Study on metal microparticle content of the material transferred with Absorbing Film Assisted Laser Induced Forward Transfer when using silver absorbing layer

Absorbing Film Assisted Laser Induced Forward Transfer (AFA-LIFT) is a modified LIFT method where a high absorption coefficient thin film coating of a transparent substrate is used to transform the laser energy into kinetic in order to transfer the “target” material spread on it. This method can be used for the transfer of biomaterials and living cells, which could be damaged by direct irradiation of the laser beam. In previous experiments, ∼50-100 nm thick metal films have been used as absorbing layer. The transferred material can also contain metal microparticles originating from the absorbing thin film and acting as non-desired impurities in some cases. The aim of our work was to study how the properties (number, size and covered area) of metal particles transferred during the AFA-LIFT process depend on film thickness and the applied fluence. Silver thin films with different thickness (50-400 nm) were used as absorbing layers and real experimental conditions were modeled by a 100 μm thick water layer. The particles transferred without the use of water layer were also studied. The threshold laser fluence for the complete removal of the absorber from the irradiated area was found to strongly increase with increasing film thickness. The deposited micrometer and submicrometer particles were observed with optical microscope and atomic force microscope. Their size ranged from 100 nm to 20 μm and depended on the laser fluence. The increase in fluence resulted in an increasing number of particles of smaller average size.     

Probing thermal properties of vanadium dioxide thin films by time-domain thermoreflectance without metal film

Vanadium dioxide(VO_2) is a strongly correlated material, and it has become known due to its sharp metal–insulator transition(MIT) near room temperature. Understanding the thermal properties and their change across MIT of VO_2 thin film is important for the applications of this material in various devices. Here, the changes in thermal conductivity of epitaxial and polycrystalline VO_2 thin film across MIT are probed by the time-domain thermoreflectance(TDTR) method.The measurements are performed in a direct way devoid of deposition of any metal thermoreflectance layer on the VO_2 film to attenuate the impact from extra thermal interfaces. It is demonstrated that the method is feasible for the VO_2 films with thickness values larger than 100 nm and beyond the phase transition region. The observed reasonable thermal conductivity change rates across MIT of VO_2 thin films with different crystal qualities are found to be correlated with the electrical conductivity change rate, which is different from the reported behavior of single crystal VO_2 nanowires. The recovery of the relationship between thermal conductivity and electrical conductivity in VO_2 film may be attributed to the increasing elastic electron scattering weight, caused by the defects in the film. This work demonstrates the possibility and limitation of investigating the thermal properties of VO_2 thin films by the TDTR method without depositing any metal thermoreflectance layer.     

原子层沉积AlO_x薄膜对单晶硅太阳能电池钝化机制的影响

采用原子层沉积设备在p型单晶制绒硅上制备了不同厚度的AlO_x薄膜。通过研究AlO_x薄膜厚度对样品的反射率、少数载流子寿命以及电容-电压特性的影响,发现沉积32 nm的AlO_x薄膜样品具有最好的钝化效果。另外,通过计算Si/AlO_x界面处的固定电荷密度和缺陷态密度,发现32 nm厚的AlO_x薄膜样品具有最低的缺陷态密度。系统研究了单晶硅材料的表面钝化机制,给出了影响样品载流子寿命的根本来源。     

Thickness-dependent tunable characteristics of (Ba0.5Sr0.5)0.925K0.075TiO3 thin films prepared by pulsed laser deposition

The thickness-dependent dielectric properties and tunability of pulsed laser deposited (Ba_0.5Sr_0.5)_0.925K_0.075TiO₃ (BSKT) thin films with different thickness ranging from 80 to 300 nm has been investigated. Dielectric properties of the BSKT thin films are substantially improved as the BSKT film thickness increases, which can be explained by the model of a low-permittivity dead layer that is connected in series with the bulk region of the film. The estimated values of thickness and the average dielectric constant for the dead layer are 2.4 nm and 23.5, respectively, in a Pt/BSKT/Pt capacitor structure. The tunability and figure of merit increased with increasing film thickness, which are attributed to the change in lattice parameter and the dead layer effect.     

