Surface plasmon scattering on polymer-bimetal layer covered fused silica gratings generated by laser induced backside wet etching

Large amplitude fused silica gratings are prepared by combining the UV laser induced backside wet etching technique (LIBWE) and the two-beam interference method. The periodic patterning of fused silica surfaces is realized by s-polarized fourth harmonic beams of a Nd:YAG laser, applying saturated solution of naphthalene in methyl-methacrylate as liquid absorber. Atomic force microscopy is utilized to analyze how the modulation amplitude of the grating can be controlled by the fluence and number of laser pulses. Three types of plasmonic structures are prepared by a bottom-up method, post-evaporating the fused silica gratings by gold-silver bimetal layers, spin-coating the metal structures by thin polycarbonate films, and irradiating the multilayers by UV laser. The effect of the bimetal and polymer-coated bimetal gratings on the surface plasmon resonance is investigated in a modified Kretschmann arrangement allowing polar and azimuthal angle scans. It is demonstrated experimentally that scattering on rotated gratings results in additional minima on the resonance curves of plasmons excited by second harmonic beam of a continuous Nd:YAG laser. The azimuthal angle dependence proves that these additional minima originate from back-scattering. The analogous reflectivity minima were obtained by scattering matrix method calculations realized taking modulation depths measured on bimetal gratings into account.     

Gas pressure effects on the structure of CNx thin films deposited by laser ablation

Carbon nitride thin films with different nitrogen concentration have been deposited at different N₂ and N₂/Ar mixed partial pressures. Time-integrated optical emission spectroscopy measurements have been performed to gather information on the nature of the chemical species present in the plasma. Both the CN and C₂ molecular species have been observed. Fast photography imaging of the expanding plume revealed the change of the dynamics from a free expansion at low pressure to a shock wave formation followed then by the plume stopping upon increasing the gas pressure values. Raman and XPS spectroscopy measurements performed on the deposited thin films revealed that the films, structure strongly depends on the dynamics of the expansion plasma regime rather than on the partial pressure at which the deposition takes place.     

Effect of the structure of a graphite target on the parameters of carbon films obtained by the laser plasma method

We have used Raman light scattering and electron paramagnetic resonance methods to study carbon films obtained by laser plasma deposition, using different types of graphite targets. We have established that the films deposited in this way have a diamond-like structure and are a nanostructured composite containing clusters of both sp² and sp³-hybridized carbon. We have shown that an increase in structural perfection of the graphite target causes an improvement in the structure of the carbon films obtained from it and an increase in the content of sp³-hybridized carbon in it. Thermal stimulation of the substrate during application of a coating leads to the same effect. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 539–546, July–August, 2008.     

ZnSe films deposited on crystalline GaAs and amorphous quartz substrates by means of pulsed laser ablation technique

ZnSe films were deposited by pulsed laser ablation on a crystalline GaAs substrate and on an amorphous quartz substrate. The deposition process was performed with the same growth parameters. The films were investigated by means of X-ray diffraction, reflectance and photoluminescence spectroscopy. The X-ray diffraction spectra have demonstrated that the films grow in a highly oriented way but having different orientations, i.e. the films deposited on GaAs grow (100)-oriented and the films deposited on quartz grow (111)-oriented. Reflectance spectra as a function of the temperature have been analysed by means of the classical oscillator model, in order to obtain the temperature dependence of the band gap energy. This gives results comparable to those of ZnSe single crystals for ZnSe on GaAs, but it is red-shifted for ZnSe on quartz, because of lattice and thermal strains. The photoluminescence measurements at T = 10 K confirm the better quality of ZnSe deposited on GaAs and show that pulsed laser ablation is a promising technique to grow films having intrinsic luminescence even on an amorphous substrate. Received 29 May 2002 Published online 31 October 2002 RID="a" ID="a"e-mail: giuseppe.perna@ba.infn.it     

