Influence of deposition parameters on physico-chemical and optical properties of sputtered PbTiO3 thin films

Abstract

Stoichiometric thin films of lead titanate (PbTiO₃) have been grown “in situ” without postannealing on (0001) sapphire substrates by rf magnetron sputtering technique. X-ray diffraction scans have revealed that as-grown films consist of the perovskite phase and are polycrystalline with a high (111) orientation. The structure, the microstructure and the optical properties have been studied as a function of the process parameters i.e., substrate temperature, gas pressure and the target composition, in particular the lead content. We report the dependence of the deposition conditions on the optical constants. The optimum experimental conditions (100m Torr and 600°C) to produce thin films with high transparency and refractive indices (n = 2.61 at 633 nm), similar to values for bulk materials, are given in this paper.     

Fabrication of Er3+/Pr3+ Co-doped soda-lime glass thin films using RF magnetron sputtering method and optical property characterization

Er^3+/Pr³⁺ co-doped soda-lime glass thin films have been fabricated using RF magnetron sputtering method and their structural and optical properties have been studied. Deposition rate, crystallinity, and composition of glass thin films were investigated by scanning electron microscopy, transmission electron microscopy, and electron probe micro area analysis. Refractive index, birefringence and binding characteristics have been investigated using a prism coupler and X-ray photoelectron spectroscopy. Er³⁺/Pr³⁺ co-doped soda lime glass thin films were prepared by changing substrate temperature (room temp. ∼550^∘C), RF power (90 W–130 W), and Ar/O₂ gas flow ratio at processing pressure of 4 mTorr. Glass thin films could be obtained at the optimized processing condition at 350^∘C, RF power of 130 W, and gas flow of Ar:O₂ = 40:0 with maximum deposition rate of 1.6 μm/h. Refractive index and birefringence increased from 1.5614 to 1.5838 and from 0.000154 to 0.000552, respectively, as the content of Pr³⁺ increased. Binding energy of Pr3d also increased as the content of Pr³⁺ increased.     

Thickness dependent ferroelectric properties of BSTO thin films deposited by RF magnetron sputtering

The thickness dependence of ferroelectric permittivity of (Ba, Sr)TiO₃ has been investigated. The BST films could be obtained to have a simple cubic perovskite structure, space group Pm3m, and practically c-axis epitaxial structure deposited at 800^∘C. Through post-annealing process, we have improved the dielectric properties; dielectric permittivity, dielectric loss, and tunability. The change in dielectric properties before and after annealing is attributed to the change in film strain and the contraction in film lattice. As the thickness of BST films increases from 55 nm to 350 nm, the dielectric constant of BST films increases from about 100 to above 670 due to the reduction of interfacial dead layers with low dielectric constant between films and top electrodes. The dielectric loss of BST thin films decreased as the thickness increases. The existence of interfacial dead layers in a thinner film had a larger effect on the effective dielectric constant than tensile strain between the BST films and MgO substrate.     

Diluted magnetic semiconductor properties of Zn1 − x Cox O: 1 at% Al thin films prepared by pulsed DC magnetron sputtering

Zn_{1 − x} Co_xO: 1 at% Al(x = 0−0.3) films were grown on corning 7059 glass by asymmetrical bipolar pulsed dc magnetron sputtering. The c-axis orientation along the (002) plane was enhanced with increasing Co concentration. The ZnCoO thin films are grown to the fibrous grains of tight dome shape. The transmittance spectra showed that sp-d exchange interactions and typical d-d transitions become activated with increasing Co concentration. The electrical resistivity of ZnCoO films increased ranging from ∼10^{− 3} to ∼10⁻² Ω ⋅ cm with increasing Co concentration, especially it increased greatly at 30 at% Co. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster in the ZnCoO films is formed and room temperature ferromagnetism is exhibited. These electrical and magnetic properties of ZnCoO films suggest a potential application of dilute magnetic semiconductor devices.     

Electrical and optical properties of microwave dielectric thin films prepared by pulsed laser deposition

Abstract

Bi₂(Zn_1/3Nb_2/3)₂O₇, BiZN, materials possess high dielectric constant and low loss factor in microwave frequency region. They have good potential for device application, especially in the form of thin films. However, the microwave dielectric properties of a thin film are very difficult to be accurately measured. Evaluation on the dielectric behavior of the films through the performance of the microstrip line devices made of these films involves metallic conduction and stray field losses. A novel measuring technique, which can directly evaluate the microwave dielectric properties of a thin film is thus urgently needed.

