Mechanical Properties and Microstructural Characterization of Amorphous SiCxNy Thin Films After Annealing Beyond 1100°C

The effect of thermal annealing on structure and mechanical properties of amorphous SiC_xN_y (y ≥ 0) thin films was investigated up to 1500°C in air and Ar. The SiC_xN_y films (2.2–3.4 μm) were deposited by reactive DC magnetron sputtering on Si, Al₂O₃ and α‐SiC substrates without intentional heating and at 600°C. The SiC target with small excess of carbon was sputtered at various N₂/Ar gas flow ratios (0–0.48). The nitrogen content in the films changes in the range 0–43 at.%. Hardness and elastic modulus (nanoindentation), change in film thickness, film composition, and structure (Raman spectroscopy, XRD) were investigated in dependence on annealing temperature and nitrogen content. All SiC_xN_y films preserve their amorphous structure up to 1500°C. The hardness of all as‐deposited and both air‐ and Ar‐annealed SiC_xN_y films decreases with growth of nitrogen content. The annealing in Ar at temperatures of 1100°C–1300°C results in noticeable hardness growth despite the ordering of graphite‐like structure in carbon clusters in nitrogen free films. Unlike the SiC, this graphitization leads to hardness saturation of SiCN films starting above 900°C, especially for films with higher nitrogen content (deposited at higher N₂/Ar). This indicates the practical hardness limit achievable by thermal treatment for SiC_xN_y films deposited on unheated substrates. The ordering in carbon phase is facilitated by the presence of nitrogen in the films and its extent is controlled by the N/C atomic ratio. The suppression of graphitization was observed for N/C ranging between 0.5–0.7. Films deposited at 600°C show higher hardness and oxidation resistance after annealing in comparison with those deposited on unheated substrates. Hardness reaches 40 GPa for SiC and ~28 GPa for SiC_xN_y (35 at.% of nitrogen). Such a high hardness of SiC film stems from its partial crystallization. Annealing of SiC_xN_y film (35 at.% of N) in Ar at 1400°C is accompanied by formation of numerous hillocks (indicating heterogeneous structure of amorphous films) and redistribution of film material.     

Air-based sputtering deposition of titanium oxynitride-based single,gradient, and multi-layer thin films for photoelectrochemical applications

Titanium oxynitride (TiN_xO_y) thin films exhibiting tunable physical and chemical properties can be used in many fields. Air-based sputtering deposition of the films with diverse O/N ratios was employed to produce gradient and multilayer films. By solely altering the air/Ar flow ratio, obtained TiN_xO_y films could change from a crystalline to a mainly amorphous feature. Moreover, the carrier concentration, Hall mobility, and hence resistivity of the films could be modified to a large range. The optical bandgaps of the films could also be tailored to a wide extent. Based on these results, the gradient TiN_xO_y layer and TiN_xO_y/TiN(O) multilayer were also deposited on TiN(O)-coated glass substrates for the assessment of photoelectrochemical performance. Compared with the TiN_xO_y/TiN(O) bilayer with the best photoelectrochemical performance, the photoelectrochemical currents of gradient TiN_xO_y films could be improved from 99 ± 2 μA⋅cm⁻² to 164 ± 2 μA⋅cm⁻² by taking advantage of bandgap engineering. Additionally, the photoelectrochemical currents of TiN_xO_y/TiN(O) multilayer were further improved to 175 ± 6 μA⋅cm⁻². This is mainly due to conductive nano TiN(O) layers providing multiple high-transport paths while allowing light transmission. The enhancement mechanisms of the gradient and multilayer films have also been elaborated.     

Composition and annealing effects on the linear electro-optic response of solution-deposited barium strontium titanate

Chemical solution deposition was used to deposit epitaxial Ba_xSr_(1−x)TiO₃ thin films on SrTiO₃ template layers on Si(001) for x = 1.0, 0.7, 0.5, 0.3, and 0.0. Effective Pockels coefficients were determined as a function of film composition both for as-deposited films (crystallized at 600°C) and for the films after annealing at 750°C for 10 hours. Pockels response decreased monotonically with decreasing Ba content and coefficients were higher for annealed films, reaching 89 ± 3 pm/V for annealed BaTiO₃. These results are contextualized with the aid of X-ray diffraction and high-resolution transmission microscopy, which illuminated the crystallinity and defect nature of the films.     

