• <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 ?

    Sr-doping effects on conductivity,charge transport,and ferroelectricity of Ba0.7La0.3TiO3 epitaxial thin films?

    2021-03-11 08:34:04QiangLi李強DaoWang王島YanZhang張巖YuShanLi李育珊AiHuaZhang張愛華RuiQiangTao陶瑞強ZhenFan樊貞MinZeng曾敏GuoFuZhou周國富XuBingLu陸旭兵andJunMingLiu劉俊明
    Chinese Physics B 2021年2期
    關(guān)鍵詞:張巖國富愛華

    Qiang Li(李強), Dao Wang(王島), Yan Zhang(張巖), Yu-Shan Li(李育珊),Ai-Hua Zhang(張愛華),?, Rui-Qiang Tao(陶瑞強), Zhen Fan(樊貞), Min Zeng(曾敏),Guo-Fu Zhou(周國富), Xu-Bing Lu(陸旭兵),?, and Jun-Ming Liu(劉俊明)

    1Institute for Advanced Materials,South China Academy of Advanced Optoelectronics,South China Normal University,Guangzhou 510006,China

    2Guangdong Provincial Key Laboratory of Optical Information Materials,South China Academy of Advanced Optoelectronics,South China Normal University,Guangzhou 510006,China

    3National Center for International Research on Green Optoelectronics,South China Normal University,Guangzhou 510006,China

    4Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures,Nanjing University,Nanjing 210009,China

    Keywords: Sr-doping,transport mechanism,BSLTO thin film,ferroelectric metal

    1. Introduction

    As typical perovskite oxide materials,BaTiO3(BTO)and SrTiO3(STO)have been most extensively studied and utilized as capacitors, transducers, and nonvolatile memories.[1–3]Their stoichiometric compounds are band-gap insulators.When doped with donor ions or deposited in an oxygendeficient atmosphere, the n-type semiconductive or metallic conduction can be obtained, resulting in various intriguing physical properties and broad application prospects.[4–6]For example,the ferroelectric semiconducting BTO oxide materials have received wide attention for their applications in photovoltaic solar cell[7]and resistive memory.[8]Moreover,the superconductivity is even observed in the rare-earth substituted STO film,which implies broad application prospect in reducing the energy consumption of electronic devices.[9]

    Although both BTO and STO have a simple perovskite structure and similar electronic band structures,significant differences exist among their conductive compounds. For example, small substitution of pentavalent ions for Ti4+ions or trivalent ions for Sr2+ions can tune the conventional insulating STO from an insulating to semiconducting or even metallic state.[10,11]In contrast to Sr-based compounds, BTO undergoes those transitions at much higher doping levels.[12]In addition, the carrier concentration in the obtained metallic BTO(n ≈1021cm?3)[13]is almost two orders higher than that in STO (n ≈1019cm?3).[14]Another interesting observation is that the conductive STO exhibits weak temperature dependence of Hall effect and resistivity,whereas the BTO system is opposite.[13]Such differences should be related to their local structures. The ferroelectric BTO has a polar structure,which would cause the itinerant electrons to be localized. Nevertheless,such a polar structure is absent for the paraelectric STO,and the localized electrons are greatly reduced.[15]It is quite interesting to know how the carrier transport characteristics of polar BTO will change when it is doped with paraelectric STO.

    The undoped BTO is a well-known classical ferroelectric material. The introduction of electron into this material will screen long-range Coulomb interaction, thus destroying its ferroelectricity.[16]The coexistence of metallic conduction and ferroelectric ordering are believed to be two incompatible physical effects. The study on their coexistence is desirable to discover novel physical phenomena and corresponding mechanisms embedded in it and develop its applications in future microelectronic and optoelectronic devices. Recently,Ladoped BTO films were particularly intriguing. It is reported that the polar phase and experimental metallic conduction can be obtained in those films.[17]As is well known,the ferroelectric polarization in BTO originates from the displacement of Ti ion in the Ti–O octahedron. The replacement of Sr2+at the Ba2+site in BSLTO film will not damage the displacement of Ti ion,which means that the ferroelectricity of the BSLTO film will not be deteriorated.

    In this work, we prepare Ba0.7?xSrxLa0.3TiO3(BSLTO)epitaxial thin films, and systematically study their microstructures,conductivities,ferroelectricity,and carrier transport mechanisms. It is generally believed that the increase of material conductivity should be achieved by doping higher- or lower-valence ions into lattice site. Our work demonstrates that the equivalent valence doping of Sr2+(non-electron doping) can also increase electrical conductivity of BSLTO thin films while not deteriorating its ferroelectricity, which provides a novel idea to increase the material conduction and obtain ferroelectric metal for other perovskite oxides.

