Effect Of Post-deposition Thermal Annealing Research Articles

Plasma assisted pulsed laser deposition of WO3 films for thermochromism

Tungsten trioxide (WO3) is one of the extensively investigated transition metal oxides. Its excellent chromogenic properties make WO3 promising for a variety of scientific and technological applications. We report a new method for reactively depositing WO3 films by plasma assisted pulsed laser deposition that combines electron cyclotron resonance microwave discharge and pulsed laser ablation. The plasma formed during film deposition was spectroscopically characterized by optical emission measurement, revealing that the plasma contains high density of reactive gaseous oxygen and tungsten species which are essential for efficiently synthesizing WOx precursors and depositing WO3 films. The structure of the deposited films and the effect of post-deposition thermal annealing on the film structure were characterized by X-ray diffraction and Raman spectroscopy. The as-deposited WO3 film appears amorphous in nature. Annealing resulted in the growth of crystalline grains and the improvement in the crystallinity of monoclinic WO3. Optical properties of the prepared WO3 films were studied by measuring ultraviolet–visible–near infrared transmission spectra. With the increase of annealing temperature, the WO3 films show a continuous change in color, decline in transmittance, red shift in absorption edge, and narrowing in band gap, clearly manifesting the thermochromic features of the deposited WO3 films.

Annealing Impact on the Evolution of Crystalline Phases and Emission in Si-Rich HfO2:Nd Films Obtained By Magnetron Sputtering

Hafnium oxide films doped with Si and Nd atoms have been produced by radio-frequency magnetron sputtering in pure argon plasma followed by an annealing in nitrogen atmosphere for 1-60 minutes at the temperature 1000 °C. The effect of post-deposition thermal annealing on the transformation of crystalline phases and photoluminescence spectra was investigated by the non-destructive methods (scanning electronic microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman scattering and photoluminescence(PL)). The XRD analysis of these samples demonstrate the phase separation process which depends on the time range and the annealing temperature. In the studed samples, the formation of the tetragonal HfO2, tetragonal SiO2 and cubic Si phases was observed by XRD and confirmed by the Raman study. Thermal annealing influents also on PL spectra where the main bands were detected at 380, 450, 550, 780 and 880 nm. The emission and excitation mechanisms for the Nd radiative defects, and the impact of phase transformation in studied films, are analyzed and discussed.

Structure and Emission Evolution in Si-Rich HfO2:Pr Films Versus Annealing Temperature

Pr-doped Si-rich-HfO2 films with specific emitting and structural properties have been prepared by radio-frequency magnetron sputtering using standard pure argon plasma approach. The effect of post-deposition thermal annealing on the transformation of crystalline phases, their compositions and photoluminescence spectra was investigated by means of the Energy Dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), scanning electronic microscopy (SEM), Raman scattering and photoluminescence (PL) methods. Thermal annealing was carried out at 800 °C, 900 °C, 1000 °C and 1100 °C within time of 30 min in nitrogen atmosphere. The SEM images demonstrate the grains with the size about 40 nm. It was observed that the influence of temperature at annealing causes the phase transformation and separation processes. In studied samples, the formation of the tetragonal HfO2 and SiO2 phases, were detected at XRD study after the annealing at 1000 and 1100 °C. PL spectra of these films are complex and demonstrate several PL bands centered at 442, 479, 523, 607, 637 and 716 nm. Their contribution depends on the annealing temperature and governs the shape of total PL spectra. The impact of crystalline phase separation on the peculiarities of PL spectra and XRD are analyzed and discussed.

