• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    High Yield Transfer of Clean Large-Area Epitaxial Oxide Thin Films

    2021-01-18 07:26:10BowenZhangChaoYunJudithMacManusDriscoll
    Nano-Micro Letters 2021年2期

    Bowen Zhang, Chao Yun, Judith L. MacManus-Driscoll

    ABSTRACT In this work, we have developed a new method for manipulating and transferring up to 5 mm × 10 mm epitaxial oxide thin films. The method involves fixing a PET frame onto a PMMA attachment film, enabling transfer of epitaxial films lifted-off by wet chemical etching of a Sr3Al2O6 sacrificial layer. The crystallinity, surface morphology, continuity, and purity of the films are all preserved in the transfer process. We demonstrate the applicability of our method for three different film compositions and structures of thickness ~ 100 nm. Furthermore, we show that by using epitaxial nanocomposite films, lift-off yield is improved by ~ 50% compared to plain epitaxial films and we ascribe this effect to the higher fracture toughness of the composites. This work shows important steps towards large-scale perovskite thin-film-based electronic device applications.

    KEYWORDS Free-standing oxide thin films; High yield transfer; Wet etching; Crack prevention

    1 Introduction

    Functional oxide thin films are of great interest for their broad spectrum of physical properties, e.g. in dielectrics and ferroelectrics [1, 2], magnetics [3, 4], superconductors [5, 6], ionic conductors [7, 8], photovoltaics [9, 10], resistive switching [11, 12], etc. Furthermore, with the rapid development of two-dimensional (2D) materials and van der Waals heterostructures in the last decades, it is highly anticipated that exemplary functionalities will be achieved from lowdimensional, single-crystalline functional oxide thin films, particularly on flexible and semiconductor substrates [13]. In this way, it would be possible to integrate the unrivalled properties of low dimensional oxides with CMOS, and also obtain flexible sensors for IoT [14] and biological devices [15], and low-power consumer electronics [16], etc.

    Single-crystalline oxide thin films are usually strictly bound to a limited range of hard substrates, which provide the appropriate lattice and thermal matching conditions for their epitaxial growth. Such substrates are usually inorganic crystals and therefore unable to bring mechanical flexibility to the films. The strong chemical bonds in the interface make it a challenge to separate the oxide thin films from the substrates, which limits their further applications.

    Many approaches are reported to grow or transfer perovskite oxide thin films to a device-compatible substrate, including mechanical exfoliation [17, 18], van der Waals epitaxy [19—22], dry etching release methods [23—26], and wet etching release methods [27—32]. Among those methods, the wet etching release method has higher selectivity and is more cost-effective. It involves a selective chemical etching process to remove the substrate or sacrificial layers, and retains the high-quality growth of the epitaxial films. The sacrificial method typically results in less damage after transfer than the aforementioned methods [33]. Recently, there are many notable examples of free-standing perovskite thin films and superlattices prepared by dissolution of a sacrificial layer (Sr3Al2O6) in water inspired by the pioneering work by Hwang’s group [32, 34]. The resultant lifted-off films have minimized contaminant caused by the etchant solution. Hence, the wet etching method is arguably the most promising approach for producing free-standing single-crystalline oxide thin films for large-scale device applications.

    In a typical wet etching release method, the first step is the detachment of the thin film from the substrate or sacrificial layer, which is then followed by the transfer process. While most current works are focusing on different etching methods, the upper limit of the film area and quality is usually dependent on the latter lift-off and transfer step. The key issue for a good transfer is to prevent the crack formation and minimize contamination. We note that while free-standing thin films of metals and some oxides have been shown to be relatively flexible [33, 35] compared to their bulk counterparts, it is clear that ceramic films are still brittle in thin film form and if crack initiation sites are present, the films will behave in a brittle manner [36, 37].

    Existing thin-film transfer methods use well-developed transfer methods designed for graphene transfer. A support layer, e.g. PMMA [38], PDMS [39] or polystyrene (PS) [30], is employed and coated on the whole film surface before the wet etching process to prevent fracture. For oxide films, an important challenge during the transfer process is the introduction of cracks and tears. Also, in a typical graphene transfer process, the PMMA/graphene stack usually floats on the solution surface. This method cannot be simply applied to oxide thin films owing to their larger density and thickness, which makes it difficult to for surface floatation.

    Several groups have explored the possibilities of the wet etching approach. In 2016, Bakaul et al. developed a PMMA-based method to transfer single-crystalline ferroelectric thin film onto Si-wafers at hundreds of micrometre length scale [40]. More recently, Shen et al. transferred a large area (5 × 10 mm2) thin film onto polyimide (PI) substrates by directly adhering the PI tape on thin film [41]. Ji et al. synthesized and transferred free-standing SrTiO3and BiFeO3ultrathin films down to one unit-cell via abovementioned Sr3Al2O6wet etching approach [39].

    In this paper, a new way to achieve high yield, large-area (5 × 10 mm2, the maximum substrate area explored) oxide thin film transfer is developed. We use a wet chemical lift-off process using Sr3Al2O6sacrificial layers, and a new PMMAmediated transfer approach which involve attachment of a PET window layer to the PMMA, to provide extra rigidity and give easier handling of the film. The method avoids the physical damage introduced by the mechanical lifting process and gives a high yield transfer rate (~ 72%) onto Si- and flexible polymer (PET) substrates. Furthermore, we show that when epitaxial vertically aligned nanocomposite (VAN) films are used, the yield is further improved. Possible mechanisms related to an increased fracture toughness are proposed. Overall, three different film compositions/forms are demonstrated: SrRuO3,CeO2, and CeO2/STO VAN. The successfully transferred films do not show macroscopic cracks. The lack of microscopic cracks is proven by showing minimal changes in resistivity of metallic SrRuO3after lift-off compared to before.

    2 Experimental

    2.1 Film Fabrication by Pulsed Laser Deposition (PLD)

    In this experiment, thin films are grown by pulsed laser deposition with a KrF excimer laser (λ= 248 nm). All the targets used in PLD are polycrystalline and prepared through solid-state reaction. For Sr3Al2O6target, a stoichiometric mixture of SrO and Al2O3powders was mixed together and then sintered in air at 1350 °C for 48 h with an intermediate grinding and pelletizing steps. For the CeO2and SrRuO3target, the raw powders were weighed to achieve a stoichiometric amount of mixture and were subsequently mixed and sintered using the same steps as we did for Sr3Al2O6target. For the CeO2/STO target, CeO2and SrTiO3were mixed at a 50:50 molar ratio.