    2. Experimental details

    We fabricated BSLTO films with Sr=0.00, 0.20, 0.30,and 0.40 on(001)MgO single crystal substrates at 650?C by using the pulsed laser deposition(PLD)technique. During the deposition,a KrF excimer laser with a wavelength of 248 nm was operated at 2 Hz and the laser fluence was fixed to be 1.7 J·cm?2. The crystal structures of the films were studied by using x-ray diffraction(XRD)equipped with a PANalytical X’Pert Pro diffractometer, including 2θ scans and reciprocal space mapping (RSM) measurement. The force strength between ions was characterized by Raman spectroscopy with a 532-nm excitation laser(RAMAN INVIA,RENISHAW).The temperature dependence of electrical resistivity and Hall effect for each of the BSLTO thin films were measured by the van der Pauw method with a physical property measurement system(PPMS9,Quantum Design).

    3. Results and discussion

    Figure 1(a) shows the XRD patterns of the BSLTO thin films with Sr=0.00,0.20,0.30,and 0.40 grown on the MgO(001) substrate. Only (00l) diffraction peaks appear, and no other oriented peaks can be observed, indicating that all the films are grown epitaxially on the MgO(001)substrate. In order to obtain the precise lattice constants of the BSLTO thin films,the reciprocal space around the(113)reflection is measured (see Fig.A1 in Appendix A), and the corresponding in-plane (a) and out-of-plane (c) lattice constants calculated from their RSM results are shown in Fig.1(b). It can be seen from Fig.1(b) that each of all the thin films has a tetragonal structure. Furthermore, as the Sr content increases, both of the lattice parameters decrease, implying that the introduction of Sr leads the unit cell of BSLTO thin film to contract. This is because Sr2+ion radius (1.44 ?A) is smaller than Ba2+ion radius (1.61 ?A).[18]In order to explore the influence of lattice shrinkage on the force strength between ions,the Raman spectra of BSLTO films with Sr=0.00,0.20,0.30, and 0.40 in a frequency range of 100 cm?1–850 cm?1are recorded. The main Raman peaks for BSLTO films can be assigned to A1(TO), B1,E(TO+LO), E(TO),A1(TO), and A1(LO),E(LO),[19]as shown in Fig.1(c). The phonon modes around 320 cm?1and 720 cm?1(marked by arrows)are specific to the tetragonal phase of the BaTiO3,[20]which are consistent with the XRD results. In addition, the frequency of the A1(LO)/E(TO) mode around 720 cm?1increases monotonically as Sr content increases. The upward shift reflects the tighter bonding between the cations and anions,caused by lattice shrinkage, which could result in the increase of phonon energy in the film.[21]

    Figure 2(a) shows temperature-dependent resistivity for BSLTO thin film with Sr=0.00, 0.20, 0.30, and 0.40. It can be seen that the resistivity of the thin film shows a clear dependence on Sr-doping content, exhibiting that the resistivity decreases markedly as Sr content increases. For Sr=0.00,0.20,the resistivity decreases with the increase of temperature over the entire measurement temperature range,demonstrating typical semiconductive conduction behavior. When Sr content reaches to 0.30,an interesting semiconductor–metal transition begins to occur. As shown in Fig.2(b), this transition is observed at 330 K.For Sr=0.40,there is still a semiconductor–metal transition as shown in Fig.2(c), and the corresponding temperature position moves to a lower location at 295 K.The BTO films can become increasingly conductive as the content of donor doping ions increases, because donor doping introduces electron into the films.[4,22]The clear increase of the conductivity of the BSLTO thin films by an equivalent valence doping of Sr2+(non-electron doping) into the A-site is worthy to be further discussed. Figure 2(d) shows temperaturedependent Hall coefficient RHcurves for the BSLTO films.The negative Hall coefficient indicates that the carriers in the films are mainly composed of electrons. The electron concentration is calculated from the formula: RH=1/en,and the results are shown in Fig.2(e), where it can be seen that the electron concentration increases with temperature increasing at low temperature, indicating that the electrons in the films are in a localized state.[17]As the temperature increases, the localized electrons are gradually to be released, and finally at one certain high temperature the electron concentrations of all the films with different Sr contents will reach almost the same level. For the present BSLTO thin films with the same La content,the carriers in these films originate from the donor effect that La3+enters into the A-site and provides extra electrons.[22]Therefore, it is observed that when the electron releasing is completed,the electron concentration in each film is not obviously changed. Figure 2(f)shows the variations of temperature of carrier mobility with temperature for BSLTO thin films. It can be clearly seen from Fig.2(f)that the Sr doping can improve the mobility. As mentioned above, the electron concentration in each film does not change significantly,implying that the decreasing of resistivity of the film is mainly ascribed to the increasing of carrier mobility.The intrinsic carrier transport mechanism of the films should be related to the increase of carrier mobility and will be discussed below.

