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Review

Sputtered LiNbO3 Thin Films for Application in Integrated Photonics: A Review

by
Igor Kuznetsov
1,*,
Anton Perin
1,2,
Angelina Gulyaeva
1 and
Vladimir Krutov
1
1
Laboratory of Photonic Integrated Circuits, Tomsk State University of Control Systems and Radioelectronics, Tomsk 634050, Russia
2
Laboratory of Radiophotonics, V.E. Zuev Institute of Atmospheric Optics SB RAS, Tomsk 634055, Russia
*
Author to whom correspondence should be addressed.
Crystals 2025, 15(3), 270; https://doi.org/10.3390/cryst15030270
Submission received: 18 February 2025 / Revised: 8 March 2025 / Accepted: 12 March 2025 / Published: 14 March 2025
(This article belongs to the Section Inorganic Crystalline Materials)
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Abstract

:
LiNbO3 plays a significant role in modern integrated photonics because of its unique properties. One of the challenges in modern integrated photonics is reducing chip production cost. Today, the most widespread yet expensive method to fabricate thin films of LiNbO3 is the smart cut method. The high production cost of smart-cut chips is caused by the use of expensive equipment for helium implantation. A prospective method to reduce the cost of photonic integrated circuits is to use sputtered thin films of lithium niobite, since sputtering technology does not require helium implantation equipment. The purpose of this review is to assess the feasibility of applying sputtered LiNbO3 thin films in integrated photonics. This work compares sputtered LiNbO3 thin films and those fabricated by widespread methods, including the smart cut method, liquid-phase epitaxy, chemical vapor deposition, pulsed laser deposition, and molecular-beam epitaxy.

