductivity and extinction coefficient increased with annealing. The dispersion energy, oscillator energy, dielectric constant and oscillator strength increased with annealing temperature while the electrical susceptibility decreased upon annealing. The 3rd order optical susceptibility and nonlinear refractive index were found to be increased with annealing temperature. The influence of different annealing temperatures on the variation of different parameters were elaborately explained on the basis of defect states in localized region. The structure remained unchanged while the heteropolar to homopolar bond conversion was noticed from the XPS and Raman spectroscopy. The changes in both nonlinear and linear optical properties by annealing shows that annealing temperature can be used as an important tool for controlling the optical constants of As40Se50Te10 chalcogenide film which could be a suitable candidate for numerous photonic applications.

Enhanced ferroelectric switching speed of Si-doped HfO2 thin film tailored by oxygen deficiency

Investigations concerning oxygen deficiency will increase our understanding of those factors that govern the overall material properties. Various studies have examined the relationship between oxygen deficiency and the phase transformation from a nonpolar phase to a polar phase in HfO2 thin films. However, there are few reports on the effects of oxygen deficiencies on the switching dynamics of the ferroelectric phase itself. Herein, we report the oxygen- deficiency induced enhancement of ferroelectric switching properties of Si-doped HfO2 thin films. By controlling the annealing conditions, we controlled the oxygen deficiency concentration in the ferroelectric orthorhombic HfO2 phase. Rapid high-temperature (800 °C) annealing of the HfO2 film accelerated the characteristic switching speed compared to low-temperature (600 °C) annealing. Scanning transmission electron microscopy and electron energy-loss spectroscopy (EELS) revealed that thermal annealing increased oxygen deficiencies, and first-principles calculations demonstrated a reduction of the energy barrier of the polarization flip with increased oxygen deficiency. A Monte Carlo simulation for the variation in the energy barrier of the polarization flipping confirmed the increase of characteristic switching speed.

In-vacuum measurements of optical scatter versus annealing temperature for amorphous Ta2O5 and TiO2:Ta2O5 thin films.

Optical coatings formed from amorphous oxide thin films have many applications in precision measurements. The Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo use coatings of SiO2 (silica) and TiO2:Ta2O5 (titania-doped tantala) and post-deposition annealing to 500°C to achieve low thermal noise and low optical absorption. Optical scattering by these coatings is a key limit to the sensitivity of the detectors. This paper describes optical scattering measurements for single-layer, ion-beam-sputtered thin films on fused silica substrates: two samples of Ta2O5 and two of TiO2:Ta2O5. Using an imaging scatterometer at a fixed scattering angle of 12.8°, in-situ changes in the optical scatter of each sample were assessed during post-deposition annealing to 500°C in vacuum. The scatter of three of the four coated optics was observed to decrease during the annealing process, by 25-30% for tantala and up to 74% for titania-doped tantala, while the scatter from the fourth sample held constant. Angle-resolved scatter measurements performed before and after vacuum annealing suggest some improvement in three of the four samples. These results demonstrate that post-deposition, high-temperature annealing of single-layer tantala and titania-doped tantala thin films in vacuum does not lead to an increase in scatter, and may actually improve their scatter.

Effect of structural disorder on the physical properties and electronic structure of the DC magnetron sputtered Ni films

The effect of the structural disorder in Ni films on their magnetic, magneto-optical (MO), transport, optical properties, and the spin polarization degree of conduction electrons as well as the electronic structure has been investigated. Room temperature (RT) DC magnetron sputtered onto glass substrates Ni films have been found to be amorphous. It was experimentally shown that an amorphous Ni films (i) are not ferromagnetically ordered at least for T>78K temperature range, (ii) do not show any MO response at RT, (iii) have 10 times larger resistivity than crystalline phase which nearly does not depend on temperature, (iv) exhibit the optical conductivity (OC) spectrum without interband absorption peaks typical for crystalline Ni, (v) have spin polarization degree of conduction electrons close to zero. Annealing of amorphous Ni films at T = 600 K causes their crystallization with the formation of the face-centered-cubic phase and restores the physical properties typical for crystalline Ni. The experimental OC spectrum of crystalline Ni film exhibits an intense interband absorption peaks located at E = 1.4 and 4.55 eV; it is in reasonable correspondence with the calculated interband OC spectrum of Ni. Main absorption peaks in the experimental OC spectrum were put in correspondence with the electron excitations between definite electronic states of the E(k) structure of Ni. The experimentally determined spin polarization degree of conduction electrons of crystalline Ni films was found to be close to that for bulk Ni and consists of P≈40%.