    The substrate we used in this work is single-side polished SrTiO3(001). Before deposition, the substrates were cleaned using an ultrasonic bath with different solutions, i.e. DIH2O, acetone, and isopropanol for 10 min each. After that, the substrates were pre-annealed at an oxygen partial pressure (pO2) of 1 × 10—5mbar for 30 min at 950 °C to achieve atomically flat single-terminated surfaces.

    Then, a Sr3Al2O6buffer layer was grown on the annealed SrTiO3(001) substrate at a substrate temperatureTg= 700 °C andpO2= 1 × 10—6mbar, while using 1.25 J cm-2laser fluence and a repetition rate of 1 Hz.

    Finally, the target films, SRO, CeO2, and CeO2/STO nanocomposite films were grown in situ atTg= 750 °C andpO2= 0.2 mbar, using 1.5 J cm-2laser fluence and a repetition rate of 2—5 Hz. After deposition, the films were postannealed at 650 °C for 1 h under apO2of 0.4 bar to ensure equilibrium oxygen stoichiometry and to minimize the creation of oxygen vacancies inside the films.

    2.2 Exfoliation and Transfer of Thin Films

    In our new method VI, to load the support layer, a PMMA solution (Mw = 950 K, 4 wt% in anisole) was spin coated (2,000 RPM, 30 s) onto the thin film with the substrate and then naturally dried for 12 h to obtain a thin-film embedding structures with thickness about 300 nm. Then, a PET membrane was tailored as shown in Fig. 1 and then attached to the film (PMMA side) with moderate pressure. The thin film together with the PMMA layer and tape frame layer was immersed into room-temperature DI water to dissolve the Sr3Al2O6buffer layer and remove the substrate. Before transfer, the Si wafer was processed by an oxygen plasma via reactive ion etching (RIE) in order to form a hydrophilic SiO2layer and increase the adhesion of free-standing films. After etching in water, the supports with the thin films were placed on another substrate (e.g. Si wafer) and then soaked in acetone to dissolve the PMMA layer. The floating tape frame was then collected and disposed, while the thin film remained on the new substrate.

    For the control group, we followed the method reported in Di Lu et al. [32] and Dianxiang Ji et al. [39] This is method III, the thermal release tape method, the most standard method for oxide film transfer. To transfer the free-standing oxide film to Si, the sample was stuck onto silicone-coated PET and released in the same manner (etching in water). After dissolving in water, the film/silicone-coated PET was attached to the new substrate. Finally, the free-standing film remained on the new substrate after peeling off the silicone-coated PET by heating at 70 °C for 10 min.

    2.3 Characterizations

    AFM images were acquired in tapping mode using a Bruker Digital Instrument Nanoscope III. The SEM images and EDX analysis were done using an FEI Nova NanoSEM. The XRD data were taken using a high-resolution Bruker D8 with graded mirror and CuKα radiation. Data were recorded via 2θ—ωscans, with 2θf(wàn)rom 10° to 110°, step size = 0.01°, and the time for one scan is 1.5 h.

    Electrical measurements are taken using a four-point probe station with a Keithley 2440 source-meter, with voltage applied to Pt electrodes of 0.1 mm diameter, formed by sputtering on the film surface. The thin-film samples were mounted with an in-line four-point probe configuration as shown in Fig. S3.

    Fig. 1 Schematics of four different wet-etching-based methods to fabricate oxide thin films. Methods I-III are known methods, and method IV is the new method developed in this work

    3 Results and Discussion

    3.1 New Method to Transfer Epitaxial Oxide Thin Films

    Figure 1 shows the four different methods based on the wet etching approach which have been studied for transferring single crystalline oxide thin films to Si wafers. The main difference between these methods is the support layer, which significantly influences the quality of final transferred films. Method I is the most commonly used 2D material transfer method, and it relies on the use of a sacrificial polymethyl-methacrylate (PMMA) film to support the 2D layers and to prevent them from folding or cracking during the etching and transferring process [42]. However, the PMMA approach is not applicable for oxide thin films as the films have high densities compared to 2D materials, which makes it difficult for the films to float on the surface and detach from the substrate. Besides, even 2D films of higher thickness have been reported to more likely to get broken during PMMA removal step [43]. In method II, PI tape (pressure sensitive adhesive tape) is used to support and protect the film. Although previous reported results showed that large area oxide thin film can be transferred to the PI tape, it is almost impossible to release the films to other non-adhesive substrates like Si wafers [41]. In method III, the sample is adhered to the thermal release tape or silicone-coated PET instead of the pressure sensitive tape in order to release the films by heating [32, 39]. However, it is difficult to obtain continuous coverage using this method. The appearance of voids, cracks, and some residues from the thermal release tape is inevitable after the transfer [44].

    The last method, method IV, is a two-layer structure support method, and is newly introduced in this work. It combines the advantages of the PMMA-mediated transfer method [45] (i.e. prevention of film folding or cracking during transfer and gives almost continuous coverage) and the thermal release tape method (easy for manipulating large area films) [32]. As we already mentioned, oxide thin films are very brittle and fragile. Also, as already mentioned, oxide thin films are much denser than conventional 2D materials (e.g. CeO2has a density of 7.22 g cm-3as compared to graphene’s density of 2.27 g cm-3), and so they will not float on water.

    The potential advantages of our new PMMA-mediated method in IV over other three standard methods of Fig. 1 are:

    1. Reduction of film cracking. This is because the PET membrane is much more mechanically stable than the PMMA layer, allowing the free-standing film to be carefully manipulated, without flexing.

    2. Film continuity. The spin-coated PMMA layer provides full coverage of the film and allowing the lifted-off film to be continuous. Besides, the spin-coated PMMA layer can be easily removed by acetone/chloroform.

    3. Film flotation. The additional PET frame on the PMMA should stop the film from sinking. This is because the overall support + film density is < 1 g cm-3.

    4. Reduction of film buckling. The rigidity of the frame structure should also reduce the effect of turbulence during the dissolution of PMMA.