Oxidation behavior of CVD star-shaped TiN coating in ambient air

Star-shaped 800-TiN and 850-TiN coatings were deposited on the surface of 310S stainless steel foils by CVD and their oxidation behavior was investigated in ambient air, from 300 °C to 800 °C for 1800 s by XRD, SEM, EDX and Raman spectroscopy. Initial oxidation of 850-TiN coating with a partial color change occurs at 350 °C, remarkable oxidation of 850-TiN coating occurring between 400 °C and 450 °C. The EDX results show that obvious oxidation of 850-TiN starts at 400 °C with about 9 at% oxygen detected; no N atoms could be detected while the O content reaching a maximum of ca. 70% at oxidation temperature above 700 °C. The XRD and Raman results show that only rutile-TiO₂ formed on the surface of oxidized TiN coating. The oxidation of star-shaped TiN coating can be divided into three stages. In the case of mild oxidation (below 500 °C), TiN coating can maintain the star-shaped microstructure although oxygen diffuses into the TiN lattice resulting in replacement of N by O atoms. For moderate oxidation (550–600 °C), the star-shaped microstructures start to crack along the (111) twin planes, and the boundary of particles remains clear with oxide and oxynitride layer coexisting on the surface of 850-TiN coating. For severe oxidation (650–750 °C), the cracks of the star-shaped microstructures start to expand and become apparent, meanwhile the boundary of particles become uncertain. After oxidizing at 800 °C, the 850-TiN coating will lose efficacy due to the bad spalling resistance.     

Sol–Gel Synthesis and Characterization of Na0.5Bi0.5TiO3–NaTaO3Thin Films

Thin films with the composition 70 mol% Na_0.5Bi_0.5TiO₃ + 30 mol% NaTaO₃ were prepared by sol–gel synthesis and spin coating. The influence of the annealing temperature on the microstructural development and its further influence on the dielectric properties in the low‐ (kHz–MHz) and microwave‐frequency (15 GHz) ranges were investigated. In the low‐frequency range we observed that with an increasing annealing temperature from 550°C to 650°C the average grain size increased from 90 to 170 nm, which led to an increase in the dielectric permittivity from 130 to 240. The temperature‐stable dielectric properties were measured for thin films annealed at 650°C in the temperature range between ?25°C and 150°C. The thin films deposited on corundum substrates had a lower average grain size than those on Si/SiO₂/TiO₂/Pt substrates. The highest average grain size of 130 nm was obtained for a thin film annealed at 600°C, which displayed a dielectric permittivity of 130, measured at 15 GHz.     

The ultraviolet emission mechanism of ZnO thin film fabricated by sol–gel technology

ZnO thin films were successfully deposited on SiO₂/Si substrate by sol–gel technology. The as-grown ZnO thin films were annealed under an ambient atmosphere from 600 to 900 °C by rapid thermal annealing (RTA) process. X-ray diffraction and scanning electron microscopy analyses reveal the physical structures of ZnO thin films. From PL measurement, two ultraviolet (UV) luminescence bands were obtained at 375 and 380 nm, and the intensity became stronger when the annealing temperature was increased. The strongest UV light emission appeared at annealing temperature of 900 °C. The chemical bonding state in ZnO films was investigated by using X-ray photoelectron spectrum. The mechanism of UV emission was also discussed.     