X-Ray Photoelectron Spectroscopy Depth Profiling of As-Grown and Annealed Titanium Nitride Thin Films

Titanium nitride thin films were grown on Si(001) and fused silica substrates by radio frequency reactive magnetron sputtering. Post-growth annealing of the films was performed at different temperatures from 300 °C to 700 °C in nitrogen ambient. Films annealed at temperatures above 300 °C exhibit higher surface roughness, smaller grain size and better crystallinity compared to the as-grown film. Bandgap of the films decreased with the increase in the annealing temperature. Hall effect measurements revealed that all the films exhibit n-type conductivity and had high carrier concentration, which also increased slightly with the increase in the annealing temperature. A detailed depth profile study of the chemical composition of the film was performed by x-ray photoelectron spectroscopy confirming the formation of Ti-N bond and revealing the presence of chemisorbed oxygen in the films. Annealing in nitrogen ambient results in increased nitrogen vacancies and non-stoichiometric TiN films.

Multilevel operation of GdOx-based resistive switching memory device fabricated by post-deposition annealing

Resistive switching memory has been studied actively for next-generation computing. Several binary oxides, such as HfO2 and Ta2O5, are widely adapted as resistive switching layers; however, there are several limitations to obtaining an energy- and area-efficient operation with sufficient reliability. Rare-earth oxide materials exhibit interesting resistive switching properties because of their reactivities with active anion species. In this study, atomic-layer-deposited GdOx films were investigated as an active switching layer for resistive switching memory. Post-deposition annealing of as-grown GdOx films enhanced the tunability of the resistance states, which can be useful for the multilevel operation of nonvolatile memory and neuromorphic computing applications. The effects of the crystallization and hygroscopic nature of the GdOx film are investigated for elucidating the change in the resistive switching characteristics and its underlying mechanism.

Effects of post-deposition annealing temperature in nitrogen/oxygen/nitrogen ambient on polycrystalline gallium oxide films

Polycrystalline Ga2O3 films were obtained after post-deposition annealing of as-deposited Ga2O3 films via radio frequency magnetron sputtering at different temperatures (400, 600, 800, and 1000 °C) in nitrogen/oxygen/nitrogen ambient. The Ga2O3 films obtained at lower temperatures (400 and 600 °C) demonstrated semiconducting property while the films obtained at higher temperatures (800 and 1000 °C) demonstrated insulating property based upon the leakage current density-voltage characteristics. The semiconducting properties were originated from the presence of oxygen vacancies as well as nitrogen incorporation as the scattering centre in the films, which could serve as the conducting path of electrons, encouraging a higher leakage current. The acquisition of a smaller direct and indirect band gap by these films further supported the fact that electrons would overcome the potential barrier easier. On the other hands, the presence of oxygen vacancies and nitrogen incorporation as well as preferred orientation of film growth accompanied with dislocation affected the leakage current density-voltage characteristics. Detailed investigation in the aspects of structural, morphological, optical, and electrical characteristics of the films was demonstrated.

Tuning of defects induced visible photoluminescence by swift heavy ion irradiation and thermal annealing in zinc oxide films

Present study reports the influence of electronic energy deposition on sol-gel grown zinc oxide thin films with different type of microstructures for tailoring the defects induced photoluminescence properties. The microstructure of the films was modified by the controlled thermal annealing and the nature of defects were tuned by swift heavy ions (SHI) irradiations at varying ion fluences of such thin films. It is observed that all the films show two emission bands in the spectral range of 350 nm–1000 nm; (i) a very weak UV-emission band and (ii) a broad visible emission band. The UV-emission band is attributed to the band to band transition while the visible emission to the deep-level defects. The maximum visible emission lies in the green emission region which enhanced with increasing annealing temperature for the samples annealed in controlled Argon gas environment in comparison of samples annealed in an oxygen environment. The intensity of the visible emission band was found to be increased with ion irradiation at low ion fluences while showing reduction at higher ion fluences along with peak broadening. The films annealed at higher annealing temperature exhibit shifting of peak maximum from green region to red region at higher fluences. The peak shifting and peak broadening at higher ion fluences could be attributed to the formation of the high density of complex defects such vacancies cluster and ionized oxygen vacancies in the lattice as tuned under the influence of electronic energy deposition through SHI irradiations. Thus, it is suggested that the intense luminescence induced by the defects could be tuned in controlled manner by selecting the proper irradiations parameters and thus it would be very interesting for the development of the optoelectronic applications.