    Fig.1. (a)The 2θ scan patterns,(b)lattice parameters,and(c)Raman spectra of BSLTO films with Sr=0.00,0.20,0.30,and 0.40.

    Fig.2. Temperature-dependent resistivities of BSLTO films (a) with Sr=0.00, 0.20, 0.30, and 0.40, (b) with Sr=0.30 (300 K–400 K), (c) with Sr=0.40(260 K–400 K);temperature-dependent(d)Hall coefficient,(e)carrier density and(f)Hall carrier mobility for BSLTO films with Sr=0.00,0.20,0.30,and 0.40.

    Fig.3. Fitting results using (a) VRH model and (b) SPH model for BSLTO films with Sr=0.00, 0.20, 0.30, and 0.40; (c) thermal phonon scattering mode for the BSLTO film with Sr=0.30;(d)thermal phonon scattering mode for the BSLTO film with Sr=0.40.

    To reveal the carrier transport mechanisms of the BSLTO films with Sr=0.00, 0.20, 0.30, and 0.40, their R–T curves from low temperature to high temperature are fitted by various models.In particular,R–T curves for the films with Sr=0.30,0.40 can be divided into semiconducting and metallic regime,while the corresponding carrier transport mechanisms are discussed separately. For the present films that exhibit semiconducting behaviors,the transport model changes from variable range hopping (VRH) to small polaron hopping (SPH) when the measurement temperature increases, and the results are shown in Figs. 3(a) and 3(b), respectively. The metalic conductive behaviors in the films with Sr=0.30,0.40 all conform to thermal phonon scattering mode as shown in Figs.3(c)and 3(d),respectively. The various transport models and their corresponding temperature ranges are summarized in Table 1. In our previous researches, it has been put forward that the carrier transport mechanism of La-doped BTO thin films is dominated by electron–phonon coupling.[23,24]When it is at low temperature, the weak electron–phonon coupling is hard to form small polarons,the electron can absorb energy to hop to a remote location with lower potential barriers to realize charge transport. This kind of charge transport is characterized by the variable range hopping mode: ln(ρ)∝T?1/4.[25]As the temperature rises to a certain value, the enhanced electron–phonon coupling can form small polarons,and then the charge transport follows the small polaron transition mode: ln(ρ)∝T3/2exp(WH/KBT),where WHis the activation energy,and kBis the Boltzmann constant.[26]With the introduction of Sr,the enhanced phonon energy can provide more energy to promote the hopping of small polarons. Thus, the calculated activation energy of small polarons in the film with Sr=0.00,0.20,0.30, and 0.40 sequentially decrease, and their WHvalues are 0.055,0.046,0.038,and 0.032 eV,respectively. The lower activation energy is responsible for the higher mobility,causing the resistivity of the film with non-electron doping to decrease.In addition,Mott and Ihrig pointed out that the polaron binding energy Wpwould be approximately twice the activation energy WH(Wp≈2WH).[27,28]Thus, the small polarons with low activation energy are easy to be thermally dissociated. For films with Sr <0.30,their activation energy values are smaller than those of the films with Sr=0.30, 0.40. Consequently,slightly lower carrier concentration is observed. In addition,lower carrier mobility values are also observed for the films with Sr=0.00, 0.20 due to different electron–phonon interactions. We propose that the low carrier concentration and carrier mobility should be the two dominant reasons which are responsible for the non-metallic conduction behaviors of films with Sr=0.00,0.20. When temperature is increased to 350 K,the film with Sr=0.30 begins to exhibit metallic conductive behavior due to the dissociated small polarons. As to film with Sr=0.40, the same metalic conductive behavior occurs at a lower temperature (295 K), which is attributed to lower activation energy caused by the enhanced phonon energy. The conduction behavior of the dissociated electrons is dominated by thermal phonon scattering, and the associated transport mechanism conforms to the model: ρ ∝T3/2.[26]

    The present films have so high electron concentration that it is difficult to obtain macroscopic ferroelectric reversal signals. In this experiment, the piezoelectric force microscopy(PFM)is adopted to explore the micro-region ferroelectricity.After ±9 V writing in the two adjacent areas, figure 4 shows the room-temperature measurements of out-of-plane PFM amplitudes (Figs. 4(a)–4(d)) and phase images (Figs. 4(e)–4(h))of the BSLTO films with Sr=0.00, 0.20, 0.30, and 0.40, respectively. The clear contrast of the PFM amplitudes and phase images of all samples demonstrate that the current films have obvious characteristics of ferroelectricity. In particular,the BSLTO film with Sr=0.40 is in metallic conduction state at room temperature, implying that the coexistence of ferroelectricity and metalic conductivity can be realized in BSLTO film with Sr=0.40. For the present films, after Sr doping,the polar tetragonal structure could be maintained. Most importantly, Sr improves the carrier mobility by increasing the phonon energy, thereby obtaining the metallic BSLTO film with Sr=0.40. This way of achieving metalic conduction does not introduce extra electrons,thereby weakening the electrons to shield the long-range Coulomb effect,which is beneficial to the stability of ferroelectricity. Therefore, Sr doping provides a novel idea to obtain ferroelectric metal for other perovskite oxides.