Dielectric properties and electrical behaviors of tunable Bi1.5MgNb1.5O7 thin films

The Bi_1.5MgNb_1.5O₇ (BMN) thin films were prepared on Au-coated Si substrates by rf magnetron sputtering. We systematically investigated the structure, dielectric properties and voltage tunable property of the films with different annealing temperatures. The relationships of leakage current and breakdown bias field with annealing temperature were firstly studied and a possible explanation was proposed. The deposited BMN thin films had a cubic pyrochlore phase when annealed at 550 °C or higher. With the increasing of annealing temperature, the dielectric constant and tunability also went up. BMN thin films annealed at 750 °C exhibited moderate dielectric constant of 106 and low dielectric loss of 0.003–0.007 between 10 kHz and 10 MHz. The maximum tunability of 50% was achieved at a bias field of 2 MV/cm. However, thin films annealed at 750 °C had lower breakdown bias field and higher leakage current density than films annealed below 750 °C. The excellent physical and electrical properties make BMN thin films promising for potential tunable capacitor applications.     

Optical and Microwave Dielectric Properties of Phase Pure (K0.5Na0.5)NbO3 Thin Films Deposited by RF Magnetron Sputtering

(K_0.5Na_0.5)NbO₃ (KNN) thin films have been deposited onto Pt/Ti/SiO₂/Si and quartz substrates by RF magnetron sputtering. The films were deposited at 400°C with the variation in oxygen mixing percentage (OMP) ratio from 0% to 100% and annealed at 700°C in oxygen atmosphere. The crystallinity of the films is found to be increased with increased OMP. Dielectric properties of the films were examined over the frequency range from 1 kHz to 1 MHz and the temperature range of 30°C to 400°C. The Curie temperature of the films was found to be in the range 369°C–373°C. For the first time, the split postdielectric resonator (SPDR) method was used to measure the microwave (10–20 GHz) dielectric properties of KNN thin films. The optical properties of as‐deposited and annealed KNN thin films were investigated by means of transmittance spectra. The optical bandgap is calculated by using the Tauc relation, and found to be in the range 4.34–4.40 eV and 4.29–4.37 eV for the as‐deposited and annealed films, respectively. The refractive index (n_700nm) of the films found to be in the range 1.98–2.01 and 1.99–2.07 for as‐deposited and annealed films, respectively. The refractive index dispersion is analyzed by using Wemple–DiDomenico (W–D) single‐oscillator model. The effect of annealing and OMP on the refractive index, packing density and W–D parameters has been investigated. The average single oscillator energy (E_o) and dispersion energies (E_d) of the annealed KNN thin films are in the range of 6.17–7.16 eV and 18.77–22.19 eV, respectively. AC‐conductivity of the annealed films was analyzed by using double power law. Ag/KNN/Pt thin films followed the ohmic conduction (J ∝ E^α, where α ~1) and the low leakage current density obtained for the deposited at 100% O₂ is 3.14 × 10^?5 A/cm² at 50 kV/cm.     

Photocatalytic activities of N-doped nano-titanias and titanium nitride

TiO₂ doped with various loadings of nitrogen was prepared by nitridation of a nano-TiO₂ powder in an ammonia/argon atmosphere at a range of temperatures from 400 to 1100 °C. The nano-TiO₂ starting powder was produced in a continuous hydrothermal flow synthesis (CHFS) process involving reaction between a flow of supercritical water and an aqueous solution of a titanium salt. The structures of the resulting nanocatalysts were investigated using powder X-ray diffraction (XRD) and Raman spectroscopy. Products ranging from N-doped anatase TiO₂ to phase-pure titanium nitride (TiN) were obtained depending on post-synthesis heat-treatment temperature. The results suggest that TiN started forming when the TiO₂ was heat-treated at 800 °C, and that pure phase TiN was obtained at 1000 °C after 5 h nitridation. The amounts and nature of the Ti, O and N at the surface were determined by X-ray photoelectron spectroscopy (XPS). A shift of the band-gap to lower energy and increasing absorption in the visible light region, were observed by increasing the heat-treatment temperature from 400 to 700 °C.     

