• <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 ?

    Thermodynamic criterion for searching high mobility two-dimensional electron gas at KTaO3 interface*

    2021-07-30 07:35:36WenXiaoShi時文瀟HuiZhang張慧ShaoJinQi齊少錦JinZhang張金娥HaiLinHuang黃海林BaoGenShen沈保根YuanShaChen陳沅沙andJiRongSun孫繼榮
    Chinese Physics B 2021年7期
    關(guān)鍵詞:張慧時文黃海

    Wen-Xiao Shi(時文瀟) Hui Zhang(張慧) Shao-Jin Qi(齊少錦) Jin-E Zhang(張金娥)Hai-Lin Huang(黃海林) Bao-Gen Shen(沈保根) Yuan-Sha Chen(陳沅沙) and Ji-Rong Sun(孫繼榮)

    1Beijing National Laboratory for Condensed Matter Physics and Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China

    2School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China

    3Fujian Innovation Academy,Chinese Academy of Sciences,Fuzhou 350108,China

    4Songshan Lake Materials Laboratory,Dongguan 523808,China

    5Spintronics Institute,University of Jinan,Jinan 250022,China

    Keywords: two-dimensional electron gas,oxygen vacancies,thermodynamic criterion,Hall mobility

    1. Introduction

    In 2004, Ohtomo and Hwang discovered a metallic conductive interface between insulating oxides SrTiO3(STO)and LaAlO3,[1]opening a new avenue for oxide electronics research. Since then, researchers have carried out a lot of works on the oxide heterojunctions based on STO substrates,[2-12]and a series of novel physical properties are revealed,such as two-dimensional superconductivity,[13,14]interfacial magnetism,[15-17]quantum Hall effect,[18]and efficient spin-to-charge conversion.[19,20]With the deepening of research, Zouet al.[21]discovered a new two-dimensional electron gas(2DEG)at the interface of LaTiO3/KTaO3(KTO)system. KTO is similar to STO in many aspects. It exhibits a high dielectric constant[22]and is quantum paraelectricity.[23]However,it is different from STO by owning a strong atomic spin-orbit coupling,[24]about 20 times as high as that of STO.Therefore, distinct features are expected for the corresponding 2DEG. Comparing with the investigations on STO-based 2DEG, the work on KTO-based 2DEG is limited. In addition to the work of Zouet al., the only reported 2DEGs at bilayer interfaces are amorphous-LaAlO3/KTO[25,26]and EuO/KTO.[27]Effects associated with the distinct characters of KTO are far from being fully explored.

    Herein, we take the amorphous-ABO3/KTO system as the research object to study the relationship between the interface conductivity and the redox property of B-site metal in the amorphous film. Firstly, we report on the fabrication of a series of high-quality amorphous-ABO3/KTO heterostructures.Secondly, the electric properties, such as the dependence of the sheet resistance (Rs) on temperature (T) and Hall resistance(Rxy),were measured.Finally,we adopted the formation heat of metal oxide,ΔHof,and work function of the metal,Φ,to characterize the redox property of B-site metal. By comparing the interface conductivity of these samples with the thermodynamic phase diagram of B-site metals as shown in Fig.5,we obtained the thermodynamic criterion for the formation of 2DEG at amorphous-ABO3/KTO interface. Our results show that the smaller absolute value of ΔHofand the larger value ofΦof the B-site metal would result in higher mobility of the two-dimensional electron gas that formed at the corresponding amorphous-ABO3/KTaO3interface(under the premise of satisfying the thermodynamic criterion).

    2. Experimental methods

    For the systematic study, various amorphous-ABO3oxides were selected to form the amorphous-ABO3/KTaO3interfaces, including CaZrO3(CZO), LaAlO3(LAO),(LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7(LSAT), SrTiO3(STO),KTaO3(KTO), SrNbO3(SNO), NdGaO3, LaMnO3, LaFeO3,LaCoO3,and LaCrO3. All the amorphous-ABO3layers were grown on the(001)-oriented KTO substrates(3×3×0.5 mm3)by the technique of pulsed laser deposition (PLD). The laser fluence was 2 J/cm2and the pulse frequency was 2 Hz. During the growth process, the oxygen pressure was maintained at 2×10-3Pa. The temperature of the substrate was fixed at 100°C. After the growth process, all the samples were furnace cooled to room temperature without changing oxygen pressure.

