新型脉冲激光能量计用无铅(Na_(1-x)K_x)_(0.5)Bi_(0.5)TiO_3铁电薄膜的制备及其激光感生热电电压信号的研究

采用脉冲激光沉积(PLD)技术,分别在LaA lO3(LAO)、(La,Sr)(A l,Ta)O3(LAST)及SrTiO3(STO)三种不同的单晶衬底上制备了一系列无铅(Na1-xKx)0.5B i0.5TiO3(x=0.00,0.08,0.19,0.30,NKBT)铁电薄膜材料。利用X射线衍射(XRD)仪对薄膜结构进行了分析,结果表明在单晶平衬底上生长的薄膜都是单取向生长的外延膜,其中摇摆曲线的半高宽(FWHM)显示在(La,Sr)(A l,Ta)O3单晶衬底上生长的薄膜结晶质量最好。另外,在20°倾斜的(La,Sr)(A l,Ta)O3单晶衬底上生长的(Na1-xKx)0.5B i0.5TiO3铁电薄膜中还首次观察到了激光感生热电电压(LITV)信号。发现在能量为0.48mJ/pulse的紫外脉冲激光辐照下,其最大激光感生热电电压为31mV,完全满足了制作脉冲激光能量计探测元件的要求,有望开发出可集成的新型脉冲激光能量计。     

氧缺失对Nd0.7Sr0.3MnO3外延膜结构和输运性的影响

不同厚度的Nd0.7Sr0.3MnO3(NSMO)外延膜是由脉冲激光沉积生长在(LaAlO3)0.3(Sr2AlTaO6)0.7(LSAT)(001)衬底上的。X射线衍射(XRD)和电阻率测量结果显示,沉积氧压为21.333Pa时薄膜c轴参数随着膜厚的减小而增加,同时金属-绝缘体的转变温度TP下降,电阻率增大;另一组生长在27.999Pa氧压下,厚度为120nm的薄膜单胞体积随着退火温度的升高而增大,同时电阻率升高,TP下降。上述结果归因于低的原位沉积氧压和真空退火引起的氧缺失导致n(Mn3+)/n(Mn4+)的增大以及MnO6八面体的畸变。结果表明,对超薄的应变薄膜,要获得较高的TP值,较高的沉积氧压是必需的,同时应仔细考虑真空退火对薄膜性能的影响。     

脉冲激光沉积法在Si(111)衬底上生长高c轴取向LiNbO3薄膜

在氧压20Pa,衬底温度600℃,靶材与衬底距离4cm的最优化条件下,利用脉冲激光沉积(PLD)技术首次在无诱导电压和任何缓冲层的情况下,在单晶Si(111)衬底上生长具有优良结晶品质和高c轴取向的LiNbO3晶体薄膜.利用X射线衍射(XRD)、扫描电子显微镜(SEM)和原子力显微镜(AFM)对LiNbO3薄膜的结晶品质,择优取向性以及表面形貌进行了系统的分析.结果表明生长出了具有优异晶体质量的c轴取向LiNbO3薄膜,表面光滑平整且无裂纹产生,表面粗糙度约4.8nm,有利于硅基光电子器件的制备和利用.     

衬底温度和生长氧压对La0.67Sr0.33MnO3:Ag0.08薄膜激光感生电压效应的影响

通过化学共沉淀法制备了La_0.67Sr_0.33MnO₃:Ag_0.08 (LSMO:Ag_0.08)多晶材料, 然后采用脉冲激光沉积(PLD)技术在LaAlO₃ (LAO)倾斜衬底上制备了LSMO:Ag_0.08薄膜。研究了衬底温度和生长氧压对薄膜结构、电输运特性及激光感生电压(LIV)效应的影响。结果表明: 当衬底温度为790℃、生长氧压为45 Pa时, 薄膜具有最大峰值电压(U_p)、优值(F_m)和各向异性Seebeck系数(ΔS); 在优化的衬底温度和生长氧压条件下, 长程Jahn-Teller协变引起ΔS数值提高, 这是LIV信号增强的主要原因。     

