Characteristics of highly orientated BiFeO3 thin films on a LaNiO3-coated Si substrate by RF sputtering

BiFeO₃ (BFO) films were grown on LaNiO₃-coated Si substrate by a RF magnetron sputtering system at temperatures in the range of 300-700 °C. X-ray reflectivity and high-resolution diffraction measurements were employed to characterize the microstructure of these films. For a substrate temperature below 300 °C and at 700 °C only partially crystalline films and completely randomly polycrystalline films were grown, whereas highly (001)-orientated BFO film was obtained for a substrate temperature in the range of 400-600 °C. The crystalline quality of BFO thin films increase as the deposition temperature increase except for the film deposited at 700 °C. The fitted result from X-ray reflectivity curves show that the densities of the BFO films are slightly less than their bulk values. For the BFO films deposited at 300-600 °C, the higher the deposition temperature, the larger the remnant polarization and surface roughness of the films present.     

Low-temperature deposition of iridium thin films by pulsed laser deposition

Extremely smooth iridium (Ir) thin films were deposited on Si(1 0 0) substrate at lower temperature than 300 °C by pulsed laser deposition (PLD) technique using Ir target in a vacuum atmosphere. The crystal orientation, surface morphology, and resistivity of the Ir thin films were systematically determined as a function of substrate temperature. Well-crystallized and single-phase Ir thin films with (1 1 1) preferred orientation were obtained at substrate temperature of 200-300 °C. The surface roughness increased with the increasing of substrate temperature. Likewise, the room-temperature resistivity of Ir thin films decreased with increasing substrate temperature, showing a low value of (10.7±0.1) μΩ cm at 300 °C.     

Thin films of tetragonal zirconia (3Y-TZ) deposited by reactive sputtering

Thin films of tetragonal zirconia (TZ), comprised of 3 mol% Y₂O₃ (3Y-TZ), were deposited onto silicon, oxide-coated silicon, slide glass and aluminum oxide substrates by reactive sputtering of metallic targets in mixtures of oxygen and argon. The texture of deposited films varied with oxygen-to-argon flow ratios with which the target surface altered between metal and oxide compound constituents. Thin films of TZP with (2 0 0) preferred orientation were obtained from sputter deposition in the metallic mode whereas (1 1 1) texture was obtained in the compound mode at ambient temperature. The film texture tends to align along the 〈1 1 1〉 direction while the substrate was heated to 300 °C during the deposition. The texture of all these films was stable upon annealing at 900 °C in air. The reasons for the texture development are discussed.     

Optimization in fabricating bismuth telluride thin films by ion beam sputtering deposition

N-type bismuth telluride (Bi₂Te₃) thermoelectric thin films were deposited on BK7 glass substrates by ion beam sputtering method. Various substrate temperatures were tried to obtain optimal thermoelectric performance. The influence of deposition temperature on microstructure, surface morphology and thermoelectric properties was investigated. X-ray diffraction shows that the films are rhombohedral with c-axis as the preferred crystal orientation when the deposition temperature is above 250 °C. All the films with single Bi₂Te₃ phase are obtained by comparing X-ray diffraction and Raman spectroscopy. Scanning electron microscopy result reveals that the average grain size of the film is larger than 500 nm when the deposition temperature is above 300 °C. Thermoelectric properties including Seebeck coefficient and electrical conductivities were measured at room temperature, respectively. It is found that Seebeck coefficients increase from − 28 μV k^− 1 to − 146 μV k^− 1 and the electrical conductivities increase from 1.87 × 10³ S cm^− 1 to 3.94 × 10³ S cm^− 1 when the deposition temperature rose to 250 °C and 300 °C, respectively. An optimal power factor of 6.45 × 10^− 3 Wm^− 1 K^− 2 is gained when the deposition temperature is 300 °C. The thermoelectric properties of bismuth telluride thin films have been found to be strongly enhanced by increasing the deposition temperature.     

