Effect of substrate temperature and annealing temperature on the structural, electrical and microstructural properties of thin Pt films by rf magnetron sputtering

Influence of both substrate temperature, T_s, and annealing temperature, T_a, on the structural, electrical and microstructural properties of sputtered deposited Pt thin films have been investigated. X-ray diffraction results show that as deposited Pt films (T_s = 300, 400 °C) are preferentially oriented along (1 1 1) direction. A little growth both along (2 0 0) and (3 1 1) directions are also noticed in the as deposited Pt films. After annealing in air (T_a = 500-700 °C), films become strongly oriented along (1 1 1) plane. With annealing temperature, average crystallite size, D, of the Pt films increases and micro-strain, e, and lattice constant, a₀, decreases. Residual strain observed in the as deposited Pt films is found to be compressive in nature while that in the annealed films is tensile. This change in the strain from compressive to tensile upon annealing is explained in the light of mismatch between the thermal expansion coefficients of the film material and substrate. Room temperature resistivity of Pt films is dependant on both the T_s and T_a of the films. Observed decrease in the film resistivity with T_a is discussed in terms of annihilation of film defects and grain-boundary. Scanning electron microscopic study reveals that as the annealing temperature increases film densification improves. But at an annealing temperature of ∼600 °C, pinholes appear on the film surface and the size of pinhole increases with further increase in the annealing temperature. From X-ray photoelectron spectroscopic analysis, existence of a thin layer of chemisorbed atomic oxygen is detected on the surfaces of the as deposited Pt films. Upon annealing, coverage of this surface oxygen increases.     

Influence of deposition temperature on the structural and morphological properties of Be3N2 thin films grown by reactive laser ablation

Be₃N₂ thin films have been grown on Si(1 1 1) substrates using the pulsed laser deposition method at different substrate temperatures: room temperature (RT), 200 °C, 400 °C, 600 °C and 700 °C. Additionally, two samples were deposited at RT and were annealed after deposition in situ at 600 °C and 700 °C. In order to obtain the stoichiometry of the samples, they have been characterized in situ by X-ray photoelectron (XPS) and reflection electron energy loss spectroscopy (REELS). The influence of the substrate temperature on the morphological and structural properties of the films was investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The results show that all prepared films presented the Be₃N₂ stoichiometry. Formation of whiskers with diameters of 100-200 nm appears at the surface of the films prepared with a substrate temperature of 600 °C or 700 °C. However, the samples grown at RT and annealed at 600 °C or 700 °C do not show whiskers on the surface. The average root mean square (RMS) roughness and the average grain size of the samples grown with respect the substrate temperature is presented. The films grown with a substrate temperature between the room temperature to 400 °C, and the sample annealed in situ at 600 °C were amorphous; while the αBe₃N₂ phase was presented on the samples with a substrate temperature of 600 °C, 700 °C and that deposited with the substrate at RT and annealed in situ at 700 °C.     

Early-stage ordering in in-situ annealed Fe51Pt49 films

We evidenced an early-stage ordering (ESO) in Fe₅₁Pt₄₉ film before the appearance of superlattice diffraction (long-range-order, LRO) using 40-nm-thick films prepared by magnetron sputtering onto quartz substrate. The appearance of L1₀ phase for samples deposited at substrate temperatures (T_s) 400 °C and higher was verified by X-ray diffraction. Surface roughness of Fe₅₁Pt₄₉ films, obtained via X-ray specular reflectivity with computational fitting, increases from 3.8 to 11 Å as T_s is increased from 25 to 275 °C. As further increase of T_s to 375 °C, the roughness drops to 3.2 Å and then increases again to 38 Å with T_s up to 700 °C. Measurement on residual strain demonstrates that it is initially compressive at T_s<400 °C. Thereafter the strain transfers to a tensile one and increases in magnitude as increasing T_s up to 700 °C corresponding to LRO transformation. Local atomic rearrangement is observed for samples deposited at T_s>250 °C by using extended X-ray absorption fine structure. Coercivity of films increases from 10 to 460 Oe as T_s increase from 25 to 375 °C (ESO) and then from 460 to 10,700 Oe with T_s 375-700 °C (normal LRO). The worked out quantitative estimation of ESO engages with that of LRO before T_s 400 °C.     