    The thickness of different amorphous-ABO3layer keeps at 5 nm,as evidenced by small angle x-ray reflectivity(XRR)measurements. The surface topography and flatness of these samples were observed by atomic force microscope (AFM).The transport behaviors were measured by a Quantum-Design physical property measurement system (PPMS) adopting the van der Pauw geometry.

    3. Results and discussion

    We take the amorphous-LAO/KTO sample as an example. Figure 1(a)shows the results of XRR measurements. The good agreement of the XRR oscillations between the testing result and simulation data indicates the high planeness of the as-deposited LAO layer. Curve fitting(black curve)reveals a layer thickness of 5 nm. Figure 1(b)is the surface topography of the film measured by AFM.The film is very smooth with a mean square root roughness of 0.2 nm in the area of 5×5 μm2.These features were also confirmed in other samples,indicating the high quality of our amorphous-ABO3/KTO samples.

    Fig.1. (a)XRR curve of the amorphous-LAO film grown on KTO substrate. Black line is the fitting curve. (b)AFM image of the amorphous-LAO film deposited on KTO substrate.

    Figure 2(a) is a schematic diagram of the device for measuring the electrical transport properties of amorphous-ABO3/KTO heterostructure. Figure 2(b) shows the temperature dependence of the sheet resistance (Rs) for selected amorphous-ABO3/KTO interfaces, which displays good metallic behavior: with the decrease of temperature,the sheet resistance decreases continuously. We characterize the metallicity by the ratio of sheet resistance measured at 300 K and 2 K.The higherR(300 K)/R(2 K)ratio means better metallicity. We find thatR(300 K)/R(2 K)varies in a wide range, from the maximal ratio of~212 for the amorphous-KTO/KTO interface to the minimal ratio of~11 for the amorphous-LAO/KTO interface,i.e.,the 2DEG formed at the KTO/KTO interface exhibits better metallicity. Notably, the metallic 2DEG appears only when the cap layer is LAO,CZO,STO,SNO,LSAT,or KTO.Obviously,the intrinsic properties of these cap layers will strongly affect the conduction characteristic at the interface. Hereafter, we will focus on these conducting interfaces.

    Fig.2. (a)A sketch for the measurements of sheet resistance and Hall resistance. (b)Sheet resistance of amorphous-ABO3/KTO interfaces as a function of temperature. The labels in the figure refer to the composition of the deposited amorphous-ABO3 film.

    To get further information about 2DEG,we performed the measurement of Hall resistance(Rxy)in the temperature interval from 2 K to 300 K. As an example, Fig. 3(a) shows the Hall resistance at 2 K, as a function of magnetic field (H).Rxyexhibits a linear variation with the applied field for all samples, i.e., only one species of charge carriers exists in the 2DEGs.[28]However,theRxy-Hslope(RH)undergoes a considerable change with the cap layer, implying different carrier density(ns)in different 2DEGs. In Fig.3(b)we summarize the relationship between the carrier density and the cap layer, wherensis determined byns=-1/(e·RH). Corresponding to the maximal and minimalR(300 K)/R(2 K)ratios,amorphous-KTO/KTO exhibits the minimal carrier density of 2.9×1013cm-2and amorphous-LAO/KTO exhibits the maximal carrier density of 7.3×1013cm-2, respectively. Obviously,the capability to generate mobile electrons for different cap layers varies~2.5 times. Similar feature is observed in theRxy-Hcurve obtained at other temperatures(not shown).

    Fig.3. (a)Hall effect of amorphous-ABO3/KTO interfaces at 2 K(the labels in the figure refer to the composition of the deposited amorphous-ABO3 film). (b)The sheet carrier density,ns,versus the composition of the cap layer,obtained at 2 K.

    To get a general idea about the temperature dependence of the carrier density, in Fig. 4 we shownsand the corresponding mobility as functions ofT, where the mobility is calculated based on the formulaμs=1/(e·ns·Rs). The carrier density is the largest at 300 K and undergoes a decrease upon cooling. This feature is especially obvious in the interface with CaZrO3cap layer. It is an indication of charge localization. Correspondingly,the mobility experiences a rapid increase with the decrease of temperature. At low temperature,the dielectric constant of KTO grows, screening the electron scatter from ionic impurities. The maximal mobility at 2 K is 2209.41 cm2/V·s, occurring at the amorphous-KTO/KTO interface. From the amorphous-KTO/KTO to the amorphous-LAO/KTO interface,the mobility shows a rapid decrease.