Annealing effects on the microstructure and magnetic properties of Y3Fe5O12 films deposited on Si/SiO2 substrates by RF magnetron sputtering

Crack-free Yttrium iron garnet (Y₃Fe₅O₁₂, YIG) thin films were successfully deposited on Si/SiO₂ substrates by RF magnetron sputtering, through controlling the annealing temperature and cooling rate during post-annealing process. The annealing condition dependences of crystallinity, microstructures and magnetic properties of YIG films were investigated. With the increase of the annealing temperature, the saturation magnetization of YIG films increases and the coercive field decreases, while the ferromagnetic resonance (FMR) linewidth becomes wider. The films annealed at 750 °C with cooling rate of 1 °C/min are crack-free and present excellent comprehensive performances, the corresponding coercive field is 32 Oe and the FMR linewidth is 57 Oe at 9.4 GHz. These results indicate that high-quality crack-free YIG films with excellent magnetic properties can be achieved on Si/SiO₂ substrates by controlling the annealing process, which makes it more convenient to fabricate low-loss microwave integrated devices.     

Reaction of palladium thin films with an Si-rich 6H-SiC(0001)(3×3) surface

The reaction of Pd thin films evaporated in ultrahigh vacuum on a clean and Si-rich 6H-SiC(0001)(3×3) surface has been investigated in situ by low-energy electron diffraction (LEED) and photoelectron spectroscopy (UPS and XPS), and ex situ by atomic force microscopy (AFM) and glancing-incidence X-ray diffraction (GIXRD). For studying the interface formation, submonolayer amounts of Pd were sequentially deposited up to ∼20 Å on the substrate maintained at room temperature. This deposit was subsequently annealed to 600–800 °C. At room temperature, Pd starts to react with SiC when the thickness attains ∼2.5 Å, giving an interface Pd₂Si silicide. Under annealing the film is transformed into Pd₂Si islands standing on the SiC (1×1) surface. No extra-structure of C 1s is observed in the two cases; only an energy shift of about 0.25 eV is detected during the metal deposition, which is attributed to a change in the band bending. Further deposition of ∼100 Å of Pd on this annealed surface gives an epitaxial Pd(111) film, despite a lattice mismatch of more than 10% between the metal and the semiconductor. The film is disrupted after annealing at 600–800 °C. The combination of XPS, AFM and GIXRD analyses indicates that the film annealed at 800 °C is discontinuous and formed of sharp epitaxial Pd₂Si islands and graphite which probably surrounds the islands.     

Microstructure evolution of polycrystalline Ti2AlN MAX phase film during post-deposition annealing

Polycrystalline Ti₂AlN MAX phase films were fabricated by post-deposition annealing of Ti-Al-N film at annealing temperature in the range of 600?°C–800?°C in high vacuum. The temperature-dependent microstructure evolution from Ti-Al-N film to polycrystalline Ti₂AlN film has been investigated. It was found that after post-deposition annealing above 600?°C, the as-deposited amorphous Ti-Al-N film transformed to polycrystalline Ti₂AlN film. With the increase of annealing temperature from 600?°C to 700?°C, the crystallinity of polycrystalline Ti₂AlN film was improved. At 800?°C, the surface Ti₂AlN grains completely decomposed and transformed to TiN phase while inner grains was partial decomposed and surrounded by amorphous Al-rich phase. The polycrystalline Ti₂AlN film exhibited a highest hardness of 34.1?GPa while the hardness of amorphous Ti-Al-N film was only 24.2?GPa. The mechanism of texture changes and phase transformation as well as its effect on thermal stability was also discussed.     

In-situ X-ray diffraction studies and magneto-optic Kerr effect on RF sputtered thin films of BaTiO3 and Co,Nb co-doped BaTiO3

The effect of annealing on structural and magnetic properties of the RF sputtered BaTiO₃ and Co, Nb co-doped BaTiO₃ thin films on Si (001) substrates were studied. The structure of the as-deposited (amorphous) films was changed into cubic perovskite phase during the in-situ X-ray diffraction from room temperature to 900 °C. The enhancement of crystalline quality with respect to the increase of annealing temperature was observed by the in-situ XRD. The magnetic properties of the films before and after annealing were studied by the measurement of Magneto-Optic Kerr Effect (MOKE). The pure BaTiO₃ revealed a paramagnetic behavior, whereas the Co and Nb co-doped BaTiO₃ films exhibited room temperature ferromagnetism. The increase in ferromagnetic response was observed in the Co and Nb co-doped BaTiO₃ films annealed at 900 °C rather than the as-deposited film.     