Effects of substrate temperature on properties of NbNx films grown on Nb by pulsed laser deposition

NbN_x films were deposited on Nb substrate using pulsed laser deposition. The effects of substrate deposition temperature, from room temperature to 950 °C, on the preferred orientation, phase, and surface properties of NbN_x films were studied by X-ray diffraction, atomic force microscopy, and electron probe micro analyzer. We find that the substrate temperature is a critical factor in determining the phase of the NbN_x films. For a substrate temperature up to 450 °C the film showed poor crystalline quality. With temperature increase the film became textured and for a substrate temperature of 650−850 °C, mix of cubic δ-NbN and hexagonal phases (β-Nb₂N + δ′-NbN) were formed. Films with a mainly β-Nb₂N hexagonal phase were obtained at deposition temperature above 850 °C. The c/a ratio of β-Nb₂N hexagonal shows an increase with increased nitrogen content. The surface roughness of the NbN_x films increased as the temperature was raised from 450 to 850 °C.     

Effects of oxygen partial pressure and substrate temperature on the structure and optical properties of MgxZn1−xO thin films prepared by magnetron sputtering

Deposited with different oxygen partial pressures and substrate temperatures, Mg_xZn_1−xO thin films were prepared using a Mg_0.6Zn_0.4O ceramic target by magnetron sputtering. The structural and optical properties of the prepared thin films were investigated. The X-ray diffraction spectra reveal that all the films on quartz substrate are grown along (2 0 0) orientation with cubic structure. The lattice constant decreases and the crystallite size increases with the increase of substrate temperature. Both energy dispersive X-ray spectroscopy and calculated results suggest the ratio of Mg/Zn increases with increasing substrate temperature. The thin film deposited with T_s = 500 °C has a minimal rms roughness of 7.37 nm. The transmittance of all the films is higher than 85% in the visual region. The optical band gap is not sensitive to the oxygen partial pressure, while it increases from 5.63 eV for T_s = 100 °C to 5.95 eV for T_s = 700 °C. In addition, the refractive indices calculated from transmission spectra are sensitive to the substrate temperature. The photoluminescence spectra of Mg_xZn_1−xO thin films excited by 330 nm ultraviolet light indicate that the peak intensity of the spectra is influenced by the oxygen partial pressure and substrate temperature.     

Influence of substrate temperature on structures and dielectric properties of pyrochlore Bi1.5Zn1.0Nb1.5O7 thin films prepared by pulsed laser deposition

The influence of substrate temperature on structural and dielectric properties of cubic pyrochlore Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films prepared by pulsed laser deposition process has been investigated. BZN thin films were deposited on Pt/Ti/SiO₂/Si(1 0 0) substrate and in situ annealed at 700 °C. The results indicate that the substrate temperature has a significant effect on the structural and dielectric properties of BZN thin films. The films exhibit a cubic pyrochlore structure in the substrate temperature range from 550 °C to 700 °C and at the annealing temperature of 700 °C. With further increase of substrate temperature to 750 °C, the phases of Bi₂O₃, BiNbO₄ and Bi₅Nb₃O₁₅ can be detected in the XRD pattern due to the Zn loss. The dielectric constant and loss tangent of the films deposited at 650 °C are 192 and 6 × 10⁻⁴ at 10 kHz, respectively. The tunability is 10% at a dc bias field of 0.9 MV/cm.     

