The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform

Claude Amra - One of the best experts on this subject based on the ideXlab platform.

Carole Deumie - One of the best experts on this subject based on the ideXlab platform.

B. Wehner - One of the best experts on this subject based on the ideXlab platform.

  • Pulsed Laser Deposition of Laterally Graded X-Ray Optical Multilayers on Substrates of Technical Relevance
    MRS Online Proceedings Library, 2011
    Co-Authors: R. Dietsch, Th. Holz, H. Mai, R. Scholz, R. Krawietz, B. SchÖneich, S. VÖllmar, B. Wehner
    Abstract:

    Pulsed Laser Deposition (PLD) is used for the preparation of Ni/C, W/C, and Mo/Si Multilayers having X-ray Optical quality. For the synthesis of layer stacks involving a uniform or a graded thickness distribution across 4"-wafers the conventional thin film deposition equipment of PLD has been modified. This modification provides a precise spatial control of the plasma plume orientation in the deposition chamber. With this arrangement the emission characteristic of the plasma source can be computer controlled and the desired coating profile can be tailored across an extended substrate via a stepper-motor-driven target manipulator. Thus film thickness uniformity (δt_s < 2%) is obtained on substrates up to 4" diameter even for smaller target-substrate distances. For laterally graded Ni and C individual layers linear thickness gradients of dts/dx = 3.2 × 10^−8 were confirmed over the total substrate length by spectroscopic ellipsometry. The parameters deduced from single layer deposition were applied for the synthesis of laterally graded Ni/C Multilayers. A mean value of the gradient of the stack period thickness dt/dx = 6.2 × 10^−8 confirmed by X-ray reflectometry (nominal value: dt_0 /dx = 6.4×10^−8 ) characterizes precision and reproducibility of the coating process.

  • High precision large area PLD of X-ray Optical Multilayers
    Applied Surface Science, 1998
    Co-Authors: R. Dietsch, Th. Holz, H. Mai, C.-f. Meyer, R. Scholz, B. Wehner
    Abstract:

    Abstract To realize high quality X-ray Optical multilayer stacks on large areas a double-beam PLD source was integrated into a commercial MBE system. Optimization of ablation conditions and film growth regime, resp., for various kinds of homogeneous thin films and multilayer systems has been realized by a reproducible variation of pulse energy and repetition rate of each of the two Nd:YAG-lasers. In addition, the lasers can be independently controlled by a predetermined pulse delay. Thus, plasma parameters of two plumes generated from locally separated origins can be influenced by the pulse delay of the Nd:YAG-lasers, too. The influence of laser parameters and pulse delay on thin film growth is investigated by the deposition of Ni/C layer stacks. Optimum irradiation conditions are zero delay and moderate pulse energies. Multilayer interface roughnesses on the order of σ R ≈0.1 nm are deduced from high resolution electron microscopy (HREM)-micrographs. The interface roughness increases with higher pulse energy. For changing the pulse delay from τ =0 ns to τ =2.5 ms, a destruction of the layer stack is observed. Laterally graded Ni/C Multilayers showing X-ray Optical activity were synthesized with these optimized deposition parameters in the period thickness range from 3 to 5 nm. Average values of thickness gradients typically Δ t /Δ x ≈2×10 −8 for 4″ substrate length in maximum and period thickness variations on the order of σ t ≈0.1 nm are confirmed by grazing incidence X-ray reflectometry and HREM.

R. Dietsch - One of the best experts on this subject based on the ideXlab platform.

  • Pulsed Laser Deposition of Laterally Graded X-Ray Optical Multilayers on Substrates of Technical Relevance
    MRS Online Proceedings Library, 2011
    Co-Authors: R. Dietsch, Th. Holz, H. Mai, R. Scholz, R. Krawietz, B. SchÖneich, S. VÖllmar, B. Wehner
    Abstract:

    Pulsed Laser Deposition (PLD) is used for the preparation of Ni/C, W/C, and Mo/Si Multilayers having X-ray Optical quality. For the synthesis of layer stacks involving a uniform or a graded thickness distribution across 4"-wafers the conventional thin film deposition equipment of PLD has been modified. This modification provides a precise spatial control of the plasma plume orientation in the deposition chamber. With this arrangement the emission characteristic of the plasma source can be computer controlled and the desired coating profile can be tailored across an extended substrate via a stepper-motor-driven target manipulator. Thus film thickness uniformity (δt_s < 2%) is obtained on substrates up to 4" diameter even for smaller target-substrate distances. For laterally graded Ni and C individual layers linear thickness gradients of dts/dx = 3.2 × 10^−8 were confirmed over the total substrate length by spectroscopic ellipsometry. The parameters deduced from single layer deposition were applied for the synthesis of laterally graded Ni/C Multilayers. A mean value of the gradient of the stack period thickness dt/dx = 6.2 × 10^−8 confirmed by X-ray reflectometry (nominal value: dt_0 /dx = 6.4×10^−8 ) characterizes precision and reproducibility of the coating process.

  • Deposition of high-resolution Carbon/Carbon Multilayers on large areas for X-ray Optical applications
    Applied Physics A, 2004
    Co-Authors: M. Menzel, R. Dietsch, D. Weissbach, P. Gawlitza, A. Leson
    Abstract:

    To synthesize X-ray Optical Multilayers showing both high resolution and high reflectivity spacer and absorber materials with low absorption coefficients for the desired spectral range are required. Simulations of C/C Multilayers with different period thicknesses, d, and single layer densities, ϱ, show that a reflectance R ( [ _Cu]Kα)>80% and a resolving power of about λ/Δλ≈600 can be achieved for C/C layer stacks with d=3 nm and N=1000 periods. An advanced large area PLD technique was used to deposit C/C single- and Multilayers onto Si-substrates up to 6^′′ in diameter. By variation of the laser parameters, we achieved densities of the carbon single layers in the range of ϱ_C=2.0...2.7 g/cm^3 (measured by XRR) and surface roughnesses σ_C=0.13...0.19 nm (measured by AFM). Due to the interface intermixing and penetration depth of highly energetic ions, especially during the deposition of the absorber layers, the density contrast of Multilayers with period thicknesses lower than 5 nm is noticeably reduced. C/C Multilayers with period thicknesses d=1.1...7.0 nm, more than 500 periods and density contrasts of about 0.2 g/cm^3 were deposited.

  • High precision large area PLD of X-ray Optical Multilayers
    Applied Surface Science, 1998
    Co-Authors: R. Dietsch, Th. Holz, H. Mai, C.-f. Meyer, R. Scholz, B. Wehner
    Abstract:

    Abstract To realize high quality X-ray Optical multilayer stacks on large areas a double-beam PLD source was integrated into a commercial MBE system. Optimization of ablation conditions and film growth regime, resp., for various kinds of homogeneous thin films and multilayer systems has been realized by a reproducible variation of pulse energy and repetition rate of each of the two Nd:YAG-lasers. In addition, the lasers can be independently controlled by a predetermined pulse delay. Thus, plasma parameters of two plumes generated from locally separated origins can be influenced by the pulse delay of the Nd:YAG-lasers, too. The influence of laser parameters and pulse delay on thin film growth is investigated by the deposition of Ni/C layer stacks. Optimum irradiation conditions are zero delay and moderate pulse energies. Multilayer interface roughnesses on the order of σ R ≈0.1 nm are deduced from high resolution electron microscopy (HREM)-micrographs. The interface roughness increases with higher pulse energy. For changing the pulse delay from τ =0 ns to τ =2.5 ms, a destruction of the layer stack is observed. Laterally graded Ni/C Multilayers showing X-ray Optical activity were synthesized with these optimized deposition parameters in the period thickness range from 3 to 5 nm. Average values of thickness gradients typically Δ t /Δ x ≈2×10 −8 for 4″ substrate length in maximum and period thickness variations on the order of σ t ≈0.1 nm are confirmed by grazing incidence X-ray reflectometry and HREM.

G. Soriano - One of the best experts on this subject based on the ideXlab platform.