Studies on the residual stress of fluorine-doped SnO2 film deposited by chemical vapor deposition

Fluorine-doped tin oxide films were deposited on Na-Ca-Si glass substrate at 650 °C by chemical vapor deposition, and then heat treatment was carried out at 200 °C, 400 °C and 600 °C for 4 min in a resistance furnace. The residual stress in SnO₂:F films was systematically measured using the sin²Ψ method based on X-ray diffraction. The incidence angle was adopted as Ψ = 0°, 15°, 20°, 25° and 30°. The results showed that the films were polycrystalline with tetragonal SnO₂ structure, together with a weak peak of SnO phase. All the films exhibited a preferred orientation with the (200) plane. The minimum value of residual stress (− 0.24 ± 0.01 GPa) was obtained when the films were heat-treated at 200 °C.     

Influence of deposition temperature on structure and morphology of nanostructured SnO2 films synthesized by pulsed laser deposition

Nanostructured tin oxide thin films were deposited on the Si (100) substrate using the pulsed laser deposition technique at different substrate temperatures (300, 450 and 600 °C) in an oxygen atmosphere. The structure and morphology of the as-deposited films indicate that the film crystallinity and surface topography are influenced by the deposition temperature by changing from an almost amorphous to crystalline microstructure and smoother topography at a higher substrate temperature. The photoluminescence measurement of the SnO₂ films shows three stable emission peaks centered at respective wavelengths of 591, 554 and 560 nm with increasing deposition temperature, contributed by the oxygen vacancies.     

Deposition of silicon nitride thin films by hot-wire CVD at 100 °C and 250 °C

Silicon nitride thin films for use as passivation layers in solar cells and organic electronics or as gate dielectrics in thin-film transistors were deposited by the Hot-wire chemical vapor deposition technique at a high deposition rate (1-3 ?/s) and at low substrate temperature. Films were deposited using NH₃/SiH₄ flow rate ratios between 1 and 70 and substrate temperatures of 100 °C and 250 °C. For NH₃/SiH₄ ratios between 40 and 70, highly transparent (T ~ 90%), dense films (2.56-2.74 g/cm³) with good dielectric properties and refractive index between 1.93 and 2.08 were deposited on glass substrates. Etch rates in BHF of 2.7 ?/s and < 0.5 ?/s were obtained for films deposited at 100 °C and 250 °C, respectively. Films deposited at both substrate temperatures showed electrical conductivity ~ 10^− 14 Ω^− 1 cm^− 1 and breakdown fields > 10 MV cm^− 1.     

The electrical and optical properties of indium zinc tin oxide thin films with different Sn/Zn ratio

Indium zinc tin oxide (IZTO) thin films with two different chemical compositions, i.e. IZTO15 and IZTO25, where In content was fixed at 60 at.% and Sn content was 15 and 25 at.%, respectively, were deposited onto alkaline-free glass substrate at temperature from 37 °C to 600 °C. The deposition process was carried out in argon using an RF magnetron sputter. After deposition, the films were annealed in argon atmosphere at 450 °C for 30 min. The effect of substrate temperature and annealing treatment was investigated, and the minimum resistivity value of 3.44 × 10^− 4Ω.cm was obtained from the film deposited at 400 °C using IZTO25 target followed by rapid thermal annealing at 450 °C for 30 min. The average optical transmittance was kept fairly high over 80%. It was proven that both substrate temperature and thermal annealing were important parameters in lowering the electrical resistivity without deteriorating optical properties.     

ZnO thin films prepared by pulsed laser deposition

Zinc oxide (ZnO) thin films were deposited on soda lime glass substrates by pulsed laser deposition (PLD) in an oxygen-reactive atmosphere. The structural, optical, and electrical properties of the as-prepared thin films were studied in dependence of substrate temperature and oxygen pressure. High quality polycrystalline ZnO films with hexagonal wurtzite structure were deposited at substrate temperatures of 100 and 300 °C. The RMS roughness of the deposited oxide films was found to be in the range 2-9 nm and was only slightly dependent on substrate temperature and oxygen pressure. Electrical measurements indicated a decrease of film resistivity with the increase of substrate temperature and the decrease of oxygen pressure. The ZnO films exhibited high transmittance of 90% and their energy band gap and thickness were in the range 3.26-3.30 eV and 256-627 nm, respectively.     