Thermal stability of MgO film on Si grown by atomic layer deposition using Mg(EtCp)2 and H2O

MgO films were deposited on Si via atomic layer deposition (ALD) using Mg(EtCp)₂ and H₂O precursors and their thermal stability was examined as a function of the post-deposition annealing (PDA) temperature. The characteristic self-limiting behavior of the ALD process was confirmed by changing several parameters, such as precursor pulsing times, deposition temperature, and number of cycles. The exceptional resulting step coverage was verified on a patterned wafer with a high aspect ratio. The band gap and dielectric constant of the as-deposited ALD-MgO film were extracted to be approximately 7.5 eV and 8.4, respectively, and were stable up to the PDA temperature of 700 °C. However, considerable outward diffusion of the underlying Si atoms toward MgO started to occur above 700 °C, and most of the MgO film was converted to an amorphous Mg-silicate phase at 900 °C with a thin layer of remaining MgO on top.     

Annealing temperature-dependent structural and electrical properties of (Ta2O5)1-x - (TiO2)x thin films,x ≤ 0.11

(Ta₂O₅)_1-x- (TiO₂)_x (TTO_x) thin films, with x = 0, 0.03, 0.06, 0.08, and 0.11, were deposited using magnetron direct current (DC) sputtering method onto the P/boron-silicon (1 0 0) substrates by varying areas of Tantalum and Titanium metallic targets, in oxygen environment at ambient temperature. The as-deposited thin films were annealed at temperatures ranging from 500 to 800 °C. Generally, the formation of the Ta₂O₅ structure was observed from the X-ray diffraction measurements of the annealed films. The capacitance of prepared metal– oxide– semiconductor (MOS) structures of Ag/TTO_x/p-Si was measured at 1 MHz. The dielectric constant of the deposited films was observed altering with varying composition and annealing temperature, showing the highest value 71, at 1 MHz, for the TTO_x films, x = 0.06, annealed at 700 °C. With increasing annealing temperature, from 700 to 800 °C, the leakage current density was observed, generally decreasing, from 10^?5 to 10^?8 A cm^?2, for the prepared compositions. Among the prepared compositions, films with x = 0.06, annealed at 800 °C, having the observed value of dielectric constant 48, at 1 MHz; and the leakage current density 2.7 × 10^?8 A cm^?2, at the electric field of 3.5 × 10⁵ V cm^?1, show preferred potential as a dielectric for high-density silicon memory devices.     

Highly Conductive p‐Type Zinc blende SiC Thin Films Fabricated on Silicon Substrates by Magnetron Sputtering

Polycrystalline silicon carbide (SiC) thin films were fabricated on Si(100) substrates using radio‐frequency magnetron sputtering followed by annealing at 1300°C in an Ar atmosphere. The SiC films exhibited a zinc blende structure with planar and point defects as detected by X‐ray diffraction and Raman spectroscopy. The SiC films were p‐type conductive with electrical resistivity as low as 2.8 × 10^?3 Ω·cm at room temperature. The p‐type character of the SiC films can be explained in terms of the Si vacancies in the C‐rich environment as evidenced by Raman spectroscopy.     

Mechanical properties and thermal stability of SiBCN films prepared by ion beam assisted sputter deposition

The high hardness, exceptional high temperature stability, and oxidation resistance of bulk Si–B–C–N ceramics have led to the expectation that these materials will be good candidates for superior coating materials in high-temperature applications. In this study, SiBCN films were prepared using ion beam assisted sputter (IBAS) deposition, and the mechanical properties and thermal stabilities of the films at 600, 700, and 800 °C in air were investigated. In particular, the effects of the ion beam assist on the properties of the SiBCN films were examined. The SiBCN films were deposited on Si plates by sputtering a target composed of Si + BN + C using a 2-keV Ar⁺ ion beam. A low-energy N₂⁺ and Ar⁺ mixed ion beam irradiated the samples during the sputter deposition. The Si content in the SiBCN films was controlled by changing the Si/(BN + C) ratio of the target. BCN films were also deposited for comparison. The composition and chemical bonding structure of the prepared films were investigated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. We found that c-BN bonds were formed in the ion-assisted BCN film. The oxide layer thickness on the SiBCN films after thermal annealing decreased due to the IBAS deposition and an increase in the Si content. Ion-assisted SiBCN films annealed at 800 °C showed the highest hardness of 20 GPa.     