    The origin of the 2DEG is in hot debate since the discovery of the 2DEG in 2004. Three explanations are widely accepted,including polar discontinuity,[29]electron doping by oxygen vacancy,[30]and cation interdiffusion.[31]Compared with crystalline interface,the polar discontinuity at amorphous interface is strongly suppressed. Because of the low deposition temperature (100°C), cation interdiffusion should be negligible. In contrast, previous experimental results have demonstrated that the outward oxygen diffusion plays a dominative role in the formation of 2DEG at the amorphous-LAO/STO interface.[32]We therefore ascribe the 2DEG at the amorphous-ABO3/KTO interface to the redox reaction effect.Besides obtaining oxygen from the background atmosphere,in fact,the cap layer will also extract oxygen from the interfacial layer of the KTaO3substrate.When the content of oxygen vacancies is high enough,2DEG forms.

    Fig.4. (a),(b)Carrier density,ns,and Hall mobility,μs,versus temperature,respectively,for all the KTO-based heterostructures. The corresponding cap layers are denoted in(b). The solid lines are guides to the eyes.

    Fuet al.[33]have performed a research on the redox reaction when a metal film is deposited on the surface of SrTiO3at room temperature. They put forward a thermodynamic criterion for redox reaction. According to this work,redox reaction has a close relation to the formation heat of metal oxide,ΔHof, and the work function of the metal,Φ. The former describes the ability to get oxidized for an element and the latter characterizes the electronegativity. Obviously,a high ΔHofimplies a strong tendency towards oxidization for an element.For the B-site metal in amorphous films, formation heat of metal oxide ΔHofand work functionΦcan be obtained from former literature[34]that are summarized in Fig. 5. The Bsite metals marked by red circles represent for the insulated ABO3/KTO interfaces, whereas the B-site metals marked by green symbols correspond to the interfaces with metallic conductivity. The orange-colored diamond represents for a special case,the semiconductive amorphous-NdGaO3/KTaO3interface. Moreover, for the metallic ABO3/KTO interfaces, a small ΔHoffor the B-site metals usually gives higher mobility,which are marked as green stars. Correspondingly,the B-site metals with large ΔHofand lower mobility are marked as green squares. Based on this analysis, we obtain a thermodynamic criterion for the redox reactions at the KTO interface, which is labeled as the shaded area. The formation heat of metal oxide, ΔHof, should be lower than-350 kJ/(mol O) and the work function of the metal,Φ, should locate in the range of 3.75 eV<Φ <4.4 eV.

    Remarkably, Nb and Ta, corresponding B-site metals of SrNbO3and KTaO3,locate on the border region for the occurrence/nonoccurrence of redox reaction. This explains the low carrier density at the interface of the amorphous-KTO/KTO and the amorphous-SNO/KTO samples. On the other hand,the carrier density at their interface is low but the carrier mobility is high. Among them, the carrier mobility of the amorphous-KTO/KTO interface can reach 2209.41 cm2/V·s at 2 K.This provides a guide to prepare KTaO3-based 2DEGs of high mobility at a deposition temperature of 100°C, that is,for the B-site metal in deposited amorphous-ABO3film, the absolute value of the formation heat of metal oxide is as small as possible and the value of the work function of the metal is as large as possible (under the premise of satisfying the thermodynamic criterion mentioned above).

    Fig.5. Formation heat of metal oxides versus the work function of Bsite metals for the ABO3/KTO interfaces. For metallic interfaces, the B-site metals locate mainly in the region of ΔHof <-350 kJ/(mol O)and 3.75 eV<Φ <4.4 eV(shaded area).

    4. Conclusion

    In summary, we systematically investigated the effect of the redox properties of the B-site metal on 2DEGs transport characteristics at amorphous-ABO3/KTaO3interfaces,by varying the composition of the cap layer.We found that metallic conductive interface can be created when the amorphous film has Zr,Al,Ti,Ta,or Nb elements at the B sites. Whereas the interface is insulating when the overlayer has Mn, Fe,Co, or Cr elements at the B sites. By summarizing the interface conductivity of these samples, we obtained the thermodynamic criterion for the redox reaction at the transition metal oxide/KTO interface. Finally, we provided a guideline on searching for KTaO3-based 2DEGs of high mobility. This work has certain guiding significance for finding high performance two-dimensional electron gas,and takes a solid step for the application of oxide electronic devices.

