LiTaO3 Thin Films Research Articles

An Infrared Near-Sensor Reservoir Computing System Based on Large-Dynamic-Space Memristor with Tens of Thousands of States for Dynamic Gesture Perception.

To efficiently process the massive amount of sensor data, it is demanding to develop a new paradigm. Inspired by neurobiological systems, an infrared near-senor reservoir computing (RC) system, consisting of infrared sensors and memristors based on single-crystalline LiTaO3 and LiNbO3 (LN) thin film respectively, is demonstrated. The analog memristor is used as a reservoir in the RC system to process sensor signals with spatiotemporal characteristics. LN crystal structure stacked with oxygen octahedra provides favorable conditions for reliable Mott variable-range hopping conduction, which provides the memristor with tens of thousands of reservoir states within a large dynamic range. With the characteristics, the analog sensor signals with high data fidelity can be directly fed to the memristive reservoir, and the spatiotemporal features can be separated and mapped. The system demonstrated a dynamic gesture perception task, achieving an accuracy of 99.6%, which highlights the great application potential of the memristor in signal sensor processing and will advance the application of artificial intelligence in sensor systems. Crystal ion slicing techniques are used to fabricate a single-crystalline thin film for both the memristor and sensor, which opens up the possibility of realizing monolithic integration of a memristor-based near-sensor computing system.

Performance of LiTaO3 Crystals and Thin Films and Their Application

Lithium tantalate (LiTaO3, or LT) crystal is widely used in optical applications, infrared detection, and acoustic surface wave devices because of its excellent piezoelectric, pyroelectric, and nonlinear optical properties. In this paper, we discuss the defect structure of LT; the preparation method for LT; the influence of doping on LT; and LT’s application in optical, acoustic, and electrical devices. We mainly analyzed the structure and physical properties of LT crystal, the preparation of LT crystal and LT thin films, the periodic polarization of LT crystal, the reduction of LT wafers, and the application potential of LT crystals in lasers and acoustic surface filters according to the most recent research. We also provide an overview of future research directions for LT in the fields of acoustics, optics, and other fields. The applications of LT in 5G, 6G, SAW filters, nonlinear optical devices, and waveguides are expected to provide additional breakthroughs.

Influence of annealing ambience on structural and piezoelectric properties of single crystal LiTaO3 thin film

The crystal-ion-slicing technology is a promising technology for fabricating high-quality single crystal piezoelectric thin films. This work attempted to investigate the influence of annealing ambience on the properties of LiTaO3 thin films fabricated by crystal-ion-slicing technology. Here, two 4-inch 42° rotated Y-X propagation LiTaO3 thin films were fabricated, as well as the LiTaO3 thin films were annealed in vacuum and O2 environment, respectively. The results demonstrate that the LiTaO3 thin films annealed in O2 environment possesses more homogeneous and denser structure and fewer defects. The Zratio of the resonators fabricated on the LiTaO3 thin films annealed in O2 environment is approximately 85.3 dB and the Q-factor reaches 5107, indicating the excellent piezoelectric properties of thin films.

The Effect of Cerium Doping on LiTaO3 Thin Film on Band Gap Energy

Lithium tantalite LiTaO3 was grown on a Si Type-P (100) substrate by chemical solution deposition and spin coating methods at a speed of 3000 rpm for 30 seconds with an annealing temperature of 800 ° C, 900 ° C. This study aims to determine the effect of temperature variations on the band gap energy. The results show that the energy band gap value of the thin film has a significant impact on the interpretation of annealing temperature. It can be seen that a high energy band gap peak occurs at an annealing temperature of 900 ° C and a time of 15 hours of the energy band gap of 1,49 eV. This shows the effect of temperature variations on the energy band gap to move from the valence band to the conduction band, which will produce current.