    Table 1. List of various transport models and their corresponding temperature ranges and WH for the BSLTO films with Sr=0.00,0.20,0.30,and 0.40.

    Fig.4. (a)–(d)Out-of-plane PFM amplitude and(e)–(h)phase images for BSLTO films with Sr=0.00,0.20,0.30,and 0.40,respectively,and poling bias voltage of±9 V.

    4. Conclusions

    In the present research, the microstructure, electrical conduction, charge transport, and ferroelectricity of epitaxial BSLTO thin films with Sr=0.00,0.20,0.30,and 0.40 are systematically investigated. The introduction of Sr can make the unit cell of BSLTO films contracted,which is responsible for the enhanced phonon energy in the films. The R–T measurements show that the increase of Sr content in the BSLTO can gradually reduce electrical resistivity,and the metallic conduction can be found in films with Sr=0.30, 0.40. The Sr doping effects on carrier transport mechanisms of BSLTO films are clarified. The fitting results of R–T curves indicate that Sr increasing phonon energy is responsible for lower activation energy of small polaron hopping, higher carrier mobility, lower electrical resistivity. The PFM results demonstrate that the metalic conducting films with Sr=0.30, 0.40 could possess ferroelectricity, indicating that Sr doping provides a novel idea to explore ferroelectric metal materials for other perovskite oxides.

    Appendix A:Supporting information

    The reciprocal space maps around the(113)reflection are shown in the following figures.

    Fig.A1. Reciprocal space maps of BSLTO films with (a) Sr=0.00, (b)Sr=0.20,(c)Sr=0.30,(d)Sr=0.40.