    猜你喜歡
    張慧時文黃海
    痛風(fēng)的多組學(xué)研究進(jìn)展
    遺傳(2023年8期)2023-08-25 07:00:20
    幼兒合作意識培養(yǎng)“進(jìn)行時”
    教育家(2022年17期)2022-04-23 22:21:35
    東方濕地 黃海明珠
    華人時刊(2020年21期)2021-01-14 01:32:28
    談時文閱讀在小學(xué)寫作教學(xué)中的應(yīng)用
    黃海簡介
    三角恒等變換去哪兒了
    靈活運(yùn)用時文閱讀,有效提高學(xué)生的讀寫能力
    Flux Footprint Climatology Estimated by Three Analytical Models over a Subtropical Coniferous Plantation in Southeast China
    王洪永?陳英俊?張慧
    智 珠
    亚洲av.av天堂| 网址你懂的国产日韩在线| 久久亚洲国产成人精品v| 欧美最黄视频在线播放免费| 国产精品久久久久久久电影| 国产伦精品一区二区三区视频9| 亚洲精品粉嫩美女一区| 51国产日韩欧美| 国产久久久一区二区三区| 国产伦在线观看视频一区| 大型黄色视频在线免费观看| 国产一区二区三区在线臀色熟女| 99热6这里只有精品| 亚洲三级黄色毛片| 国产成人精品久久久久久| 国产蜜桃级精品一区二区三区| 免费看美女性在线毛片视频| 欧美成人精品欧美一级黄| 在线播放无遮挡| 国产一级毛片七仙女欲春2| 亚洲第一区二区三区不卡| 成人特级黄色片久久久久久久| 日本-黄色视频高清免费观看| 我的老师免费观看完整版| 男人舔奶头视频| 亚洲成人中文字幕在线播放| 国产蜜桃级精品一区二区三区| 床上黄色一级片| 日韩成人av中文字幕在线观看| 亚洲婷婷狠狠爱综合网| 成人av在线播放网站| 男人狂女人下面高潮的视频| 亚洲天堂国产精品一区在线| kizo精华| 国产白丝娇喘喷水9色精品| 国产伦一二天堂av在线观看| 日本黄大片高清| 我的女老师完整版在线观看| 国产精品国产三级国产av玫瑰| 一夜夜www| 久久久国产成人精品二区| 欧美日韩国产亚洲二区| 精品久久久久久久久亚洲| 我要搜黄色片| 午夜福利成人在线免费观看| 97超碰精品成人国产| 欧美变态另类bdsm刘玥| 国产亚洲精品av在线| 欧美+亚洲+日韩+国产| 床上黄色一级片| 国产精品久久久久久精品电影小说 | 久久综合国产亚洲精品| 99热全是精品| 亚洲,欧美,日韩| 日本与韩国留学比较| 激情 狠狠 欧美| 最近的中文字幕免费完整| 国产精品野战在线观看| 午夜福利在线在线| a级毛片a级免费在线| 久久精品夜色国产| 看黄色毛片网站| 日韩一本色道免费dvd| 国产一区二区激情短视频| 国产精品久久久久久精品电影小说 | av在线亚洲专区| 1000部很黄的大片| 2022亚洲国产成人精品| 91av网一区二区| 久久久久久久久大av| 成人午夜高清在线视频| 国产在视频线在精品| 小说图片视频综合网站| 国产av不卡久久| 国产老妇伦熟女老妇高清| 日韩大尺度精品在线看网址| 成人毛片a级毛片在线播放| 99热只有精品国产| 熟女人妻精品中文字幕| 尾随美女入室| 日韩精品有码人妻一区| 国模一区二区三区四区视频| 男女那种视频在线观看| 日韩一本色道免费dvd| 噜噜噜噜噜久久久久久91| 三级毛片av免费| 国产伦精品一区二区三区四那| 两个人的视频大全免费| 乱人视频在线观看| 一卡2卡三卡四卡精品乱码亚洲| 欧美激情久久久久久爽电影| 色吧在线观看| 三级毛片av免费| 亚洲无线观看免费| 