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

The effect of indium oxide (In2O3) dopant on the electrical properties of LiTaO3 thin film-based sensor

The effect of the indium oxide (In2O3) dopant on the electrical properties of the lithium tantalate (LiTaO3) thin film-based sensor was investigated in this study. LiTaO3 thin film was made on p-type Si (100) substrates by applying the chemical solution deposition (CSD) method. The LiTaO3 thin film was annealed at the temperature of 850 °C for 15 h. Surface morphology and elemental characterization analysis were obtained by using SEM-EDX (scanning electron microscopy–energy-dispersive X-ray spectroscopy). Then, the dielectric constant value and the photoresistive characteristic of LiTaO3 thin film were measured to determine the effect of the In2O3 dopant on the electrical properties of the thin film. From the SEM-EDX measurement, it is observed that the surface of the thin film is still non-homogeneous; therefore, the electron flow will be obstructed. Based on the elemental atomic composition analysis, it appears that the Indium atoms have appeared in the LiTaO3 thin films doped by In2O3 2%, 4%, and 6%. From the results of thin film dielectric constant calculation, it can be seen that the dielectric constant value between undoped and In2O3-doped LiTaO3 thin film does not change, which is 2.44. The photoresistive value shows that the Indium dopant decreases the resistivity but increases the conductivity of the thin film. Based on the photoresistive characteristic measurement results, it can be concluded that the LiTaO3 thin film can be used as a light sensor, and In2O3dopant can increase the conductivity of the LiTaO3 thin film.

Iron-Doped Lithium Tantalate Thin Films Deposited by Magnetron Sputtering: A Study of the Iron Role in the Structure and the Derived Magnetic Properties

Fe-doped LiTaO3 thin films with a low and high Fe concentration (labeled as LTO:Fe-LC and LTO:Fe-HC, respectively) were deposited by magnetron sputtering from two home-made targets. The dopant directly influenced the crystalline structure of the LiTaO3 thin films, causing the contraction of the unit cell, which was related to the incorporation of Fe3+ ions into the LiTaO3 structure, which occupied Li positions. This substitution was corroborated by Raman spectroscopy, where the bands associated with Li-O bonds broadened in the spectra of the samples. Magnetic hysteresis loops, zero-field cooling curves, and field cooling curves were obtained in a vibrating sample magnetometer. The LTO:Fe-HC sample demonstrates superparamagnetic behavior with a blocking temperature of 100 K, mainly associated with the appearance of Fe clusters in the thin film. On the other hand, a room temperature ferromagnetic behavior was found in the LTO:Fe-LC layer where saturation magnetization (3.80 kAm−1) and magnetic coercivities were not temperature-dependent. Moreover, the crystallinity and morphology of the samples were evaluated by X-ray diffraction and scanning electron microscopy, respectively.

Formation of Corrosion Resistant Hard Coating of Litao3 by Anodizing in Molten Lino3

Background: Lithium tantalate (LiTaO3) thin film was synthesized and in situ coated on tantalum substrate via anodic oxidation. Methods: The effects of temperature, voltage and time on composition, morphology and hardness of film were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Vickers hardness, respectively. Results: Our results showed that surface hardness of all coated samples has been increased compared with that of pure tantalum. The value of hardness was found to gradually increase with temperature, voltage and reaction time of the coating process. Selected specimens, after coating, were immersed into 10 wt% NaOH solution at 50oC for 96h to explore their anti-corrosion performance. Immersing results indicated that LiTaO3 coated samples have a smaller mass loss and corrosion rate compared to those of pure Ta substrate. Pure tantalum sample and those coated by LiTaO3 thin film were further examined by electrochemical methods including open-circuit potential (OCP), potentiodynamic polarization curves and electrochemical impedance spectra (EIS). Conclusion: We have found that samples coated with LiTaO3 thin film exhibit higher potentials and lower corrosion current densities than those of pure tantalum substrate, according to the results and analysis of OCP curves and potentiodynamic polarization curves. Upon anodic oxidation, samples display higher polarization resistance with higher resistance to corrosion.

