Post-annealed Thin Films Research Articles

Highly oriented GeSe2 thin film growth using a facile low-vacuum annealing method

Germanium diselenide (GeSe2), a chalcogen-based wide-bandgap semiconductor, has recently attracted interest as a low-symmetry layered material with peculiar in-plane anisotropy. The excellent air stability of ultra-thin GeSe2 flakes and impressive preliminary results for photodetection-based applications in the ultra-violet light region also make a new promising material in the field of optoelectronics. The throughput of thin GeSe2 crystal production on compatible substrates, however, has been extremely low, and accordingly, an improvement is essential. Herein, we report the preparation of crystalline GeSe2 thin films from non-crystalline continuous films of a Ge-Se mixture deposited on a-SiO2/Si substrates, and the crystal structure of the post-annealed thin films characterized by X-ray crystallography. Well-oriented crystalline grains with lateral sizes up to 50 µm were observed after an appropriate annealing procedure. This self-aligned growth could establish a facile approach for scaling-up production of oriented crystalline thin films of other Van der Waals layered materials besides GeSe2.

Effect of oxygen pressure and post-annealing on the properties of reactively sputtered zinc oxide thin films

• ZnO thin films are grown at room temperature on glass using radio-frequency sputtering. • As-grown ZnO films have wurtzite crystalline structure and direct bandgap behavior. • ZnO grown in O-rich and O-deficient plasmas shows annealing-sensitive crystallinity. • Bandgap energy evolution with deposition duration and post-annealing is investigated. • ZnO films with stable morphology and optical behavior are grown under some conditions. Using radio-frequency sputtering in the reactive regime at a fixed radio-frequency power of 200 W, we deposited zinc oxide thin films at room temperature on glass substrates in argon-oxygen sputtering atmospheres with different sputtering durations, and various oxygen contents from 20% to 70%. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmittance spectrophotometry were used to probe structural, morphological, chemical and optical properties of as-grown and post-annealed thin films in air at medium temperatures (up to 500 °C). The as-grown samples were found to present a hexagonal crystalline structure with a major (0 0 2) orientation and direct bandgap energies ranging from 3.27 to 3.3 eV. The post-annealing results in the improvement of crystallinity of ZnO thin films deposited at low oxygen contents and in the deterioration then the recrystallization of films deposited in oxygen-rich plasma. The optimal properties and thermal stability were obtained for 30% of oxygen in the sputtering environment, with an annealing-induced shrinkage of the bandgap smaller than 100 meV.

Magnetic Property of CoTbNi Ternary Alloy Thin Films

The structure and magnetic property of as prepared and post-annealed thin films of CoTbNi ternary alloy have been investigated. (Co0.85Tb0.15)1-xNix alloy thin films with x = (0.54, 0.63, 0.72, 0.81) were grown on Si-substrate by co-sputtering of Ni element and Co0.85Tb0.15 alloy using dc magnetron sputtering. These films have been crystallized in amorphous form, as confirmed by X-ray diffraction (XRD) measurement. The magnetization versus field measurements shows that these films exhibit room temperature ferromagnetism. The magnetic properties of these alloy films have a strong dependency on the Ni concentrations. It is observed that the saturation magnetization and coercivity of these alloy thin films decreases with increase of Ni content of the films. One of the striking features was the observation of perpendicular magnetic anisotropy (PMA) for x = 0.63 and 0.72 thin films. However, the observed PMA disappears upon post-annealing of the films. The M-T measurement shows that the ferromagnetic transition temperatures of these materials are much higher than the room temperature.

Rapid and Scalable Wire-bar Strategy for Coating of TiO2 Thin-films: Effect of Post-Annealing Temperatures on Structures and Catalytic Dye-Degradation.

Titanium dioxide (TiO2) thin films were rapidly coated on Corning glass substrates from the precursor solution using the wire-bar technique at the room temperature and then post-annealed at 400, 500 and 600 °C for 1 h under atmospheric conditions. The structural, morphological, optical, wettability and photocatalytic properties of the films were studied. X-ray diffraction analysis confirmed the formation of an anatase TiO2 structure irrespective of the post-annealing temperatures. The optical transparency of the films in the visible range was measured to be > 70%. A water contact angle (WCA) of ~0° was observed for TiO2 thin-film, post-annealed at 400 °C and 500 °C. However, WCA of 40.3° was observed for post-annealed at 600 °C. The photocatalytic dye-degradation using post-annealed thin-film was investigated indicating a steady improvement in the dye-degradation percentage (from 24.3 to 29.4%) with the increase of post-annealing temperature. The demonstrated TiO2 thin-films deposited by wire-bar coating technique showed promises for the manufacturing of large-area cost-effective self-cleaning window glass.