Lead telluride nanocrystalline thin films: Structure,optical characterization and a broadband dielectric spectroscopy study

Nanocrystalline PbTe thin films were deposited on a glass substrate by thermal evaporation technique with two thicknesses namely, 45 and 250 nm. The structural studies revealed that the films have nanocrystalline cubic structure and the particle size was found to be 11 and 20.7 nm, for low and high thicknesses respectively. The FE-SEM study shows that the surface grains increase for higher thickness film. This indicates that samples lying under the strong regime of confinement for PbTe thin films. The optical properties confirm the occurrence of confinement process as the optical band gap are 1.67 and 0.9 eV for 45 and 250 nm films, respectively. The dielectric results indicated that the conductivity increases by about two orders of magnitude with increasing the thickness from 45 to 250 nm. Moreover, the permittivity shows a higher dispersion step at lower frequencies in both samples due to the hopping conduction mechanism in addition to the interfacial polarization in such heterogeneous structures. Another small dispersion step is noticed in case of the lower thickness. It is attributed to the polarization of the accumulated charge carriers near the grain boundaries interfaces. No indication of any electrode phenomena in both samples is shown here.     

纳米金表面修饰与表面等离子体共振传感器的相互作用研究

为了分析纳米金表面修饰对表面等离子体共振(SPR)的放大作用,以及其对传感器本身的影响,首先,基于色散介质的吸收理论,通过建立波长型SPR生物传感器四层膜结构的数学模型,理论分析了传感器表面所吸附纳米金对传感器的影响:纳米金的表面修饰,改变了表面等离子体传感器中棱镜表面各介质层内电磁场的能量分布,削弱了金属膜在共振吸收中的作用,从而使SPR曲线的半波宽度增加,最小反射系数增大,金膜的最优膜厚度也随之改变.其次,通过不同厚度的金膜外吸附纳米金的对比试验,验证了此理论.金膜厚45nm、表面修饰10nm纳米金颗 关键词： 表面等离子体共振 生物传感器 纳米金 金属膜     

Characteristic difference between ITO/ZrCu and ITO/Ag bi-layer films as transparent electrodes deposited on PET substrate

The metallic-glass film of ZrCu layer deposited by co-sputtering was utilized as the metallic layer in the bi-layer structure transparent conductive electrode of ITO/ZrCu (IZC) deposited on the PET substrate using magnetron sputtering at room temperature. In addition, the pure Ag metal layer was applied in the same structure of transparent conductive film, ITO/Ag, in comparison with the IZC film. The ZrCu layer could form a continuous and smooth film in thickness lower than 6 nm, compared with the island structure of pure Ag layer of the same thickness. The 30 nm ITO/3 nm ZrCu films could show the optical transmittance of 73% at 550 nm wavelength. The 30 nm ITO/12 nm ZrCu films could show the better sheet resistance of 20 Ω/sq, but it was still worse than that of the ITO/Ag films. It was suggested that an alloy system with lower resistivity and negative mixing heat between atoms might be another way to form a continuous layer in thickness lower than 6 nm for metal film.     

对硅片上自组装生长的Pentacene薄膜生长机制及其结晶相态的研究

采用热蒸发的方法在硅片衬底上自组装生长的Pentacene薄膜,薄膜在80℃温度下经2 h恒温真空热处理,通过原子力显微镜(AFM)对Pentacene薄膜表面形貌及其生长机制进行研究.结果得到,在硅片上生长的Pentacene薄膜足以台阶岛状结构生长,其岛状直径约为100 nm.且Pentacene分子以垂直于衬底的方向生长,台阶岛状结构中每个台阶的平均高度约为1.54 nnl·s-1,与Pentacene分子的沿长轴方向的长度相近.从Pentacene薄膜的XRD图谱中可以看出,薄膜在形成的过程中会因条件的不同而形成不同的结晶相,分别为薄膜相和三斜体相,且薄膜的结晶相将随着薄膜厚度的增加向三斜体相转变,其临界厚度为80和150 nm,当薄膜大于150 nm时,薄膜的三斜体相占主导地位,而当Pentacene薄膜的厚度小于80 nm时,Pentacene薄膜呈薄膜相存在.     