Optical properties of ITO/TiO2 single and double layer thin films deposited by RPLAD

Indium tin oxide (ITO) and titanium dioxide (TiO₂) single layer and double layer ITO/TiO₂ films were prepared using reactive pulsed laser ablation deposition (RPLAD) with an ArF excimer laser for applications in dye-sensitized solar cells (DSSCs). The films were deposited on SiO₂ substrates either at room temperatures (RT) or heated to 200-400 °C. Under optimized conditions, transmission of ITO films in the visible (vis) range was above 89% for films produced at RT and 93% for the ones deposited at higher temperatures. Increasing the substrate temperature from RT to 400 °C enhances the transmission of TiO₂ films in the vis-NIR from about 70% to 92%. High transmission (≈90%) was observed for the double layer ITO/TiO₂ with a transmission cut-off above 900 nm. From the transmission data, the energies gaps (E_g), as well as the refractive indexes (n) for the films were estimated. n ≈ 2.03 and 2.04, respectively for ITO films and TiO₂ film deposited at 400 °C in the visible region. Post-annealing of the TiO₂ films for 3 h at 300 and 500 °C was performed to enhance n. The refractive index of the TiO₂ films increases with the post-annealing temperature. The direct band gap is 3.6, 3.74 and 3.82 eV for ITO films deposited at RT, 200, and 400 °C, respectively. The TiO₂ films present a direct band gap of 3.51 and 3.37 eV for as deposited TiO₂ films and when annealed at 400 °C, respectively. There is a shift of about 0.1 eV between ITO and ITO/TiO₂ films deposited at 200 °C. The shift decreases by half when the TiO₂ film was deposited at 400 °C. Post-annealing was also performed on double layer ITO/TiO₂.     

Effects of rapid thermal annealing on structural, magnetic and optical properties of Ni-doped ZnO thin films

XPS depth profiles were used to investigate the effects of rapid thermal annealing under varying conditions on the structural, magnetic and optical properties of Ni-doped ZnO thin films. Oxidization of metallic Ni from its metallic state to two-valence oxidation state occurred in the film annealed in air at 600 °C, while reduction of Ni²⁺ from its two-valence oxidation state to metallic state occurred in the film annealed in Ar at 600 and 800 °C. In addition, there appeared to be significant diffusion of Ni from the bottom to the top surface of the film during annealing in Ar at 800 °C. Both as-deposited and annealed thin films displayed obvious room temperature ferromagnetism (RTFM) which was from metallic Ni, Ni²⁺ or both with two distinct mechanisms. Furthermore, a significant improvement in saturation magnetization (M_s) in the films was observed after annealing in air (M_s = 0.036 μ_B/Ni) or Ar (M_s = 0.033 μ_B/Ni) at 600 °C compared to that in as-deposited film (M_s = 0.017 μ_B/Ni). An even higher M_s value was observed in the film annealed in Ar at 800 °C (M_s = 0.055 μ_B/Ni) compared to that at 600 °C mainly due to the diffusion of Ni. The ultraviolet emission of the Ni-doped ZnO thin film was restored during annealing in Ar at 800 °C, which was also attributed to the diffusion of Ni.     

Defects in nanocrystalline Nb films: Effect of sputtering temperature

Thin niobium (Nb) films (thickness 350-400 nm) were prepared on (1 0 0)Si substrate in a UHV chamber using the cathode beam sputtering. The sputtering temperature T_s was varied from 40 up to 500 °C and the influence of the sputtering temperature on the microstructure of thin Nb films was investigated. Defect studies of the thin Nb films sputtered at various temperatures were performed by slow positron implantation spectroscopy (SPIS) with measurement of the Doppler broadening of the annihilation line. SPIS was combined with transmission electron microscopy (TEM) and X-ray diffraction (XRD). We have found that the films sputtered at T_s = 40 °C exhibit elongated, column-like nanocrystalline grains. No significant increase of grain size with T_s (up to 500 °C) was observed by TEM. The thin Nb films sputtered at T_s = 40 °C contain a high density of defects. It is demonstrated by shortened positron diffusion length and a high value of the S parameter for Nb layer compared to the well-annealed (defect-free) bulk Nb reference sample. A drastic decrease of defect density was found in the films sputtered at T_s ≥ 300 °C. It is reflected by a significant increase of the positron diffusion length and a decrease of the S parameter for the Nb layer. The defect density in the Nb layer is, however, still substantially higher than in the well-annealed reference bulk Nb sample. Moreover, there is a layer at the interface between the Nb film and the substrate with very high density of defects comparable to that in the films sputtered at T_s < 300 °C. All the Nb films studied exhibit a strong (1 1 0) texture. The films sputtered at T_s < 300 °C are characterized by a compressive macroscopic in-plane stress due to lattice mismatch between the film and the substrate. Relaxation of the in-plane stress was observed in the films sputtered at T_s ≥ 300 °C. The width of the XRD profiles of the films sputtered at T_s ≥ 300 °C is significantly smaller compared to the films sputtered at lower temperatures. This is most probably due to a lower defect density which results in reduced microstrains in the films sputtered at higher temperatures.     