Effects of high temperature and film thicknesses on the texture evolution in Ag thin films

In situ high-temperature X-ray diffraction techniques were used to study the effect of high temperatures (up to $ 600 {}^{\circ}{\rm C}$ on the texture evolution in silver thin films. Ag thin films with different thicknesses of 40, 80, 120 and 160nm were sputtered on the Si(100) substrates at room temperature. Then, microstructure of thin films was determined using X-ray diffraction. To investigate the influence of temperature on the texture development in the Ag thin films with different thicknesses, (111), (200) and (220) pole figures were evaluated and orientation distribution functions were calculated. Minimizing the total energy of the system which is affected by competition between surface and elastic strain energy was a key factor in the as-deposited and post annealed thin films. Since sputtering depositions was performed at room temperature and at the same thermodynamic conditions, the competition growth caused the formation of the $ \{122\} \langle uvw \rangle$ weak fiber texture in as-deposited Ag thin films. It was significantly observed that the post annealed Ag thin films showed $ \{111\} \langle uvw \rangle$ orientations as their preferred orientations, but their preferred fiber texture varied with the thickness of thin films. Increasing thin film thickness from 40nm to 160nm led to decreasing the intensity of the $ \{111\} \langle uvw \rangle$ fiber texture.

Studies on the surface morphology and hydrophobic property of NiTi thin films under in situ and post annealing various temperatures

Surface morphology and hydrophobic property of NiTi thin films are investigated under various in situ and post annealing temperatures. The XRD and AFM results reveal that in situ annealed NiTi thin films crystallize at lower temperature and have larger surface roughness than post annealed samples. Heating during sputtering provides energy for atoms to move to position of equilibrium, thus more regular crystal structure is observed in in situ annealed NiTi thin films. Another reason for the smoother surface observed in post annealed thin films is that large amount of Ni4Ti3 precipitation in hinders the formation of B19′ phase. The contact angle becomes larger with the increase of surface roughness and the maximum contact angle of 123.5° is achieved in 600°C in situ annealed thin film with 41.7nm surface roughness.

Crystal growth of antimony substituted cobalt ferrites thin films deposited by electron beam

A series of antimony substituted cobalt ferrites (CoSb0.3Fe1.7O4) thin films have been deposited employing Electron Beam Deposition technique. The as deposited thin films have been post annealed at different temperature such as 200, 300, 400 and 500°C. The structural, surface, magnetic and optical properties of as-deposited and post annealed thin films have been studied using X-ray diffractometer, Raman spectroscopy, and Atomic Force Microscope, Vibrating Sample Magnetometer, spectroscopy ellipsometry and UV–vis techniques respectively. The X-ray diffraction and Raman spectroscopy analysis have confirmed the growth of single phase cubic spinel structure in thin films after post annealing. It is observed that the roughness of the thin films decreases and magnetization increases as the annealing temperature increases but not exceeded to as-deposited film. As the post annealing temperature increases the band gap energy increases which shows that the density of defects decreases and structure turn towards crystalline state from amorphous.

Microstructure evolution and crystallography of the phase-change material TiSbTe films annealed in situ

In this work, the morphology, crystallization process and crystal structure of the phase-change material TiSbTe (TST) alloy have been successfully established, which is essential for applying this alloy in phase-change memory. Specifically, atomic force microscopy (AFM) was employed to characterize the as-deposited and post-annealed thin films, and transmission electron microscopy (TEM) analyses of the films annealed in situ were used in combination with selected-area electron diffraction (SAED) and radial distribution function (RDF) analyses to investigate the structural evolution from the amorphous phase to the polycrystalline phase. Moreover, the presence of structures with medium-range order in amorphous TST, which is beneficial for high-speed crystallization, was indicated by the structure factors S(Q)s. The crystallization temperature was determined to be approximately 170 °C, and the grain size varied from several to dozens of nanometers. As the temperature increased, particularly above 200 °C, the first single peak of the rG(r) curves transformed into double shoulder peaks due to the increasing impact of the TiTe bonds. In general, the majority of Ti atoms were doped into the SbTe lattice and tended to form structural defects, whereas the remainder of the Ti atoms aggregated, leading to the appearance of TiTe2 phase separation, as confirmed by the SAED patterns, high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images and corresponding energy-dispersive X-ray (EDX) mappings.