脉冲激光沉积法制备Pt薄膜的研究

采用脉冲激光沉积技术在(0001)取向的蓝宝石基片上外延生长了Pt单晶薄膜,研究了沉积温度和激光能量对Pt薄膜的晶体结构,表面形貌及电学性能的影响规律.X射线衍射(XRD)分析结果表明,在沉积温度650℃、激光脉冲频率1Hz和激光能量280mJ的条件下,制备得到的Pt(111)单晶薄膜,其(111)面ω摇摆曲线半高宽(FWHM)仅为0.068°.原子力显微镜(AFM)分析表明外延的Pt薄膜表面具有原子级平整度,其表面均方根粗糙度(RMS)约为1.776nm.四探针电阻测试结果显示薄膜方阻为1/962Ω/□,满足铁电薄膜的制备工艺对Pt底电极的要求.     

Si（111）基片上Mg2Si薄膜的脉冲激光沉积

采用脉冲激光沉积方法在Si(111)基片上制备了Mg2Si薄膜。研究了激光能量密度、退火气氛及压强、退火温度、退火时间等工艺条件对Mg2Si薄膜生长的影响。用X射线衍射仪分析了Mg2Si薄膜的物相,用原子力显微镜、高分辨场发射扫描电镜表征了薄膜的形貌。实验结果表明:在激光能量密度为2.36 J/cm2,Si(111)基片上室温、真空(真空度10-6Pa)条件下沉积,在Ar气压强为10 Pa,500℃,30 min条件下原位退火得到了纯相、结构均匀、表面平整、厚度约为900 nm的Mg2Si多晶薄膜。     

激光分子束外延SrTiO3薄膜退火过程中表面扩散的研究

用激光分子束外延研究了SrTiO3同质外延时原位退火中,反射高能电子衍射(RHEED)强度的恢复--驰豫时间,导出了高真空下表面扩散的活化能为0.31 eV,与低真空下的结果相比要小许多,这反映了粒子达到基片时的能量差.对沉积不同厚度的薄膜退火研究,表明当薄膜厚度增加时,表面恢复情况减弱,而导致随后的沉积时RHEED振荡周期的改变.     

激光脉冲外延生长Pb(Zr0.52Ti0.48)O3薄膜及其特性研究

利用激光脉冲法在LaAlO3衬底上沉积制备LaNiO3薄膜作为底电极并外延生长(100) Pb(Zr0.52Ti0.48)O3铁电薄膜,系统研究了生长温度对PZT外延结构和电学特性的影响.研究发现当生长温度高于550℃时即可得到外延(100)PZT薄膜.在对所制备的PZT薄膜的结构和性能测试表明,650℃下生长的PZT薄膜外延性最佳,并且表现出优异的介电和铁电性能,介电常数ε、剩余极化Pr和矫顽场Ec分别为900、26.5 μC/cm2和52.1kV/cm.试验还证实这种外延PZT薄膜具有优良的抗疲劳特性,可用于铁电存储器的制备中去.     

Si(100)衬底上PLD法制备高取向度AlN薄膜

采用脉冲激光沉积法(PLD),以KrF准分子为脉冲激光源,Si(100)为衬底,同时引 入缓冲层TiN和Ti_0.8Al_0.2N,制备了结晶质量优异的A1N薄膜,X射线衍射(XRD)及反射 式高能电子衍射(RHEED)分析表明A1N薄膜呈(001)取向、二维层状生长.研究发现,薄膜 的生长模式依赖于缓冲层种类,直接在Si衬底上或MgO／Si衬底上的A1N薄膜呈三维岛状生 长;而同时引入缓冲层TiN和Ti_0.8Al_0.2N时,A1N薄膜呈二维层状生长.此外,激光能量密 度大小对A1N薄膜的结晶性有显著的影响,激光能量密度过大,薄膜表面粗糙,有颗粒状沉积 物生成.在氮气气氛中沉积,能使薄膜的取向由(001)改变为(100).     