Annealing of silicon carbonitride nanostructured thin films: interdependency of hydrogen content, optical, and structural properties

Silicon carbonitride (SiCxNy) materials, inspired by their outstanding multifunctional properties, are finding increasing applications in a variety of fields, including as next generation solar cells and hard coatings. Hydrogenated SiCxNy thin films, along with binary submatrices of stoichiometric SiC and SiN3 as a reference, were deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition. We described a comparative study of the effects of post-deposition thermal annealing, from 300 to 1200 °C, on the evolution of hydrogen-rich a-SiC1.2N0.7:H1.4 thin films. Concurrently, two featured annealing temperatures (500 and 900 °C) were found to have the significant influence on the morphology, optical, and microstructural properties of the films. During annealing the amorphous phase of SiC1.2N0.7:H1.4 thin films was fully maintained according to the transmission electron microscopy and X-ray diffraction analyses. The hydrogen density was quantitatively analyzed employing two different experimental techniques, elastic recoil detection and Fourier transform infrared spectroscopy, showing the associate annealing temperatures of hydrogen desorption, breaking of all hydrogen-terminated bonds, and depletion of all hydrogen content. The refractive indices and optical band gap of the films were calculated using variable angle spectroscopic ellipsometer. Thermal annealing resulted in hydrogen desorption and consequently layer densification along with an increase in the refractive index. During the annealing process, first the optical band gap widened, and then narrowed due to hydrogen out-diffusion or chemical bond restructuring, depending on the annealing temperature. In addition, Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy were performed. These findings are discussed in the context of the interdependency of the hydrogen desorption and thermally induced changes in chemical bonds, mass density, and optical properties.

Thermal annealing effect on nitrogen-doped TiO2 thin films grown by high power impulse magnetron sputtering plasma power source

The work reports plasma assisted growth of nitrogen-doped titanium dioxide (N-TiO2) thin films using high power impulse magnetron sputtering (HiPIMS) power source and effect of post-deposition thermal annealing. The films were deposited at low pressure. The binding energies of elements of interest, the energy gap, crystallinity and morphology of the films were analyzed before and after annealing. The results showed an increase in binding energies, a fact attributed to enhanced oxidation, after the annealing process. Only nitrogen doped samples grown by HiPIMS exhibited the presence of substitutional nitrogen. The energy gap of the films was found to decrease after doping and annealing. Improvement in crystallinity with a small shift in the crystalline peaks indicating decrease in lattice parameter, which could be seen by surface smoothing, was observed after thermal annealing. As a result of the growth of films by HiPIMS, nitrogen doping and post-deposition thermal annealing, improvements in the properties of the films which have relevance for photocatalytic and energy applications were observed.

Thermal annealing effect on ZnO surface acoustic wave-based ultraviolet light sensors on glass substrates

Surface acoustic wave (SAW) based ultraviolet (UV) light sensors have a high sensitivity and have been extensively studied and explored for application. However, all of them were made of piezoelectric (PE) bulk materials or PE thin films on crystalline substrates such as Si and sapphire. This paper reports the fabrication of ZnO thin film SAW UV-light sensors on glass substrates and the effect of post-deposition thermal annealing on the sensing performance. It was found that annealing at temperatures higher than 300 °C can improve the properties of ZnO films and the sensing performance of the UV-sensors remarkably. When the ZnO film annealed at 400 °C was used for sensors, the UV light induced resonant frequency shift increased more than 20 times with the response speed reduced to less than 2.4 s, much better than those made on ZnO films with lower temperature annealing.

SrTiO<sub>3</sub> Thin Films Deposition Using Pulsed Laser Deposition Technique

Strontium titanate (SrTiO3) thin film has been deposited on Si (100) substrate using pulsed laser deposition technique. Film deposition was carried out at low temperature (150°C) by maintained the pressure at 10-4 Torr. Nanometer-thick SrTiO3 film on Si substrate was characterized using SEM, AFM, XRD, and Raman Spectroscopy. SEM and AFM images show that SrTiO3 film has growth on Si substrate uniformly. Raman and XRD spectroscopy also support the growth of SrTiO3 film on Si substrate. Furthermore, to investigate the effect of post-deposition thermal annealing, the samples were annealed up to 900°C. Thermal stability of SrTiO3/Si structure was studied by mean XRD spectra. The X-Ray Diffraction pattern indicates the crystallinity improvement through atomic arrangements during thermal annealing process.