1. Introduction

Lithium niobate (LiNbO3) is a ferroelectric material that is characterized by the appearance of a number of physical effects, including linear electro-optic, piezoelectric, photorefractive, and pyroelectric effects [1]. LiNbO3 was first synthesized in 1949 at Bell Labs by Matthias and Remeika [2], and the first single-crystal LiNbO3 was obtained using the Czochralski method by Ballman in 1965 [3]. The unique properties of LiNbO3 include transparency across a wide spectrum of optical radiation values (from 0.25 to 5.3 μm), high electro-optical coefficients (r33 = 30.8 pm/V), a high Curie temperature of 1210 °C, and a wide bandgap of 3.7 eV [1,4,5,6,7,8,9,10]. LiNbO3 crystals belong to the space group R3c. The lattice constants are a = b = 5.148 Å and c = 13.863 Å [11]. A schematic illustration of the LiNbO3 structure is shown in Figure 1.
Because of its unique properties, LiNbO3 has many applications. These applications include fabricating photonic and electronic devices, for example, second-harmonic generators, electro-optic and acousto-optic modulators and sensors, FeRAM, and other devices [12,13,14,15,16,17]. Considering the current trend in photonics of a transition from devices made of bulk crystals to photonic integrated circuits (PICs), thin films of LiNbO3 (TFLNs) are becoming relevant.
The most widespread TFLNs today are non-epitaxial films obtained by the smart cut method. Smart cut is a method of the ion-cutting of crystals in combination with methods of gluing plates. Smart cut uses the process of the implantation of helium ions into the LiNbO3 substrate to form TFLNs. The result of this process is the formation of an implanted LiNbO3 layer which can later be separated from the LiNbO3 substrate. The thickness of the implanted layer depends on the implantation energy; for example, at an implantation energy of 195 keV, the layer thickness is 670 nm. The implanted substrate is then connected to a LiNbO3 substrate; on its surface, there is a 2 μm thick layer of benzocyclobutene (BCB). Afterwards, the sample is heated to 220 °C, which allows the implanted layer to be separated from the donor substrate. Then, the transferred film is annealed at 300 °C for several hours. Finally, the film surface is etched with Ar+ to smooth the surface. The described method allows for the production of TFLNs of both x- and y-cuts with a surface roughness of about 4 nm [18].
The disadvantage of smart cut is that it needs the implantation of helium at a certain depth to obtain a TFLN of the required thickness. As mentioned above, the depth of implantation depends on the implantation energy, and this process requires expensive helium implantation equipment. In addition, this method requires mechanical grinding equipment to reduce surface roughness, which is important because it affects the magnitude of loss in optical waveguides.
Unlike smart cut, the epitaxial deposition of TFLNs requires no helium implantation apparatus; thus, epitaxy is a potentially cheaper alternative. There are many well-known methods of TFLN epitaxy, such as Sol–Gel, pulsed laser deposition (PLD), chemical vapor deposition (CVD), liquid-phase epitaxy (LPE), radio-frequency sputtering (RFS), radio-frequency magnetron sputtering (RFMS), etc. [19,20,21,22,23,24]. However, not all of these methods are suitable for depositing TFLNs on a semiconductor substrate. This is because the temperature of the synthesis process exceeds the threshold for the onset of solid-phase reactions at the substrate–film interface. For example, LPE and CVD are carried out at temperatures above 900 °C.
Sputtering methods are alternative methods to modern TFLN fabrication techniques. Unlike the smart cut method, sputtering methods do not require expensive equipment for helium implantation. Both RFS and RFMS allow for the deposition of LiNbO3 thin films and the control of thickness and stoichiometry with high variability in deposition parameters. These parameters affect the chemical composition as well as crystal structure and properties of the thin film.
Sputtered TFLNs have both potential advantages and disadvantages. The advantages of sputtering methods include a relatively low process temperature (about 500 °C) and the absence of the need to use precursors. An obvious disadvantage of sputtered TFLNs is their polycrystalline structure. Because of such a structure, it is necessary to control the orientation of the films by choosing substrate orientation and deposition parameters. In addition, the boundaries between the crystallites may cause additional optical loss as a result of light scattering on the surface defects and reflections on the interfaces between the crystallites. Moreover, the possible mismatch between the thermal expansion coefficient of a substrate and LiNbO3 could limit the maximum thickness of a deposited TFLN [19]. If a TFLN is too thin, it will be complicated to fabricate an optical waveguide.
It is debatable whether the disadvantages of sputtered TFLNs have a significant impact on their properties and suitability for integrated photonics. The purpose of this paper is to estimate the possibility of the application of sputtered TFLNs in integrated photonics.
The rest of the paper is organized as follows: Section 2 provides the history of sputtered LiNbO3 thin films and a brief description of the sputtering process to review the basic principles of sputtering methods. Section 3 describes the optical properties of sputtered TFLNs and estimates the influence of deposition parameters on the quality and optical properties of the TFLNs to estimate the suitability of sputtered TFLNs for integrated photonics. In Section 4, we compare sputtered TFLNs with those obtained by other methods.