Temperature dependence of the microstructure and resistivity of indium zinc oxide films deposited by direct current magnetron reactive sputtering

Indium zinc oxide (IZO) films were deposited as a function of the deposition temperature using a sintered indium zinc oxide target (In₂O₃:ZnO = 90:10 wt.%) by direct current (DC) magnetron reactive sputtering method. The influence of the substrate temperature on the microstructure, surface roughness and electrical properties was studied. With increasing the temperature up to 200 °C, the characteristic properties of amorphous IZO films were improved and the specific resistivity was about 3.4 × 10^− 4 Ω cm. Change of structural properties according to the deposition temperature was also observed with X-ray diffraction patterns, transmission electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. IZO films deposited above 300 °C showed polycrystalline phases evolved on the amorphous IZO layer. Very flat surface roughness could be obtained at lower than 200 °C of the substrate temperature, while surface roughness of the films was increased due to the formation of grains over 300 °C. Consequently, high quality IZO films could be prepared by DC magnetron sputtering with O₂/Ar of 0.03 and deposition temperature in range of 150-200 °C; a specific resistivity of 3.4 × 10^− 4 Ω cm, and the values of peak to valley roughness and root-mean-square roughness are less than 4 nm and 0.5 nm, respectively.     

Processing dependence of structural and physical properties of Mg2Ge thin films prepared by pulsed laser deposition

Magnesium germanide (Mg₂Ge) thin films were deposited on MgO (001) substrates using pulsed laser deposition technique. The films were deposited at various substrate temperatures, ranging from 300 to 600 °C. The effects of substrate temperature on structural, electrical and optical properties were studied. All the films, except the samples prepared at 300 °C, were polycrystalline with major diffraction from (200) plane. The highest electrical conductivity of 141.86 Ω^− 1 m^− 1 measured at room temperature was observed for the sample deposited at the highest temperature, with the corresponding charge carrier mobility and concentration of 2.62 cm² V/s and 8.66 × 10¹⁸ cm^− 3, respectively. The carrier concentration dependence of the optical absorption edge energy is accounted for by the Burstein-Moss shift. The variation of strain value may have also contributed to the change in bandgap energy. The reduction in direct bandgap energy was found to vary from 2.20 to 2.00 eV with increasing the deposition temperature.     

Growth and characterization of Bi2Se3 thin films by pulsed laser deposition using alloy target

Bi₂Se₃ thin films were deposited on the (100) oriented Si substrates by pulsed laser deposition technique at different substrate temperatures (room temperature −400 °C). The effects of the substrate temperature on the structural and electrical properties of the Bi₂Se₃ films were studied. The film prepared at room temperature showed a very poor polycrystalline structure with the mainly orthorhombic phase. The crystallinity of the films was improved by heating the substrate during the deposition and the crystal phase of the film changed to the rhombohedral phase as the substrate temperature was higher than 200 °C. The stoichiometry of the films and the chemical state of Bi and Se elements in the films were studied by fitting the Se 3d and the Bi 4d5/2 peaks of the X-ray photoelectron spectra. The hexagonal structure was seen clearly for the film prepared at the substrate temperature of 400 °C. The surface roughness of the film increased as the substrate temperature was increased. The electrical resistivity of the film decreased from 1 × 10⁻³ to 3 × 10⁻⁴ Ω cm as the substrate temperature was increased from room temperature to 400 °C.     