SrTiO<sub>3</sub> Thin Films Deposition Using Pulsed Laser Deposition Technique

Strontium titanate (SrTiO3) thin film has been deposited on Si (100) substrate using pulsed laser deposition technique. Film deposition was carried out at low temperature (150°C) by maintained the pressure at 10-4 Torr. Nanometer-thick SrTiO3 film on Si substrate was characterized using SEM, AFM, XRD, and Raman Spectroscopy. SEM and AFM images show that SrTiO3 film has growth on Si substrate uniformly. Raman and XRD spectroscopy also support the growth of SrTiO3 film on Si substrate. Furthermore, to investigate the effect of post-deposition thermal annealing, the samples were annealed up to 900°C. Thermal stability of SrTiO3/Si structure was studied by mean XRD spectra. The X-Ray Diffraction pattern indicates the crystallinity improvement through atomic arrangements during thermal annealing process.

Improvement in carrier transport properties by mild thermal annealing of PbS quantum dot solar cells

We studied the effect of post-deposition thermal annealing in the preparation of PbS quantum dot (QD) solar cells. We find an optimal annealing temperature that improves the power conversion efficiency by a factor of 1.5 for different sized QDs with bandgaps of 1.65 and 1.27 eV. We examined the onset of the photocurrent response and correlated that with domain grain growth and find that annealing the PbS QD array at 120 °C causes little change in the PbS QD size, bandgap, and open-circuit voltage and yet leads to an increase in the carrier transport as realized by an improved current response. We also find a decrease in the activation energy of a shallow trap, which also likely contributes to the improvement in the solar cell efficiency.

Synthesis and effect of post-deposition thermal annealing on morphological and optical properties of ZnO thin film

Zinc oxide thin films have been deposited on glass substrates by the chemical bath deposition method; a surfactant, cetyltrimethylammonium bromide (CTAB); was used as capping agent. The films were annealed at two different temperatures: 200 and 300 °C. The structural features were investigated by X-ray diffraction analysis which exhibited hexagonal wurtzite structures along with c-axis orientations. Crystallite size was estimated and found to be around 33–41 nm. The effect of post-deposition thermal annealing on the morphological and optical properties has been investigated by scanning electron microscopy and photoluminescence spectra at room temperature. The band gap energies of uncapped and CTAB-capped ZnO films were found to be 3.28 and 3.48 eV, respectively.

Postdeposition thermal annealing and material stability of 75 °C hydrogenated nanocrystalline silicon plasma-enhanced chemical vapor deposition films

This paper examines the material stability and effects of postdeposition thermal annealing of highly crystalline undoped hydrogenated nanocrystalline silicon (nc-Si:H) films prepared by conventional 13.56-MHz plasma-enhanced chemical vapor deposition at 75 °C. Electrical, structural, and chemical composition properties of the nc-Si:H films at ambient atmosphere were studied before and after the thermal annealing. The as-grown nc-Si:H films showed not only a low dark conductivity (σdark) of the order of 10−7–10−6S∕cm but also good stability after exposure to ambient atmosphere due to low oxygen concentration (CO∼2×1018atoms∕cm3) and stable hydrogen passivation of grain boundaries. On the other hand, the σdark and photoconductivity (σphoto) of the nc-Si:H films showed instability during annealing at temperatures higher than the deposition temperature and subsequent exposure to ambient atmosphere. Here, both the σdark and σphoto increased after annealing and then decreased with exposure to ambient atmosphere. In particular, the σdark decreased below the as-grown value proportional to the annealing temperature. This was not observed in nc-Si:H films which have a hydrogenated amorphous silicon nitride (a-SiN:H) passivation layer on the same time scale. There was no significant change in the microstructure of the films. However, the hydrogen concentration (CH) decreased slightly after annealing, while the CO increased. The conductivity instability is therefore strongly related to oxygen desorption and absorption due to thermal annealing and subsequent exposure to ambient atmosphere, respectively. Based on the experimental results, we propose a simple model in terms of hydrogen effusion-assisted oxygen absorption.