    猜你喜歡
    張巖國富愛華
    把實事真正辦到群眾心坎里
    雷鋒(2022年2期)2022-04-12 00:08:12
    岜沙苗寨繡花女
    金秋(2020年12期)2020-12-03 23:04:07
    Investigation on pulsed discharge mode in SF6-C2H6 mixtures
    第一次拔牙
    神奇的光
    春天里的發(fā)現(xiàn) 等
    《工程力學》課程中PBL教學模式的應用探討
    新年獻詞
    茶博覽(2017年1期)2017-02-24 08:50:14
    在廈金胞張愛華孝親牽起兩岸情
    海峽姐妹(2016年2期)2016-02-27 15:15:48
    李愛華:我希望過上這樣的生活
    免费人成在线观看视频色| 青春草亚洲视频在线观看| 村上凉子中文字幕在线| 欧美日韩精品成人综合77777| 国产精品无大码| 国产精品国产三级国产av玫瑰| 色综合站精品国产| 床上黄色一级片| 免费看美女性在线毛片视频| 国产精品久久久久久精品电影| 成人三级黄色视频| 中文欧美无线码| 亚洲精品日韩av片在线观看| 国产午夜精品久久久久久一区二区三区| 精品人妻偷拍中文字幕| 欧美三级亚洲精品| 你懂的网址亚洲精品在线观看 | 精品人妻熟女av久视频| 亚洲成人久久爱视频| 啦啦啦啦在线视频资源| 韩国av在线不卡| 久久午夜福利片| 在线观看美女被高潮喷水网站| 亚洲精品色激情综合| 97超视频在线观看视频| 色吧在线观看| 国产黄a三级三级三级人| 91麻豆精品激情在线观看国产| 国产一区亚洲一区在线观看| 三级国产精品欧美在线观看| 亚洲人成网站在线播放欧美日韩| 久久久久久久久久久免费av| 免费一级毛片在线播放高清视频| 熟女人妻精品中文字幕| 久久久精品欧美日韩精品| 亚洲欧洲国产日韩| 国产国拍精品亚洲av在线观看| 变态另类丝袜制服| 少妇裸体淫交视频免费看高清| 亚洲av熟女| 精品久久久久久久末码| 1024手机看黄色片| 极品教师在线视频| 青春草视频在线免费观看| 波多野结衣巨乳人妻| 国产亚洲精品av在线| 麻豆成人av视频| 国内精品一区二区在线观看| 麻豆久久精品国产亚洲av| 日韩欧美 国产精品| 两个人的视频大全免费| 97人妻精品一区二区三区麻豆| 最好的美女福利视频网| 日韩欧美三级三区| 亚洲av一区综合| 卡戴珊不雅视频在线播放| 中国美女看黄片| 亚洲精品久久国产高清桃花| 日本三级黄在线观看| 伊人久久精品亚洲午夜| 日韩欧美精品v在线| 青春草亚洲视频在线观看| 韩国av在线不卡| 91精品一卡2卡3卡4卡| 中文字幕av成人在线电影| 国产国拍精品亚洲av在线观看| 在现免费观看毛片| 国产在线男女| 国产精品无大码| 国产黄色小视频在线观看| 色视频www国产| 国产精品不卡视频一区二区| 精华霜和精华液先用哪个| 少妇裸体淫交视频免费看高清| 女人被狂操c到高潮| 国产精品99久久久久久久久| 国产高清激情床上av| 卡戴珊不雅视频在线播放| 女的被弄到高潮叫床怎么办| 国产av麻豆久久久久久久| 99精品在免费线老司机午夜| 亚洲美女搞黄在线观看| 一卡2卡三卡四卡精品乱码亚洲| 国产精品伦人一区二区| 麻豆乱淫一区二区| 中文字幕制服av| 中国美白少妇内射xxxbb| 黄色配什么色好看| 一个人看的www免费观看视频| 免费av不卡在线播放| 国内精品美女久久久久久| 亚洲精品日韩在线中文字幕 | 男人的好看免费观看在线视频| 成人av在线播放网站| 午夜精品国产一区二区电影 | 久久这里有精品视频免费| 亚洲人成网站在线观看播放| 亚洲性久久影院| 在线观看免费视频日本深夜| 91aial.com中文字幕在线观看| 国产精品av视频在线免费观看| 国产一区亚洲一区在线观看| 在线观看美女被高潮喷水网站| 99riav亚洲国产免费| 国产日本99.免费观看| 中文字幕人妻熟人妻熟丝袜美| 人人妻人人看人人澡| 国产精品久久久久久亚洲av鲁大| 久久6这里有精品| 亚洲精品乱码久久久v下载方式| 一个人看的www免费观看视频| 美女国产视频在线观看| 亚洲欧美中文字幕日韩二区| 波多野结衣巨乳人妻| 日韩精品青青久久久久久| 99九九线精品视频在线观看视频| 内地一区二区视频在线| 熟女电影av网| 精品久久久久久成人av| av.