Preparation and characterization of pulsed laser deposited CdTe thin films at higher FTO substrate temperature and in Ar + O2 atmosphere

Pulsed laser deposition (PLD) is one of the promising techniques for depositing cadmium telluride (CdTe) thin films. It has been reported that PLD CdTe thin films were almost deposited at the lower substrate temperatures (<300 °C) under vacuum conditions. However, the poor crystallinity of CdTe films prepared in this way renders them not conducive to the preparation of high-efficiency CdTe solar cells. To obtain high-efficiency solar cell devices, better crystallinity and more suitable grain size are needed, which requires the CdTe layer to be deposited by PLD at high substrate temperatures (>400 °C). In this paper, CdTe layers were deposited by PLD (KrF, λ = 248 nm, 10 Hz) at different higher substrate temperatures (T_s). Excellent performance of CdTe films was achieved at higher substrate temperatures (400 °C, 550 °C) under an atmosphere of Ar mixed with O₂ (1.2 Torr). X-ray diffraction analysis confirmed the formation of CdTe cubic phase with a strong (1 0 0) preferential orientation at all substrates temperatures on 60 mJ laser energy. The optical properties of CdTe were investigated, and the band gaps of CdTe films were 1.51 eV and 1.49 eV at substrate temperatures of 400 °C and 550 °C, respectively. Scanning electron microscopy (SEM) showed an average grain size of 0.3–0.6 μm. Thus, under these conditions of the atmosphere of Ar + O₂ (15 Torr) and at the relatively high T_s (500 °C), an thin-film (FTO/PLD-CdS (100 nm)/PLD-CdTe (~1.5 μm)/HgTe: Cu/Ag) solar cell with an efficiency of 6.68% was fabricated.     

Synthesis of SrSnO3 thin films by pulsed laser deposition: Influence of substrate and deposition temperature

SrSnO₃ thin films were prepared by pulsed laser deposition on amorphous silica and single crystal substrates of R-sapphire, (100)LaAlO₃ and (100)SrTiO₃. High quality epitaxial (100) oriented films were obtained on LaAlO₃ and SrTiO₃ while a texture was revealed for films on sapphire deposited at the same deposition temperature of 700 °C. Amorphous films were obtained on silica but a post annealing at 800 °C induced crystallization with a random orientation. The screening of deposition temperature showed epitaxial features on SrTiO₃ from 650 °C while no crystallization was observed at 600 °C. The influence of substrate and deposition temperature was confirmed by Scanning Electron Microscopy and Atomic Force Microscopy observations.     

The effect of substrate temperature on Al-doped ZnO characteristics for organic thin film transistor applications

The influence of substrate temperature on the structural, electrical, and optical properties of aluminum-doped zinc oxide (AZO) films fabricated by radio frequency (RF) magnetron sputtering was investigated. The AZO films were deposited at various substrate temperatures, and the effect of AZO gate electrode conductivity on organic thin film transistor (OTFT) performance was examined. While an increase in the substrate temperature from 100 °C to 300 °C led to an improvement in crystallinity, substrate temperatures over 300 °C caused degradation of the electrical and surface properties. We fabricated OTFTs using AZO films prepared at various substrate temperatures and obtained good device performance. Thus, the performance of an OTFT can be determined by the conductivity of the AZO gate electrode.     

Deposition of hydroxyapatite thin films by Nd:YAG laser ablation: a microstructural study

Hydroxyapatite (HA) thin films has been successfully deposited by Nd:YAG laser ablation at λ = 532 nm. The morphology and microstructure of the deposited layers was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Polycrystalline HA films were directly obtained with the substrate at 300 °C and without introducing water vapors in the deposition chamber. Electron paramagnetic resonance (EPR) measurements show that the oxygen stoichiometry in the HA films is also maintained. Depositions performed at λ = 335 nm laser wavelength and 300 °C substrate temperature resulted in polycrystalline layers of mixed composition of HA and tricalciumphosphate (TCP).     

