The effects of oxygen partial pressure on BST thin films deposited on multilayered bottom electrodes

Ba_0.5Sr_0.5TiO₃ (BST) thin films have been deposited by r.f. magnetron sputtering on silicon and platinum-coated silicon substrates with different buffer and barrier layers. BST films deposited on Si/SiO₂/SiN/Pt and Si/SiO₂/Ti/TiN/Pt multilayer bottom electrode have been used for the fabrication of capacitors. XRD and SEM studies were carried out for the films. It was found that the crystallinity of the BST thin film was dependent upon oxygen partial pressure in the sputtering gas. The role of multilayered bottom electrode on the electrical properties of Ba_0.5Sr_0.5TiO₃ films has been also investigated. The dielectric properties of BST films were measured. The results show that the films exhibit pure perovskite phase and their grain sizes are about 80–90 nm. The dielectric properties of the BST thin film on Si/SiO₂/Ti/TiN/Pt electrode was superior to that of the film grown on Si/SiO₂/SiN/Pt electrode.     

Thin film growth of epitaxial, polycrystalline and amorphous SrRuO3

The SrRuO₃ thin films were grown on amorphous fused silica and (100) single crystal LaAlO₃ substrates by pulsed laser deposition method. On fused silica substrates, polycrystalline SrRuO₃ thin film was obtained and below the crystallization temperature, SrRuO₃ thin films show an amorphous phase. For the case of epitaxial growth on (100) single crystal LaAlO₃ substrate, the crystallization temperature of SrRuO₃ thin film was increased by ∼ 100 °C indicating that additional energy is necessary in order to obtain the epitaxial thin film. By using the eclipse method and the control of substrate temperature, the variations of surface morphologies and grain size were observed by atomic force microscope. Below the crystallization temperature, amorphous SrRuO₃ thin film shows hopping transport property of an insulator.     

Epitaxial growth of SrRuO<Subscript>3</Subscript> thin films by RF sputtering and study of surface morphology

We report on the epitaxial growth of SrRuO₃ (SRO) thin films on Pt (111)/γ-Al₂O₃ (111) nSi (111) substrates. The grown thin films are crystalline and epitaxial as suggested by RHEED and XRD experiments. With the use of γ-Al₂O₃ (001)/nSi (001) and γ-Al₂O₃ (111)/nSi (111) substrates, crystalline but not epitaxial films have grown successfully. This result implies that lattice mismatch between nSi and SRO prevents the epitaxial growth of SRO film directly on nSi. However, the buffer Pt (111) layer mitigates lattice mismatch that provides to grow epitaxial film on nSi of quality. Morphological study shows a good surface with moderate roughness. Film grown at 700°C is smoother than the film grown at 750°C, but the variation of temperature does not affect significantly on the epitaxial nature of the films.     

Synthesis and characterization of platinum thin film as top electrodes for multifunctional layer devices by PLD

Platinum thin films were grown onto (001) oriented SrTiO₃ substrates by means of the pulsed laser deposition technique. Structural and morphological characterizations were performed using XRD and AFM. The influence of substrate temperature and deposition rate was analyzed on the crystallographic properties of the film. As a result, an increment in the crystallinity of the film due to the change on the temperature was observed. On the other hand, Pt films showed a granular morphology and its roughness was related to the fluence and low deposition temperature. Finally their electrical properties were analyzed and discussed as a function of the previous morphological results.     

Epitaxial growth of SrRuO3 thin films by RF sputtering and study of surface morphology

We report on the epitaxial growth of SrRuO₃ (SRO) thin films on Pt (111)/γ-Al₂O₃ (111) nSi (111) substrates. The grown thin films are crystalline and epitaxial as suggested by RHEED and XRD experiments. With the use of γ-Al₂O₃ (001)/nSi (001) and γ-Al₂O₃ (111)/nSi (111) substrates, crystalline but not epitaxial films have grown successfully. This result implies that lattice mismatch between nSi and SRO prevents the epitaxial growth of SRO film directly on nSi. However, the buffer Pt (111) layer mitigates lattice mismatch that provides to grow epitaxial film on nSi of quality. Morphological study shows a good surface with moderate roughness. Film grown at 700°C is smoother than the film grown at 750°C, but the variation of temperature does not affect significantly on the epitaxial nature of the films.     

