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- ItemCharacteristics of diamond turned NiP smoothed with ion beam planarization technique(London : [Springer], 2017) Li, Yaguo; Takino, Hideo; Frost, FrankBackground: Diamond turning is widely used in machining metals and semiconductors but the turning marks are incurred on machined components due to the mechanics of the technology. The marks are generally harmful to the systems comprising of the machined components. Therefore, the capability of ion beam planarization (IBP) to reduce turning marks of diamond turned metal surfaces was investigated using NiP as an example. Methods: The turning marks and thereby roughness was reduced by IBP with respect to different spatial wavelengths and amplitudes of turning marks. Different thickness of coating resist was also examined in order to find out the potential effects of resist thickness on the reduction of turning marks and roughness. Additionally, the effect of multiple planarization steps was also analyzed. Results: The spatial wavelength and depth of turning marks have only minor impact on the degree of surface roughness reduction. Thicker coating tends to achieve smoother surface after coating turned NiP while ion beam etching can keep surface roughness almost unchanged in our experiments. The surface roughness of diamond turned NiP drops exponentially with processing steps under experimented conditions. Using up to five IBP steps, the surface roughness can be reduced up to one order of magnitude (from Rq ~ 6.5 nm to Rq ~ 0.7 nm). Conclusions: IBP technique performs very well in reducing turning marks on diamond turned NiP surfaces. The surface roughness can be further improved by optimizing the properties of planarizing resist layer and coating processes to enhance the IBP technique as a final surface finishing technology.
- ItemReactive ion beam figuring of optical aluminium surfaces(Bristol : IOP Publ., 2017) Bauer, Jens; Frost, Frank; Arnold, ThomasUltra-smooth and arbitrarily shaped reflective optics are necessary for further progress in EUV/XUV lithography, x-ray and synchrotron technology. As one of the most important technological mirror optic materials, aluminium behaves in a rather difficult way in ultra-precision machining with such standard techniques as diamond-turning and subsequent ion beam figuring (IBF). In particular, in the latter, a strong surface roughening is obtained. Hence, up to now it has not been possible to attain the surface qualities required for UV or just visible spectral range applications. To overcome the limitations mainly caused by the aluminium alloy structural and compositional conditions, a reactive ion beam machining process using oxygen process gas is evaluated. To clarify the principle differences in the effect of oxygen gas contrary to oxygen ions on aluminium surface machining, we firstly focus on chemical-assisted ion beam etching (CAIBE) and reactive ion beam etching (RIBE) experiments in a phenomenological manner. Then, the optimum process route will be explored within a more quantitative analysis applying the concept of power spectral density (PSD) for a sophisticated treatment of the surface topography. Eventually, the surface composition is examined by means of dynamic secondary ion mass spectrometry (SIMS) suggesting a characteristic model scheme for the chemical modification of the aluminium surface during oxygen ion beam machining. Monte Carlo simulations were applied to achieve a more detailed process conception.
- ItemSolvent influence on the surface morphology of P3HT thin films revealed by photoemission electron microscopy(Cambridge : Royal Society of Chemistry, 2019) Niefind, Falk; Karande, Shubhangi; Frost, Frank; Abel, Bernd; Kahnt, AxelOnly rigorous understanding of the relationship between the nanoscale morphology of organic thin films and the performance of the devices built from them will ultimately lead to design rules that can guide a structured development on the field of organic electronics. Despite great effort, unraveling the nanoscale structure of the films is still a challenge in itself. Here we demonstrate that photoemission electron microscopy can provide valuable insights into the chain orientation, domains size and grain boundary characteristics of P3HT films spun cast from different solvents at room as well as at elevated temperatures. © 2019 The Royal Society of Chemistry.