在线天堂| 欧美精品国产亚洲| 精品无人区乱码1区二区| 国产亚洲精品av在线| 久久国产乱子免费精品| 一边摸一边抽搐一进一小说| 国产午夜精品一二区理论片| 日产精品乱码卡一卡2卡三| 亚洲av一区综合| 麻豆乱淫一区二区| a级毛色黄片| 天美传媒精品一区二区| 天天一区二区日本电影三级| 成人特级黄色片久久久久久久| 亚洲精品自拍成人| 久久久成人免费电影| 18禁在线播放成人免费| 毛片女人毛片| 久久亚洲精品不卡| 在线免费十八禁| 一卡2卡三卡四卡精品乱码亚洲| 变态另类成人亚洲欧美熟女| 国产成年人精品一区二区| 麻豆成人午夜福利视频| 成人高潮视频无遮挡免费网站| 国产精品福利在线免费观看| 久久久久九九精品影院| 亚洲无线观看免费| 爱豆传媒免费全集在线观看| 日本撒尿小便嘘嘘汇集6| 看免费成人av毛片| 91麻豆精品激情在线观看国产| 日本欧美国产在线视频| av专区在线播放| 免费看a级黄色片| 色播亚洲综合网| 国产 一区 欧美 日韩| 日本黄色视频三级网站网址| 嫩草影院精品99| 女的被弄到高潮叫床怎么办| 亚洲无线观看免费| 亚洲色图av天堂| 午夜激情欧美在线| 晚上一个人看的免费电影| 国产在线精品亚洲第一网站| 中文字幕av在线有码专区| 18+在线观看网站| 午夜精品一区二区三区免费看| 久久久久久久久久久丰满| 国产91av在线免费观看| 国产成人freesex在线| 亚洲成人久久性| 色综合亚洲欧美另类图片| 偷拍熟女少妇极品色| 男人和女人高潮做爰伦理| 欧洲精品卡2卡3卡4卡5卡区| 亚洲经典国产精华液单| 搡女人真爽免费视频火全软件| 青春草亚洲视频在线观看| 国产淫片久久久久久久久| 99久久成人亚洲精品观看| 久久精品国产亚洲av涩爱 | 成人av在线播放网站| 日韩国内少妇激情av| 日日撸夜夜添| 极品教师在线视频| 又粗又爽又猛毛片免费看| 两个人视频免费观看高清| 亚洲人成网站高清观看| 日韩精品有码人妻一区| 在线免费十八禁| 黄色配什么色好看| 中文精品一卡2卡3卡4更新| 久久久久九九精品影院| 国产黄色视频一区二区在线观看 | 欧美日韩一区二区视频在线观看视频在线 | 久久久久久久亚洲中文字幕| 99久久九九国产精品国产免费| 两个人的视频大全免费| 亚洲精品日韩在线中文字幕 | 老司机福利观看| 黄色欧美视频在线观看| 中文字幕av在线有码专区| 亚洲精品乱码久久久久久按摩| 日韩欧美一区二区三区在线观看| 国产成人影院久久av| 女的被弄到高潮叫床怎么办| 变态另类成人亚洲欧美熟女| 精品久久久久久久久亚洲| 超碰av人人做人人爽久久| 少妇熟女欧美另类| 日韩一区二区视频免费看| av在线蜜桃| 变态另类丝袜制服| 又爽又黄无遮挡网站| 人妻制服诱惑在线中文字幕| 免费观看a级毛片全部| 亚洲精品粉嫩美女一区| 久久精品国产亚洲网站| 国产亚洲精品av在线| 国产精品一区二区在线观看99 | 人妻少妇偷人精品九色| 六月丁香七月| 色播亚洲综合网| 国产成人精品婷婷| 国产不卡一卡二| 日本与韩国留学比较| 久久国产乱子免费精品| www.色视频.com| avwww免费| 久久久久久久午夜电影| 天美传媒精品一区二区| 一本一本综合久久| 欧美一区二区亚洲| 亚洲无线在线观看| 丰满人妻一区二区三区视频av| 日本黄色视频三级网站网址| 国产在线男女| 丝袜喷水一区| 啦啦啦啦在线视频资源| 在线免费十八禁| 精品一区二区三区视频在线| 男人的好看免费观看在线视频| 国产麻豆成人av免费视频| 国产精品麻豆人妻色哟哟久久 | 国产成人精品婷婷| 一夜夜www| 最近2019中文字幕mv第一页| 日本三级黄在线观看| 两性午夜刺激爽爽歪歪视频在线观看| 成年女人看的毛片在线观看| 亚洲国产欧美在线一区| 亚洲国产精品成人久久小说 | 国产一区亚洲一区在线观看| 日本一二三区视频观看| 别揉我奶头 嗯啊视频| 麻豆一二三区av精品| 老熟妇乱子伦视频在线观看| 2022亚洲国产成人精品| 国产一区亚洲一区在线观看| 国产高清有码在线观看视频| 一卡2卡三卡四卡精品乱码亚洲| 久久久久久久久中文| 日韩一本色道免费dvd| 亚州av有码| 少妇猛男粗大的猛烈进出视频 | 婷婷色av中文字幕| 99热精品在线国产| 美女脱内裤让男人舔精品视频 | 黑人高潮一二区| 最近中文字幕高清免费大全6| 干丝袜人妻中文字幕| 久久久a久久爽久久v久久| av在线亚洲专区| 插逼视频在线观看| avwww免费| 超碰av人人做人人爽久久| 久久午夜亚洲精品久久| 欧美另类亚洲清纯唯美| 两性午夜刺激爽爽歪歪视频在线观看| 夜夜看夜夜爽夜夜摸| 亚州av有码| 国产亚洲av嫩草精品影院| 久久久久性生活片| 熟妇人妻久久中文字幕3abv| 亚洲av中文av极速乱| 久久久久久国产a免费观看| 久久久久性生活片| 色5月婷婷丁香| 日产精品乱码卡一卡2卡三| 69人妻影院| 