Control of a- and c-plane preferential orientations of ZnO thin films

We report orientation-controllable growth of ZnO thin films and their orientation-dependent electrical characteristics. ZnO thin films were deposited on single-crystalline (1 0 0) LaAlO₃ and (1 0 0) SrTiO₃ substrates using pulsed laser deposition (PLD) at different substrate temperatures (400-800 °C). It was found that the orientation of ZnO films could be controlled by using different substrates of single-crystalline (1 0 0) LaAlO₃ and (1 0 0) SrTiO₃. The a-plane () and c-plane (0 0 0 2) oriented ZnO films are formed on LaAlO₃ and SrTiO₃, respectively. In both cases, the degree orientation increased with increasing deposition temperature T_s. Both the surface free energy and the degree of lattice mismatch are ascribed to play an important role for the orientation-controllable growth. Further characterization show that the grain size of the films with both orientations increases for a substrate temperature increase (i.e. from T_s = 400 °C to T_s = 800 °C), whereas the electrical properties of ZnO thin films depend upon their crystalline orientation, showing lower electrical resistivity values for a-plane oriented ZnO films.     

Influence of substrate temperature on the texture of barium ferrite film by magnetron sputtering

Barium ferrite thin films have been prepared by radio frequency magnetron sputtering on a sapphire (0 0 1) substrate at substrate temperature of 500 °C and 650 °C, respectively. The films were further annealed in air at 1000 °C for 5 h. X-ray diffraction shows that the films at the lower substrate temperatures have a good epitaxial relation with respect to the substrate, while the samples under the higher substrate temperatures have (1 0 9) planes parallel to the substrate. The remanence ratio decreases from 0.82 to 0.47 when the substrate temperature is increased. We attribute the variation of the growth direction to the enhanced vertical mobility of the deposited atoms when the substrate temperature is increased.     

Effect of thermal process on magnetic anisotropy in FeCoB soft underlayer

Relationship between magnetic anisotropy field H_k and thermal processes during the preparation has been studied for FeCoB thin films. The FeCoB films deposited on the glass substrates by facing targets sputtering successfully showed strong magnetic anisotropy when the substrate was heated at the substrate temperature T_s above 100 °C. Additionally, the lattice spacing of FeCo(1 1 0) in the perpendicular direction was found to decrease depending on the substrate temperature T_s. Among various temperature histories, the heating processes with a phase of increasing T_s revealed the further improvement of H_k. Meanwhile, high H_k in the films disappears after the post-deposition annealing at the temperature above 400 °C.     

The Effect of Substrate Temperature on the Properties of Nanostructured Silicon Carbide Films Deposited by Hypersonic Plasma Particle Deposition

Nanostructured silicon carbide films have been deposited on molybdenum substrates by hypersonic plasma particle deposition. In this process a thermal plasma with injected reactants (SiCl₄ and CH₄) is expanded through a nozzle leading to the nucleation of ultrafine particles. Particles entrained in the supersonic flow are then inertially deposited in vacuum onto a temperature-controlled substrate, leading to the formation of a consolidated film. In the experiments reported, the deposition substrate temperature T_s has ranged from 250°C to 700°C, and the effect of T_s on film morphology, composition, and mechanical properties has been studied. Examination of the films by scanning electron microscopy has shown that the grain sizes in the films did not vary significantly with T_s. Micro-X-ray diffraction analysis of the deposits has shown that amorphous films are deposited at low T_s, while crystalline films are formed at high T_s. Rutherford backscattering spectrometry has indicated that the films are largely stoichiometric silicon carbide with small amounts of chlorine. The chlorine content decreases from 8% to 1.5% when the deposition temperature is raised from 450°C to 700°C. Nanoindentation and microindentation tests have been performed on as-deposited films to measure hardness, Young's modulus and to evaluate adhesion strength. The tests show that film adhesion, hardness and Young's modulus increase with increasing T_s. These results taken together demonstrate that in HPPD, as in vapor deposition processes, the substrate temperature may be used to control film properties, and that better quality films are obtained at higher substrate temperatures, i.e. T_s700°C.     