衬底温度对PLD制备的Mo薄膜结构及表面形貌的影响

运用脉冲激光沉积(PLD)技术在Si(100)基片上沉积了金属Mo薄膜。在激光重复频率2 Hz,能量密度5.2 J/cm2,本底真空10－6 Pa的条件下,研究Mo薄膜的结构和表面形貌,讨论了衬底温度对薄膜形貌与结构的影响。原子力显微镜(AFM)图像和X射线小角衍射(XRD)分析表明,薄膜表面平整、光滑,均方根粗糙度小于2 nm。沉积温度对Mo薄膜结构和表面形貌影响较大,在373~573 K范围内随着温度升高,薄膜粗糙度变小,结晶程度变好。     

衬底温度对PLD制备的Mo薄膜结构及表面形貌的影响

 运用脉冲激光沉积(PLD)技术在Si(100)基片上沉积了金属Mo薄膜。在激光重复频率2 Hz,能量密度5.2 J/cm²,本底真空10^－6 Pa的条件下,研究Mo薄膜的结构和表面形貌,讨论了衬底温度对薄膜形貌与结构的影响。原子力显微镜(AFM)图像和X射线小角衍射(XRD)分析表明,薄膜表面平整、光滑,均方根粗糙度小于2 nm。沉积温度对Mo薄膜结构和表面形貌影响较大,在373~573 K范围内随着温度升高,薄膜粗糙度变小,结晶程度变好。     

溅射功率对直流磁控溅射Ti膜结构的影响

 采用直流磁控溅射方法制备了纯Ti膜,研究了不同功率下Ti膜的沉积速率、表面形貌及晶型结构,并对其应力进行了研究。研究表明：薄膜的沉积速率随溅射功率的增加而增加,当溅射功率为20 W时,原子力显微镜(AFM)图像显示Ti膜光洁、致密,均方根粗糙度最小可达0.9 nm。X射线衍射(XRD)分析表明薄膜的晶体结构为六方晶型,Ti膜应力先随溅射功率增大而增大,在60 W时达到最大值（为945.1 MPa）,之后随溅射功率的增大有所减小。     

溅射功率对直流磁控溅射Ti膜结构的影响

采用直流磁控溅射方法制备了纯Ti膜,研究了不同功率下Ti膜的沉积速率、表面形貌及晶型结构,并对其应力进行了研究。研究表明：薄膜的沉积速率随溅射功率的增加而增加,当溅射功率为20 W时,原子力显微镜(AFM)图像显示Ti膜光洁、致密,均方根粗糙度最小可达0.9 nm。X射线衍射(XRD)分析表明薄膜的晶体结构为六方晶型,Ti膜应力先随溅射功率增大而增大,在60 W时达到最大值（为945.1 MPa）,之后随溅射功率的增大有所减小。     

Study of the structure and electrical properties of the copper nitride thin films deposited by pulsed laser deposition

Copper nitride thin films were prepared on glass and silicon substrates by ablating a copper target at different pressure of nitrogen. The films were characterized in situ by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and ex situ by X-ray diffraction (XRD). The nitrogen content in the samples, x = [N]/[Cu], changed between 0 and 0.33 for a corresponding variation in nitrogen pressure of 9 × 10⁻² to 1.3 × 10⁻¹ Torr. Using this methodology, it is possible to achieve sub-, over- and stoichiometric films by controlling the nitrogen pressure. The XPS results show that is possible to obtain copper nitride with x = 0.33 (Cu₃N) and x = 0.25 (Cu₄N) when the nitrogen pressure is 1.3 × 10⁻¹ and 5 × 10⁻² Torr, respectively. The lattice constants obtained from XRD results for copper nitride with x = 0.25 is of 3.850 Å and with x = 0.33 have values between 3.810 and 3.830 Å. The electrical properties of the films were studied as a function of the lattice constant. These results show that the electrical resistivity increases when the lattice parameter is decreasing. The electrical resistivity of copper nitride with x = 0.25 was smaller than samples with x = 0.33.     