基于金属掺杂ITO透明导电层的紫外LED制备

为降低ITO薄膜对紫外波段的光吸收,制备低电压高功率的紫外LED,研究了一种基于金属掺杂ITO透明导电层的365 nm紫外LED的制备工艺。利用1 cm厚的石英片生长了不同厚度ITO薄膜以及在ITO上掺杂不同金属的新型薄膜,并研究了在不同的退火条件下这种薄膜的电阻和透过率,分析了掺杂金属ITO薄膜的带隙变化。将这种掺杂的ITO薄膜生长在365 nm外延片上并完成电极生长,制备成14 mil×28 mil的正装LED芯片。利用电致发光（EL）设备对LED光电性能进行测试并对比。实验结果表明:掺Al金属的ITO薄膜能够相对ITO薄膜的带隙提高0.15 eV。在600℃退火后,方块电阻降低6.2 Ω/□,透过率在356 nm处达到90.8%。在120 mA注入电流下,365 nm LED的电压降低0.3 V,功率提高14.7%。ITO薄膜掺金属能够影响薄膜带隙,改变紫光LED光电性能。     

氧化钛薄膜调控金属铜的表面等离子体共振特性研究

提出了一种利用氧化钛薄膜对金属铜薄膜表面等离子体共振特性调制的想法。实验中首先使用电子束蒸发制备一批同等厚度的氧化钛薄膜,再利用磁控溅射方法在氧化钛薄膜上沉积厚度为5～80 nm不等的金属铜薄膜。测试结果表明,氧化钛膜层对不同厚度的金属铜薄膜表面等离子体共振增强具有不同调制效果,金属铜薄膜厚度小于20 nm时,底层的氧化钛薄膜对Cu薄膜表面等离子体共振增强效果显著,且随着金属Cu膜层厚度增加表面等离子体共振峰发生蓝移,而当金属铜膜层的厚度超过20 nm时,共振增强效果因金属Cu薄膜消光能力的上升而开始减弱。     

Size quantization of electronic states in very thin platinum films

The Quantum Size Effect (QSE) is expected to exist in metal films. It has been discussed in a number of theoretical papers. The experimental verification is difficult because of the very short Fermi wave length of the charge carriers in metals. Surface roughness of the films and diffuse scattering of the charge carriers from the film surface usually prevent the observation of QSE. We succeeded in preparing Pt-films with surface roughness below 0.3 nm, which also exhibited partly specular reflection of the electrons from the film surface. Oscillations of the conductivity with the film thickness, due to QSE, were observed in the thickness range from 0.5 nm to 2.0 nm. Band splitting was observed in the thickness range from 5 nm to 20 nm by means of tunneling spectroscopy. From the results we suggest that electrons as well as holes in closed Fermi surfaces participate in the QSE. Holes in open Fermi surfaces, despite their larger density, could not be observed. The measurements allow the determination of the Fermi energy and the effective masses of both electrons and holes in quasi amorphous films.     

A theory of thin metal films: electron density,potentials and work function

Electron densities, potentials, and work functions of thin metal films are calculated self-consistently. The planar uniform-background model and the density-functional formalism are used similarly as in the theory of metal surfaces by Lang and Kohn. Electron densities and potentials are discussed for r_s = 4 both as function of the position in the film and of film thickness. Numerical results for the dependence of the work function on film thickness are given for r_s = 2, 3, 4, 5, 6. As functions of film thickness electron densities, potentials and work functions show oscillations with a period of one-half the Fermi wavelength. The amplitude of the oscillations in potentials and work functions is about 1 eV for one monolayer and 0.1 eV for films of 20 Å thickness. A comparison with non-self-consistent calculations reveals the necessity of self-consistent computations. The relevance of the results to work function measurements and to investigations of thermodynamic and transport properties are discussed. The influence of the film geometry on calculations designed for surfaces per se is examined.     