Influence of thermal annealing on structural and optical properties of RF-sputtered LiTaO3 thin films

ABSTRACTNear stoichiometric ratio lithium tantalate (LiTaO3) thin film possesses unique performance advantages compared with bulk LiTaO3 single crystal in applying in thermal sensors and detectors. Here, LiTaO3 thin film is prepared on Pt/Ti/SiO2/Si(100) substrate by the method of RF magnetron sputtering. The authors conduct research on the structure and optical properties of LiTaO3 thin film under the conditions of annealing temperatures varying from 550 °C to 700 °C. Besides, the authors also study on optical constants of the LiTaO3 thin film which includes refractive indices, extinction coefficients and optical band gap energy by spectroscopic ellipsometry. The results show that optical band gap energy Eg will increase along with the grain size’s increase. Moreover, the results demonstrate that the best annealing temperature is 600 °C. Under the best annealing condition, the obtained refractive index, extinction coefficient k and optical band gap energy Eg is 2.05, 2 × 10−5 and 3.82 eV, respectively. These values are consistent with that of lithium tantalate single crystal. All results above mentioned proving that lithium tantalate (LiTaO3) thin film prepared by RF magnetron sputtering possesses a good crystallinity and ordered structure.

Response of LiTaO3 thin film to X-band short microwave pulse

The response of the LiTaO3 thin film detector to the X-band pulse with large power (of order 10 W/cm2) and short duration (of order 0.1 μs) is investigated experimentally and explained from the viewpoint of dielectric relaxation. With the output voltage signal of the detector, the current through the LiTaO3 thin film and its electric polarization are computed and used to examine the observation in a more fundamental manner. In contrast to the common step excitation, the short pulse can provide a delta-type excitation and the response is more appropriate for exploring the interaction mechanism. It is demonstrated from the viewpoint of energy that the response of the detector is not caused by the temperature change in the film, which is the core component in the traditional model of the pyroelectric detector. The polarizations under different pulse conditions show that the interaction is nonlinear, so the linear superposition assumption in the dielectric relaxation theory cannot be used any more. It is found that the polarization can be fitted quite well with a sine function and a time-dependent frequency can be defined. An empirical equation is derived for the dynamics of polarization, and the accelerating and damping effects in the relaxation process can be explained with the relative change in this frequency. The dynamics analysis indicates that the electromagnetic energy is mainly dissipated through driving the domain wall in the crystal.

Toward High‐Quality Epitaxial LiNbO3 and LiTaO3 Thin Films for Acoustic and Optical Applications

Over the past five decades, LiNbO3 and LiTaO3 single crystals and thin films have been studied intensively for their exceptional acoustic, electro‐optical, and pyroelectric and ferroelectric properties. Today, LiNbO3 single crystals in electro‐optics are equivalent to silicon in electronics, and about 70% of radio‐frequency (RF) filters, based on surface acoustic waves, are fabricated on these single crystals. These materials in the form of thin films are needed urgently for the development of the next‐generation of high‐frequency and/or wide‐band RF filters or tuneable frequency filters adapted to the fifth generation of infrastructures/networks/communications. The integration of LiNbO3 films in guided nanophotonic devices will allow higher operational frequencies, wider bandwidth, and miniaturized optical devices in line with improved electronic conversion. Here, the challenges and the achievements in the epitaxial growth of LiTaO3 and LiNbO3 thin films and their integration with silicon technology and to acoustic and guided nanophotonic devices are discussed in detail. The systematic representation and classification of all epitaxial relationships reported in the literature have been carried out in order to help the prediction of the epitaxial orientations in the new heterostructures. Future prospects of potential applications and the expected performances of thin film devices are overviewed, as well.

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.

The effect of annealing temperature variation on the optical properties test of LiTaO3 thin films based on Tauc Plot method for satellite technology

The purpose of the present research is to observe the energy gap of thin films made from LiTaO3 in 1 M-solubility deposited on n-type Si (111) substrates with annealing temperature variation. The manufacture of thin films has been formed by Chemical Solution Deposition (CSD) method using spin coater on 3000 rpm speed for 30 seconds and performed annealing process using furnace (Nabertherm type B180) at a temperature of 750°C, 800°C and 850°C for 15 hours. The absorbance of thin films is measured by using an Ocean Optics USB2000 device and processed into the energy gap curve using Tauc Plot method. The result shows that the energy gap of thin films associated with indirect transitions are increased from 2.78 eV to 2.93 eV with the rise of annealing temperature. The research shows that the thin films on n-type Si (111) substrates made of LiTaO3 produces sensitivity to violet light spectrum and have the potential to be developed as a sensor on satellite technology.