Low-temperature preparation of phosphorus doped μc-Si:H thin films by low-frequency inductively coupled plasma assisted chemical vapor deposition

The phosphorus doped n-type hydrogenated microcrystalline silicon (n-μc-Si:H) thin films are prepared, at the two low substrate temperatures of room temperature and 200 °C, through a low-frequency inductively coupled plasma assisted chemical vapor deposition. The effect of the substrate temperature on the structural properties of the thin films, such as the X-ray Diffraction (XRD) patterns and the Raman spectra, is studied. The XRD measurements show that the diffraction orientations of the thin films present an obvious change when the radio frequency power is increased from 1300 W to 2300 W. The Raman spectra of the thin films deposited at room temperature unambiguously present a phase transition from the amorphous structure to microcrystalline structure whereas no structural phase transition is observed for the thin films deposited at 200 °C. The effect of the substrate temperature on the crystalline volume fraction of the thin films presents a large difference for the radio frequency power in the range of 1300 W-1700 W, while the difference becomes small when the power is increased from 1700 W to 2300 W. The deposition rate and the radio frequency power-sheet resistance curve of the thin films deposited at room temperature are obviously different from those of the thin films prepared at 200 °C. It is attributed to the joint effect of the radio frequency power and substrate temperature on the doping concentration. The electron energy distribution function of the species in the chamber is mainly distributed in a low energy range.     

Pulsed electron beam deposition of transparent conducting Al-doped ZnO films

Good quality transparent conducting Al-doped ZnO films were deposited on quartz substrates from a high purity target using pulsed electron deposition (PED). Two series of films were made, one deposited at room temperature but at four pressures, viz., 0.7, 1.3, 2.0 and 2.7 Pa of oxygen and one deposited at 1.3 Pa oxygen pressure but at the substrate temperature ranged from room temperature to 600 °C. In order to evaluate the effect of substrate temperature and oxygen pressure on the properties of obtained films, various characterization techniques were employed including X-ray diffraction, stylus profiler, scanning electron microscope, optical spectrophotometer and electrical resistivity. For the first series films, the optimal oxygen pressure of 1.3 Pa was found to bring about the appropriate energetic deposition atoms which results in the best crystallinity. For the second series films, the lowest resistivity was obtained in the film grown at 400 °C. An attempt was made to reduce the resistivity by lowering the oxygen pressure to 0.5 Pa which was the lower limit of working pressure of the PED system. The obtained results indicate that PED is a suitable technique for growing transparent conducting ZnO films.     

The mechanical properties and resistivity of Au/NiCr/Ta multi-layered films on Si-(111) substrate

Au/NiCr/Ta multi-layered metallic films were deposited on Si substrate by magnetron sputtering at different substrate temperatures. The residual stress, hardness and resistivity were investigated as a function of substrate temperature by laser polarization phase shift technique, nanoindentation technique and four point probe method, respectively. The residual stress in as-deposited films at different substrate temperatures was tension with 385 MPa-606 MPa. Nanoindentation tests at shallow indentation depths (h ≤ t/4) where the hardness is reliable for metal films on hard substrate. Au film at deposition temperature 200 °C has the highest hardness 4.2 GPa. The resistivity in the deposited films reached the lowest value 3.1 μΩ.cm at substrate temperature 200 °C. The most interesting facts are that the hardness decreases with increasing residual stress and resistivity increases with increasing residual stress. The relationship of residual stress and resistivity may hint that there is a definite correlation between the mechanical properties and electrical properties in the metallic films.     

Transparent conducting Al and Y codoped ZnO thin film deposited by DC sputtering

Transparent conducting Al and Y codoped zinc oxide (AZOY) thin films with high transparency and low resistivity were deposited by DC magnetron sputtering. The effects of substrate temperature on the structural, electrical and optical properties of AZOY thin films deposited on glass substrates have been investigated. X-ray diffraction spectra indicate that no diffraction peak of Al₂O₃ or Y₂O₃ except that of ZnO (0 0 2) is observed. The AZOY thin film prepared at substrate temperature of 250 °C has the optimal crystal quality inferring from FWHM of ZnO (0 0 2) diffraction peak, but the AZOY thin film deposited at 300 °C has the lowest resistivity of 3.6 × 10⁻⁴ Ω-cm, the highest mobility of 30.7 cm² V⁻¹ s⁻¹ and the highest carrier concentration of 5.6 × 10²⁰ cm⁻³. The films obtained have disorderly polyhedral surface morphology indicating possible application in thin film solar cell with good quality and high haze factor without the need of post-deposition etching.