SPR Sensor-Based Sensitivity Performance Investigation Using an H-Shaped Model with Supportive Metal Variation

This study demonstrates considerable sensitivity response using different materials for an H-shaped surface plasmon resonance (SPR) sensor. The phenomenon provides selective sensitivity response with different organic materials. The structure consists of coupled metal along with an analyte. Analyte that employs the SPR effects which is sensitive to material changes with the surrounding refractive index. The optical properties of used metals are evaluated on the emerged permeability and permittivity ascertained by the combined Drude and Lorentz model. Varieties of some organic materials to control the SP are investigated. Annealing of gold, palladium, titanium, and silver thin films, the model is formed. These metals can monitor the sensitivity changes of the concentration on the surface of sensor. In this study, the range of wavelength is 320–620 nm with an achieved refractive index of 1.37–1.42. The evaluated sensitivity is maximum while for silver among various metals which is almost $$\sim$$ 2.17 × 104 nm/RIU.

Synthesis of π-SnS thin films through chemical bath deposition: effects of pH, deposition time, and annealing temperature

In this work, details of deposition and characterization of π-SnS thin films with uniform and compact morphology deposited through chemical bath deposition are reported. Non-toxic tartaric acid is used as complexing agent. The effect of pH, deposition time, and annealing temperature on morphological, structural, chemical, optical, and electrical properties is investigated. The results show an increase in particle size with pH (5–8) and deposition time (2–6 h) in the as-deposited films, having values of 72–162 and 127–170 nm, respectively. Similarly, thickness increases with pH and deposition time in the range of 117–215 and 100–200 nm. The formation of π-SnS is demonstrated by XRD and TEM analyses (lattice parameter a ~ 11.556 A). Besides, Raman, FTIR, and XPS spectroscopy confirm the presence of some additional phases (SnO2) and impurities (CO− and COH). Optical measurements show that films have absorption coefficient higher than 104 cm−1, while band-gap values are in the range of 1.72–2.01 and 1.53–2.00 eV for the as-deposited and annealed films. Electrical studies exhibit an increase in the dark and photoconductivity with pH and deposition time. Finally, the influence of CO−, COH, and SnO2 on solar cells' performance is discussed.

Optical, electrical and morphological studies of βHgS thin film prepared by improved chemical bath deposition technique

Polycrystalline mercury sulphide (HgS) thin film at room temperature and in acidic condition was deposited on amorphous glass substrate by using improved chemical bath deposition technique. The structural and morphological analysis of as-deposited and annealed films was carried out by X-ray diffraction and scanning electronic microscopic technique. Ultraviolet and d.c. electrical resistivity measurement were made to study electrical and optical properties of the thin films. The outcome indicates formation of well-crystallized pure βHgS thin films having good electrical and optical properties. For this reason, HgS thin film in acidic medium was deposited properly by using chemical bath deposition technique.

Fabrication, micro-structure characteristics and transport properties of co-evaporated thin films of Bi2Te3 on AlN coated stainless steel foils

N-type bismuth telluride (Bi2Te3) thin films were prepared on an aluminum nitride (AlN)-coated stainless steel foil substrate to obtain optimal thermoelectric performance. The thermal co-evaporation method was adopted so that we could vary the thin film composition, enabling us to investigate the relationship between the film composition, microstructure, crystal preferred orientation and thermoelectric properties. The influence of the substrate temperature was also investigated by synthesizing two sets of thin film samples; in one set the substrate was kept at room temperature (RT) while in the other set the substrate was maintained at a high temperature, of 300 °C, during deposition. The samples deposited at RT were amorphous in the as-deposited state and therefore were annealed at 280 °C to promote crystallization and phase development. The electrical resistivity and Seebeck coefficient were measured and the results were interpreted. Both the transport properties and crystal structure were observed to be strongly affected by non-stoichiometry and the choice of substrate temperature. We observed columnar microstructures with hexagonal grains and a multi-oriented crystal structure for the thin films deposited at high substrate temperatures, whereas highly (00 l) textured thin films with columns consisting of in-plane layers were fabricated from the stoichiometric annealed thin film samples originally synthesized at RT. Special emphasis was placed on examining the nature of tellurium (Te) atom based structural defects and their influence on thin film properties. We report maximum power factor (PF) of 1.35 mW/m K2 for near-stoichiometric film deposited at high substrate temperature, which was the highest among all studied cases.