Thermal Annealing of Patterned Metal Surfaces

The fabrication of nano/micropatterned metallic samples by deposition techniques is one of the most relevant topics in modern technologies. The physical properties of the patterned film depend markedly on the morphology and size of the grains that constitute the building blocks of the system. Therefore, the study of possible routes for modifying grain size without distortion of the nano/micropattern is a crucial point for the fabrication of metallic samples with specific structural and physical properties. Here, we study the effect of postdeposition thermal annealing on nano/micropatterned standing free copper films. Results show that for temperatures T < 0.5Tm, with Tm being the melting temperature, thermal treatment for short times increases grain size and improves the electric conductivity of the sample without distortion of nano/micropatterns with wavelengths in the micrometer range.

Characteristics of copper films deposited on H2-plasma-treated TaN substrate by chemical vapor deposition

This work investigates the chemical vapor deposition Cu films deposited on the TaN substrate with and without an H2-plasma treatment prior to Cu film deposition and the effect of postdeposition thermal annealing. The Cu films deposited on the H2-plasma-treated TaN substrate have a number of favorable properties over the films deposited on the TaN substrate without the plasma treatment. These include an increased (111)-preferred orientation, smoother film surface, and a larger effective deposition rate. However, the Cu films deposited on the H2-plasma-treated substrate have a higher electrical resistivity, presumably due to the smaller grain size. The postdeposition thermal annealing enhanced the (111)-preferred orientation and decreased the resistivity of the as-deposited Cu films. We presume that the H2-plasma treatment, resulted in a dense and uniform distribution of hydrogen radicals adsorbed on the substrate surface, leading to the shortening of incubation time and the formation of Cu films with a smoother surface and enhanced (100)-preferred orientation. A combined process including H2-plasma substrate treatment prior to Cu film deposition and postdeposition thermal annealing at an appropriate temperature in N2 ambient, is proposed for the advantage of low-resistivity and high (111)-oriented Cu film deposition.

Effects of substrate defect density and annealing temperature on the nature of Pt clusters vapor deposited on the basal plane of highly oriented pyrolytic graphite

The influence of substrate defect sites on the morphology of Pt vapor deposited on the basal plane of highly oriented pyrolytic graphite (HOPG(bp)) has been investigated in situ (in ultrahigh vacuum (UHV)) by X-ray photoelectron spectroscopy (XPS), and ex situ by high-resolution scanning electron microscopy (HRSEM), and scanning tunneling microscopy (STM). Defects were introduced on selected sections of HOPG(bp) surfaces via Ar + bombardment by employing specially designed masks. The effect of such defects on the electronic and structural nature of the Pt clusters formed was examined by evaporating the metal simultaneously on both damaged and nominally pristine sections of HOPG(bp). HRSEM and STM images of Pt deposits formed at 300 K on pristine HOPG(bp) were found to display three-dimensional fractal-type aggregates. Image analysis of such Pt clusters gave a fractal dimension D L=1.7 for Pt on Pt, using area ( A)/perimeter ( P) relations, and D L=1.5 for Pt on HOPG(bp), based on the count box method. Possible origins of this difference include higher cluster edge atom diffusion rates for Pt in the first monolayer (ML) and/or small cluster mobilities as in the model investigated by Meakin [Phys. Rev. Lett. 51 (1983) 1119.]. This overall behavior was unlike that observed for Pt vapor deposited on sections of Ar +-bombarded HOPG(bp) surfaces, which yielded instead clusters roughly circular in shape, ca. 1 nm in diameter, and one to two atomic layers high. Such disparate morphologies, however, are in agreement with models proposed in the literature which predict formation of highly ramified structures for diffusion limited aggregation (DLA) on substrates with low density of defect sites and small round clusters when the defect density is increased. Also studied in this work were the effects of post-deposition thermal annealing on the nature of the deposits.