    The first step in the process of getting a perfect freestanding film is to grow the target single-crystal oxide thin film with a well-defined orientation. Several studies using pulsed laser deposition (PLD) and molecular-beam epitaxy (MBE) have demonstrated growth of single crystalline films on Sr3Al2O6sacrificial layers [32, 39, 46, 47]. The layer is coherently strained to the STO when it is very thin (around 10 nm). Since Sr3Al2O6is soluble in water, this avoids the use of acid etchants. Hence, it is the most suitable layer for most oxide thin films with perovskite structures [32]. In this work, we use PLD to grow the films on Sr3Al2O6on (001) SrTiO3single crystal substrates.

    Fig. 2 Schematic of PET frame on PMMA support for lifting off and placing a film on a new substrate. a Placement of PET frame on PMMA support. (i) Top view. (ii) Side view; b schematic of the whole process developed in this work based on method IV in Fig. 1

    A sketch of the film with PMMA and PET membrane frame on top can be seen in Fig. 2a. After spin-coating a PMMA layer onto the film surface, a frame-shaped PET membrane is then attached on the top of the PMMA layer. (The experimental details are presented in Experimental Section.)

    The whole thin film transfer process flow is shown in Fig. 2b. Three main parts are combined: (i) the epitaxial growth of Sr3Al2O6sacrificial layer followed by in situ growth of target oxide thin film; (ii) lift-off process; (iii) transfer of film onto new substrate.

    We successfully fabricated and transferred three different composition/structure oxide films to single crystal Si wafers: SrRuO3,CeO2, and CeO2/STO nanocomposite films. In order to make sure all films are grown epitaxially with high quality, the films are grown on a 10-nm-thick Sr3Al2O6buffer layer which preserves the perovskite step-and-terrace structure of underlying SrTiO3substrate and this can be seen in AFM images (Fig. S1a, b).

    We explored SrRuO3because it has a perovskite structure and is metallic. The pseudocubic lattice parameter for SrRuO3is 0.3923 nm which is quite similar to that of STO (0.3905 nm) with only - 0.46% lattice mismatch. Hence, it should grow coherently to the buffer with low interfacial defects. Since it is metallic, then after lift-off its structural integrity and connectivity can be assessed by undertaking electrical resistivity measurements.

    We explored CeO2as it is structurally mismatched (fluorite structure) to the buffer and will grow by domain matching epitaxy (DME) with a high concentration of misfit dislocations near the interface. This higher defect concentration may reduce structural integrity after lift-off, and thus, this system can be used to verify how effective the new transfer process is. To date, as far as known, only perovskite structured films have been grown and transferred by the Sr3Al2O6buffer layer approach and so the process would be further validated by transfer of a non-perovskite film.

    The CeO2/STO VAN films were tested to determine whether the presence of a nanostructured second phase within a film could help block crack growth (as composite structures are known to do so in the field of mechanical ceramics) [48—50] and thus to determine whether it is possible to enhance the yield of lifted-off films using composite systems. CeO2/STO VAN films were chosen as a good reference to the plain CeO2films, and also because they have interesting ionic properties [8, 11, 51]. In these films, vertical nanocolumns of CeO2grow embedded in a supporting matrix of SrTiO3[51]. It is noted, however, that while composites could be advantageous on the one hand, and on the other hand, the Tb/inch2density of vertical interfaces in VAN films may be defective, and so could lead to sites of crack initiation and degrade the mechanical properties.

    3.2 CeO2 Free-standing Films

    For the CeO2film, we compare lift-off using our new support method (no. IV in Figs. 1 and 2) with the thermal release tape methods (no. III in Fig. 1). We use no. III as the control method because it is most widely used for oxide thin film transfer [39, 47]. The other methods (I and II) are not suitable (and also not reported) for the transfer of oxide thin films to Si substrates.

    We consider results for the CeO2film first. In Fig. 3a, b, we show a 5 × 5 mm2CeO2single crystal thin film (100 nm thick) transferred to Si using our new method. The film is free from macroscopic cracks over an area of 4 × 4 mm2with a small crack at top right corner (as seen from the SEM image in Fig. 3a). A very small amount of PMMA residue of < 100 nm is observed on the film surface (Fig. 3b). No organic polymer residual particles or layers were observed after searching the entire film area.

    We compare the transferred film by our new method (Fig. 3a, b) to a film transferred by the thermal release tape transfer process. The SEM results are shown in Fig. 3c, d). We see that bubbles are introduced by the heating step, and large area organic adhesive residues are introduced by the adhesive. The mechanical forces from the peeling step also result in large cracks. These features are quite standard for the thermal release method [52].

    3.3 SrRuO3 Free-standing Films

    Fig. 3 a Image of the surface of a CeO2 film (5 × 5 mm2) transferred by the new optimized method IV of Figs. 1 and 2. b SEM image of the CeO2 film. c Image of the surface of the film transferred by the thermal release tape assisted method III of Fig. 1. Bubbles due to heating process and cracks can be seen. d SEM image of the film. A thin layer of residual adhesives (white area) and a large hole can be seen. (Color figure onine)

    Next, we studied a lifted-off film of 100-nm-thick metallic SrRuO3transferred to Si. We recall that SrRuO3is well-lattice matched and fully structurally matched to the Sr3AlO6films on SrTiO3. We explored the structural integrity of the film by measuring the electrical transport. Hence, if there are very tiny and/or buried cracks which are not easily observable with surface microscopy images, they would still lead to higher resistivity in the films. Figure 4 shows an image of a transferred film on Si (Fig. 4a) and the resistivity—temperature curve measured using a four-point probe method for the SRO thin film before and after transfer (Fig. 4b). Figure 4c, d shows magnified images of the film, revealing no macroscopic cracking. The resistivity (ρ) is only slightly increased from 203 to 223 μΩ cm (9.9%) at 297 K. This may be explained by the release of - 0.46% inplane compressive strain in the film, as SrRuO3is reported to have lower resistivity when compressively strained [53, 54]. However, small random cracks might also contribute to the marginally higher resistivity. Overall, the film performance is not degraded to any great extent after transfer, indicative of large-scale continuity and no influence of surface contamination from the transfer process. This contrasts with other reports which show larger increases in resistivity (e.g. 80% in LSMO reported by Di Lu et al. [32], ~ 700% in LSMO reported by Zengxing Lu et al. [46]).

    3.4 CeO2/STO Nanocomposite Free-standing Films

    We now turn to the CeO2/STO VAN nanocomposite films. With these films, we aim to further explore the cleanliness of our new transfer process, but more importantly to also determine whether the complex VAN microstructure (a 3D schematic of the structure is shown in Fig. 5a, a surface schematic in Fig. 5b, and a real image in Fig. 5c) assists or hinders the transfer process.