Development of transparent conductive indium and fluorine co-doped ZnO thin films: Effect of F concentration and post-annealing temperature

In the present work ZnO, In doped ZnO and In-F co-doped ZnO (IFZO) films were synthesized on heated glass substrates (350°C) by the chemical spray technique. The effect of fluorine concentration on the structural, morphological, optical and electrical properties was studied. It was observed from X-ray diffraction (XRD) that the films have a polycrystalline structure and the intensity of the peaks depend on the doping and co-doping concentration. No diffraction peak related to dopants in XRD patterns along with shift in peaks angles to ZnO proved that In and F ions were doped into ZnO thin films. The Raman spectra confirm the hexagonal structure of the as-deposited films, and demonstrated an enhancement of the surface phonon mode of doped and co-doped films as compared to undoped films. The as-deposited films showed an average transmittance above 70%, in the wavelength range of 400–800nm. A minimum electrical resistivity, in the order of 5.2×10−2Ωcm was obtained for the IFZO thin film with 5at.% F doping. Moreover, the electrical properties of doped and co-doped films were enhanced after post-deposition annealing. It was found that post-annealed thin films at 350°C showed a decrease of one order of magnitude of the resistivity values. Such a transparent and conducting thin film can be suitable for optical and electrical applications owing to their low resistivity combined with high transmittance in the visible range.

Influence of addition of indium and of post-annealing on structural, electrical and optical properties of gallium-doped zinc oxide thin films deposited by direct-current magnetron sputtering

Abstract In this study, both gallium-doped zinc oxide (GZO) and indium-added gallium-doped zinc oxide (IGZO) thin films were deposited on commercial glasses by magnetron dc-sputtering in argon atmosphere. The crystal structure, electrical conductivity and optical transmission of as-deposited as well as post-annealed thin films of both GZO and IGZO were investigated for comparison. A small amount of indium introduced into GZO thin films had improved their polycrystalline structure and increased their electrical conductivity by over 29%. All obtained GZO and IGZO thin films have strong [002] crystalline direction, a characteristic orientation of ZnO thin films. Although post-annealed in air at high temperatures up to 500 °C, IGZO thin films still had very low sheet resistance of 6.6 Ω/□. Furthermore, they had very high optical transmission of over 80% in both visible and near-infrared regions.

Effect of Al doping on structural, optical and electrical properties of SnO2 thin films synthesized by pulsed laser deposition

Aluminium-doped (Al = 0–5 wt.%) SnO2 thin films with low-electrical resistivity and high optical transparency have been successfully synthesized by pulsed laser deposition technique at 500 °C. Structural, optical and electrical properties of the as-deposited and post-annealed thin films were investigated. X-ray diffraction patterns suggest that the films transform from crystalline to amorphous state with increasing aluminium content. The root mean square (Rq) surface roughness parameter, determined by atomic force microscopy decreases upon annealing of the as-deposited film. While resistivity of the film is the lowest (9.49 × 10−4 Ω-cm) at a critical doping level of 1 wt.% Al, optical transparency is the highest (nearly 90%) in the as-deposited condition. Temperature dependence of the electrical resistivity suggests that the Mott’s variable range hopping process is the dominant carrier transport mechanism in the lower temperature range (40–135 K) for all the films whereas, thermally activated band conduction mechanism seems to account for conduction in the higher temperature region (200–300 K).

Influences of post-annealing conditions on the formation of delafossite–CuFeO2 thin films