2. Sputtering of LiNbO3: Principles and History

The sputtering process takes place in a chamber containing an anode and a cathode. A substrate, which can be heated if required, is placed on the anode, while the cathode is connected to the RF signal source and holds the target. The chamber is then filled with the working gas, typically Ar or Ar + O2, which will be a source of surface-bombarding ions. When subjected to RF radiation, the gas becomes ionized and moves towards the cathode, colliding with the surface atoms of the target and dislodging some of them. These atoms are then directed towards the anode and deposited onto the substrate [25]. During the deposition process, LiNbO3 islands are formed on the substrate. Subsequently, these islands merge to form a polycrystalline TFLN [26,27]. Figure 2 shows a schematic of the sputtering chamber of an RFMS unit during the deposition process.
The RFS deposition of LiNbO3 was first described in 1974 [28,29]. A thin film of LiNbO3 was deposited on a c-plate Al2O3 substrate heated to 500 °C. The authors obtained a thin film oriented along the c-axis, with an optical loss of 9 dB/cm at a wavelength of 632.8 nm.
In 1982, Hewig et al. studied the effect of deposition parameters and substrate orientation on the structure of sputtered TFLNs [30]. The authors deposited thin films on both single-crystal and amorphous substrates and investigated the effects of substrate temperature, gas composition, and RF power on the film structure. The authors concluded that the use of heated single-crystal substrates allows for the deposition of polycrystalline thin films, while unheated single-crystal and amorphous substrates allow for the production of amorphous TFLNs. The authors estimated an optical loss of 10 dB/cm for the polycrystalline thin films and 3 dB/cm for the amorphous thin films.
The RFMS method was introduced in the second half of the 1980s [19,31]. Its advantages over RFS include a lower gas pressure, lower RF source power, and higher deposition rate. The difference between RFMS and RFS is that in the RFMS process, a magnetic field holds electrons close to the target surface, which allows for a decrease in the distance from the ion formation point to the point of the surface collision. This magnetic field increases the efficiency of gas ionization and prevents plasma discharge, which in turn increases the deposition rate [25].
In 2001, Lansiaux et al. introduced a multistep process for the epitaxy of thick LiNbO3 films on the Al2O3 substrate using a sputtering system [32]. They managed to deposit a 630 nm thick film of LiNbO3 (0006) on an Al2O3 (0001) substrate at a temperature of 490 °C. Prior to the introduction of the multistep process, the maximum achieved thickness of a sputtered TFLN on an Al2O3 substrate was only about 200 nm because there was a significant thermal expansion mismatch between the film and the Al2O3 substrate [33,34]. The authors repeated the sputtering process several times to achieve the desired thickness. The resulting films exhibited a record low optical loss of 1.2 dB/cm.
Currently, investigations are being carried out into heterostructures consisting of sputtered LiNbO3 and Si and the potential doping of sputtered TFLNs [35,36,37]. Nowadays, doped sputtered TFLNs are being investigated [38,39,40]. These doping modifications allow for changes in the parameters of sputtered LiNbO3 thin films; for example, magnesium allows for the increasing of the optical damage threshold, while iron and zinc doping allow for the control of electrical and photoelectrical properties.
There are also many different variations of possible doping materials, such as titanium oxide, erbium, vanadium, and others, which are implemented in bulk crystals, but not for sputtered TFLNs [41,42,43,44]. Not only components but also their proportions affect the optical and electrical properties of the crystal, which indicates the necessity of research for every specific application.