    To be sure of the validity of any positive VAN results, we studied transfer onto both Si and flexible PET. We compare to the results to the plain CeO2films. First, we investigated the influence of any chemical reaction effects. In Fig. 6a, we show X-ray diffraction (XRD) 2θ—ωscans of the CeO2film before and after transferring to PET. The blank PET membrane is also shown. After transfer, all the STO substrate peaks and Sr3AlO6buffer peaks have gone, while all CeO2peaks have been preserved. This is as expected for successful selective dissolution and transfer. The CeO2(002) and (004) peaks show that the aligned crystalline structure is retained after the transfer process. Minor CeO2(111) and CeO2(311) peaks are also present (~ 1/1000 intensity of main (002) peak), in both the untransferred and transferred film.

    Fig.4 a Optical image of the surface of a SrRuO3 film (5 × 5 mm2) transferred by the optimized method IV of Figs. 1 and 2. b Resistivity measurements for the SrRuO3 film before and after transfer. c, d SEM image of the SrRuO3 film showing the surfaces of the columnar grains at the film surface

    Fig. 5 Schematic diagram of CeO2/STO nanocomposite film. a Side view showing the structure of the film. b Top view showing how 2 different cracks might propagate through the STO matrix. In scenario 1, a crack (blue) is stopped at a pillar. In scenario 2, a crack (red) propagates around the pillars. c Real surface scanning transmission electron micrograph of a CeO2/STO nanocomposite film. Image adapted from Zhu et al. [70]. (Color figure onine)

    Figure 6b shows the XRD 2θ—ωscan of the CeO2film transferred to Si. Similar to Fig. 6a, the CeO2(002), CeO2(004), and Si (004) are also clearly observed. The peak positions, shapes, and intensities are preserved for the transferred CeO2membrane compared to the as-grown film. As shown in Fig. S2, the XRD pattern for the CeO2/STO VAN film shows the same effect as the CeO2thin films, i.e. that all of the film peaks remain the same after lift-off. Hence, for the VAN film clear film CeO2and STO matrix peaks are present both before and after lifting off the STO substrate onto the PET substrate.

    Fig. 6 X-ray diffractograms (intensity on a log scale) for CeO2 film grown on Sr3Al2O6 buffer grown on SrTiO3 in different stages of transfer onto PET membrane or Si. a XRD 2θ—ω scan of CeO2 film before transfer, CeO2 film after transfer to PET, and blank PET membrane. U = unidentified peak. b XRD 2θ—ω scan of CeO2 film transferred to Si wafer

    Fig. 7 Top view SEM and AFM images of transferred VAN CeO2/STO film on a Si substrate. a EDS images. b SEM image. c, d show blow ups of EDS image for all-element mapping showing clear nanopillars (light green dots) of CeO2 embedded in STO matrix of film after transfer. e AFM image of the surface morphology of the film. Some nanopillars are circled with green dashes. The nanopillar structure of CeO2 is observed in both the EDS image of (d) and the AFM image of (e) and is perfectly preserved after transfer. (Color figure onine)

    Top view SEM image and EDS elemental distribution maps of the CeO2/STO VAN film transferred onto Si are shown in Fig. 7. The bottom left region of the elemental maps in Fig. 7a shows the Si substrate, i.e. there is a high intensity of Si. A clear boundary is observed between the Si and the VAN CeO2/STO film at the upper right regions of the maps, where Ce, Ti, and O are observed in high intensity. Figure 7b shows an SEM image of the film on the Si, showing the film uniformity and again, clear boundary. An all element map is shown in Fig. 7c, with an enlarged area in Fig. 7d. Circular regions of high concentration of Ce are observed surrounded by regions with no Ce. This confirms the formation of the CeO2pillars (circles in 2D) in the SrTiO3matrix. An AFM image showing the same pillar features is shown in Fig. 7e. The diameter of the nanopillar (CeO2) is observed to be around ~ 30 nm in both Fig. 7d, e, in agreement with the TEM image of Fig. 1c. The columnar structure of film is not degraded by the transfer process and is very smooth (root mean square (RMS) roughness of 0.88 nm, obtained by squaring each height value in the dataset, then taking the square root of the mean).

    Table 1 Statistics of different result types from each thin film composition

    3.5 Higher Yield Transfer Obtained from Nanocomposite Structure

    We now explore the efficacy of our new transfer method and also whether VAN films improve or degrade the process. In Table 1 and Fig. 8, we show the transfer success rates and other transfer characteristics. We divided the success information into 4 groups (successful transfers, and then, if unsuccessful, the nature of this, i.e. ‘Fail to detach’, ‘Crack/damage’ or ‘Broken’). ‘Fail to detach’ indicates the film did not get fully removed from the substrate. The last 2 groupings relate to formation of wrinkles, cracks, and folds introduced by the transfer process. Films had obvious cracks or damage are in the “Crack/Damage” group, whereas in the ‘Broken into Pieces’ group, the films were cracked into small pieces.

    The overall yields for SrRuO3, CeO2, and CeO2/STO are 59.09%, 55.93%, and 72.31%, respectively. It is clear that the CeO2/STO VAN nanocomposite films have a higher yield (72.31%) in the transfer process with less crack/damage (13.85%) or breakage (6.15%).

    From a fracture toughness point of view, combining SrTiO3with CeO2should make the system more brittle owing to lower fracture toughness of SrTiO3[55, 56]. However, our composite films are not more brittle as compared to the single-phase plain films: films can be transferred without cracks and the transfer yield is higher. Therefore, this improvement in the composite films must be due to (an) other mechanism(s). We consider key possible mechanisms below.

    Fig. 8 Distribution of different result types from each thin film composition/form

    Assuming no handling stresses in the films after lift-off, the stress will originate from the residual stress induced by the lattice mismatch. CeO2has a cubic fluorite structure with lattice constanta= 0.5411 nm. Epitaxial (001) CeO2is expected to grow with its [100] direction in [110] direction of the STO (001) substrate, i.e. the in-plane crystalline orientations of CeO2are rotated byφ= 45° with respect to STO. Therefore, CeO2has an effective lattice parametera= 0.5411/■2 ≈ 0.3826 nm, which resulting a 2% lattice mismatch with STO substrates (a= 0.3905 nm). The residual stress between plain CeO2and the STO substrate can be up to 3.3 GPa, as reported by Aline Fluri et al. [57] This represents an upper limit stress because the STO matrix component in the film (~ 50% volume fraction) has no lattice mismatch with the substrate.