In this paper, BiZN thin films were grown on [100] MgO single crystal substrates using pulsed laser deposition process. The high-frequency dielectric properties of thus obtained thin films were determined using optical transmission spectroscopy (OTS). The [100] preferentially oriented films with pyrochlore structure can be obtained for the thin films deposited at 400–600°C substrate temperature under 0.1 mbar oxygen pressure. OTS measurements reveal that the index of refraction (n=1.95–2.35) and absorption coefficient (k=0.28x10^?4-2.25 × 10^?4 nm^?1) of the films vary insignificantly with the crystallinity of the BiZN films.     

Structural and electrical properties of Sb-doped p-type ZnO thin films fabricated by RF magnetron sputtering

We investigated the Sb-doping effects on ZnO thin film using RF (radio frequency) magnetron sputtering and RTA (rapid thermal annealing). The structural and electrical properties of the thin films were measured by X-ray diffraction, SEM (scanning electron microscope), and Hall effect measurement. Thin films were deposited at a high temperature of 800°C in order to improve the crystal quality and were annealed for a short time of only 3 min. The structural properties of undoped and Sb-doped films were considerably improved by increasing oxygen content in the Ar-O₂ gas mixture. Sb-doping also significantly decreased the electron concentration, making the films p-type. However, the crystallinity and surface roughness of the films degraded and the mobility decreased while increasing Sb-doping content, likely as a result of the formation of smaller grain size. From this study, we observed the transition to the p-type behavior at 1.5 at.% of Sb. The thin film deposited with this doping level showed a hole concentration of 4.412?×?10¹⁷ cm^?3 and thus is considered applicable to p-type ZnO thin film.     

基片温度对Ni81Fe19薄膜结构和各向异性磁电阻的影响

利用磁控溅射方法制备了一系列Ta(x)/Ni81Fe19(100nm)/Ta(3nm)磁性薄膜。着重研究基片温度、缓冲层厚度对薄膜结构和各向异性磁电阻的影响。利用X射线衍射仪分析了薄膜结构、晶粒取向;用四探针法测量了薄膜的电阻率和各向异性磁电阻。结果表明,基片温度对薄膜的各向异性磁电阻及饱和场有显著影响,随着基片温度的升高,薄膜各向异性磁电阻随之增大,饱和场则相反。基片温度在400℃时制备的Ni81Fe19薄膜具有较大的各向异性磁电阻比和较低的磁化饱和场,薄膜最大各向异性磁电阻比为4.23%,最低磁化饱和场为739.67A/m;随着缓冲层厚度的增加,坡莫合金薄膜的AMR值先变大后减小,在x=5nm时达到最大值。     

Effect of Gd doping on crystalline orientation,structural and electric properties of PZT thin films prepared by Sol-Gel methods

Gadolinium (Gd)-doped lead zirconium titanate (PGZT) thin films have been prepared by Sol-Gel methods to investigate the effects of Gd doping on crystalline orientation, structural and electric properties of lead zirconium titanate (PZT) films according to doping concentration from 0% to 5%. Conventional heat process and appropriate doping concentration, without introducing a single crystal seed layer, were used for obtaining (100)-oriented PGZT thin films with dense columnar structures. The maximum dielectric constant (1310.35 at 100 Hz) and the optimum ferroelectric properties were obtained for 2% Gd-doped film. 1% Gd-doped PZT film exhibited excellent piezoelectric properties.     

溅射功率对CoFeB薄膜磁与结构特性的影响

以不同功率溅射制备了CoFeB合金薄膜样品并在高真空下退火处理。发现低功率生长的薄膜始终具有磁各向同性,而高功率生长的薄膜随着退火温度的升高,由起始的单轴磁各向异性逐渐向磁各向同性转变。X射线衍射分析也印证了CoFeB薄膜随退火温度的升高,薄膜由非晶态逐渐向结晶态转变。当退火温度高于400℃时,低功率生长的CoFeB样品的矫顽力大于高功率生长薄膜的矫顽力。同时发现低功率生长的CoFeB的(110)峰值高于高功率生长的样品峰值,表明低功率生长的薄膜晶粒尺寸更大。     

Dielectric and electrooptic properties of acetate derived PLZT X/65/35 thin films

Abstract

PLZT solutions were prepared from the as-received acetate precursors by means of a simple mixing procedure which produced a stock solution of approximately 10% oxide solids. Films were fabricated via dip coating and heat treating at 700°C for two minutes per layer. As many as 150 layers were deposited with an automatic dip coating system. All of the resulting films were optically transparent and well crystallized in the perovskite phase. The films were evaluated with respect to dielectric and electrooptic properties. Shutter contrast ratios as high as 1000 to 1 were measured.     