欧美潮喷喷水| 国产不卡一卡二| 男人的好看免费观看在线视频| 日本一本二区三区精品| 色综合色国产| 精品国产三级普通话版| 国产成人精品一,二区 | 日韩高清综合在线| 中文字幕久久专区| 亚洲欧美日韩无卡精品| 91久久精品国产一区二区成人| 亚洲久久久久久中文字幕| 亚洲成人av在线免费| 美女黄网站色视频| 一级av片app| 一进一出抽搐gif免费好疼| 变态另类丝袜制服| 国产成人a∨麻豆精品| 秋霞在线观看毛片| 亚洲三级黄色毛片| 亚洲乱码一区二区免费版| 欧美zozozo另类| 国产大屁股一区二区在线视频| 不卡一级毛片| а√天堂www在线а√下载| 日本黄色片子视频| 可以在线观看毛片的网站| 网址你懂的国产日韩在线| 国产精品一区二区性色av| av在线蜜桃| 自拍偷自拍亚洲精品老妇| www.色视频.com| a级毛片a级免费在线| 插阴视频在线观看视频| 国产69精品久久久久777片| 国产成人a区在线观看| 免费无遮挡裸体视频| 亚洲精品成人久久久久久| 插阴视频在线观看视频| 亚洲国产高清在线一区二区三| 一区二区三区免费毛片| 三级男女做爰猛烈吃奶摸视频| 卡戴珊不雅视频在线播放| 日本熟妇午夜| 狠狠狠狠99中文字幕| 欧美+日韩+精品| 激情 狠狠 欧美| 国产伦精品一区二区三区四那| 精品午夜福利在线看| 中文在线观看免费www的网站| 久久精品国产亚洲av香蕉五月| 国产精品蜜桃在线观看 | 久久久久九九精品影院| 欧美日韩一区二区视频在线观看视频在线 | 1024手机看黄色片| 我的老师免费观看完整版| 亚洲四区av| 女同久久另类99精品国产91| 午夜福利视频1000在线观看| 欧美三级亚洲精品| 麻豆国产av国片精品| 免费观看在线日韩| 国内精品宾馆在线| 99久久久亚洲精品蜜臀av| 最近手机中文字幕大全| 亚洲第一区二区三区不卡| 成人无遮挡网站| 亚洲色图av天堂| 少妇猛男粗大的猛烈进出视频 | 亚洲欧美日韩高清专用| 成人毛片60女人毛片免费| 日本欧美国产在线视频| 成人毛片a级毛片在线播放| 日本欧美国产在线视频| 天堂中文最新版在线下载 | 欧美激情久久久久久爽电影| 亚洲七黄色美女视频| 国产探花极品一区二区| 色播亚洲综合网| h日本视频在线播放| 性插视频无遮挡在线免费观看| 看十八女毛片水多多多| 日韩欧美精品免费久久| 不卡一级毛片| 最近2019中文字幕mv第一页| 亚洲真实伦在线观看| 麻豆精品久久久久久蜜桃| 国产三级中文精品| 成人鲁丝片一二三区免费| 99久久久亚洲精品蜜臀av| 少妇猛男粗大的猛烈进出视频 | 欧美+日韩+精品| 麻豆国产97在线/欧美| 亚洲在线自拍视频| 久久99热这里只有精品18| 亚洲国产精品成人久久小说 | 天美传媒精品一区二区| 午夜精品一区二区三区免费看| 国产真实伦视频高清在线观看| 亚洲va在线va天堂va国产| 搞女人的毛片| 国产国拍精品亚洲av在线观看| 中文字幕免费在线视频6| 久久精品人妻少妇| 欧美成人a在线观看| av福利片在线观看| 亚洲最大成人手机在线| 中文字幕av成人在线电影| 秋霞在线观看毛片| 日本色播在线视频| 色尼玛亚洲综合影院| 国产私拍福利视频在线观看| 精品国内亚洲2022精品成人| 综合色av麻豆| 熟妇人妻久久中文字幕3abv| 性插视频无遮挡在线免费观看| 精品不卡国产一区二区三区| 99久久精品国产国产毛片| 亚洲一区二区三区色噜噜| 午夜爱爱视频在线播放| 日本与韩国留学比较| 晚上一个人看的免费电影| 亚洲欧洲国产日韩| 亚洲av成人精品一区久久| 99在线人妻在线中文字幕| 国产av麻豆久久久久久久| 日韩强制内射视频| 伊人久久精品亚洲午夜| 午夜福利在线观看吧| 插逼视频在线观看| 亚洲欧美中文字幕日韩二区| 人人妻人人澡欧美一区二区| 最近的中文字幕免费完整| 1000部很黄的大片| 性色avwww在线观看| 波多野结衣巨乳人妻| 在线免费观看的www视频| 麻豆av噜噜一区二区三区| 亚洲一区二区三区色噜噜| 一边摸一边抽搐一进一小说| 婷婷精品国产亚洲av| 亚洲无线在线观看| 国产成人a区在线观看| 黄片wwwwww| 国产中年淑女户外野战色| 夜夜看夜夜爽夜夜摸| 亚洲国产精品成人综合色| 精品少妇黑人巨大在线播放 | 久久综合国产亚洲精品| 久久久久久久久中文| 欧美精品国产亚洲| 国产综合懂色| 久久这里只有精品中国| 99久国产av精品| 亚洲精品自拍成人| 久久精品国产亚洲网站| 少妇丰满av| 观看免费一级毛片| 成年女人永久免费观看视频| 伊人久久精品亚洲午夜| 一本久久精品| 国产三级中文精品| 中文字幕免费在线视频6| 