男人舔女人下体高潮全视频| 日本欧美国产在线视频| 国产成人午夜福利电影在线观看| 男人舔女人下体高潮全视频| 1024手机看黄色片| 国产午夜精品论理片| 免费观看a级毛片全部| 日本免费a在线| 国产精品久久久久久久久免| 中文字幕av在线有码专区| 久久精品国产亚洲av涩爱 | 欧美性猛交黑人性爽| 国产片特级美女逼逼视频| 黄色欧美视频在线观看| 国产精品无大码| 亚洲aⅴ乱码一区二区在线播放| 亚洲av不卡在线观看| 国产探花极品一区二区| 亚洲精品成人久久久久久| 夜夜爽天天搞| 99热这里只有精品一区| 色尼玛亚洲综合影院| 天堂av国产一区二区熟女人妻| 男的添女的下面高潮视频| 狂野欧美激情性xxxx在线观看| 亚洲成a人片在线一区二区| 搞女人的毛片| 最新中文字幕久久久久| 日韩亚洲欧美综合| 久久亚洲国产成人精品v| 婷婷色综合大香蕉| 18禁在线无遮挡免费观看视频| 老师上课跳d突然被开到最大视频| 国产午夜福利久久久久久| 国产一区二区激情短视频| 国产精品一二三区在线看| 日韩国内少妇激情av| 99久久精品热视频| 一进一出抽搐动态| 99久久九九国产精品国产免费| 亚洲av男天堂| 欧美色欧美亚洲另类二区| 日韩国内少妇激情av| 精品一区二区免费观看| 亚洲av免费高清在线观看| 午夜视频国产福利| 久久婷婷人人爽人人干人人爱| 69av精品久久久久久| 午夜福利视频1000在线观看| 老司机影院成人| 久久精品国产亚洲av天美| av.在线天堂| 亚洲欧洲日产国产| 九九爱精品视频在线观看| 亚洲中文字幕日韩| 亚洲精品国产成人久久av| 男人狂女人下面高潮的视频| 国产老妇女一区| 变态另类丝袜制服| 国产精品蜜桃在线观看 | 一夜夜www| 中文字幕人妻熟人妻熟丝袜美| 人妻夜夜爽99麻豆av| 久久久久久大精品| 久久精品国产亚洲av天美| 精品一区二区三区人妻视频| 日日干狠狠操夜夜爽| 日韩欧美国产在线观看| 亚洲真实伦在线观看| 亚洲欧美日韩卡通动漫| 成人午夜精彩视频在线观看| 色综合亚洲欧美另类图片| 亚洲欧美日韩高清专用| 黄色一级大片看看| 干丝袜人妻中文字幕| 午夜免费男女啪啪视频观看| 亚洲成人中文字幕在线播放| 麻豆成人午夜福利视频| 国产白丝娇喘喷水9色精品| 亚洲精品色激情综合| 麻豆精品久久久久久蜜桃| 免费无遮挡裸体视频| 99热只有精品国产| 女的被弄到高潮叫床怎么办| 欧美一区二区精品小视频在线| 成人特级av手机在线观看| 如何舔出高潮| 在线观看av片永久免费下载| 久久久精品欧美日韩精品| 国产亚洲精品久久久com| 久久精品国产99精品国产亚洲性色| 久久精品国产亚洲av天美| 99久久九九国产精品国产免费| 亚洲av免费在线观看| 久久精品国产亚洲网站| .国产精品久久| 亚洲熟妇中文字幕五十中出| 成人亚洲精品av一区二区| 亚洲一区二区三区色噜噜| av在线天堂中文字幕| 午夜激情欧美在线| 欧美高清性xxxxhd video| 日韩成人伦理影院| 99久久精品热视频| 女人被狂操c到高潮| 亚洲人成网站在线播放欧美日韩| 综合色丁香网| 一级毛片aaaaaa免费看小| 免费观看a级毛片全部| 国内精品宾馆在线| 久久久久久久久久久免费av| 丰满乱子伦码专区| 老女人水多毛片| 久久欧美精品欧美久久欧美| 久久韩国三级中文字幕| 中文字幕av在线有码专区| 婷婷六月久久综合丁香| 久久99热6这里只有精品| 在线a可以看的网站| 久久久久久国产a免费观看| 亚洲av电影不卡..