3. The Results of Sputtered TFLN Studies

In this section, we will review the optical and crystallographic properties of sputtered TFLNs and the deposition parameters of these films. As previously stated, the orientation of the substrate impacts the orientation of the thin film sputtered onto it [19]. For applications in integrated photonics, the refractive index of the substrate should be lower than that of LiNbO3 to ensure the possibility of total internal reflection.
One common solution is to grow silicon dioxide (SiO2), a prevalent amorphous optical insulator, on a Si substrate [45]. The refractive index of SiO2 at a wavelength of 1.55 μm is approximately 1.44, which enables the creation of a high-contrast waveguide [46]. Huang and Rabson investigated a LiNbO3 thin film that was sputtered onto a Si (100)/SiO2 substrate [47]. Specifically, they used a 938 nm thick LiNbO3 (104) film and a Si/SiO2 substrate. The 2500 nm thick SiO2 layer was heated to 550 °C. The optical loss in the film was measured to be 1.9 dB/cm [47].
In 2022, H. Akazawa [48] presented the results of a study of the crystallography of sputtered TFLNs deposited on various silicon dioxide substrates including α-SiO2 and quartz (0001). The author utilized an electron cyclotron resonance (ECR) plasma sputtering apparatus and concluded that it was challenging to deposit highly c-axis-oriented TFLNs on silicon dioxide substrates. It was noted that both α-SiO2 and quartz (0001) exhibited a limited capacity to effectively orient films.
An alternate substrate material, sapphire (Al2O3), has a refractive index of 1.75 [49]. In 1974, Takada et al. utilized the RF sputtering system to deposit a LiNbO3 thin film on an Al2O3 substrate [29]. The orientation of the sapphire substrate and the deposited LiNbO3 thin film was not specified by the authors. The deposited TFLN had a thickness of 180 nm and an optical loss of 9 dB/cm.
In 1999, Dogheche et al. utilized the RFMS method to deposit a LiNbO3 (006) thin film on an Al2O3 (0001) substrate [50]. The optical loss in the film was measured to be 2 dB/cm.
Shimizu et al. described TFLNs deposited onto sapphire substrates [51]. The authors suggested that the high attenuation may be attributed to the presence of oxygen vacancies in the films and interference at the boundary between the film and substrate.
Silicon nitride (Si3N4) has also been also considered as a substrate material [52]. For example, Tan et al. deposited a LiNbO3 thin film on Si/SiO2 and Si/SiO2/Si3N4 substrates. The authors also noted an additional peak at 2Θ = 29° in the XRD data of the annealed TFLN. The peak is attributed by the authors to Li diffusion into the substrate and the subsequent formation of Li oxide. Furthermore, Li accumulation was detected at the interface between SiO2 and LiNbO3, using electron spectroscopy. A barrier is mandatory in this case to prevent Li diffusion into the substrate, and Si3N4 can function as material for such a barrier. Additionally, the authors deposited pure LiNbO3 (006) onto the Si (200) substrate [52].
In another study of theirs, Tan et al. also investigated the impact of Si3N4 deposition parameters on the orientation of LiNbO3 deposited on this material [53]. The authors discovered that a nitrogen flow rate of 4 SCCM is required to achieve LiNbO3 (006) orientation through Si3N4 deposition.
Zinc oxide (ZnO) is another potential substrate for the sputtering of LiNbO3 [51,54]. One study [51] specifically focuses on the deposition process of sputtered LiNbO3 (006) onto substrates such as Si/SiO2 and Corning 7059 with ZnO (001) buffer layers. In both cases, thin films of predominantly LiNbO3 (006) were deposited only when the substrate temperature exceeded 450 °C. Additionally, elevating the substrate temperature to 750 °C facilitated an increase in the LiNbO3 (006) proportion. The reported optical loss was 21.9 dB/cm.
Another study [54] examines the deposition process of a sputtered LiNbO3 (006) thin film onto a Si/ZnO (002) substrate with a 100 nm thick ZnO buffer layer. The least stressed film was deposited at a substrate temperature of 450 °C, a pressure of 10 mTorr, and a gas composition of 80% Ar + 20% O2 [54].
In [48], the effect of a ZnO buffer layer on the crystallography of a sputtered TFNL was also studied. The TFLN was deposited using an ECR apparatus on an α-SiO2 substrate with a 70 nm thick ZnO (002) buffer layer at 460 °C. The only XRD peak of a TFLN was of LiNbO3 (006).
One study [55] examines the deposition of a TFLN onto an Al2O3 substrate by an RFS apparatus. The target consisted of LiNbO3 powder with 10% Li2O to compensate for Li loss during the deposition process.
The deposition parameters of TFLNs deposited using RFS or RFMS mentioned above are listed in Table 1.
In [56], the authors studied the effect of thermal annealing treatment on TFLNs deposited on Si substrates at room temperature utilizing a sputtering apparatus. The authors studied the dependence of TFLN crystallinity on both annealing temperatures and temperature ramping rates. The authors concluded that the orientation and texture of the TFLN is highly dependent on the annealing temperature and the temperature ramping rate. The texture degree is maximized for annealing at 950 °C for 100 °C/min. The authors also noted that regardless of the temperature ramping rate, annealing leads to the formation of the Li-deficient phase LiNb3O8. In addition, the authors found that annealing with a temperature ramping rate of 100 °C/min leads to the formation of defects on the TFLN surface. Typical sputtered TFLN surface defects include cracks and pores. Figure 3 shows a SEM image of a sputtered TFLN with defects deposited on a Si (111) substrate.
Considering that TFLNs in integrated photonics are mainly used for electro-optic modulators, it is crucial to ensure high electro-optic efficiency during film deposition. Most of the modern electro-optic modulators are based on Z-cut LiNbO3 because this configuration provides the lowest value of VπL. Therefore, a favorable substrate for sputter-deposited TFLN is Al2O3(001), which provides LiNbO3(006) [50,55]. In addition, one must ensure the minimum amount of the Li-deficient phase in the TFLN. Based on the above-mentioned facts, we can conclude that when producing sputtered TFLNs for photonic applications, it is better to avoid post-deposition high-temperature annealing treatment because the defects may cause additional optical power loss and the formation of the Li-deficient phase might reduce electro-optic efficiency.

