LiTaO3 Films Research Articles

The Effect of Niobium and Rubidium Doping on the Energy Band Gap of a Lithium Tantalate (LiTaO3) Thin Film

Chemical solution deposition (CSD) is a technique for making a film by keeping synthetic arrangements on the outer layer of the substrate. The outcomes show that the band gap energy of the LiTaO3 film is 1 eV. Electrons are more effectively invigorated to the valence band than to the conduction band on the grounds that the energy required is not excessively huge. Niobium-doped LiTaO3 film has a band gap energy of 1.15 eV. A large amount of energy is needed for electrons to be energized from the valence band to the conduction band. The rubidium-doped LiTaO3 film has a band gap energy of 1.30 eV.

Magnetic properties regulation by electric-field for α-Fe2O3/LiTaO3 thin film at room temperature

Ion migration driven by electric-field may cause multiple changes in stoichiometry, defect, and structure, thus provide approach for modulating properties. α-Fe2O3 have attracted tremendous attention as anode materials for lithium ion batteries. The magnetic properties of weakly-ferromagnetic α-Fe2O3/LiTaO3 films can be manipulated non-volatilely at room temperature by the applied room temperature electric-field. The regulation of magnetic properties induced by the room temperature electric-field may relate to the migration effects of lithium ions. A theoretical investigation on the microstructure and magnetic properties before and after the insertion of lithium ion into α-Fe2O3 shows that the insertion of lithium ion induces local structural distortion, charge redistribution and the magnetic moment increase. This study makes a step forward for electric control of magnetism in solid-state ferrite film and provides opportunities for the development of multifunctional structures

High-performance complementary resistive switching in ferroelectric film

The complementary resistive switch (CRS) offers a promising logic-in-memory functionality and is a potential solution to the “von Neumann bottleneck” problem, but the CRS structure composed of two anti-serially connected bipolar resistive switching cells limits device application. In this work, we report a high-performance CRS in a single layer of ferroelectric LiTaO3 film. The device has continuous tunable steady-states, stable operating voltages, a maximum off/on ratio more than 102, good retention longer than 105 s, and a good endurance of over 107 cycles. Besides, the energy consumption of the CRS is tunable by defect engineering. Experiments suggest that the ferroelectric domain switching with charged domain walls possibly contributes to the stability of the CRS in LiTaO3 film.

Interdependence of piezoelectric coefficient and film thickness in LiTaO3 cantilevers

AbstractElectromechanical energy demands on homogenous thick films of piezoceramics with sufficiently large piezoelectric constant and reproducible performance. Single‐phase LiTaO3 films deposited by sol‐gel processing have been fabricated as cantilevers to investigate the interdependence of dielectric and piezoelectric properties as a function of film thickness. Phase pure LiTaO3 films with varying thickness in the range of 2.07‐4.37 µm on stainless steel substrates were obtained after calcination of samples at 650°C. The relative permittivity of optimized spin‐coated films peaked at 479.73 (1 kHz), whereas the piezoelectric coefficient (d33 mode) determined by piezoresponse force microscopy was in the range of 21‐24 pm/V. The effect of poling was studied through the butterfly and phase curves. A figure of merit (FOM) up to 3.29 (10−18 m2/V2) was determined for cantilever devices, which were able to generate a peak‐to‐peak voltage of 0.046‐0.15 V using a 1 MΩ resistor as an impedance load at a fixed acceleration of 1.5 m/s2. While the power density was in the range of ~4‐20 × 10−9 W/m3, which increased with the increasing film thickness. The leakage current density decreased in the range of 4 × 10−5‐6 × 10−7 A/m2 in the same direction. As both ferroelectric and piezoelectric properties of LiTaO3 films are dependent on film thickness, an optimal energy conversion efficiency was obtained for a thickness of ~3 µm. Furthermore, these devices were tested up to a temperature of 150°C for voltage generation. Given the need for lead‐free piezoelectric materials for environmental applications, these LiTaO3 cantilevers are very promising for vibrational energy harvester (VEH) applications especially due to their cost effectiveness, small size, stability at higher temperatures, and repeatable properties, which makes them suitable for MEMS devices for industrial applications.

Unusual Response of Thin LiTaO3 Films to Intense Microwave Pulses.