高介电栅介质材料HfO_2掺杂后的物理电学特性(英文)

采用激光分子束外延法(LMBE)在P型Si(100)衬底上沉积了(HfO2)x(Al2O3)Y(NiO)1-x-y,栅介质薄膜,研究了其热稳定性以及阻挡氧扩散的能力.X射线衍射表明在HfO2中掺入Ni和Al元素明显提高了其结晶温度.原子力显微镜测试显示:在N2中退火后薄膜表面是原子级平滑连续的,没有发现针孔.900℃N2中退火后的薄膜在高分辨透射电镜下没有发现硅酸盐界面层.实验结果表明在氧化物薄膜与硅衬底之间引入Ni-Al-O置入层能够防止硅酸盐低介电界面层的生成,这有利于MOS晶体管的进一步尺度缩小.     

Laser patterning with beam shaping on indium tin oxide thin films of glass/plastic substrate

In this research the laser beam shaper component has been used to obtain top-hat intensity distribution laser beam to perform line scribing and to perform electrode patterning on Indium thin oxide (ITO) thin films deposited on glass and plastic substrate. ITO films were removed with third harmonic Nd:YAG laser processing system. The pulse duration, laser output power, pulse repetition rate and scanning speed parameters of straight line patterning and electrode patterning on different types of substrates were discussed, respectively. The experimental results are measured by optical microscope and scanning electron microscope to evaluate the processing parameters and surface properties of ITO thin films.     

Annealing effect on the photoluminescence of Si nanocrystallites thin films

Si nanocrystallites thin films on p-type (100) Si substrate have been fabricated by pulsed laser deposition (PLD) using a Nd:YAG laser.After deposition, samples were annealed in several environmental gases at the temperature range from 400 to 800 °C. Strong violet-indigo photoluminescence has been observed at room temperature (RT) from nitrogen ambient-annealed Si nanocrystallites. The variation of photoluminescence (PL) properties of Si nanocrystallites thin films has been investigated depending on annealing temperatures. As the results of PL and high-resolution transmission electron microscope (HRTEM) measurements, we could suggest that the origin of violet-indigo PL from the films was related to the quantum size effect of Si nanocrystallites.     

Deposition of CdS thin films onto Si(111) substrate by PLD with femtosecond pulse

The effect of laser fluence (laser incident energy in the range of 0.5-1.5 mJ/pulse with the same laser spot size of 0.5 mm × 0.7 mm) on the structural quality and optical properties synthesized by femtosecond pulsed-laser deposition has been studied. The structural quality and optical properties of the deposited CdS thin films were investigated by X-ray diffraction, atomic force microscopy and photoluminescence measurement. The studies revealed an improvement in the structural quality and optical properties of the CdS thin films with increasing the laser fluence in some range. However, too high laser fluence could lead to the structural quality and optical properties of the CdS thin films to degrade. We defined the optimum laser incident energy was around 1.2 mJ/pulse. And the kinetic energy of the plasma produced by femtosecond laser strongly affects the structure and properties of the deposited CdS thin films.     

Growth of cubic and hexagonal CdTe thin films by pulsed laser deposition

The paper reports the growth of cadmium telluride (CdTe) thin films by pulsed laser deposition (PLD) using excimer laser (KrF, λ=248 nm, 10 Hz) on corning 7059 glass and SnO₂-coated glass (SnO₂/glass) substrates at different substrate temperatures (T_s) and at different laser energy pulses. Single crystal target CdTe was used for deposition of thin films. With 30 min deposition time, 1.8- to ∼3-μm-thick films were obtained up to 200 °C substrate temperature. However, the film re-evaporates from the substrate surface at temperatures >275 °C. Atomic force microscopy (AFM) shows an average grain size ∼0.3 μm. X-ray diffraction analysis confirms the formation of CdTe cubic phase at all pulse energies except at 200 mJ. At 200 mJ laser energy, the films show hexagonal phase. Optical properties of CdTe were also investigated and the band gap of CdTe films were found as 1.54 eV for hexagonal phase and ∼1.6 eV for cubic phase.     