Effect of substrate temperature on the surface and interface oxidation of NiTi thin films

NiTi shape memory alloy thin films are deposited on pure Cu substrate at substrate ambient temperatures of 300 °C and 450 °C. The surface and interface oxidation of NiTi thin films are characterized by X-ray photoelectron spectroscopy (XPS). After a subsequent annealing treatment the crystallization behavior of the films deposited on substrate at different temperatures is studied by X-ray diffraction (XRD). The effects of substrate temperature on the surface and interface oxidation of NiTi thin films are investigated. In the film surface this is an oxide layer composed of TiO₂. The Ni atom has not been detected on surface. In the film/substrate interface there is an oxide layer with a mixture Ti₂O₃ and NiO in the films deposited at substrate temperatures 300 °C and 450 °C. In the films deposited at ambient temperature, the interface layer contains Ti suboxides (TiO) and metallic Ni.     

Annealing effects on the bonding structures, optical and mechanical properties for radio frequency reactive sputtered germanium carbide films

The effects of thermal annealing in vacuum on the bonding structures, optical and mechanical properties for germanium carbide (Ge_1−xC_x) thin films, deposited by radio frequency (RF) reactive sputtering of pure Ge(1 1 1) target in a CH₄/Ar mixture discharge, are investigated. We find that there are no significant changes in the bonding structure of the films annealed below 300 °C. The fraction of Ge-H bonds for the film annealed at temperatures (T_a) above 300 °C decreases, whereas that of C-H bonds show a decrease only when T_a exceeds 400 °C. The out-diffusion of hydrogen promotes the formation of Ge-C bonds at T_a above 400 °C and thus leads to a substantial increase in the compressive stress and hardness for the film. The refractive indices and optical gaps for Ge_1−xC_x films are almost constant against T_a, which can be ascribed to the unchanged ratios of Ge/C and sp²-C/sp³-C concentrations. Furthermore, we also find that the excellent optical transmission for an antireflection Ge_1−xC_x double-layer film on ZnS substrate is still maintained after annealing at 700 °C.     

Enhanced ferroelectric properties of vanadium doped bismuth titanate (BTV) thin films grown by pulsed laser ablation technique

Bi_3.99Ti_2.97V_0.03O₁₂ (BTV) thin films were grown by pulsed laser deposition at substrate temperatures ranging between 650 and 750 °C. The structural phase, and orientation of the deposited films were investigated in order to understand the effect of the deposition parameters on the properties of the BTV films. As the substrate temperature was increased to 700 °C, the films started showing a tendency of assuming a c-axis preferred orientation, while at lower temperatures polycrystalline films were formed. The Au/BTV/Pt capacitor showed an interesting dependence of the remnant polarization (P_r) as well as dc leakage current values on the growth temperature. The film deposited at 675 °C showed a very large 2P_r of 42 μC cm⁻², which is the largest for BTV thin films among the values reported so far.     

In-plane magnetization with high coercivity in terbium iron garnet thin films deposited on Pt/Si substrate by PLD

We report on the growth of terbium iron garnet (TbIG, Tb₃Fe₅O₁₂) thin films having anomalously large coercivity and in-plane easy axis of magnetization. The TbIG thin films were prepared at room temperature (RT) on Pt/Si(1 0 0) substrates by pulsed laser deposition technique. The films deposited at RT were X-ray amorphous and do not show any magnetic order. Annealing of the RT deposited film at 900 °C resulted into fully textured (532) TbIG film. Atomic force microscopy and cross-sectional scanning electron microscopy studies of the TbIG films showed good surface quality with an average surface roughness of 5.0 nm and thickness of about 300 nm, respectively. The M-H loops measured at 20 K for TbIG films, exhibit about an order of magnitude enhancement in the coercivity value (H_c) than the single crystal. In-plane and out-of-plane M-H loops revealed that the easy axis of the magnetization lies within the film’s plane. In-plane magnetization combining with large H_c value of the TbIG thin film may be of scientific interest for the possible applications.     