    The key question is what is the critical crack size is for this level of in-plane biaxial stress. We assume an infinite plate with a microcrack under biaxial tensile stress (shown by the red arrows in Fig. 5b). We need to determine whether the presence of the CeO2nanopillars will prevent the critical crack size in the VAN films from being reached. To estimate this, we turn to the Griffith crack criterion for brittle materials which indicates that when a crack reaches a certain critical length, the crack will propagate unstably. If it is prevented from reaching this value, it will be stable [58]:

    KICis the plane strain fracture toughness,a0is the length of edge crack,σcriticalandacriticalare the critical stress and critical crack lengths.a0represents the length of a microcrack in the film.

    HereKICfor CeO2[55] and STO [56] is 1.3 and 0.89 MPa m1/2, respectively. From Eqs. (1) and (2),acriticalof CeO2and STO is calculated to be 78 and 37 nm, respectively.

    acriticalfor the STO film matrix is 37 nm and this < the shortest distance,d, between the nanopillars in the matrix. Hence, the crack could be blocked from reachingacritical. But this will only occur if the energetics at the crack tip allow this. There are several possibilities for making the crack opening less favourable. (1) The CeO2nanopillar regions has a higherKIC(~ 50% higher for CeO2than STO) which will increase the toughening. (2) There is a room-temperature phase transition in nano-CeO2films [59] which could be activated by the stress at the crack tip. This phase transition could then absorb the energy at the tip and arresting its progression. This situation is similar to the phase transformation toughening shown by ZrO2particles embedded in ceramics [60—62]. This crack blocking by nanopillar is schematically shown as Scenario 1 (blue crack) in Fig. 5b.

    We also note, however, that there will be cracks of less favourable orientation than Scenario 1 which pass directly between two nanopillars. In Scenario 2 (Fig. 5b), a crack can weave through the STO matrix, by moving around the nanopillars. Here, several different toughening mechanisms can come into effect to increase the resistance to crack propagation, as in conventional composite ceramics, where finely dispersed nanoparticles in a matrix give significantly enhanced fracture toughness [49, 63—65]. These include particle—matrix interfacial debonding, microvoiding, matrix shear yielding, crack bridging, crack deflection and increased tortuosity [66—69].

    Since the structural mismatched vertical interface is more defective than the CeO2pillars themselves [70], the cracks in the STO will passaroundthe weaker CeO2pillars rather than through them. Whenacriticalis reached, then catastrophic failure would occur. Foracriticalof ~ 37 nm, as shown in Fig. 5b, the crack would pass around 2 nanopillars. The length for this circular crack can be estimated as 2 semi-circles, i.e. lengthl= (π/2)d, where d is the distance between start and end. The extra length for this crack (from start to end) compared to a straight crack is ~ 57%, and hence, the energy to fracture because of this tortuosity is higher by this amount also. Moreover, a tortuous crack path means that the stress will be less effective in opening up the crack tip as the stress will not be perpendicular to the crack in all regions.

    Overall, by invoking different fracture mechanisms of either prevention of crack propagation, inducing a higher fracture energy associated with a more tortuous crack path, and/or reduction of the operative stress, the higher yield of the transfer process obtained for the VAN films compared to plain films can be understood.

    4 Conclusions

    In summary, we have developed a new method, based on PMMA membranes, for transferring large-area (up to 5 × 10 mm2, so far) oxide thin films from SrTiO3substrates onto different substrates. Three different types of thin films (in terms of crystal structure and film form—plain or composite) were successfully transferred with good yield and quality. Cracks, wrinkles, and damages which are commonly introduced by conventional transfer processes, are prevented by the new transfer method. Furthermore, by adding STO into CeO2to form a nanocomposite structure, we showed improved lift-off yield rates by ~ 50%. Overall, we have demonstrated two approaches to significantly improve the transfer process of free-standing 2D single-crystalline functional oxide materials. The work has the potential to enable a wide range of oxide films to be transferred to different substrates for next-generation low-dimensional electronic devices.

    AcknowledgementsBZ would like to thank Cambridge Trust and China Scholarship Council for their funding. JLM-D would like to thank the support from the UK Royal Academy of Engineering, grant CiET1819_24, EPSRC grants EP/L011700/1, EP/N004272/1, EP/P007767/1 (CAM-IES), and EP/T012218/1.

    Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat iveco mmons.org/licen ses/by/4.0/.

    Supplementary information The online version of this article (https://doi.org/10.1007/s4082 0-020-00573-4).