SmTbCo/Cr薄膜的磁特性与温度特性研究

采用射频磁控溅射法在玻璃基片上成功地制备了SmTbCo/Cr非晶垂直磁化膜,对薄膜的磁特性与温度特性进行了研究.薄膜组分为(Sm0.286Tb0.714)31Co69/Cr时,其饱和磁化强度为330kA/m,矫顽力为398kA/m,薄膜的磁各向异性能值高达415kJ/m3;该种薄膜的居里温度在220℃左右,补偿温度在室...     

Mesophase configurations and optical properties of mesoporous TiO2 thin films

Highly ordered mesoporous TiO₂ thin films have been successfully synthesized via a copolymer templating sol-gel route. A configuration transition from hexagonal, to cubic, and then to a channel-like structure was observed when the copolymer-templated thin film was thermally annealed from 110 to 450^∘C. In the mesoporous TiO₂ film annealed at 450^∘C, mesopores were merged in a preferential direction, forming a channel-like structure consisting of a semicrystalline (anatase) framework. These films exhibit excellent optical transparency with transmittance higher than 85% in the visible region. A blue shift in UV-Vis absorption onset was shown for the mesoporous TiO₂ films, indicating a size quantization effect of nanocrystalline titania.     

Aging and Annealing Effects of ZnO Thin Films on GaAs Substrates Deposited by Pulsed Laser Deposition

Zinc oxide (ZnO) thin films were deposited on GaAs (100) substrates at different temperatures in the pulsed laser deposition (PLD) system. From the measurements of X-ray diffraction (XRD) at room temperature, 300–500°C were found to be good condition for the crystallization of the thin films. From the photoluminescence (PL) measurements, 500°C was found to be the optimized temperature for its optical property. Samples grown at 100, 200, 300, and 400°C showed near band-edge (NBE) emissions and deep-level emissions. The intensity of deep-level emissions decreased as time goes on, which is believed to originate from oxygen vacancies or zinc interstitials in thin films. While for the sample grown at 500°C, bright NBE emissions were observed at room temperature, and no deep-level emissions observed. This means that the high-optical-quality thin film was grown at 500°C. At the same time, annealing process of ZnO thin films grown at room temperature was carried out in PLD chamber. It was found that the annealing temperature of 600°C has strong effects on its PL. Aging and annealing effects in ZnO thin films grown on GaAs substrates by PLD were observed for the first time.     

Microstructures and dielectric properties of Zn2SnO4 thin films by sputtering from a ZnO doped ceramic target

The dielectric properties of Zn₂SnO₄ thin films with various degrees of ZnO dopant concentration were investigated. Zn₂SnO₄ thin films were prepared using the radio frequency magnetron sputtering. The X-ray diffraction patterns of the 0 and 75 mole % ZnO doped Zn₂SnO₄ thin films revealed that Zn₂SnO₄ is the main crystalline phase, which is accompanied by a little SnO₂ as the second phase. The second phase SnO₂ in specimens vanished when the extent of ZnO additive was increased to 100 mole%. A dielectric constant of 15–40 and a loss factor of 0.10–0.14 of Zn₂SnO₄ thin films were measured at 1 MHz with ZnO dopant concentration in the range of 0–100 mole%.     

Investigation of the effects of milling ceramic targets on the optical and electrical properties of BST thin films deposited by RF sputtering

Abstract

The RF sputtering method was utilized to deposit thin films of Ba_1-xSr_xTiO₃ (BST). The targets utilized in these experiments were prepared from ceramic powders with different particle size. The goal of this work is to examine whether the particle size distribution of the target can affect the properties of the thin films fabricated by the sputtering method. The Atomic Force Microscope (AFM) was used to examine the grain size in the thin films. The composition of the thin films and the bulk materials were examined by Fourier Transform Infrared (FTIR) spectroscopy. The dielectric properties of the thin films were measured and compared to its bulk counterparts. It was found that on lattice matched electrodes of SrRuO₃ on LaAlO₃ substrates, the thin films deposited from ceramic targets manufactured from ball-milled powders had finer grain size than those deposited from targets made from unmilled powders. However, this phenomenon was not observed in the case of polycrystalline films deposited on platinized silicon wafers.     