在线观看| 91久久精品电影网| 日韩av在线大香蕉| 赤兔流量卡办理| 搡女人真爽免费视频火全软件| 亚洲人与动物交配视频| 成人特级黄色片久久久久久久| 一边亲一边摸免费视频| 高清在线视频一区二区三区 | 亚洲精品日韩av片在线观看| 午夜激情欧美在线| 国产精品一区二区性色av| av在线播放精品| 亚洲第一电影网av| 人体艺术视频欧美日本| 亚洲乱码一区二区免费版| 欧美一区二区国产精品久久精品| av在线老鸭窝| 精品国产三级普通话版| 亚洲人与动物交配视频| 一级黄色大片毛片| 最近中文字幕高清免费大全6| 亚洲在线自拍视频| 久久99热这里只有精品18| 99热全是精品| 男的添女的下面高潮视频| av卡一久久| 赤兔流量卡办理| 日日撸夜夜添| 九九爱精品视频在线观看| 久久欧美精品欧美久久欧美| av女优亚洲男人天堂| 人人妻人人澡人人爽人人夜夜 | 午夜福利在线在线| 简卡轻食公司| 夜夜看夜夜爽夜夜摸| 搡老妇女老女人老熟妇| 人人妻人人看人人澡| 97超视频在线观看视频| 亚洲不卡免费看| 日产精品乱码卡一卡2卡三| 久久国内精品自在自线图片| 久久国产乱子免费精品| 长腿黑丝高跟| 亚洲av.av天堂| 国产成人影院久久av| 99久久成人亚洲精品观看| 日本黄色视频三级网站网址| 九九热线精品视视频播放| 国产精品一二三区在线看| 国产精品99久久久久久久久| 亚洲精品成人久久久久久| 嫩草影院入口| 国产成人a区在线观看| 久久欧美精品欧美久久欧美| 欧美日韩乱码在线| 高清毛片免费看| 夜夜看夜夜爽夜夜摸| 一边亲一边摸免费视频| 中文在线观看免费www的网站| 少妇人妻一区二区三区视频| 非洲黑人性xxxx精品又粗又长| 亚洲人成网站在线播放欧美日韩| 亚洲婷婷狠狠爱综合网| 国产午夜精品论理片| 国产一区二区在线av高清观看| 内地一区二区视频在线| 欧美区成人在线视频| 97超视频在线观看视频| 能在线免费看毛片的网站| 精品日产1卡2卡| 亚洲av二区三区四区| АⅤ资源中文在线天堂| 久久久a久久爽久久v久久| 久久精品国产自在天天线| a级毛色黄片| 我的老师免费观看完整版| 国产精品久久视频播放| 国产黄片美女视频| 亚洲欧美日韩卡通动漫| 色5月婷婷丁香| 国产av不卡久久| 老女人水多毛片| 国内精品美女久久久久久| 国产精品人妻久久久影院| 男人和女人高潮做爰伦理| 国产成人精品一,二区 | 99热全是精品| 黄色一级大片看看| 国产真实伦视频高清在线观看| 超碰av人人做人人爽久久| 99热全是精品| 成人高潮视频无遮挡免费网站| 免费不卡的大黄色大毛片视频在线观看 | 成人高潮视频无遮挡免费网站| 亚洲一级一片aⅴ在线观看| 欧美成人精品欧美一级黄| 日本与韩国留学比较| 狂野欧美白嫩少妇大欣赏| av在线蜜桃| 国模一区二区三区四区视频| 女同久久另类99精品国产91| 亚洲婷婷狠狠爱综合网| 亚洲av中文av极速乱| 久久久久九九精品影院| 全区人妻精品视频| 丝袜美腿在线中文| 观看免费一级毛片| 在线天堂最新版资源| 嫩草影院精品99| 嘟嘟电影网在线观看| 久久精品人妻少妇| 一进一出抽搐动态| 不卡一级毛片| 99久国产av精品国产电影| 小说图片视频综合网站| 亚洲婷婷狠狠爱综合网| 亚洲成人av在线免费| 狂野欧美激情性xxxx在线观看| 亚洲丝袜综合中文字幕| 国国产精品蜜臀av免费| 午夜免费男女啪啪视频观看| 嫩草影院精品99| 中文字幕av在线有码专区| 亚洲精品粉嫩美女一区| 国产乱人偷精品视频| 男人舔女人下体高潮全视频| 内地一区二区视频在线| 久久婷婷人人爽人人干人人爱| 午夜精品国产一区二区电影 | 男人和女人高潮做爰伦理| 亚洲中文字幕日韩| 午夜精品在线福利| av.在线天堂| 最后的刺客免费高清国语| 国产精品1区2区在线观看.