Ferroelectric and piezoelectric properties of Ba0.85Ca0.15Ti0.90Zr0.10O3 films in 200 nm thickness range

Lead-free piezoelectric Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ (BCZT) thin films were fabricated on Si/SiO₂/TiO₂/Pt (100) substrates following chemical solution deposition technique. Microstructure of the nano-sized BCZT particles crystallized in the thin film was thoroughly characterized. Ferroelectric, dielectric and piezoelectric properties of the films were investigated in detail. The BCZT films annealed at 800°C temperature exhibited high remanent polarization of 25 ± 1 μC/cm², energy density of 17 J/cm³, dielectric constant of 1550 ± 50 and dielectric tunability of 50%. Converse piezoelectric coefficients (d₃₃) obtained from piezo-response force microscopy (PFM) measurements on BCZT grains of different grain size (20-100 nm) distributed on the BCZT 700 film varied widely from 90 to 230 pm/V. The same for BCZT 800 measured on different grain size (30-130 nm) varied from 120 to 295 pm/V. These BCZT thin films with high dielectric, ferroelectric, and piezoelectric properties might be good alternative to the PZT films for thin film piezoelectric device applications.     

High–Energy‐Storage Density Capacitors of Bi(Ni1/2Ti1/2)O3–PbTiO3 Thin Films with Good Temperature Stability

High–energy‐storage density capacitors with thin films of 0.5Bi(Ni_1/2Ti_1/2)O₃–0.5PbTiO₃ (BNT–PT) were fabricated by chemical solution deposition technique on Pt/Ti/SiO₂/Si substrates. The dense thin films with pure‐phase perovskite structure could be obtained by annealing at 750°C. High capacitance density (~1925 nF/cm² at 1 kHz) and extremely high‐energy density (~45.1 J/cm³) under an electric field of 2250 kV/cm were achieved at room temperature. The energy‐storage density and efficiency varied little in a wide temperature range from ?190°C to 250°C. The high–energy‐storage density and good temperature stability make BNT–PT films promising candidates for high power electric applications.     

Effects of annealing temperature on the phase formation,optical, photoluminescence and magnetic properties of sol-gel YFeO3 films

YFeO₃ (YFO) thin films were deposited onto quartz substrates via sol-gel spin-coating technique and annealed at different temperature ranged between 650 and 900 °C. The impact of annealing temperature on the phase formation, microstructural, optical, photoluminescence (PL) and magnetic properties of the films were systematically investigated. X-ray diffraction analysis revealed an amorphous structure in film annealed at 650 °C and formation of hexagonal-YFO (h-YFO) phase in films annealed at 750–800 °C. The films annealed at 850–900 °C exhibited an orthorhombic-YFO (o-YFO) structure. Atomic force microscopy images of h-YFO films showed homogeneous surface with uniform particles size and shape. The particle size increased and had irregular shape in o-YFO films. The average particle size was 44 and 117 nm, while the root square roughness was 1.38 and 2.55 nm for h- and o-YFO films annealed at 750 and 850 °C, respectively. The optical band gap (E_g) was 2.53 and 2.86 eV for h- and o-YFO films annealed at 750 and 850 °C, respectively. The PL spectra of h-YFO films were red-shifted compared with that of o-YFO films. The PL emission related to near band edge was observed at 459.0 and 441.9 nm for h- and o-YFO films annealed at 750 and 850 °C, respectively. The magnetization was enhanced with the increasing of annealing temperature and has the value of 4.8 and 12.5 emu/cm³ at 5000 Oe for h- and o-YFO films annealed at 750 and 850 °C, respectively.