Synthesis and magnetic study on Mg-substituted Li-Mn spinel oxides

LiMn_2−xMg_xO₄ (X<0.5) cubic spinel oxide was synthesized by the sol-gel technique using Li-nitrate, Mn-acetate and Mg-acetate salts. The gel precursors were decomposed at 300 °C in air and then annealed at temperatures ranging from 500 to 850 °C in an oxygen flow. For a fixed annealing temperature of 700 °C, the lattice constant decreased with an increase in the substitution degree X and a discontinuity was found around X=0.3. With a further increase in X>0.3, the space group of the crystal structure was converted from Fd3m to P4₃32 by the cation ordering in the octahedral site. The low-temperature magnetization increased with X, and the Weiss constant moved in the positive direction and changed its sign from negative to positive around X=0.3. In the case of X=0.5, all the specimens showed P4₃32 structure and ferromagnetic character. The maximum Curie temperature (T_c=23 K) and the maximum magnetization (M_s=4.68 μ_B per the chemical formula unit) were attained simultaneously for the specimen obtained around 700 °C. The Mn valence state was sensitive not only to the substitution but also to the preparation conditions. Hence, it was possible to explain these variations by considering the magnetic interactions between transition metal ions.     

Influence of temperature on structure as well as adhesion and friction and wear behavior of hydrogenated carbon nitride films prepared on silicon substrate

Hydrogenated-carbon nitride (CN_x:H) films were synthesized on silicon substrate in a large quantity by the pyrolysis of ethylenediamine in a temperature range of 700-950 °C. The influence of temperature on the morphology, structure, adhesion to substrate, and friction and wear behavior of CN_x:H films was investigated. It has been found that CN_x:H films obtained at 700 °C and 800 °C are amorphous, and those prepared at 900 °C and 950 °C consist of carbon nitride nanocrystal. Besides, CN_x:H film sample obtained at 700 °C has the maximum N content of 9.1 at.% but the poorest adhesion to Si substrate, while the one prepared at 900 °C has the lower N content and the highest adhesion to substrate. As a result, nanocrystalline CN_x:H (nc-CN_x:H) film synthesized at 900 °C possesses the best wear resistance when slides against stainless steel counterpart. N atom is incorporated into the graphitic network in three different bonding forms, and their relative content is closely related to temperature, corresponding to different adhesion as well as friction and wear behavior of the films obtained at different temperatures. Furthermore, the friction coefficient and antiwear life of as-deposited CN_x:H films vary with varying deposition temperature and thickness, and the film with thickness of 1.3 μm, obtained at 900 °C, has the longest antiwear life of over 180,000 s.     

Seebeck and magnetoresistive effects of Ga-doped ZnO thin films prepared by RF magnetron sputtering

In this paper, Ga-doped ZnO (GZO) films were deposited on glass substrates at different substrate temperatures by RF magnetron sputtering. The effect of substrate temperature on the structural, surface morphological properties, Seebeck and magnetoresistive effects of GZO films was investigated. It is found that the GZO films are polycrystalline and preferentially in the [0 0 2] orientation, and the film deposited at 300 °C has an optimal crystal quality. Seebeck and magnetoresistive effects are apparently observed in GZO films. The thermoelectromotive forces are negative. Decreasing substrate temperature and annealing in N₂ flow can decrease carrier concentration. The absolute value of the Seebeck coefficient increases with decreasing carrier concentration. The maximal absolute value of Seebeck coefficient is 101.54 μV/K for the annealed samples deposited at the substrate temperature of 200 °C. The transverse magnetoresistance of GZO films is related to both the magnetic field intensity and the Hall mobility. The magnetoresistance increases almost linearly with magnetic field intensity, and the films deposited at higher substrate temperature have a stronger magnetoresistance under the same magnetic field, due to the larger Hall mobility.