Effects of TaN Substrate Pretreatment by Ar Plasma on Copper Chemical Vapor Deposition

CVD Cu films deposited on TaN substrates with and without an Ar plasma treatment prior to Cu film deposition and the effects of postdeposition thermal annealing were investigated. Cu films deposited on an Ar-plasma-treated TaN substrate have a number of favorable properties over the films deposited on a TaN substrate without the plasma treatment. These include a smoother film surface, regular arrangement of Cu grains, and increased (111)-preferred orientation. The postdeposition thermal annealing enhanced the (111)-preferred orientation and decreased the resistivity of the as-deposited Cu films. As the results of Ar plasma substrate pretreatment, we presume that the smoother and amorphous-like surface layer of the TaN substrate enhanced the formation of the most stable (111) texture Cu films, and that the higher substrate surface energy resulted in Cu films with smoother surface and regularly shaped smaller grains. Thus, a combined process including Ar plasma substrate treatment prior to Cu film deposition and postdeposition thermal annealing at an appropriate temperature in ambient is proposed for the advantages of low-resistivity and high (111)-oriented Cu film deposition. © 2002 The Electrochemical Society. All rights reserved.

Chemically Vapor Deposited Cu Films on Ar-Plasma-Treated TiN Substrate

Chemically vapor deposited (CVD) Cu films on TiN substrates with and without Ar plasma treatment prior to Cu film deposition and the effects of postdeposition thermal annealing were investigated. Cu films deposited on an Ar-plasma-treated TiN substrate have a number of favorable properties over films deposited on a TiN substrate without the plasma treatment. These include a smoother film surface, regular arrangement of Cu grains, and markedly increased (111)-preferred orientation. The postdeposition thermal annealing enhanced the (111)-preferred orientation and decreased the resistivity of the as-deposited Cu films. A combined process including Ar plasma substrate treatment prior to Cu film deposition and postdeposition thermal annealing at an appropriate temperature in N2 ambient is proposed in order to achieve low-resistivity and highly (111)-oriented Cu film deposition. In this way, Cu films with a resistivity of 1.90 µΩ·cm and a Cu(111)/Cu(200) peak ratio of 7.08 were obtained.

Effect of interface structure modifications on the properties of some magnetic multilayers

The effect of post-deposition thermal annealing on the interface structures of crystalline Fe–Tb multilayers and the associated changes in perpendicular magnetic anisotropy (PMA) has been studied using X-ray reflectivity, X-ray diffuse scattering and conversion electron Mössbauer spectroscopy. The main effect of annealing is a demixing at the interfaces attributed to a positive heat of mixing between Fe and Tb. Demixing is accompanied by a decrease in PMA due to increased shape anisotropy of the crystalline Fe layer. The results are compared with the effect of heavy ion irradiation in the same system.

Evolution of the Molecular Organization in Bis(n-propylimido)perylene Films under Thermal Annealing

Submicron thin solid films of bis(n-propylimido)perylene have been fabricated on several substrates by vacuum evaporation. The effect of postdeposition thermal annealing on the molecular orientation was examined using in situ reflection absorption infrared spectroscopy. The interpretation of the vibrational infrared and Raman spectra of the neat material and films was first undertaken to provide the vibrational backgrounds for the interpretation of changes observed on thermal annealing by reflectance spectroscopy. The spectroscopic characterization include FT Raman, electronic, and emission spectra of solutions, bulk solid, and nanometric films.

Structure and properties of thermally annealed fullerene films

The effects of postdeposition thermal annealing on the structure and properties of C 60 films are investigated. Non-oxygenated C 60 films are heated at 200°C under vacuum. UV/visible absorption spectroscopy shows a decrease in the intensities of the allowed transitions and a red-shift of up to 50 run. IR analyses show no indication of chemical alteration of the sample. X-ray studies reveal cubic symmetry in the unannealed thin films, while the annealed films show a mixture of face-centred cubic and hexagonal close-packed phases and a higher degree of crystallinity. Room-temperature Raman studies in the region of the pentagonal pinch mode reveal the presence of two components. The first component, at 1468 cm −1, is photochemically unstable, as is the pristine material. The second component, positioned at 1464 cm −1, remains stable under prolonged low-intensity illumination. The effects of thermal annealing of oxygen-free films are contrasted to those of thermal treatment under oxygen and it is concluded that the modifications are structural in nature.