Fundamentally different responses of a LiTaO thin film detector are observed when it is subjected to short microwave pulses as the pulse intensity is altered over a wide range. We start from weak microwave pulses which lead to only trivial pyroelectric peak response. However, when the microwave pulses become intense, the normally expected pyroelectric signal seems to be suppressed and the sign of the voltage signal can even be completely changed. Analysis indicates that while the traditional pyroelectric model, which is a linear model and works fine for our data in the small regime, it does not work anymore in the large signal regime. Since the small-signal model is the key foundation of electromagnetic-wave sensors based on pyroelectric effects, such as pyroelectric infrared detecters, the observation in this work suggests that one should be cautious when using these devices in intense fields. In addition, the evolution of detector signal with respect to excitation strength suggests that the main polarisation process is changed in the large signal regime. This is of fundamental importance to the understanding on how crystalline solids interact with intense microwaves. Possible causes of the nonlinear behaviour is discussed.

High specific detectivity infrared detector using crystal ion slicing transferred LiTaO3 single-crystal thin films

LiTaO3 (LT) single crystalline films have been used to fabricate pyroelectric infrared detectors. Sub-micrometer thick LT films have been transferred on LT holder substrate by Crystal Ion Slicing (CIS) technology using hydrogen ions implantation and SiO2 bonding process. The surface roughness result from the Gauss distribution of hydrogen ions was decreased from 18.7 nm to 1.5 nm after Ar+ ion bombardment. The pyroelectric coefficient of CIS fabricated LT film (2 × 10−8 C/cm2·K) is comparable to that of LT bulk crystal. Detectors fabricated using the CIS fabricated LT films show larger detectivity at higher modulation frequency than the commercially available pyroelectric devices using LT bulk crystal or PZT polycrystalline thin films. The highest value of specific detectivity is 2.49 × 108 cm·Hz1/2W−1 at 300 Hz. The results demonstrate that the LT single crystal film fabricated by CIS technology is a promising material to fabricate quick response pyroelectric devices.

Characterization of Lithium Tantalate (LiTaO3) Film on the Concentration Variations of Ruthenium Oxide (RuO2) Dope

One of the ferroelectric materials that has a large potential to be developed is LiTaO3 film. LiTaO3 film has been successfully produced by doping with RuO2 concentrations of 0%, 2%, 4%, and 6% using the CSD (Chemical Solution Deposition) method with a spin coating technique at 8000 rpm and an annealing temperature of 850° C. Samples were characterized using UV-Vis Spectrophotometry, SEM, XRD, and EDX. The film thicknesses at dope concentrations of 0%, 2%, 4%, and 6% 0.2681 µm, were 0.2234 µm, 0.2234 µm, and 0.5078 µm, respectively, with bandgap energy levels of 2.38 eV, 2.29 eV, 2.04 eV, and 2.47 eV. The lattice parameters obtained were a = 5.098961 Å and c = 14.316897 Å (0% RuO2), a = 5.065135 Å and c = 14.058488 Å (2% RuO2), a = 5.069937 Å and c = 114.275256 Å (4% RuO2), and a = 5.058727 Å and c = 14.253829 Å (6% RuO2) causing the crystal structure to be hexagonal (α = β = 90° and γ = 120°) with crystal sizes for each film 0.258 µm, 0.285 µm, 0.295 µm, and 0.36 µm.

LITAO3 CHARACTERIZATION OF RUBIDIUM ON TEMPERATURE VARIATIONS

One of the studies that recently attracted the attention of physicists is research on ferroelectric material because this material is very promising for the development of new generation devices in connection with the unique properties it has. Ferroelectric materials, especially those based on a mixture of lithium tantalite (LiTaO3), are expected to be applied to the infrared sensor. Lithium tantalate (LiTaO3) is a ferroelectric material that is unique in terms of pyroelectric and piezoelectric properties that are integrated with good mechanical and chemical stability. Therefore LiTaO3 is often used for several applications such as electro-optical modulators and pyroelectric detectors. LiTaO3 is a non-hygroscopic crystal, colorless, soluble in water, has a high transmission rate and does not easily damage its optical properties. LiTaO3 is a material that has a high dielectric constant and a high load storage capacity. This research has succeeded in determining the band gap energy of the LiTaO3 film in the rubidium chamber obtained in the range of values 2.02-2.98 eV as shown in figure 4. The LiTaO3 film after the annealing process at a temperature of 650 oC, has the highest band gap energy of 2.98 eV. Large energy is needed on the electrons to be excited from the valence band to the conduction band. Whereas in the LiTaO3 film after an annealing process of 800 oC, the band gap energy obtained is 2.02 eV. This makes it easier for electrons to be excited from the valence band to the conduction band because the energy needed is not too large.