4. Comparing Sputtering Methods with Other Epitaxy Methods

In this section, we compare the optical loss of the sputtered thin films mentioned above with the optical loss of those obtained through other methods. Before a comparison can be made, it is necessary to define which optical properties of LiNbO3 are crucial for integrated photonics. As previously mentioned, the primary application of LiNbO3 in the field of photonics is the fabrication of electro-optic modulators. The fabrication of these modulators necessitates the satisfaction of two key requirements: high electro-optic effect efficiency and low optical losses. The efficiency of electro-optic modulation is defined by LiNbO3 orientation, its phase composition, and electrode configuration. As previously stated, LiNbO3(006) is the favorable TFLN orientation. The optical losses are determined by the waveguide configuration and TFLN homogeny. The waveguide configuration is contingent on TFLN thickness and optical contrast. Modern commercially available TFLNs on SiO2/Si substrates are 650 nm thick, allowing the production of low-loss single-mode waveguides with a width of 1 μm. However, it should be noted that TFLNs on Al2O3 substrates provide lower optical contrast. Therefore, it can be deduced that the sputtered TFLN should be thicker to ensure comparable optical loss.
A comparison of thin films deposited by different epitaxial methods is given in Table 2. Only those references where optical attenuation was investigated are included in the table.
As can be seen in Table 2, at certain modes of LiNbO3 sputtering, it is possible to achieve losses at a level comparable to other methods of LiNbO3 epitaxy (about 1 dB/cm). Such losses allow the use of this technology in integrated photonic applications.
The smart cut method [13,65,66,67] allows for the fabrication of submicron LiNbO3 thin films on a LiNbO3 substrate with a SiO2 interlayer as an optical insulator. The advantages of using the smart cut method over epitaxy are explained by the fact that slices of bulk LiNbO3 crystals are used in the fabrication process. This allows for the orientations of thin films to be precisely chosen and for optical losses at the boundaries between crystallites to be avoided. For example, an optical waveguide with an optical loss of 0.4 dB/cm is described in [68]. This level of loss has not been achieved to date in thin films epitaxially grown on a substrate. Meanwhile, sputtered TFLNs are mostly used as a ferroelectric material. These ferroelectric applications of LiNbO3 include SAW and FeRAM devices [12,69,70,71,72,73,74].
However, in 1993, a Pockels cell electro-optic modulator was demonstrated using a silicon and sputtered LiNbO3 parallel-electrode configuration [75]. The LiNbO3 layer, which was 0.23 μm thick, was deposited on a silicon substrate. X-ray diffraction results showed that the film was dominated by the (012) orientation normal to the substrate surface, resulting in a 57° inclination of the c-axis to the electric field direction. The inclination of the c-axis resulted in a reduction in the electro-optic effect. The authors estimated that the electro-optic coefficient of the sputtered LiNbO3 films was approximately 50% of the electro-optic coefficient of the bulk crystal.
The first integrated visible-light modulator fabricated on sputtered TFLNs was demonstrated in 2022 [76]. The modulator was fabricated according to the scheme of a Mach–Zehnder interferometer and has halfwave voltages of 1.2 to 1.9 V in the wavelength range from 473 to 638 nm, which is CMOS-compatible voltage [77]. The VπL parameters were 1.9, 1.4, and 1.2 V·cm for wavelengths of 638, 520, and 473 nm, respectively. Fukuzawa et al. [76] also measured optical loss; at wavelengths of 638, 520, and 473 nm, the optical losses were 8, 10, and 11 dB/cm, respectively. The authors note that the increase in optical loss at shorter wavelengths may be caused by the surface roughness of the thin film.
In 2024, Hara et al. [78] expanded a previous study by Fukuzawa et al. [76]. In their paper [78], a similar Mach–Zehnder modulator is demonstrated. The modulator was fabricated using sputtered LiNbO3 thin films. The VπL parameters were reduced down to 1.2, 1.0, and 0.75 V⋅cm for wavelengths of 638, 520, and 473 nm, respectively. Low halfwave voltages were obtained by using a low-dielectric material of LaAlSiInOx as an insulator between LN waveguides and electrodes, and a change in the geometrical configuration of electrodes.
Several authors have noted the possibility of integrating electronic components into a silicon substrate, although there are no studies on this topic in the scientific literature [75,79]. However, the difference in thermal expansion coefficients between LiNbO3 and the substrate material can hinder the integration of electronic components into the substrate, leading to the formation of mechanical stresses in the TFLNs or their damage [80,81].