    欧美性长视频在线观看| 国产区一区二久久| 国产成人精品无人区| 一本一本久久a久久精品综合妖精| 久久久精品区二区三区| 欧美 亚洲 国产 日韩一| 最新美女视频免费是黄的| 99热网站在线观看| 亚洲五月天丁香| 国产一区二区三区综合在线观看| 亚洲国产毛片av蜜桃av| 午夜两性在线视频| 少妇 在线观看| 亚洲,欧美精品.| 亚洲第一av免费看| 国产不卡一卡二| 久久性视频一级片| 久久人人97超碰香蕉20202| 免费高清在线观看日韩| 欧美日韩av久久| 色综合欧美亚洲国产小说| 亚洲成av片中文字幕在线观看| 亚洲色图av天堂| 在线观看66精品国产| 十八禁人妻一区二区| 精品国产一区二区三区四区第35| 午夜日韩欧美国产| 久久香蕉激情| 深夜精品福利| 国产精品99久久99久久久不卡| 精品午夜福利视频在线观看一区| 在线天堂中文资源库| 午夜视频精品福利| 国产高清国产精品国产三级| 亚洲黑人精品在线| 波多野结衣av一区二区av| 热re99久久国产66热| 亚洲熟女精品中文字幕| 欧美黑人欧美精品刺激| 国产亚洲精品久久久久久毛片 | 亚洲一码二码三码区别大吗| 午夜福利乱码中文字幕| 九色亚洲精品在线播放| 高潮久久久久久久久久久不卡| 十分钟在线观看高清视频www| 久久性视频一级片| 亚洲九九香蕉| 亚洲,欧美精品.| 亚洲精品在线观看二区| 国产精品99久久99久久久不卡| 成人精品一区二区免费| 黄色丝袜av网址大全| 国产麻豆69| 香蕉国产在线看| 亚洲av熟女| 90打野战视频偷拍视频| 精品人妻在线不人妻| 超碰97精品在线观看| 国产午夜精品久久久久久| 国产一区二区三区视频了| 国产乱人伦免费视频| 看片在线看免费视频| 国产精品永久免费网站| 免费在线观看亚洲国产| 成人手机av| 日本a在线网址| 在线看a的网站| 久久久久精品人妻al黑| 亚洲 国产 在线| 在线观看66精品国产| 老司机深夜福利视频在线观看| 高清在线国产一区| 欧美人与性动交α欧美精品济南到| 嫁个100分男人电影在线观看| 男女下面插进去视频免费观看| 国产不卡av网站在线观看| 亚洲国产欧美日韩在线播放| 无限看片的www在线观看| 成人18禁高潮啪啪吃奶动态图| 国产极品粉嫩免费观看在线| 男女下面插进去视频免费观看| videosex国产| 一本一本久久a久久精品综合妖精| 日韩免费av在线播放| 亚洲欧美日韩另类电影网站| 国产99久久九九免费精品| 99热网站在线观看| 一区二区三区精品91| 日韩视频一区二区在线观看| 久久精品国产清高在天天线| 好男人电影高清在线观看| 水蜜桃什么品种好| 又黄又爽又免费观看的视频| 中文字幕最新亚洲高清| 亚洲成a人片在线一区二区| 男女下面插进去视频免费观看| 成年人免费黄色播放视频| 在线观看一区二区三区激情| 久热爱精品视频在线9| 水蜜桃什么品种好| 色婷婷av一区二区三区视频| 最近最新免费中文字幕在线| 午夜福利乱码中文字幕| 国产日韩欧美亚洲二区| 日韩中文字幕欧美一区二区| 女人爽到高潮嗷嗷叫在线视频| 欧美另类亚洲清纯唯美| 日本wwww免费看| 在线看a的网站| 在线永久观看黄色视频| 黑人巨大精品欧美一区二区mp4| 国产成+人综合+亚洲专区| 亚洲精品久久午夜乱码| 国产区一区二久久| 亚洲一码二码三码区别大吗| 日韩三级视频一区二区三区| 中文字幕人妻丝袜一区二区| 亚洲,欧美精品.| 另类亚洲欧美激情| 久久精品熟女亚洲av麻豆精品| ponron亚洲| 成年版毛片免费区| 精品久久久精品久久久| 国精品久久久久久国模美| av网站在线播放免费| 欧美丝袜亚洲另类 | 可以免费在线观看a视频的电影网站| 久99久视频精品免费| 别揉我奶头~嗯~啊~动态视频| 久久久久久久精品吃奶| 黄频高清免费视频| 露出奶头的视频| 亚洲熟妇中文字幕五十中出 | 一进一出抽搐gif免费好疼 | 女同久久另类99精品国产91| 亚洲自偷自拍图片 自拍| 制服诱惑二区| 美女午夜性视频免费| 一个人免费在线观看的高清视频| 中文字幕另类日韩欧美亚洲嫩草| 91字幕亚洲| 成年人午夜在线观看视频| 欧美最黄视频在线播放免费 | 99re6热这里在线精品视频| 成年动漫av网址| 久久精品国产a三级三级三级| 中文亚洲av片在线观看爽 | www.999成人在线观看| 国产在线观看jvid| 亚洲全国av大片| 精品国产超薄肉色丝袜足j| 妹子高潮喷水视频| 日韩欧美国产一区二区入口| 国产欧美日韩一区二区三区在线| 国产精品一区二区精品视频观看| 色播在线永久视频| 啦啦啦在线免费观看视频4| 成人18禁在线播放| 中文字幕色久视频| 欧美日韩福利视频一区二区| 欧美乱妇无乱码| 中文欧美无线码| 午夜精品在线福利| 99香蕉大伊视频| 欧美日韩视频精品一区| 超色免费av| 一级,二级,三级黄色视频| 久久久久久久久久久久大奶| 一级片免费观看大全| 午夜福利在线观看吧| 亚洲精华国产精华精| 两性夫妻黄色片| 午夜精品久久久久久毛片777| 久久久国产成人免费| 久久久国产成人免费| 日本wwww免费看| 国产亚洲欧美98| 最新在线观看一区二区三区| 99热国产这里只有精品6| 精品一区二区三区四区五区乱码| 久久香蕉激情| av福利片在线| 母亲3免费完整高清在线观看| 大型av网站在线播放| 久久婷婷成人综合色麻豆| 色婷婷久久久亚洲欧美| 下体分泌物呈黄色| 免费日韩欧美在线观看| 九色亚洲精品在线播放| 999精品在线视频| 在线观看免费视频日本深夜| 美女福利国产在线| 国产精品一区二区在线不卡| 色综合欧美亚洲国产小说| 无人区码免费观看不卡| 国产单亲对白刺激| 亚洲精品乱久久久久久| 精品午夜福利视频在线观看一区| 日韩欧美在线二视频 | 国产乱人伦免费视频| 欧美成人午夜精品| 精品一区二区三区视频在线观看免费 | 欧美最黄视频在线播放免费 | 色94色欧美一区二区| 