Application of lithium tantalate (LiTaO3) films as light sensor to monitor the light status in the Arduino Uno based energy-saving automatic light prototype and passive infrared sensor

ABSTRACTGrowth of LiTaO3 film on a type-p silicon substrate (100) was conducted using the Chemical Solution Deposition (CSD) and spin coating methods at a speed of 3000 rpm for 30 seconds. The film on the substrate was then heated at 850oC for 15 hours. The resulting film was then characterized for its sensitivity value. The film was utilized as a light sensor to read changes in light intensity to monitor lighting status in an Arduino Uno-based energy-saving automatic light prototype. Previously, the output of the film in the form of an electrical voltage was strengthened using a voltage amplifying circuit (OP-Amp). The energy-saving automatic light prototype was manufactured in two conditions, an automatic condition (with assistance from an infrared passive sensor and real time clock) and a manual condition (with assistance from a GSM to control the lighting and LiTaO3 film as a light sensor to monitor the lighting status). In the automatic condition, the assessment of the infrared passive sensor's sensitivity was conducted at distances of 0 m, 0.5 m, 1 m, 1.5 m, 2 m, 2.5 m, and 3 m at angles of 00, 300, 450 and 600 (the source of motion was human movements). The real time clock was used to regulate the infrared passive sensor activation time (7 a.m to 5 p.m Western Indonesia Time). In the manual condition, when entering manual time (outside the 7 a.m to 5 p.m Western Indonesia Time range), to be exact, the GSM would send a message containing the duration of the lighting usage and the cost of the lighting usage. Activation of the lighting was conducted by replying to the message with the code #1 to turn on the lighting and #0 to turn it off.

Study of the crystalline and optical properties of lithium tantalate thin films deposited by high power RF magnetron sputtering

Lithium tantalate (LiTaO3) thin films were deposited by high power (250 W) RF magnetron sputtering on Pt/Ti/SiO2/Si(100) substrates and were annealed from 600 °C–700 °C in an O2 or N2 environment. The crystallinity of those films were examined by x-ray diffraction and Raman spectra to study the effects of annealing temperature and annealing gas on the crystal properties of LiTaO3 thin films. LiTaO3 thin films annealing at 650 °C in O2 have a better crystalline quality in a (012) preferential orientation. However, LiTaO3 thin films annealed at 700 °C in O2 contain impurities with titanium oxide (Ta2O5). This is attributable to the fact that the crystal structure is unstable above the Curie temperature and the tantalum reacts with oxygen in the annealing process. At the same time, the result of the Raman spectra suggests that LiTaO3 thin films annealed at 600 °C and 650 °C are closer to near-stoichiometric LiTaO3 and have less Li diffusivity and Li-deficient phases. Finally, optical constants of LiTaO3 films are also primarily probed by spectroscopic ellipsometry. For LiTaO3 thin films annealed at 650 °C in O2, the refractive index is 2.33, the extinction coefficient is 0.002 34 and the direct optical band gap energy is estimated to be minimal at 3.66 eV.

Reducing the Bandgap Energy via Doping Process in Lead-Free Thin Film Nanocomposites

There are numerous applications for the pyroelectric composite films in the medical field, military field and environmental applications field. The main focus of this research is to fabricate the higher efficiency thin films that are flexible like the polymers. PVDF is ideal when it comes to making detectors as they are flexible; possess high pyroelectric current and resistance, low dielectric constant and density. Pure PVDF and PVDF films doped with CNT and MWCNT, PVDF: LiTaO3, PVDF: LiTaO3 films doped with MWCNT thin films were fabricated using the solution casting technique. Films fabricated were characterized for their electrical, optical and structural properties using FTIR Spectroscopy, UV-Vis Spectroscopy, and Raman Spectrum. From UV-Vis spectroscopy analysis it is calculated that the indirect bandgap energy of pure PVDF is 5.99 eV, 4.85 eV for PVDF+0.5%-CNT, 4.76 eV for PVDF+1%-CNT, 5.22 eV for PVDF+LT, 4.95 eV for PVDF+LT+2%-MWCNT and 4.85 eV PVDF+LT+2.5%-MWCNT. The calculated direct bandgap energy of pure PVDF is 6.25 eV, 5.95 eV for PVDF+0.5%-CNT, 4.85 eV for PVDF+1%- CNT, 5.42 eV for PVDF+LT, 5.12 eV for PVDF+LT+2%-MWCNT and 4.95 eV PVDF+LT+2.5%-MWCNT. The decrease in the bandgap may be attributed to the presence of unstructured bulk defects. Obtained results show that doping of PVDF and its nanocomposite materials with CNT and MWCNT is enhancing the key characteristics of the materials that are beneficial for the optical devices industry.