Free surfaces cause reductions in the glass transition temperature of thin polystyrene films

The effect of free surfaces on the glass transition temperature (T(g)) of thin polystyrene films was studied. Measurements were performed on films (8 nm相似文献   

Simulation on effect of metal/graphene hybrid transparent electrode on characteristics of GaN light emitting diodes

In order to decrease the Schottky barrier height and sheet resistance between graphene(Gr) and the p-GaN layers in GaN-based light-emitting diodes(LEDs), some transparent thin films with good conductivity and large work function are essential to insert into Gr and p-GaN layers. In this work, the ultra-thin films of four metals(silver(Ag), golden(Au), nickel(Ni), platinum(Pt)) are explored to introduce as a bridge layer into Gr and p-GaN, respectively. The effect of a different combination of Gr/metal transparent conductive layers(TCLs) on the electrical, optical, and thermal characteristics of LED was investigated by the finite element methods. It is found that both the TCLs transmittance and the surface temperature of the LED chip reduces with the increase of the metal thickness, and the transmittance decreases to about 80% with the metal thickness increasing to 2 nm. The surface temperature distribution, operation voltage, and optical output power of the LED chips with different metal/Gr combination were calculated and analyzed. Based on the electrical, optical, and thermal performance of LEDs, it is found that 1.5-nm Ag or Ni or Pt, but 1-nm Au combined with 3 layered(L) Gr is the optimal Gr/metal hybrid transparent and current spreading electrode for ultra-violet(UV) or near-UV LEDs.     

Structuring of aluminum films by laser-induced local oxidation in water

A simple method for patterning of thin (15–650 nm) aluminum films on glass substrates by direct, low-power, laser-thermal oxidation in water under common laboratory conditions is demonstrated. Local heating of the metal film enhances the formation of aluminum oxide (hydrargillite, Al₂O₃–3H₂O) and provokes breakdown of the passivation layer followed by local corrosion at temperatures close to the boiling point of water. Moving the focus of an Ar-ion laser (λ=488 nm) over the aluminum film with a speed of several μm/s yields grooves flanked by hydrargillite. Upon through oxidation of the metal these structures act as electrically insulating domains. Depending on the film thickness, the minimum width of the line structures measures between 266 nm and 600 nm. The required laser irradiation power ranges from 1.7 mW to 30 mW. It is found that the photo-thermal oxidation process allows for writing of two-dimensional electrode patterns. Received: 16 July 2001 / Accepted: 23 July 2001 / Published online: 2 October 2001     

Growth of SrTiO3 on Si(001) by hybrid molecular beam epitaxy

We report the heteroepitaxial growth of SrTiO₃ thin films on Si(001) by hybrid molecular beam epitaxy (hMBE). Here, elemental strontium and the metal‐organic precursor titanium tetraisopropoxide (TTIP) were co‐supplied in the absence of additional oxygen. The carbonization of pristine Si surfaces during native oxide removal was avoided by freshly evaporating Sr into the hMBE reactor prior to loading samples. Nucleation, growth and crystallization behavior as well a structural properties and film surfaces were characterized for a series of 46‐nm‐thick SrTiO₃ films grown with varying Sr to TTIP fluxes to study the effect of non‐stoichiometric growth conditions on film lattice parameter and surface morphology. High quality SrTiO₃ thin films with epitaxial relationship (001)SrTiO₃ || (001)Si and [110]SrTiO₃ || [100]Si were demonstrated with an amorphous layer of around 4 nm thickness formed at the SrTiO₃/Si interface. The successful growth of high quality SrTiO₃ thin films with atomically smooth surfaces using a thin film technique with scalable growth rates provides a promising route towards heterogeneous integration of functional oxides on Si. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Surface morphology and surface chemical states of epitaxial Pb(Zr0.95Ti0.05)O3 thin films grown on SrTiO3(100) by sputter deposition