Experimental study on the chirped structure of the white-light continuum generation by femtosecond laser spectroscopy

The chirped structure of the white-light continuum generation (WLCG) pulse produced by focusing 800nm laser pulse with a pulse duration of 150fs (FWHM: full-width-at-half-maximum) onto a 2.4 mm thick sapphire plate was investigated by the optical Kerr gate technique with normal hexane as the optical Kerr gate medium. The observed WLCG was positively chirped, the measured anti-Stokes spectrum of WLCG ranges from 449 to 580nm with a temporal span of 2.56ps. When using metal reflecting mirrors to eliminate the group velocity dispersion (GVD) effect, we found that a span of 1.3ps still remained, indicating that the chirped pulse cannot be accounted for simply by GVD of the pulse propagation in the dispersive media. Our results suggest that the light-induced refractive index change due to the third-order nonlinear optical effect leads to an additional positive group velocity dispersion, which contributes to an important portion of the observed temporal broadening of the chirped WLCG. In addition to using reflective optical elements instead of dispersive optical elements, an effective way of reducing the chirp is to minimize the optical path length of the WLCG medium.     

PLD方法制备的纳米Fe/Al薄膜的结构及应力分析

 采用PLD方法制备了Fe/Al合金薄膜，研究了Fe/Al合金薄膜的物相、结构、应力等。研究表明薄膜的沉积速率随着衬底温度的升高而降低。原子力显微镜（AFM）图像显示，薄膜表面平整、致密且光滑，均方根粗糙度小于1 nm。等离子体发射谱（ICP）表明Fe/Al原子比为1∶1。X射线小角衍射（XRD）分析表明薄膜中的物相是Al_0.5Fe_0.5，Al_0.5Fe_0.5晶体具有简单立方结构(SC)，晶格常数为0.297 nm，平均晶粒尺寸为81.74 nm，平均微畸变为0.007 6。     

Reduced-temperature ordering of FePt nanoparticle assembled films by Fe30Pt70/Fe3O4 core/shell structure

In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine （PEI）-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly technique. The dimension of core/shell structured nanoparticles was that of 4nm core and 2 nm shell. After annealing under a flow of forming gas （50%Ar2＋30%H2） for 1 h at or above 400℃, the iron oxide shell was reduced to Fe and diffused to Pt-rieh core, which leaded to the formation of L1. phase FePt at low temperature. The x-ray diffraction results and magnetic properties measurement showed that the chemical ordering temperature of Fe30Pt70/Fe3O4 core/shell nanoparticles assembly can be reduced to as low as 400℃. The sample annealed at 400℃ showed the eoereivity of 4KOe with the applied field of 1.5T. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.[第一段]     

Nanostructuring of Fe films by oblique incidence deposition on a FeSi2 template onto Si(1 1 1): Growth, morphology, structure and faceting

The growth of thin Fe films deposited at oblique incidence on an iron silicide template onto Si(1 1 1) single crystal has been investigated as a function of Fe thickness (0 < t_Fe ? 180 monolayers (MLs)) and incidence angle (0 ? θ ? 80°). The growth mode is determined in situ by means of scanning tunnelling microscopy (STM) and low energy electron diffraction (LEED). Stripes oriented perpendicularly to the incident atomic flux are formed for θ ? 30°. Self-correlation functions are used to extract characteristic lengths from STM images. The correlation lengths in the direction of the incident flux (ξ_x) and perpendicular to the atomic flux (ξ_y) grow with different powers versus time (ξ_x∝t^σ and ξ_y∝t^ρ, with σ = 0.34 ± 0.03 and ρ = 0.67 ± 0.03) following the exact solution of the (1 + 1) dimensional Kardar-Parisi-Zhang (KPZ) equation. The root mean square roughness follows also a scaling law for t_Fe < 120 ML leading to a growth exponent β = 0.73 ± 0.02. Shadowing and steering effects are discussed on the basis of our STM data.