| 两个人视频免费观看高清| 国产成人一区二区在线| 狂野欧美激情性xxxx在线观看| 久久久a久久爽久久v久久| 免费观看a级毛片全部| 欧美xxxx性猛交bbbb| 国产精品99久久久久久久久| av又黄又爽大尺度在线免费看 | 久久99热6这里只有精品| 此物有八面人人有两片| 三级毛片av免费| 日韩av不卡免费在线播放| 亚洲人与动物交配视频| 99国产极品粉嫩在线观看| 最近的中文字幕免费完整| ponron亚洲| 国产精品一区www在线观看| 人妻夜夜爽99麻豆av| 久久久久网色| 22中文网久久字幕| 少妇人妻精品综合一区二区 | 日韩高清综合在线| 成人特级黄色片久久久久久久| 日本一二三区视频观看| 成人毛片60女人毛片免费| 亚洲四区av| 全区人妻精品视频| 国产淫片久久久久久久久| 成人毛片a级毛片在线播放| 国产人妻一区二区三区在| 国产女主播在线喷水免费视频网站 | 五月玫瑰六月丁香| 国产欧美日韩精品一区二区| 亚洲精品国产成人久久av| 日韩在线高清观看一区二区三区| 午夜亚洲福利在线播放| 看十八女毛片水多多多| 亚洲va在线va天堂va国产| 亚洲国产高清在线一区二区三| 日本一二三区视频观看| 欧美一区二区精品小视频在线| 最近2019中文字幕mv第一页| 国产亚洲5aaaaa淫片| 美女高潮的动态| 国产 一区精品| 亚洲av不卡在线观看| 久久亚洲精品不卡| 久久久a久久爽久久v久久| 精品午夜福利在线看| 亚洲欧美日韩高清在线视频| 欧美一区二区国产精品久久精品| 国产成人一区二区在线| 免费人成视频x8x8入口观看| 欧美日韩综合久久久久久| 在线观看午夜福利视频| 国产精品一区二区性色av| 人妻少妇偷人精品九色| 亚洲真实伦在线观看| 又爽又黄无遮挡网站| eeuss影院久久| 亚洲不卡免费看| 我的女老师完整版在线观看| 青春草视频在线免费观看| 精品久久久久久久久av| 日日摸夜夜添夜夜添av毛片| 69人妻影院| 一个人看的www免费观看视频| 性色avwww在线观看| 身体一侧抽搐| 日本撒尿小便嘘嘘汇集6| 男人舔奶头视频| 麻豆国产av国片精品| 国产亚洲精品久久久久久毛片| 亚洲中文字幕一区二区三区有码在线看| 爱豆传媒免费全集在线观看| 亚洲国产精品国产精品| 久久久成人免费电影| 蜜桃亚洲精品一区二区三区| av在线观看视频网站免费| 在线免费观看不下载黄p国产| 不卡一级毛片| 好男人视频免费观看在线| 一个人看视频在线观看www免费| 又粗又硬又长又爽又黄的视频 | 久久久久久久久久成人| 激情 狠狠 欧美| 成人综合一区亚洲| 中文精品一卡2卡3卡4更新| 亚洲av成人精品一区久久| 国产成年人精品一区二区| 日本三级黄在线观看| 亚洲欧美成人综合另类久久久 | 少妇熟女欧美另类| 久久久久国产网址| 国产视频首页在线观看| 亚洲丝袜综合中文字幕| 亚洲av免费在线观看| 欧美另类亚洲清纯唯美| 日产精品乱码卡一卡2卡三| 在线免费十八禁| 2022亚洲国产成人精品| 精品久久久久久成人av| 国产精品一区二区三区四区久久| 午夜免费男女啪啪视频观看| 日日摸夜夜添夜夜爱| 亚洲中文字幕日韩| 精品无人区乱码1区二区| 亚洲成人中文字幕在线播放| 中文在线观看免费www的网站| 一边亲一边摸免费视频| 欧美激情国产日韩精品一区| 午夜老司机福利剧场| 成人毛片a级毛片在线播放| 亚洲成a人片在线一区二区| 日韩精品有码人妻一区| av黄色大香蕉| 亚洲综合色惰| 亚洲图色成人| 亚洲美女视频黄频| 中出人妻视频一区二区| 精品一区二区免费观看| 国产伦精品一区二区三区四那| 观看美女的网站| 人人妻人人澡人人爽人人夜夜 | 亚洲av.av天堂| 美女被艹到高潮喷水动态| 成人漫画全彩无遮挡| h日本视频在线播放| 国内精品宾馆在线| 亚洲欧美精品专区久久| 一本精品99久久精品77| 国产精品爽爽va在线观看网站| 国产成人freesex在线| 99riav亚洲国产免费| ponron亚洲| 国内精品久久久久精免费| 少妇丰满av| 亚洲欧美精品综合久久99| 国产午夜精品久久久久久一区二区三区| 国产亚洲欧美98| 日韩制服骚丝袜av| 久久这里有精品视频免费| 精品免费久久久久久久清纯| 国产熟女欧美一区二区| 国产日本99.