精品国产一区二区三区久久久樱花| 亚洲av熟女| 丝袜人妻中文字幕| 国产精品成人在线| 国产国语露脸激情在线看| 免费不卡黄色视频| 日本vs欧美在线观看视频| 成熟少妇高潮喷水视频| 黑人猛操日本美女一级片| 午夜日韩欧美国产| 久久精品亚洲精品国产色婷小说| 欧美不卡视频在线免费观看 | av中文乱码字幕在线| 伊人久久大香线蕉亚洲五| 少妇粗大呻吟视频| 亚洲全国av大片| 亚洲美女黄片视频| 日本欧美视频一区| 18禁国产床啪视频网站| 精品亚洲成a人片在线观看| 婷婷精品国产亚洲av在线 | 国产男女超爽视频在线观看| 黄色视频,在线免费观看| 天堂√8在线中文| 久久久久精品人妻al黑| 国产一区二区三区综合在线观看| 日韩三级视频一区二区三区| 中文字幕另类日韩欧美亚洲嫩草| 亚洲av电影在线进入| 久久中文字幕人妻熟女| 国产精品 国内视频| 日韩人妻精品一区2区三区| 老鸭窝网址在线观看| 亚洲免费av在线视频| 午夜成年电影在线免费观看| 精品高清国产在线一区| 中文亚洲av片在线观看爽 | 久久午夜亚洲精品久久| 正在播放国产对白刺激| 成年版毛片免费区| 日韩制服丝袜自拍偷拍| 91麻豆精品激情在线观看国产 | 美女午夜性视频免费| 老汉色av国产亚洲站长工具| cao死你这个sao货| 亚洲人成电影免费在线| 国产精品永久免费网站| 好看av亚洲va欧美ⅴa在| 亚洲中文字幕日韩| 啦啦啦免费观看视频1| 成人亚洲精品一区在线观看| 又大又爽又粗| 亚洲精品乱久久久久久| 看片在线看免费视频| 一级黄色大片毛片| 亚洲国产精品sss在线观看 | 国产精品久久久久成人av| 动漫黄色视频在线观看| 日韩精品免费视频一区二区三区| 成在线人永久免费视频| 免费观看a级毛片全部| 熟女少妇亚洲综合色aaa.| av国产精品久久久久影院| 手机成人av网站| 午夜免费成人在线视频| 欧美激情 高清一区二区三区| 亚洲av熟女| 99久久综合精品五月天人人| 国产日韩一区二区三区精品不卡| 韩国av一区二区三区四区| 国产真人三级小视频在线观看| 日本欧美视频一区| 国产有黄有色有爽视频| 日韩有码中文字幕| www.熟女人妻精品国产| 欧美 亚洲 国产 日韩一| 日韩欧美国产一区二区入口| 欧美黄色片欧美黄色片| 满18在线观看网站| 久久这里只有精品19| 我的亚洲天堂| 欧美成人午夜精品| 久久狼人影院| 国产av精品麻豆| tocl精华| 欧美另类亚洲清纯唯美| 丁香六月欧美| 999精品在线视频| 日韩精品免费视频一区二区三区| 精品国产乱码久久久久久男人| 欧美乱妇无乱码| 欧美精品av麻豆av| 曰老女人黄片| videos熟女内射| 99国产精品免费福利视频| 一级,二级,三级黄色视频| 免费不卡黄色视频| 看片在线看免费视频| 亚洲欧美精品综合一区二区三区| 午夜影院日韩av| 午夜福利免费观看在线| 99精品久久久久人妻精品| 两个人看的免费小视频| 欧美激情久久久久久爽电影 | 亚洲av欧美aⅴ国产| 中文字幕人妻熟女乱码| 伦理电影免费视频| 欧美 亚洲 国产 日韩一| 久久久久久久国产电影| 国产精品免费一区二区三区在线 | 成人三级做爰电影| 亚洲精品av麻豆狂野| 999久久久精品免费观看国产| 精品国产美女av久久久久小说| 51午夜福利影视在线观看| 欧美丝袜亚洲另类 | 国产精品二区激情视频| 18禁美女被吸乳视频| 亚洲精品乱久久久久久| 亚洲专区字幕在线| 18禁观看日本| 五月开心婷婷网| av福利片在线| 日日夜夜操网爽| 亚洲精品中文字幕在线视频| 欧美激情 高清一区二区三区| 夜夜爽天天搞| 国产区一区二久久| 亚洲国产欧美网| 悠悠久久av| 在线永久观看黄色视频| 69av精品久久久久久| 久久久久视频综合| 亚洲中文日韩欧美视频| 好男人电影高清在线观看| 久久久水蜜桃国产精品网| 两性夫妻黄色片| 黑人欧美特级aaaaaa片| 老熟妇乱子伦视频在线观看| 亚洲国产看品久久| 日韩熟女老妇一区二区性免费视频| 欧美日韩一级在线毛片| 欧美大码av| 在线观看66精品国产| 国产精品国产av在线观看| 免费女性裸体啪啪无遮挡网站| 女警被强在线播放| 国产成人av激情在线播放| 激情在线观看视频在线高清 | 99久久精品国产亚洲精品| 亚洲色图av天堂| 精品国产美女av久久久久小说| cao死你这个sao货| 大码成人一级视频| 午夜激情av网站| 午夜福利免费观看在线| www.熟女人妻精品国产| 老汉色∧v一级毛片| 成在线人永久免费视频| 日韩有码中文字幕| 在线观看免费高清a一片| 三上悠亚av全集在线观看| 亚洲成人国产一区在线观看| 亚洲精品自拍成人| 91老司机精品| 欧洲精品卡2卡3卡4卡5卡区| 欧美老熟妇乱子伦牲交| 国产亚洲精品一区二区www | 99国产精品一区二区三区| 亚洲一卡2卡3卡4卡5卡精品中文| 可以免费在线观看a视频的电影网站| 天天躁日日躁夜夜躁夜夜| 国产亚洲精品第一综合不卡| 欧美在线一区亚洲| 国产精品一区二区在线不卡| 悠悠久久av| 国产精品自产拍在线观看55亚洲 | 欧美日韩亚洲高清精品| 视频区欧美日本亚洲| 国产单亲对白刺激| www日本在线高清视频| 亚洲片人在线观看| 欧美精品人与动牲交sv欧美| 黄色丝袜av网址大全| 久久婷婷成人综合色麻豆| 伦理电影免费视频| 麻豆乱淫一区二区| 岛国毛片在线播放| 日本vs欧美在线观看视频| 99国产精品一区二区三区| 久热这里只有精品99| 国产熟女午夜一区二区三区| netflix在线观看网站| 一级a爱片免费观看的视频| 国产精品久久视频播放| 精品国产乱子伦一区二区三区| 精品人妻1区二区| 亚洲精品中文字幕一二三四区| 国产人伦9x9x在线观看| 久久久久久久国产电影| 天堂中文最新版在线下载| 成人三级做爰电影| 一区二区三区激情视频| 国产亚洲欧美在线一区二区| 精品欧美一区二区三区在线| 