The Diffusion Coefficient of Lithium Tantalite (LiTaO3) with Temperature Variations on LAPAN-IPB Satellite Infra-red Sensor

Lithium tantalate, which has chemical formula of LiTaO3, thin films have been grown on a p-type Si substrate (100) by using chemical solution deposition and spin coating techniques at speed of 3000 rpm for 30 seconds. LiTaO3 thin films were made in concentration of 2.5 M and at annealing temperatures of 550°C, 600°C, 650°C, 700°C, 750°C, and 800°C. The purpose of this study determines the diffusion coefficient of lithium tantalate (LiTaO3) above the silicon substrate (100) on the p-type annealing temperature of 550°C, 600°C, 650°C, 700°C, 750°C and 800°C. These thin films were characterized by using LCR meter. The electrical conductivity values of LiTaO3 films were in the range of 10-6 - 10-5 S/cm, where the higher the electrical conductivity, the higher the light intensity. This indicates that the LiTaO3 films was a semiconductor material. In addition, the higher the energy that moves the particles leads to the faster the diffusion. The diffusion coefficients of Li-TaO3 films were in the range of 57 - 391 nm2/s.

Development of Lithium Tantallite (LiTaO3) for Automatic Switch on LAPAN-IPB Satellite Infra-red Sensor

Automatic switch is an automatic electrical device that uses sensor technology to detect movement, or body temperature that was detected in the switch. The sensor uses passive infra-red receiver (PIR) by using lithium tantalite (LiTaO3) that will capture a moment as a response in temperature changes. In this research, we synthesized a thin film of lithium tantalite (LiTaO3) on a substrate silicon p-type. The film was produced by chemical solution deposition (CSD) and engineering spin coatings with temperature annealing on 550°C, 600°C, 650°C, 700°C, 750°C and 800°C with 3000rpm in speed for around 30seconds. The value of high absorbent showed that the LiTaO3 film has a large number of photon energy. This research obtained the energy band-gap film LiTaO3 in the range 3.41-4.56eV. This result concludes that annealed temperatures affects the optical properties of the LiTaO3 film in the substrate of Si (100) p-type semiconductor. The sensitivity of this high intensity absorbent for energy and high value of band-gap is great and is therefore potential to be used prospectively for the automatic switch sensor on the satellite platform.

A Novel Sol-Gel Method of Preparation of the LiTaO3 Thin Film and Its Property Research

The dielectric constant and the dielectric loss of the LiTaO3 thin film derived through the experimental method which is called the Sol-Gel method, as well as its pyroelectric constant and ferroelectric hysteresis loop are explored in the manuscript. In comparison, the dielectric constant and the dielectric loss of the annealed LiTaO3 thin film derived from Pt(111)/SiO2/Si(100) substrate are superior to which are derived from Fluorine-doped tin oxide substrate. The relationships among ferroelectric hysteresis loop and pyroelectric constant as well as temperature are measured. In room temperature, the dielectric constant of LiTaO3 film is 45 at a frequency of 10 kHz, the dielectric loss is lower 0.006 than dielectric constant, The remanent polarization is 10.71 μC·cm−2. The pyroelectric coefficient is 1.43×10−8 C·cm−2·K−1 at 62 oC. This proves that the LiTaO3 thin films with high figures of merit (FV = 0.56×10−10 C·cm·J−1, FD = 0.51×10–8 C·cm·J−1) can be used widely in thermal detectors.

Preparation and characterization of LiTaO3 films derived by an improved sol-gel process

In this paper, an improved sol-gel method was suggested to obtain high-concentration LiTaO3 precursor solution for simplified experimental conditions and thicker films, by mixing lithium acetate and tantalum ethoxide in a 1, 2-Propylene glycol solution. Compared to traditional methods, the process was done without weak acidic solution and absolute dry experimental condition. Results of a comparative study of LiTaO3 thin films derived by the improved sol-gel process and a traditional process using 2-methoxy ethanol as solvent were presented. Nano-crystalline LiTaO3 films with rhombohedral structures were formed in both methods after annealing at 650 ° for 5 min. The thickness of each LiTaO3 layer coated onto the substrate increased from 25 nm to 110 nm when 2-methoxy ethanol was replaced by 1, 2-Propylene glycol. LiTaO3 films with a stronger preferential orientation were obtained in 1, 2-Propylene glycol due to its higher boiling point and slower volatilization rate. On the other hand, the diffraction peak intensity of LiTaO3 thin films prepared using 1, 2-Propylene glycol was weaker than that of the films prepared using 2-methoxy ethanol due to decreased times of annealing.