Preparation of Zr-rich PZT and La-doped PbTiO3 thin films by RF magnetron sputtering and their properties for pyroelectric applications

Abstract

Zr-rich PZT and La-doped PT films were fabricated on a PLT/Pt/Ti/SiO₂/Si or Pt/Ti/SiO₂/Si substrate by an RF planar magnetron sputtering equipment using powder targets with compositions of PbZr_{0 94}Ti_0.06O₃, PbZr_0.92Ti_0.08O₃ and Pb_0.85La_0.15 Ti_0.96O₃ with excess PbO of 20 mol%. The dielectric constants of PZT and PLT films showed anomalies at the transition temperatures of around 246 and 300°C, and their dielectric constants at room temperature were 350 and 1070, respectively. Significant pytroelectric currents were observed in both as-grown PZT and PLT films even without a poling treatment. The pyroelectric coefficients of those films were 10 and 30 nC/cm²K, respectively. Therefore, Zr-rich PZT and [111]-oriented PLT films sputtered on Pt/Ti/SiO₂/Si substrates possess desirable properties for potential applications to pyroelectric devices.     

Contribution of dielectric and metallic losses in RF/microwave tunable varactors using (Ba,Sr)TiO3 thin films

Abstract

Recently, there has been significant interest in use of (Ba,Sr)TiO₃ (BST) thin films for tunable high frequency (RF and microwave) components. In a previous work we have shown that BST thin films grown by metalorganic chemical vapor deposition (MOCVD) exhibit films very low losses (as low as 0.003–0.004) and tunabilities over 50% at low operation voltages.

In order to integrate BST thin films in tunable devices, the objectives of this work are : (i) study the effect of bottom and top electrode on the performance of thin film based capacitors, (ii) correlate low frequency (10 kHz) and high frequency (45 MHz - 1 GHz) measurements, (iii) separate the contribution of dielectric losses and metallic losses at both low and high frequency and finally (iv) show the potential usefulness of series capacitors structures.     

Effects of rapid thermal annealing in different ambients on structural, electrical, and optical properties of ZnO thin films by sol-gel method

We studied the effects of rapid thermal annealing in different ambients on the structural, electrical and optical properties of the sol-gel derived ZnO thin films. All the films after annealing showed highly degree of (002) oriented in the X-ray diffractometry (XRD) patterns. The effects of annealing ambients on electrical properties of the films were studied. Carrier concentration, resistivity and mobility were found to be distinguished after annealed in different ambients. The sample with the lowest resistivity of 0.095 ??·cm and the largest mobility of 105.1 cm²/v·s was achieved after annealing in vacuum. XPS results indicated that more oxygen vacancies existed on the ZnO surface when annealed in vacuum than that in O₂.     

Substrate effect on in-plane ferroelectric and dielectric properties of Ba0.7Sr0.3TiO3 thin films

Heteroepitaxial Ba_0.7Sr_0.3TiO₃ thin films were grown on (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.35 (001) (LSAT) and SrTiO₃ (001) (STO) single crystal substrates using pulsed laser deposition (PLD). X-ray diffraction characterization revealed a good crystallinity and a pure perovskite structure for films grown on both LSAT and STO substrates. The in-plane ferroelectric and dielectric properties of the films were studied using interdigital electrodes (IDE). The film grown on LSAT substrate exhibited an enhanced in-plane ferroelectricity, including a well-defined P-E hysteresis loop with the remnant polarization P _r = 10.5 μC/cm² and a butterfly-shaped C-V curve. Nevertheless, only a slim hysteresis loop was observed in the film grown on STO substrate. Curie temperature T _c of the film grown on LSAT substrate was found to be ∼105^∘C, which is nearly 70^∘C higher than that of the bulk Ba_0.7Sr_0.3TiO₃ ceramics. T _c of the film grown on STO substrate has almost no change compared to the bulk Ba_0.7Sr_0.3TiO₃ ceramics. The dielectric tunabilities were found to be 64% and 52% at 1 MHz for the films grown on LSAT and STO substrates, respectively.