亚洲成人免费电影在线观看| 国产一区二区激情短视频| 在线av久久热| 日本黄色视频三级网站网址 | 久久人妻av系列| 99久久人妻综合| av网站免费在线观看视频| 怎么达到女性高潮| 久久国产乱子伦精品免费另类| 久久久久国内视频| 国产成人av激情在线播放| 极品少妇高潮喷水抽搐| 色精品久久人妻99蜜桃| 国产在线精品亚洲第一网站| 丝瓜视频免费看黄片| 51午夜福利影视在线观看| 久久热在线av| 成人国产一区最新在线观看| 亚洲黑人精品在线| 精品国内亚洲2022精品成人 | 99精国产麻豆久久婷婷| 亚洲国产中文字幕在线视频| 免费在线观看影片大全网站| 午夜亚洲福利在线播放| 亚洲在线自拍视频| 波多野结衣av一区二区av| 桃红色精品国产亚洲av| 91在线观看av| 国产精品免费一区二区三区在线 | 国产日韩一区二区三区精品不卡| 精品电影一区二区在线| 国产亚洲精品久久久久5区| 国产日韩一区二区三区精品不卡| 午夜免费成人在线视频| 1024视频免费在线观看| 看免费av毛片| 一a级毛片在线观看| 后天国语完整版免费观看| 国产精品久久久久成人av| 亚洲成av片中文字幕在线观看| 亚洲成国产人片在线观看| 国产99白浆流出| 久久人妻福利社区极品人妻图片| 久久影院123| 国产深夜福利视频在线观看| 1024视频免费在线观看| 亚洲中文日韩欧美视频| 国产精品国产av在线观看| 日本wwww免费看| 麻豆成人av在线观看| 丝袜美腿诱惑在线| 国产亚洲一区二区精品| 捣出白浆h1v1| 久久久久久亚洲精品国产蜜桃av| av免费在线观看网站| 日韩三级视频一区二区三区| 777米奇影视久久| 一进一出抽搐gif免费好疼 | 天天添夜夜摸| 校园春色视频在线观看| 成人国产一区最新在线观看| av超薄肉色丝袜交足视频| 色播在线永久视频| 午夜免费观看网址| 两人在一起打扑克的视频| 18禁观看日本| 老鸭窝网址在线观看| 一级毛片高清免费大全| 久久亚洲精品不卡| 999久久久精品免费观看国产| 日韩视频一区二区在线观看| 国产精品 欧美亚洲| 天天躁狠狠躁夜夜躁狠狠躁| 久9热在线精品视频| 热99国产精品久久久久久7| 精品国产美女av久久久久小说| 别揉我奶头~嗯~啊~动态视频| 欧美国产精品va在线观看不卡| 亚洲久久久国产精品| 亚洲免费av在线视频| 国产亚洲一区二区精品| 亚洲九九香蕉| av国产精品久久久久影院| 国产xxxxx性猛交| 操出白浆在线播放| 精品福利观看| 叶爱在线成人免费视频播放| 久久人人爽av亚洲精品天堂| 久久国产精品男人的天堂亚洲| 麻豆国产av国片精品| 欧美乱色亚洲激情| 日韩欧美三级三区| 成熟少妇高潮喷水视频| 日韩欧美国产一区二区入口| 久久九九热精品免费| 757午夜福利合集在线观看| 19禁男女啪啪无遮挡网站| 国产单亲对白刺激| 国产欧美日韩一区二区三区在线| 久久亚洲真实| 午夜福利影视在线免费观看| 一二三四社区在线视频社区8| 多毛熟女@视频| 精品人妻1区二区| 中文字幕人妻熟女乱码| 亚洲欧美精品综合一区二区三区| 丝袜美腿诱惑在线| 国精品久久久久久国模美| 国产精品国产av在线观看| 久久久国产成人精品二区 | 一本大道久久a久久精品| 亚洲熟妇熟女久久| 久久ye,这里只有精品| 久久国产乱子伦精品免费另类| 午夜精品在线福利| 水蜜桃什么品种好| 亚洲精品中文字幕一二三四区| 成人永久免费在线观看视频| 亚洲熟妇熟女久久| 精品第一国产精品| 久久精品国产亚洲av香蕉五月 | 亚洲精品在线观看二区| 欧美色视频一区免费| 一边摸一边做爽爽视频免费| 18禁美女被吸乳视频| 91九色精品人成在线观看| 岛国毛片在线播放| 人人澡人人妻人| 久久天堂一区二区三区四区| 法律面前人人平等表现在哪些方面| 在线视频色国产色| 国产亚洲欧美98| 亚洲av成人不卡在线观看播放网| 亚洲熟女精品中文字幕| 在线观看www视频免费| 麻豆av在线久日| 在线十欧美十亚洲十日本专区| 国产有黄有色有爽视频| 丝袜美足系列| 色94色欧美一区二区| 国精品久久久久久国模美| 91麻豆精品激情在线观看国产 | 精品午夜福利视频在线观看一区| 男女午夜视频在线观看| 很黄的视频免费| 91字幕亚洲| 久久热在线av| 国产不卡一卡二| 久久草成人影院| 天天躁狠狠躁夜夜躁狠狠躁| 很黄的视频免费| 亚洲 国产 在线| bbb黄色大片| www.自偷自拍.com| 日韩有码中文字幕| 自线自在国产av| 久久久精品国产亚洲av高清涩受| 一进一出抽搐gif免费好疼 | 母亲3免费完整高清在线观看| 老司机亚洲免费影院| 天堂中文最新版在线下载| av电影中文网址| 久久久国产精品麻豆| 亚洲av片天天在线观看| 亚洲av电影在线进入| 一级毛片高清免费大全| 亚洲中文av在线| 啦啦啦在线免费观看视频4| 人妻一区二区av| 国产在线精品亚洲第一网站| 99精品欧美一区二区三区四区| 人人澡人人妻人| 91精品三级在线观看| 精品少妇久久久久久888优播| 99re6热这里在线精品视频| 精品久久久久久久久久免费视频 | 久久国产精品影院| 中国美女看黄片| 日韩中文字幕欧美一区二区| 国产成人影院久久av| 午夜两性在线视频| 超色免费av| 久久久久久免费高清国产稀缺| 两性夫妻黄色片| 黄色 视频免费看| bbb黄色大片| 国产精品影院久久| 欧美丝袜亚洲另类 | 人人妻人人添人人爽欧美一区卜| 99热只有精品国产| 淫妇啪啪啪对白视频| 国产欧美日韩精品亚洲av| 中文字幕av电影在线播放| 91成年电影在线观看| 一本综合久久免费| 亚洲av熟女| 侵犯人妻中文字幕一二三四区| a在线观看视频网站| 不卡一级毛片| 日本一区二区免费在线视频| 丝瓜视频免费看黄片| 亚洲一区高清亚洲精品| 精品一区二区三卡| 黄色丝袜av网址大全| 亚洲男人天堂网一区| 啦啦啦视频在线资源免费观看|