Co掺杂量对ZnO薄膜结构及光学特性的影响

采用脉冲激光沉积法(PLD)在SiO2村底上成功制备了具有c轴择优生长特性的Zn1-xCoxO(x=0.05、0.1、0.2、0.3)系列薄膜.通过X射线衍射和能谱仪研究了Co掺杂量对薄膜晶体结构和成分的影响;同时利用光致发光谱(PL)和透过率研究了薄膜的光学特性.结果表明,当掺杂浓度为10%时,薄膜生长最好,c轴择优生长最为显著;Co元素的掺入改变了薄膜的紫外、绿光和蓝光发射,分析认为主要是Co元素的掺入量改变了薄膜的禁带宽度、氧错位缺陷浓度和锌填隙缺陷的浓度;Co元素掺杂浓度为5%时,薄膜的透过率超过90%.此外,探讨了不同波段光发射的可能机理.     

MF(I)S结构设计对硅基铁电薄膜系统C-V特性的影响

为制备符合铁电场效应晶体管（ Ｆ Ｆ Ｅ Ｔ） 及铁电存储二极管（ Ｆ Ｍ Ｄ） 要求的高质量铁电薄膜,采用 Ｐ Ｌ Ｄ （ Ｐｕｌｓｅｄ Ｌａｓｅｒ Ｄｅｐｏｓｉｔｉｏｎ） 工艺, 制备了不同 Ｍ Ｆ （ Ｉ） Ｓ 结构的硅基铁电薄膜系统由 Ｃ－ Ｖ特性的对比分析可见, 影响 Ｃ－ Ｖ 特性的主要因素除了衬底类型、界面特性之外, 还有薄膜的结构设计在此基础上, 为改善铁电薄膜的 Ｃ－ Ｖ 特性提出了合理设想     

Growth and morphology of c-axis oriented Nd1.85Ce0.15CuO4−y thin films prepared by pulsed laser deposition technique

On the electron-doped superconductor of Nd_2−xCe_xCuO_4−y (NCCO) thin film, the presence of non-c-axis oriented grains, which are identified as (110) reflection peak at 2θ = 32.5^∘ in the x-ray diffraction (XRD) spectrum is always observed. Meanwhile, high quality thin films without having impurities are necessary for device applications. We study the growth of NCCO thin film prepared by pulsed laser deposition technique and found that the volume fraction of (110) oriented grains depends on the laser fluence. With the laser fluence of around 2.2 J/cm², NCCO thin film, which is free from the presence of non-c-axis oriented grains, could be obtained. The atomic force microscope images show that with the absence of (110) oriented grain the c-axis oriented grains grow into rectangular shape with a spiral growth mode. The rocking curve measurement for (004) peak give a full width at half maximum value of 0.12^∘, which confirms the superior quality of the film and this film has superconducting critical temperature (T_c) at 21 K with a transition width (ΔT_c) of 1 K.     

WO3/Si纳米晶薄膜的脉冲准分子激光沉积及结构分析

采用脉冲准分子激光大面积扫描沉积技术,在Ｓｉ（１１１）单晶衬底上沉积了 ＷＯ_ｘ薄膜．采用Ｘ射线衍射（ＸＲＤ）、喇曼光谱（ＲＳ）、付里叶红外光谱（ＦＴ－ＩＲ）及透射电镜扫描附件（ＳＴＥＭ）对不同条件下沉积的样品进行了结构分析．结果表明,氧分压和沉积温度是决定薄膜结构和成份的主要参数．在沉积温度３００℃以上及２０Ｐａ氧压下得到了三斜相纳米晶ＷＯ_３薄膜．     

MF(I)S结构设计对硅基铁电薄膜系统C-V特性的影响

为制备符合铁电场效应晶体管（ Ｆ Ｆ Ｅ Ｔ） 及铁电存储二极管（ Ｆ Ｍ Ｄ） 要求的高质量铁电薄膜,采用 Ｐ Ｌ Ｄ （ Ｐｕｌｓｅｄ Ｌａｓｅｒ Ｄｅｐｏｓｉｔｉｏｎ） 工艺, 制备了不同 Ｍ Ｆ （ Ｉ） Ｓ 结构的硅基铁电薄膜系统由 Ｃ－ Ｖ特性的对比分析可见, 影响 Ｃ－ Ｖ 特性的主要因素除了衬底类型、界面特性之外, 还有薄膜的结构设计在此基础上, 为改善铁电薄膜的 Ｃ－ Ｖ 特性提出了合理设想.