The optical band gap of LiTaO3 and Nb2O5-doped LiTaO3 thin films based on Tauc Plot method to be applied on satellite

This research observed the optical band gap of thin films made from LiTaO3 undoped (0%) and doped (5% and 10%) with Nb2O5 in the 1 M-solubility deposited on n-type Si (111) substrates. The thin films are manufactured with coating process of substrates by Chemical Solution Deposition (CSD) method using a spin coater device at a rotation speed of 3000 rpm for 30 seconds and annealed in furnace (Nabertherm B180) at a temperature of 850°C for 15 hours. The optical absorption data of thin films are obtained by using an Ocean Optics USB2000 device in the wavelength of visible light. The band gap curve is determined from optical absorption data processing using Tauc Plot method. The Tauc Plot with indirect transition shows that LiTaO3 doped with Nb2O5 provides increased optical band gap value in a range less than 3.5 eV. Based on the results of this research, it can be concluded that LiTaO3 and Nb2O5-doped LiTaO3 thin films on n-type Si (111) substrate are semiconductor materials and has the potential to be applied on satellite.

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.

Characterization of Optical and Structural of Lanthanum Doped LiTaO3 Thin Films

Undoped, 5%, and 10% lanthanum doped lithium tantalate thin films were annealed at 550°C temperature for 12.5 hours and their properties were characterized. The results showed that the dopant addition affects the crystal formation of LiTaO3, especially the 10% La2O5 dopant, where the lattice of a = 5.11 Å, c = 13.30 Å, and its crystal was hexagonal. The observed functional groups were O-H, N-H, C = C, Li-O, Ta-O. The higher La2O5 dopant concentration leads to the higher absorption of Ta-O and Li-O, the lower the energy gap, the higher the refractive index, and the smaller the particle size of thin films.

Diffusivity, solubility and thermodynamic modelling of diffusion growth of Ga3+-doped LiTaO3 thin film for integrated optics

A thermodynamic study was performed on diffusion growth of Ga3+-doped LiTaO3(LT) thin film for integrated optics. Some Ga3+-doped LT thin films were grown on LT surface by in-diffusion of homogeneously coated Ga2O3 film at the temperature range of (1273 to 1473)K. After growth, the refractive indices at Ga3+-doped and un-doped surface parts were measured by prism coupling technique and Li composition there was evaluated from the measured refractive indices. The results show that Ga3+ dopant has small effect on the LT index. Li2O out-diffusion is not measurable. The Ga3+ profile in the grown thin film was analysed by secondary ion mass spectrometry. It is found that the grown Ga3+ ions follow a complementary error function profile. A thermodynamic model for Ga3+ diffusion growth is suggested and verified experimentally. From the measured Ga3+ profiles, some thermodynamic parameters were obtained. These include diffusivity, diffusion constant, chemical activation energy, solubility, solubility constant and enthalpy of solution. These parameters are crucial to design and growth of a desired Ga3+-doped LT thin film for integrated optics. Comparison shows that Ga3+ grows in LT two orders faster than Ti4+ because of its smaller radius. Ga3+ diffusivity/solubility in LT is one order/1.5-fold lower than in LiNbO3 because Ta has a larger atomic mass and hence a lower mobility than Nb.

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 of room temperature terahertz detector with lithium tantalate crystal and thin film

Research on room temperature terahertz (THz) detector is essential for promoting the application of THz science and technology. Both lithium tantalate crystal (LiTaO3) and lithium tantalate thin film were used to fabricate the THz detector in this paper. Polishing process were used to reduce the thickness of LiTaO3 crystal slice by chemical mechanical polishing techniques and an improved sol-gel process was used to obtain high concentration LiTaO3 precursor solution to fabricate LiTaO3 thin film. Three dimension models of two THz detectors were set up and the temperature increasing map of two devices were simulated using finite element method. The lowest noise equivalent power value for terahertz detector using pyroelectric material reaches 6.8 × 10−9 W at 30 Hz operating frequency, which is suitable for THz imaging application.

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.