99久久中文字幕三级久久日本| 免费人成在线观看视频色| 最近视频中文字幕2019在线8| 伊人久久精品亚洲午夜| 不卡一级毛片| 午夜激情欧美在线| 色噜噜av男人的天堂激情| 一本精品99久久精品77| 久久精品综合一区二区三区| 特级一级黄色大片| 最后的刺客免费高清国语| 国产女主播在线喷水免费视频网站 | 国产精品三级大全| 国产精品99久久久久久久久| 国产成人影院久久av| 国内少妇人妻偷人精品xxx网站| 日本黄色片子视频| 色综合亚洲欧美另类图片| 99热精品在线国产| 午夜亚洲福利在线播放| 在线天堂最新版资源| 亚洲人与动物交配视频| 少妇丰满av| 国产成人精品一,二区 | 亚洲人成网站在线播放欧美日韩| 最近的中文字幕免费完整| eeuss影院久久| 午夜久久久久精精品| 国产国拍精品亚洲av在线观看| 91狼人影院| 好男人视频免费观看在线| 插逼视频在线观看| 最近手机中文字幕大全| 成人特级黄色片久久久久久久| 日日撸夜夜添| 一级二级三级毛片免费看| 成人亚洲精品av一区二区| 免费观看a级毛片全部| 免费观看的影片在线观看| 亚洲人成网站在线播放欧美日韩| 一区二区三区免费毛片| 97超碰精品成人国产| 丰满乱子伦码专区| 亚洲欧美日韩高清在线视频| 国产乱人视频| 97热精品久久久久久| 99视频精品全部免费 在线| 一个人观看的视频www高清免费观看| 日韩一区二区视频免费看| 国产国拍精品亚洲av在线观看| 少妇熟女欧美另类| 亚洲国产日韩欧美精品在线观看| 成年女人永久免费观看视频| 亚洲精品乱码久久久v下载方式| 久久这里只有精品中国| 高清毛片免费看| 国内揄拍国产精品人妻在线| 欧美另类亚洲清纯唯美| 国产一区二区三区av在线 | av国产免费在线观看| 乱码一卡2卡4卡精品| 国产视频首页在线观看| h日本视频在线播放| 久99久视频精品免费| 色噜噜av男人的天堂激情| 大又大粗又爽又黄少妇毛片口| 青青草视频在线视频观看| 成人亚洲欧美一区二区av| 在线免费观看不下载黄p国产| 搡女人真爽免费视频火全软件| 美女被艹到高潮喷水动态| 欧美zozozo另类| 日韩欧美 国产精品| 中文字幕制服av| 床上黄色一级片| 中国美白少妇内射xxxbb| 91在线精品国自产拍蜜月| 看十八女毛片水多多多| 亚洲va在线va天堂va国产| 全区人妻精品视频| 在现免费观看毛片| 悠悠久久av| 秋霞在线观看毛片| 日本色播在线视频| 99久久人妻综合| 亚洲综合色惰| 亚洲在线观看片| 九色成人免费人妻av| 美女被艹到高潮喷水动态| or卡值多少钱| 国产成人一区二区在线| 久久久久久久午夜电影| 免费一级毛片在线播放高清视频| 国产一区二区在线av高清观看| 国产精品电影一区二区三区| 国产黄a三级三级三级人| 久久这里有精品视频免费| 淫秽高清视频在线观看| 久久亚洲国产成人精品v| 深爱激情五月婷婷| 国产伦在线观看视频一区| 嫩草影院新地址| .国产精品久久| 一本久久精品| 悠悠久久av| 国产亚洲精品久久久com| 午夜福利高清视频| 夜夜夜夜夜久久久久| 26uuu在线亚洲综合色| 观看免费一级毛片| 国产国拍精品亚洲av在线观看| 亚洲欧美成人精品一区二区| 狠狠狠狠99中文字幕| 国产亚洲精品久久久久久毛片| av女优亚洲男人天堂| av在线观看视频网站免费| 啦啦啦啦在线视频资源| 久久亚洲精品不卡| 国产高清三级在线| 成人特级av手机在线观看| 一个人看视频在线观看www免费| av在线播放精品| 人体艺术视频欧美日本| 午夜爱爱视频在线播放| 国产午夜精品久久久久久一区二区三区| 久久精品国产亚洲av天美| АⅤ资源中文在线天堂| 中文资源天堂在线| 日韩av在线大香蕉| 亚洲一区二区三区色噜噜| 51国产日韩欧美| 91av网一区二区| 亚洲国产精品国产精品| 五月伊人婷婷丁香| 国产久久久一区二区三区| 美女黄网站色视频| 日韩视频在线欧美| 综合色丁香网| 国产精品不卡视频一区二区| 日本av手机在线免费观看| 欧美不卡视频在线免费观看| 69av精品久久久久久| 国语自产精品视频在线第100页| 一本久久中文字幕| 成人毛片60女人毛片免费| 一级黄片播放器| 久久国产乱子免费精品| 在线播放国产精品三级| 亚洲熟妇中文字幕五十中出| 97超碰精品成人国产| 少妇猛男粗大的猛烈进出视频 | 国产极品天堂在线| 九九爱精品视频在线观看| 精品午夜福利在线看| 一级毛片aaaaaa免费看小| 欧美激情在线99| 日本五十路高清| 联通29元200g的流量卡| 一边摸一边抽搐一进一小说| 免费观看a级毛片全部| 在线国产一区二区在线| 春色校园在线视频观看|