- ItemNanostructures on fused silica surfaces produced by ion beam sputtering with Al co-deposition(Heidelberg [u.a.] : Springer, 2017) Liu, Ying; Hirsch, Dietmar; Fechner, Renate; Hong, Yilin; Fu, Shaojun; Frost, Frank; Rauschenbach, BerndThe ion beam sputtering (IBS) of smooth mono-elemental Si with impurity co-deposition is extended to a pre-rippled binary compound surface of fused silica (SiO2). The dependence of the rms roughness and the deposited amount of Al on the distance from the Al source under Ar+ IBS with Al co-deposition was investigated on smooth SiO2, pre-rippled SiO2, and smooth Si surfaces, using atomic force microscopy and X-ray photoelectron spectroscopy. Although the amounts of Al deposited on these three surfaces all decreased with increasing distance from the Al target, the morphology and rms roughness of the smooth Si surface did not demonstrate a strong distance dependence. In contrast to smooth Si, the rms roughness of both the smooth and pre-rippled SiO2 surfaces exhibited a similar distance evolution trend of increasing, decreasing, and final stabilization at the distance where the results were similar to those obtained without Al co-deposition. However, the pre-rippled SiO2 surfaces showed a stronger modulation of rms roughness than the smooth surfaces. At the incidence angles of 60° and 70°, dot-decorated ripples and roof-tiles were formed on the smooth SiO2 surfaces, respectively, whereas nanostructures of closely aligned grains and blazed facets were generated on the pre-rippled SiO2, respectively. The combination of impurity co-deposition with pre-rippled surfaces was found to facilitate the formation of novel types of nanostructures and morphological growth. The initial ripples act as a template to guide the preferential deposition of Al on the tops of the ripples or the ripple sides facing the Al wedge, but not in the valleys between the ripples, leading to 2D grains and quasi-blazed grating, which offer significant promise in optical applications. The rms roughness enhancement is attributed not to AlSi, but to AlOxFy compounds originating mainly from the Al source.
- ItemCan One Series of Self-Organized Nanoripples Guide Another Series of Self-Organized Nanoripples during Ion Bombardment: From the Perspective of Power Spectral Density Entropy?(Basel : MDPI, 2023) Li, Hengbo; Li, Jinyu; Yang, Gaoyuan; Liu, Ying; Frost, Frank; Hong, YilinIon bombardment (IB) is a promising nanofabrication tool for self-organized nanostructures. When ions bombard a nominally flat solid surface, self-organized nanoripples can be induced on the irradiated target surface, which are called intrinsic nanoripples of the target material. The degree of ordering of nanoripples is an outstanding issue to be overcome, similar to other self-organization methods. In this study, the IB-induced nanoripples on bilayer systems with enhanced quality are revisited from the perspective of guided self-organization. First, power spectral density (PSD) entropy is introduced to evaluate the degree of ordering of the irradiated nanoripples, which is calculated based on the PSD curve of an atomic force microscopy image (i.e., the Fourier transform of the surface height. The PSD entropy can characterize the degree of ordering of nanoripples). The lower the PSD entropy of the nanoripples is, the higher the degree of ordering of the nanoripples. Second, to deepen the understanding of the enhanced quality of nanoripples on bilayer systems, the temporal evolution of the nanoripples on the photoresist (PR)/antireflection coating (ARC) and Au/ARC bilayer systems are compared with those of single PR and ARC layers. Finally, we demonstrate that a series of intrinsic IB-induced nanoripples on the top layer may act as a kind of self-organized template to guide the development of another series of latent IB-induced nanoripples on the underlying layer, aiming at improving the ripple ordering. The template with a self-organized nanostructure may alleviate the critical requirement for periodic templates with a small period of ~100 nm. The work may also provide inspiration for guided self-organization in other fields.
- ItemFinishing of metal optics by ion beam technologies(Bellingham, Wash. : SPIE, 2019) Bauer, Jens; Frost, Frank; Lehmann, Antje; Ulitschka, Melanie; Li, Yaguo; Arnold, ThomasUltraprecise mirror devices show considerable potential with view to applications in the visible and the ultraviolet spectral ranges. Aluminum alloys gather good mechanical and excellent optical properties and thus they emerge as important mirror construction materials. However, ultraprecision machining and polishing of optical aluminum surfaces are challenging, which originates from the high chemical reactivity and the heterogeneous matrix structure. Recently, several ion beam-based techniques have been developed to qualify aluminum mirrors for short-wavelength applications. We give an overview of the state-of-the-art ion beamprocessing techniques for figure error correction and planarization, either by direct aluminum machining or with the aid of polymer or inorganic, amorphous surface films. © The Authors.
- ItemOrientation‐dependent nanostructuring of titanium surfaces by low‐energy ion beam erosion(Chichester [u.a.] : Wiley, 2020) Bauer, Jens; Frost, FrankRegular nanoscopic ripple and dot patterns are fabricated on poly-crystalline titanium samples by irradiation with 1.5 keV argon ions at normal incidence. The morphology of the nanostructures is investigated by scanning electron microscopy and scanning force microscopy. The ripple structures exhibit a saw-tooth cross-section profile. Electron backscatter diffraction experiments are performed to analyze the local grain structure. The study suggests a distinct correlation of the nanostructure morphology to the crystallographic orientation of the titanium surface.