5. Conclusions

The literature shows that sputtered TFLNs with losses of about 1–2 dB/cm can be obtained. It has also been demonstrated that oriented LiNbO3 thin films can be deposited by their sputtering on a substrate that can serve as an optical insulator. Additionally, electro-optic modulators based on sputtered TFLNs have been fabricated and demonstrated.
Furthermore, the sputtering method offers several advantages over the smart cut method. Firstly, sputtering does not require expensive equipment for helium implantation, and thus, using sputtered TFLNs could reduce the cost of PIC production. Secondly, the thickness of sputtered TFLNs can be increased by multiple sputtering, while the maximum thickness of smart-cut TFLNs is determined by the limitations of the implantation energy.
Considering the other methods of TFLN fabrication, the advantages of sputtering methods include the absence of the need to use precursors and the higher deposition rate. However, it is important to note that optical losses in sputtered thin films are at least 2–5 times higher than in smart-cut TFLNs. One potential application of sputtered TFLNs is in integrated photonic sensors, such as electric field sensors. The high optical loss may not be a problem since the sensor does not require the transmission of optical signals over long distances. And as was demonstrated in this review, it is possible to fabricate a low-halfwave-voltage electro-optic modulator based on sputtered TFLNs.
The favorable substrate for an electro-optic device is Al2O3(001), which allows for the deposition of LiNbO3(006), ensuring high electro-optic modulation efficiency. Electro-optic modulation efficiency can be reduced due to the presence of the Li-deficient LiNb3O8 phase, which can be avoided by adding Li2O to the target and avoiding high-temperature annealing.
Since the refractive index of Al2O3 is relatively close to that of LiNbO3, the deposited TFLN should be thick (>600 nm) so that a low-loss waveguide can be fabricated. The thickening of the sputtered TFLN can be achieved using a multistep deposition process despite the difference in thermal expansion coefficients between the substrate and the TFLN.
We have to mention that at present, there is a lack of research on sputtered TFLNs. In particular, there are no published studies that consider the refractive indices of sputtered TFLNs, and some nonlinear optical properties which are well known for bulk LiNbO3 or commercially available single-crystal TFLNs, for example, the possibility of the formation of optical solitons in sputtered thin films, have not yet been studied. Also, the application potential of sputtered TFLNs has not yet been fully explored; for example, there are no publications that address photonic crystals based on such thin films.
To conclude, it is possible to use sputtered TFLNs in integrated photonic applications with certain limitations, such as higher optical loss and the need to control the orientations of crystallites.

Author Contributions

Writing—original draft preparation, I.K.; writing—review and editing, I.K., A.P.; A.G. and V.K.; supervision, A.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported of the Ministry of Science and Higher Education of the Russian Federation (Sections 1 and 2 within the state assignment of the No. FEWM-2025-0002 and Sections 3 and 4 within the state assignment of the V.E. Zuev Institute of Atmospheric Optics SB RAS).

Conflicts of Interest

The authors declare no conflicts of interest.