Preparation of LiTaO<sub>3</sub> Nano-Crystalline Films by Sol-Gel Process

Lithium tantalite (LiTaO3) thin film material shows good feasibility and potential for the application of high-performance detection system. In this paper, sol-gel process of LiTaO3 thin films on p-type (111) silicon substrates was described. Stable precursor solution with a desired viscosity was obtained using lithium acetate (LiAc) and tantalum ethoxide (Ta(OC2H5)5) as starting materials. Heat treatment process was optimized to fabricate LiTaO3 films of high crystallinity. Higher crystalline quality films were obtained when each spin-coating process was followed by an annealing operation. Microstructures and crystallization properties of LiTaO3 thin films were further studied. Nano-crystalline films were obtained after annealing at 700 °C for 5 min. The experimental results indicated that the crystallinity and mean grain size of LiTaO3 thin films were proportional to the film thickness.

Residual stresses and clamped thermal expansion in LiNbO3 and LiTaO3 thin films

Residual stresses in LiNbO3 and LiTaO3 epitaxial thin films were evaluated taking into account Li nonstoichiometry by means of Raman spectroscopy and x-ray diffraction. The epitaxial films were grown on C-cut sapphire substrates by pulsed injection metal organic chemical vapour deposition. Clamping of the epitaxial films by the substrate induced a transfer from the in plane thermal expansion to the out of plane component. The temperature of the phase transition of clamped LiTaO3 films was close to that expected for a bulk sample.

Abnormal switching of ferroelectric domains created by the tip of an atomic force microscope in a congruent LiTaO3 single-crystal thin film

Ferroelectric domains have been created in single-crystal ∼1 μm thick LiTaO3 films using the tip of an atomic force microscope. The presence of a domain with a polarization that is oriented in the opposite direction as compared to the applied field in the center of the domains created by the tip is reported. This paper aims at better understanding this phenomenon. Domains with a polarization oriented toward the bulk do not behave like domains with a polarization oriented toward the surface. The evolution of the size of the abnormal domain as a function of the parameters of the applied voltages and exerted forces is studied using a technique derived from the atomic force microscope (piezoresponse force microscopy), and its kinetics of formation is recorded by means of time resolved piezoresponse force microscopy. The possible causes for its appearance are discussed. The ferroelastic effect does not seem to play a role in the process. A possible artifact from the atomic force microscopy imaging process itself is not relevant. It appears that the most probable mechanism responsible for this phenomenon is the injection of charges during the application of the voltage pulse, which creates a strong electric field when the voltage is removed. The experimental observations are discussed in light of this hypothesis.

CVD作製したLiTaO<sub>3</sub>薄膜の特性

LiTaO3 is a key material for surface acoustic wave (SAW) devices, bulk devises, piezoelectric elements, pyroelectric sensors and other applications. However, for almost of their applications the LiTaO3 single crystal is used. In this paper, authors report the growth of LiTaO3 films on a metal electrode layer by Chemical Vapor Deposition (CVD) by changing Li source condition. The characteristics of the LiTaO3 films observed by the X-ray diffraction (XRD) and their polarity dependent on the Li source supply volume. By controlling the Li/Ta ratio, high quality ferroelectric LiTaO3 films are deposited.

Nanodomain Formation on Ferroelectrics and Development of Hard-Disk-Drive-Type Ferroelectric Data Storage Devices

In this study, several read/write (R/W) tests were conducted using a hard-disk-drive-type ferroelectric data storage test system based on scanning nonlinear dielectric microscopy (SNDM). A periodically inverted signal, which corresponded to artificial domain stripes formed on LiTaO3 single crystal, could be read correctly with a bit rate of 2 Mbps using this test system. Bit writing on a 50-nm-thick epitaxial LiTaO3 film at 20 Mbps was also demonstrated. In addition, a noncontact probe-height control technique was adapted to solve the problem of tip abrasion. The gap distance between a probe and a medium surface was successfully controlled on the nanometer order using a noncontact SNDM technique with sharp-pointed tungsten needle probes prepared by electrolytic polishing. Bit writing under a noncontact state was also studied. Artificial domain dots with diameters of less than 100 nm could be formed under the noncontact state.