Crystallization and electrical properties of Ba<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>TiO<Subscript>3</Subscript> thin films on SrRuO<Subscript>3</Subscript>/Pt hybrid bottom electrode

Ba_0.7Sr_0.3TiO₃ (BST) thin films were deposited on Pt and SrRuO₃(SRO)/Pt hybrid bottom electrodes by radio frequency magnetron sputtering. X-ray analysis indicated that both films were polycrystalline. Dielectric measurements showed that the films on SRO/Pt hybrid bottom electrode had lower dielectric constant and loss than the films on single Pt and the dielectric properties were frequency-independent. The leakage current density of Ba_0.7Sr_0.3TiO₃ thin films on hybrid bottom electrode was also lower. Leakage mechanism investigations showed that the contact between the electrode-film interfaces of thin films on SRO/Pt hybrid bottom electrode was ohmic. Based on the results, the effects of SRO/Pt hybrid bottom electrode on the crystallization and electrical properties of BST thin films were discussed.     

Structural and electrical properties of room temperature pulsed laser deposited and post-annealed thin SrRuO3 films

Good quality strontium ruthenate (SrRuO₃) thin continuous films (15 to 125 nm thick) have been synthesized on silicon (100) substrates by room temperature pulsed laser deposition under vacuum followed by a post-deposition annealing, a route unexplored and yet not reported for SrRuO₃ film growth. The presence of an interfacial Sr₂SiO₄ layer has been identified for films annealed at high temperature, and the properties of this interface layer as well as the properties of the SrRuO₃ film have been analyzed and characterized as a function of the annealing temperature. The room temperature resistivity of the SrRuO₃ films deposited by laser ablation at room temperature and post-annealed is 2000 μΩ·cm. A critical thickness of 120 nm has been determined above which the influence of the interface layer on the resistivity becomes negligible.     

Structure, morphology and electrical characterizations of direct current sputtered ZnO thin films

ZnO thin films were deposited on glass substrates by direct current (DC) sputtering technique at room temperature (RT) to 400 °C with a 99.999% pure ZnO target. Then the samples deposited at RT were annealed in air from the RT to 400 °C. The effects of substrate temperature (T_s) and annealing treatment (T_a) on the crystallization behavior and the morphology have been studied by X-ray diffraction and atomic force microscopy. We also compared the structural properties of samples deposited at 400 °C on glass to those deposited on Pt/silicon substrate. The resistivity, surface roughness and size of the grains have also been studied and correlated to the thickness of ZnO films deposited on Pt/Si substrates. The experimental results reveal that the substrate has a major influence on the structural and morphological properties. For the films deposited on glass, below 400 °C, T_s and T_a have a similar influence on the structure of the films. Moreover, the ZnO samples deposited at RT and annealed in air have poor electrical properties.     

Size- and temperature-dependent thermoelectric and electrical properties of Bi88Sb12 alloy thin films

The thin films of Bi₈₈Sb₁₂ of different thicknesses have been vacuum deposited on glass and silicon substrates using the flash evaporation method. The structural characterization was carried out by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The composition and thicknesses of as-grown and annealed films were measured by the quartz crystal thickness monitor and Rutherford back scattering spectroscopy (RBS). The thermoelectric power and electrical resistivity measurement have been carried out on the films in the temperature range 100-300 K. The thickness dependences of electrical resistivity and thermoelectric power of thin films have been analyzed using the effective mean-free path model. The thermoelectric power factors of films have been calculated and the nature of carrier scattering in these films has been reported.     

Effects of High Magnetic Field on the Structure and Magnetic Properties of Molecular Beam Vapor Deposited Fe₆₀Ni₄₀ Thin Films

The Fe₆₀Ni₄₀ (in atomic %) polycrystalline thin films with 90 nm thickness were prepared on 200 °C quartz substrate by using molecular beam vapor deposition method. The influence of 0 T and 6 T magnetic fields on the structural evolution and magnetic properties of thin films was studied by using EDXS, XRD, AFM and VSM. In this study, only α phase was formed in both thin films. It was found that the application of a 6 T magnetic field obviously decreases the RMS of surface roughness and the grain size. For the magnetic properties of the thin films, the 6 T magnetic field increases the saturation magnetism Ms in-plane and the squareness (Mr/Ms) of the hysteresis loop and decreases the coercive force Hc. This indicates the soft magnetic properties of the thin films have been notably enhanced in-plane by a high magnetic field. The relationship between the structural evolution and magnetic properties was discussed in details.     