In this study, post-annealing conditions, the partial oxygen pressures (pO2) and temperatures, influence on the formation of delafossite–CuFeO2 thin films is studied. The sol–gel derived films were annealed at 500°C in air and post-annealed at 500–850°C in pO2=10−2 to pO2=5×10−5atm. The CuO and CuFe2O4 phases appeared when the sol–gel derived films were post-annealed below 800°C for 2h in pO2=10−2atm, 650°C for 2h in pO2=10−3atm, and 550°C for 2h in pO2=5×10−5atm. Pure delafossite–CuFeO2 phase was detected as specimens were post-annealed above 800°C for 12h in pO2=10−2atm, 650°C for 12h in pO2=10−3atm, and 550°C for 12h in pO2=5×10−5atm. The surface of post-annealed thin films exhibited a nanoparticle-like morphology when the specimens exhibited CuO and CuFe2O4 phases. However, the surface revealed granular features caused by the formation of the delafossite–CuFeO2 phase. The formation of the delafossite–CuFeO2 phase, which resulted from the chemical reaction of the CuO and CuFe2O4 phases in the post-annealing process, is consistent with thermodynamics. The optical bandgaps of delafossite–CuFeO2 thin films prepared using post-annealing ranged between 3.1 and 3.2eV. The electrical conductivities of delafossite–CuFeO2 thin films were (1.62–6.37)×10−1Scm−1 and the carrier concentrations were (1.52–8.84)×1017cm−3. The pO2 and temperatures in the post-annealing process played primary roles in the formation of delafossite–CuFeO2 thin films in this study.

A comparative study of the structural and electrical properties of n-type InGaN epilayer grown by MBE and commercially

Abstract This work reports the growth of n-In 0.27 Ga 0.73 N/GaN/AlN epitaxial layer on Si(1 1 1) substrate by using plasma-assisted molecular beam epitaxy (MBE) and commercially obtained n-In 0.08 Ga 0.92 N/AlN. As-grown and commercial thin films were characterized by using field emission scanning electron microscopy, atomic force microscopy, and high-resolution X-ray diffraction. A high work function metal (Pt) was deposited as metal contact on the thin films, and the electrical characteristics of the films pre- and post-annealed at 500 °C were studied under 3 V. Results show that the electrical characteristics of post-annealed thin films are better than those of pre-annealed thin films.

Bi1.5Zn1.0Nb1.5O7 thin films deposited at low temperature and post-annealed for crystallization

Near-stoichiometric Bi1.5Zn1.0Nb1.5O7 (BZN) thin films were prepared on Pt/TiO2/SiO2/Si (100) substrates at 400 °C under an oxygen pressure of 10 Pa by using pulsed laser deposition process. The as-deposited BZN thin films were post-annealed at 700 °C for 30 min in situ vacuum chamber (in situ) and in oxygen ambient oven (ex situ). The crystallinity, microstructure and electrical properties of BZN thin films were investigated. The X-ray diffractometer results indicate that BZN thin films deposited at 400 °C are amorphous in nature and the post-annealed thin films exhibit a cubic pyrochlore structure. The as-deposited BZN thin films show permittivity of 68 and loss tangent of 0.0011 at 10 kHz, respectively. After a post-annealing at 700 °C for 30 min, the dielectric properties of thin films are significantly improved. Permittivity and loss tangent of the in situ annealed films are 127 and 0.005 at 10 kHz, respectively. And the films post-annealed in O2 oven show the largest permittivity of 170 and tangent of 0.006. The improved dielectric properties can attribute to the crystallization of thin films. BZN thin films deposited at low temperature and crystallized at high temperature show the dielectric tunability without an electric breakdown to the maximum measurement bias voltage. And BZN thin films also show the excellent leakage current properties.

Direct observation of phase transition of GeSbTe thin films by Atomic Force Microscope

GeSbTe (GST) thin films were deposited on quartz substrates using electron beam evaporation system and then annealed in nitrogen atmosphere at different temperatures, ranging from 20°C to 300°C. X-ray diffraction (XRD) and Atomic Force microscope (AFM) measurements were used to characterize the as-deposited and post-annealed thin films. Annealing treatment was found to induce changes on microstructure, surface roughness and grain size, indicating that with the increase of annealing temperature, the amorphous GST films first changed to face-centered-cubic (fcc) phase and then the stable hexagonal (hex) phase.Meanwhile, conductive-AFM (C-AFM) was used to produce crystallized GST dots on thin films. I–V spectroscopy results show that GST films can switch from amorphous state to crystalline state at threshold voltage. After switching, I–V curve exhibits ohmic characteristic, which is usually observed in crystallized GST films. By applying repeated I–V spectroscopies on the thin films, crystallized nuclei were observed. As the times of I–V spectroscopies increases, the area of written dots increases, and the center of the mark begin to ablate. The AFM images show that the shape of marks is an ablated center with a raised ring surrounding it.