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Crystals 15 00270 g001
Figure 1. The unit cell of LiNbO3 in a hexagonal lattice.
Figure 1. The unit cell of LiNbO3 in a hexagonal lattice.
Crystals 15 00270 g001
Crystals 15 00270 g002
Figure 2. Schematic of the sputtering chamber of an RFMS unit during the deposition process.
Figure 2. Schematic of the sputtering chamber of an RFMS unit during the deposition process.
Crystals 15 00270 g002
Crystals 15 00270 g003
Figure 3. SEM image of sputtered TFLN with defects.
Figure 3. SEM image of sputtered TFLN with defects.
Crystals 15 00270 g003
Table 1. The deposition parameters of sputtered TFLNs.
Table 1. The deposition parameters of sputtered TFLNs.
ReferenceSubstrateRF PowerTarget DiameterAr/O2 RatioSpacingGas PressureTemperatureTFLN Phase
[47]Si(100)/SiO250 W7.62 cm60/405 cm2–5 mTorr500–600 °C(104)
[29]Al2O350 W9 cm60/404 cm200 mTorr500 °C-
[50]Al2O3 (001)180 W7.62 cm60/406 cm20 mTorr500 °C(006)
[51]Al2O3 (001)50–200 W-80/20–60/40-5–80 mTorr600 °C(001)
[51]Al2O3 (110)50–200 W-80/20–60/40-5–80 mTorr400 °C(110)
[51]Al2O3 (110)50–200 W-80/20–60/40-5–80 mTorr600 °C(110)
[52]Si/SiO2 (1.2 μm)1 W/cm2----500–600 °C,
no annealing		(012), (110), (006)
[52]Si/SiO2 (1.2 μm)1 W/cm2----500–600 °C, annealed at 750 °C(012) + peak at 2Θ = 29°
[52]Si/SiO2 (1.2 μm)/Si3N4 (200 nm)1 W/cm2----500–600 °C(006) + LiNb3O8
[52]Si25 W5.08 cm60/40-5 mTorr530 °C(006)
[54]Si/Zno (002)75 W10.16 cm70/307.5 cm8–14 mTorr450 °C2Θ = 38.21°
[55]Al2O3 (110)150 W-60/406 cm6 mTorr580 °C(110)
[55]Al2O3 (001)150 W-60/406 cm6 mTorr580 °C(110), (006)
Table 2. Comparison of LiNbO3 epitaxy methods.
Table 2. Comparison of LiNbO3 epitaxy methods.
MethodOptical Loss, dB/cmFilm Thickness, nmSubstrateNoteReference
LPE1–53000LiTaO3-[57]
253640LiTaO3-[58]
<110,000MgO-doped Z-plate LiNbO3λ = 458 nm[59]
53000c-oriented LiTaO3TM-mode λ = 458 nm[60]
11c-oriented LiTaO3TE-mode, λ = 458 nm
CVD2120C-plate Al2O3-[33,34]
6500Z-cut LiTaO3-
40300LiTaO3 ( 10 1 ¯ 0 )-[61]
PLD<1.5140Al2O3 (001)-[62]
18260Al2O3 (001) substrateλ = 632.8 nm[63]
MBE15.750Al2O3 [64]
Sputtering9180Al2O3 [29]
1.2630Al2O3 (001)λ = 632.8 nm, TE0[32]
1.2600Al2O3 (001), (110)λ = 632.8 nm[55]
21.9-ZnO-[51]
19.8-Corning 7059Before annealing
9.13-Corning 7059After annealing
27.5-Al2O3 (110)Before annealing
25.6-Al2O3 (110)After annealing
40.2-Al2O3 (001)-
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Kuznetsov, I.; Perin, A.; Gulyaeva, A.; Krutov, V. Sputtered LiNbO3 Thin Films for Application in Integrated Photonics: A Review. Crystals 2025, 15, 270. https://doi.org/10.3390/cryst15030270

AMA Style

Kuznetsov I, Perin A, Gulyaeva A, Krutov V. Sputtered LiNbO3 Thin Films for Application in Integrated Photonics: A Review. Crystals. 2025; 15(3):270. https://doi.org/10.3390/cryst15030270

Chicago/Turabian Style

Kuznetsov, Igor, Anton Perin, Angelina Gulyaeva, and Vladimir Krutov. 2025. "Sputtered LiNbO3 Thin Films for Application in Integrated Photonics: A Review" Crystals 15, no. 3: 270. https://doi.org/10.3390/cryst15030270

APA Style

Kuznetsov, I., Perin, A., Gulyaeva, A., & Krutov, V. (2025). Sputtered LiNbO3 Thin Films for Application in Integrated Photonics: A Review. Crystals, 15(3), 270. https://doi.org/10.3390/cryst15030270

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