Influence of high temperature processing of sol-gel derived barium titanate thin films deposited on platinum and strontium ruthenate coated silicon wafers

Thin films of barium titanate (BTO) of 200 nm thickness, derived from an alkoxide-carboxylate sol-gel process, were deposited on Pt/Ti and SrRuO₃/ZrO₂-8%Y₂O₃ coated Si wafers. Films with a dense columnar microstructure were obtained by repeated deposition of thin amorphous layers from low-concentrated sols, and crystallization at 800 °C. This method added 10 nm thickness to the crystalline BTO film in each deposition step. The harsh processing conditions had a negative impact on the platinized silicon wafers, where Pt-Si silicides were formed. This led to diffusion of Si into BTO and interfacial silicate formation. The interfacial silicate layer was the cause of deteriorated dielectric and ferroelectric properties of the BTO layer. Use of SrRuO₃/ZrO₂-8%Y₂O₃/Si substrates solved the problem. No diffusion of Si was observed, and BTO films with good dielectric and ferroelectric properties were obtained.     

Preparation of Pb(Zr0.52Ti484848)O3 thin films on silicon-on-insulator substrates by excimer laser deposition combined with rapid thermal annealing

In this paper we report the fabrication of ferroelectric Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films on Si-on-Insulator (SOI) substrates with and without an electrode by pulsed excimer laser deposition combined with rapid thermal annealing. Based on the structural and interfacial characteristics analysis by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM) and automatic spreading resistance measurement (ASR), the film structure and orientation were revealed to be dependent on the annealing time and annealing temperature as well as deposition temperature. From RBS spectra and XTEM observation it is shown that the PZT thin films did not interact with the top silicon layers of SOI and that the composition of the film was similar to the target. The ASR measurements showed that the electrical properties of PZT/SOI as well as PZT/Pt/SOI were abrupt, and that the electrical properties of the SOI substrates were still good after the PZT growth.     

Characterization of Sn-doped BST thin films on LaNiO<Subscript>3</Subscript>–coated Si substrate

Sn-doped (Ba,Sr)TiO₃(BSTS) thin films have been deposited on highly (200) oriented LaNiO₃(LNO) thin films by sol-gel method. The atomic force microscope (AFM) images exhibited that the dopant Sn did not decrease the crystalline grain size of BST thin films. The structure of the BST film, determined by X-ray diffraction (XRD), presented the higher intensity (110) and (200) peaks, while the latter was distinctly induced by LNO layer. Evidently, Sn-doped BST thin films on LNO/Si substrate were found to decrease the dielectric constant and the dielectric loss, which is favourable to potentially improve the figures of merits (F _D ) of pyroelectric materials. The BSTS thin films on LNO layer also displayed an excellent leakage current property comparing with the BST thin film on Pt/Ti/SiO₂/Si and LNO/Si substrates.     

Heat treatment effects on the formation of lanthanum-modified lead zirconate titanate thin films

The microstructural and compositional properties of lanthanum-modified lead zirconate titanate (PLZT) thin films deposited on platinum coated Si substrates by RF magnetron sputtering have been studied. The heat treatment processes of substrate heating during deposition and post deposition furnace and rapid thermal annealing were compared as processes for obtaining the desired pervoskite phase. PLZT thin films deposited with in-situ substrate heating showed little evidence of micro-cracking. The XRD data obtained showed the formation of pervoskite phase at 550 °C and indicated the suppression of the pyrochlore phase for increasing temperatures. The RBS analysis revealed a film thickness of 140 nm and composition of (Pb_0.91La_0.09)(Zr_0.6Ti_0.4)O₃. Deposition performed with in-situ substrate heating at 650 °C resulted in highly (110) pervoskite orientated thin films with an average grain size around 160 to 200 nm and an RMS roughness of 3 nm.     

The effects of substrates on the thin-film structures of BaTiO3

Barium titanate (BaTiO₃) thin films prepared on magnesia, silicon and strontium titanate substrates by r.f. sputtering has been investigated. As a function of substrate and annealing temperatures, the crystal structure and shape were examined by X-ray diffraction and scanning electron microscopy. Thin films were grown on both MgO and silicon substrates; they were amorphous when deposited on MgO if the substrate temperature was less than 450 °C, while for those grown on silicon the temperature had to be less than 500 °C. Above these elevated temperatures, the films were crystalline, with cubic symmetry. After annealing the thin films on magnesia, the crystal structure changed from cubic to tetragonal phase above 1100 °C; thebe c-axis or annealing thus caused the grain growth of the BaTiO₃. The thin films on SrTiO₃ were found toc-axis oriented tetragonal films for a substrate temperature above 500 °C.     