0.95 Ti_0.05)O₃ thin films of an orthorhombic perovskite structure were obtained on SrTiO₃(100) substrates by radio frequency sputter deposition. The surface morphology of the films was investigated with atomic force microscopy, scanning electron microscopy, and reflection electron microscopy. It is shown that the film surfaces are rather bumpy. There are undulations of about 400 nm in length in an in-plane direction. The mean roughness perpendicular to the surface is 39.6 nm, for the film thickness of 0.45 μm. The surface roughening was probably caused by island-shaped nucleation and growth during the film growth. It has also been found that some gorges and a number of small pits remain at the film surfaces. The surface chemical states of the films were characterized by using X-ray photoelectron spectroscopy. A Pb enrichment layer and a large amount of adsorbed oxygen have been found at the surfaces of the films. Near the film surface Pb and Zr exist mainly in the forms of, besides Pb(Zr,Ti)0₃, metal Pb, metal Zr, oxygen-chemisorbed Pb, and various lead oxides. In addition, a small amount of lead, whose binding energy of Pb 4f_7/2 is much lower than that of metal Pb, was observed at the film surfaces, but its chemical state is unknown up to now. Received: 2 June 1997/Accepted: 22 September 1997     

ZnO/Ag/ZnO multilayer films for the application of a very low resistance transparent electrode

Transparent conductive ZnO/Ag/ZnO multilayer electrodes having much lower electrical resistance than the widely used transparent electrodes were prepared by simultaneous RF magnetron sputtering of ZnO and DC magnetron sputtering of Ag. An Ag film with different thickness was used as intermediate metallic layers. The optimum thickness of Ag thin films was determined to be 6 nm for high optical transmittance and good electrical conductivity. With about 20-25 nm thick ZnO films, the multilayer showed high optical transmittance in the visible range of the spectrum and had color neutrality. The electrical and optical properties of the multilayers were changed mainly by Ag film properties. A high quality transparent electrode, having sheet resistance as low as 3 ohm/sq and high transmittance of 90% at 580 nm, was obtained and could be reproduced by controlling the preparation parameter properly. The above property is suitable as transparent electrode for dye sensitized solar cells (DSSC).     

原子氢在Be(100)薄膜上吸附的第一性原理计算

对原子氢在Be(1010)薄膜表面的吸附性质做了第一性原理计算研究.根据原子面间距的不同,可把Be(1010)表面分为两种.计算结果表明,原子氢在这两种表面上的吸附性质显著不同.为阐明和分析这些不同,系统计算和分析了Be(1010)薄膜的表面电子结构、电子功函数、平均静电势和局域电荷密度.这些物理量都自洽地表明,吸附过程中原子氢和表面铍原子间的电荷转移过程对于两种表面是完全不同的.对于L型表面来说,电荷由吸附原子氢向表面Be原子层转移,而对于S型表面而言,电荷转移过程恰恰相反.     

原子氢在Be(1010)薄膜上吸附的第一性原理计算

对原子氢在Be(1010)薄膜表面的吸附性质做了第一性原理计算研究.根据原子面间距的不同，可把Be(1010)表面分为两种.计算结果表明，原子氢在这两种表面上的吸附性质显著不同.为阐明和分析这些不同，系统计算和分析了Be(1010)薄膜的表面电子结构、电子功函数、平均静电势和局域电荷密度.这些物理量都自洽地表明，吸附过程中原子氢和表面铍原子间的电荷转移过程对于两种表面是完全不同的.对于L型表面来说，电荷由吸附原子氢向表面Be原子层转移，而对于S型表面而言，电荷转移过程恰恰相反. 关键词： 表面能 功函数 量子尺度效应