免费观看| avwww免费| 乱码一卡2卡4卡精品| 亚洲精品国产成人久久av| 伦理电影大哥的女人| 麻豆国产av国片精品| 国产 一区精品| 十八禁国产超污无遮挡网站| 久久久精品欧美日韩精品| 天天一区二区日本电影三级| 久久久色成人| 中文欧美无线码| 乱码一卡2卡4卡精品| 日韩强制内射视频| 三级经典国产精品| 国产美女午夜福利| 搡女人真爽免费视频火全软件| 啦啦啦韩国在线观看视频| 99九九线精品视频在线观看视频| 人体艺术视频欧美日本| 日本撒尿小便嘘嘘汇集6| 99久久精品热视频| 午夜免费男女啪啪视频观看| 好男人视频免费观看在线| 91午夜精品亚洲一区二区三区| 99热这里只有精品一区| 男女边吃奶边做爰视频| 99久久九九国产精品国产免费| 麻豆成人午夜福利视频| 26uuu在线亚洲综合色| 啦啦啦韩国在线观看视频| 狠狠狠狠99中文字幕| 色哟哟哟哟哟哟| 国产精品久久久久久久久免| 国产精品一区二区三区四区久久| 免费看光身美女| 日韩亚洲欧美综合| 久久国产乱子免费精品| 国产色婷婷99| 欧美zozozo另类| 我的老师免费观看完整版| 欧美成人精品欧美一级黄| 中文精品一卡2卡3卡4更新| 免费看光身美女| 99在线视频只有这里精品首页| 欧美日韩精品成人综合77777| 中文字幕久久专区| а√天堂www在线а√下载| 国产一级毛片七仙女欲春2| 啦啦啦啦在线视频资源| 丰满人妻一区二区三区视频av| 亚洲精华国产精华液的使用体验 | 边亲边吃奶的免费视频| 精品日产1卡2卡| 精品久久国产蜜桃| 黄色日韩在线| 麻豆精品久久久久久蜜桃| 高清日韩中文字幕在线| 欧美激情国产日韩精品一区| 好男人在线观看高清免费视频| 3wmmmm亚洲av在线观看| a级一级毛片免费在线观看| 亚洲高清免费不卡视频| 久久久午夜欧美精品| 乱码一卡2卡4卡精品| 亚洲av一区综合| 永久网站在线| 亚洲av不卡在线观看| 亚洲自偷自拍三级| 精品久久久久久久人妻蜜臀av| 日本免费a在线| 99久久九九国产精品国产免费| 最近手机中文字幕大全| 少妇高潮的动态图| 午夜福利视频1000在线观看| 亚洲在久久综合| 美女内射精品一级片tv| 精品熟女少妇av免费看| 成人av在线播放网站| 91aial.com中文字幕在线观看| 内地一区二区视频在线| av免费在线看不卡| 国产色婷婷99| 噜噜噜噜噜久久久久久91| 亚洲国产精品合色在线| 亚洲五月天丁香| 高清午夜精品一区二区三区 | 中文亚洲av片在线观看爽| 能在线免费看毛片的网站| 永久网站在线| 在线免费十八禁| 人人妻人人澡欧美一区二区| 久久草成人影院| 国产一区二区在线av高清观看| av天堂中文字幕网| 久久久国产成人精品二区| 中文精品一卡2卡3卡4更新| 麻豆一二三区av精品| 成人午夜高清在线视频| 此物有八面人人有两片| 男女那种视频在线观看| 91在线精品国自产拍蜜月| 日韩av不卡免费在线播放| 观看免费一级毛片| 99国产精品一区二区蜜桃av| 久久精品人妻少妇| 国产色爽女视频免费观看| 亚洲av熟女| 午夜福利在线在线| 黄色欧美视频在线观看| 18禁在线无遮挡免费观看视频| 村上凉子中文字幕在线| av专区在线播放| 一边摸一边抽搐一进一小说| 国产精品无大码| 亚洲av中文字字幕乱码综合| 一本久久精品| 国产不卡一卡二| 日日摸夜夜添夜夜添av毛片| av女优亚洲男人天堂| 亚洲av男天堂|