Dielectric properties of YSZ high-k thin films fabricated at low temperature by pulsed laser deposition

Yttria-stabilized zirconia (YSZ) films were deposited on Pt-coated silicon substrates and directly on n-type Si substrates, respectively, by pulsed laser deposition (PLD) technique using a YSZ (5 mol% Y₂O₃-stabilized ZrO₂) ceramic target. The YSZ films were deposited in 1.5×10⁻² Pa O₂ ambient at 300 °C and in situ post-annealed at 400 °C. X-ray diffraction (XRD) and differential thermal analysis measurements demonstrated that YSZ remained amorphous. The dielectric constant of amorphous YSZ was determined to be about 26.4 by measuring Pt/YSZ/Pt capacitor structure. The 6-nm-thick amorphous YSZ films with an equivalent oxide thickness (EOT) of 1.46 nm and a low leakage current of 7.58×10⁻⁵ A/cm² at 1 V gate voltage exhibit good electrical properties. YSZ thin films fabricated at low temperature 300 °C have satisfactory dielectric properties and could be a candidate of high-k gate dielectrics.     

Ni2V2O7 thin films for negative electrode application of rechargeable microbatteries

Metallic thin films Ni/V/(Ni/V)_x/Ni were deposited under vacuum with an electron beam on Pt sheet substrates. The thickness of the films was measured in situ by the vibrating quartz method in order to achieve the atomic ratio Ni/V=1. Samples were first annealed for 30 min under vacuum at 853 K in order to initiate the metals interdiffusion and annealed for another 30 min in room atmosphere at 863 K. The films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Results show that monoclinic homogeneous Ni₂V₂O₇ thin films can be synthesized on Pt substrates by this simple technique. These Ni₂V₂O₇ were tested for their Li insertion properties in standard laboratory Li batteries. It is shown that the cycling behavior of the films is much more favorable than that of the bulk powders. The hypothesis that this behavior is linked to improved grain size and film morphology is discussed     

Structure and dielectric performance of K-doped (Pb0.5Ba0.5)ZrO3 thin films

In the present investigation (Pb_0.5Ba_0.5)ZrO₃ (PBZ) thin films doped by K (KPBZ) from 0 to 5 mol% were successfully deposited on Pt-buffered silicon substrates by a sol-gel method. The K content dependence of microstructure and electrical properties of KPBZ thin films were studied in detail. It was found that, although all the films displayed a pure perovskite structure without obvious difference, the surface roughness of KPBZ films was decreased with increasing K content. Dielectric measurements showed that the figure of merit (FOM) values of KPBZ thin films were greatly increased by K-doping, and at the same time that the temperature-dependent stability was also improved. Thus, K doping is a promising way to optimize the overall electrical properties of PBZ thin films for potential application in tunable devices.     

Effect of lattice matching on microstructure and electrical conductivity of epitaxial ARuO3 (A = Sr, Ca and Ba) thin films prepared on (001) LaAlO3 substrates by laser ablation

(001) SrRuO₃ (SRO), (001) CaRuO₃ (CRO) and (205) BaRuO₃ (BRO) thin films were epitaxially grown on (001) LaAlO₃ substrates by laser ablation, and the effect of lattice matching on the microstructure and electrical conductivity was investigated. (001) SRO and (001) CRO thin films had a terrace with orthogonal step structure, whereas (205) BRO thin film had an orthogonal structure with tetragonal grains. Epitaxial thin films showed metallic conduction, and the (001) CRO thin films exhibited the highest electrical conductivity, i.e. 1.5 × 10⁵ S m^− 1, among the (001) SRO, (001) CRO and (205) BRO thin films. The smaller misfit between thin film and substrate could be associated with the higher electrical conductivity.     

Preparation and characterization of Ba1 − xSrxTiO3 thin films deposited on Pt/SiO2/Si by sol-gel method

BST thin films have been investigated as potential candidates for use in frequency agile microwave circuit devices. Stoichiometric (Ba_1 − xSr_x)TiO₃ (BST) thin films have been prepared on Pt/SiO₂/Si substrates using sol-gel method. The BST films were characterized by X-ray fluorescence (XRF) spectroscopy analysis, X-ray diffraction (XRD), scanning electron microscope (SEM) and electrical measurements. The relationships of processing parameters, microstructures, and dielectric properties are discussed. The results show that the films exhibit pure perovskite phase through rapid thermal anneal at 700 °C and their grain sizes are about 20-40 nm. The dielectric constants of BST5, BST10, BST15 and BST20 are 323, 355, 382 and 405, respectively, at 80 kHz.