Growth of Sc-Doped TiO2 Thin Film by RF Magnetron Sputtering

Sc-doped TiO2 (Ti1-xScxO2-δ) thin film on Al2O3 substrate were prepared by RF magnetron sputtering using ceramics targets. The Ti1-xScxO2-δ thin films deposited at room temperature were crystallized by postannealing at 800 °C for 1 h in O2 atmosphere. The thin films exhibited the single phase of rutile at x=0, the single phase of anatase at x=0.01 and mixed phases of rutile and anatase at x=0.03, and 0.05. The postannealed thin films were very smooth surface. In the absorption spectra, the fundamental absorption edge of Ti0.99Sc0.01O2-δ thin film with anatase phase shifts to lower wavelength side than those of x=0, 0.03, and 0.05. The small Sc doping for TiO2 thin film contributes to the changes of band gap, lattice constant and crystal structure. The existence of acceptor-doped TiO2 may realize practical application of a wide gap semiconductor diode in blue-light region or fuel cell, which used oxide material.

Lead titanate thin film synthesis by solid-state reactions

The formation of perovskite PbTiO3 thin films by annealing in atmosphere metallic (Ti/Pb)x multilayer structure (1μm) was investigated in this work. Deposited thin films were annealed in atmosphere at different temperatures (600–650°C) and times (20–180min). The reaction processes of PbTiO3 formation were researched by changing annealing temperature and time. Structure changes, phase composition transition of as deposited and post-annealed thin films were measured and analyzed using X-ray diffraction method. The kinetic reactions and crystallites growth’s regularities in annealed thin films were investigated too. The surface morphology were investigated by SEM microscopy.

Microstructural and Electrical Characterization of Barium Strontium Titanatebased Solid Solution Thin Films Deposited on Ceramic Substrates by Pulsed Laser Deposition

AbstractFerroelectrics are multicomponent materials with a wealth of interesting and useful properties, such as piezoelectricity. The dielectric constant of the BSTO ferroelectrics can be changed by applying an electric field. Variable dielectric constant results in a change in phase velocity in the device allowing it to be tuned in real time for a particular application. The microstructure of the film influences the electronic properties which in turn influences the performance of the film. Ba0.6Sr0.4Ti1-y(A 3+, B5+)yO3 thin films, of nominal thickness of 0.65 μm, were synthesized initially at substrate temperatures of 400°C, and subsequently annealed to 750°C, on LaAlO3 (100) substrates, previously coated with LaSrCoO conductive buffer layer, using the pulsed laser deposition technique. The microstructural and physical characteristics of the postannealed thin films have been studied using x-ray diffraction, scanning electron microscopy, and nano indentation and are reported. Results of capacitance measurements are used to obtain dielectric constant and tunability in the paraelectric (T>Tc) regime.

Chemical Vapor Deposition of HfO2 Thin Films Using a Novel Carbon-Free Precursor: Characterization of the Interface with the Silicon Substrate

thin films were deposited on Si wafers by a chemical vapor deposition (CVD) technique at temperatures ranging from 200 to 400°C using a new carbon-free precursor The growth behavior was under a steady state when the interfacial oxide layer was excluded in film thickness estimation by ellipsometry. The as-grown interfacial layer formed at 200°C was apparently composed of Hf, Si, and O. Postannealing under a atmosphere at temperatures >500°C resulted in a decrease in interfacial layer thickness by decomposition of the Hf-Si-O layer to and The film showed a crystalline microstructure even in the as-deposited state when the film thickness was 170 Å. However, the films were amorphous when the film thickness was <70 Å. The dielectric constant of the as-deposited and postannealed thin films were approximately 18 and 22, respectively. © 2001 The Electrochemical Society. All rights reserved.

Transmission electron microscopy study of low-temperature post-annealed thin films

A transmission electron microscopy study was carried out on three typical low-temperature post-annealed (2212) thin films on (100) substrates. The microstructural features of the film with showed many stacking faults, grain boundaries, microcracks, large voids and large impurity particles. At the film - substrate interface the residual amorphous precursor film was present intermittently. The film with has a better microstructure than the previous film but, on the slope of the step, the film remains amorphous in structure. The film with is relatively uniform with some stacking faults. The spacing of the lattice fringes is , which corresponds to the (002) plane of 2212. This film is c-axis oriented and epitaxially grown on the substrate.