12.2% 171000 190M TOP 1% 154 6300

Both materials are most likely part of the science payload in the constellation for which ZACUBE-2 is a precursor. Structural effects of incident protons and optical transmission measurements in the ultraviolet, visible, and near-infrared were investigated. Scanning electron microscopy (SEM) was used to study the structural effects of proton irradiation on the coating.

Percent transmission of the control sample relative to the glass substrate in the UV-visible and near-IR range. This is to verify that the coating does not compromise the power output of the panel it is intended to protect.

Figure 1. Expected proton, carbon, oxygen, neon and silicon total fluences as a function of energy for the ZACUBE-2 space mission for 4 years in orbit.

Conclusion

Since this experiment was aimed at solar panel shielding, it was necessary to investigate the transparency of the coating. While the substrate was about 90% transmissive over the near ultraviolet light through the visible to near infrared spectrum, the coating was about 73% transmissive in the same range. However, the implementation of this application will require further testing and optimization, including the optical characterization of the coating after irradiation.

Acknowledgements

This is promising for solar panel applications in space, as it shows that this coating can be used as a shield to reduce the contribution of low-energy protons to solar panel breakdown if its permeability is acceptable. Finally, we thank the MSc students of the 2017 F'SATI course entitled "Engineering for the Space Environment" for their simulation of the ZACUBE-2 space environment.

Conflict of interest

Author details

Novel tungsten carbide nanorods: An intrinsic peroxidase mimetic with high activity and stability in aqueous and organic solvents.

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Ion Beams for Nanoscale Optical Data Storage

Introduction

In these computer-related technologies, rapid progress has always required improved solutions for mass data storage. Today's digital memories are subject to lifetime limitations on the order of about 10 years due to physico-chemical deterioration effects at ambient temperatures, so a huge effort is expected in continuously rewriting library archives to freshly made media. Thus, in order for cultural values of any kind to be preserved for future generations, other ways must be found that provide unlimited lifetimes.

The ever-increasing amount of digital data of the order of global zeta bytes will require new storage techniques with ultra-high density, possibly at the nanoscale [2]. Reading such nanometer-sized digital data is also subject to further technical progress. In this chapter, it is presented how ion nanobeams are used to write nanometer-diameter chunks of data on next-generation storage materials, and near-field photon technology is used to read this new type of digital memory.

Optical contrast formation in wide-bandgap materials

Ion beam-induced amorphization of wide-bandgap crystalline materials
Ion beam modification of wide-bandgap amorphous materials

Crystalline films of Group IV elements of the periodic system, such as Si, SiC, and CD (diamond), are most suitable for this new data recording process because of the marked differences in their absorption coefficients in two different phases - crystalline and amorphous (Figure 4). As shown, the optical "contrast window" for SiC and CD (diamond) is shifted towards the ultraviolet part of the spectrum due to the higher bandgap energies. On the other hand, the absolute values of the optical absorption of the starting material and the irradiated material are not important for the achieved optical contrast, but rather the relative difference between the two absorption coefficients.

The sample preparation conditions of a-SiC:H films for this study, along with the ion implantation processing parameters of the samples used, are described elsewhere. This effect is manifested by a shift of the optical transmission edge to longer wavelengths, accompanied by a decrease in the transmission coefficient, as a result of ion implantation. The difference recorded in the optical effect for the three types of ions is attributed to the different chemical nature of the implanted elements and not to the variation of the radiation effect due to the different parameters of the implanted species.

The determination of the absorption coefficient α for the highest Sn+ implantation dose (D = 1017 cm−2) is hindered by the drastic drop in transmission (Figure 6), associated with the metallization determined in this case, and is therefore not shown in the figure. Results for the dose dependence of the Tauc optical gap Ex. for cases of implantation of ions with Ge+ and Sn+ are shown in Table 2 [12]. The observed optical property modification effects caused by ion implantation of a-SiC:H films imply a change in the energy spectrum of the electronic states.

It is also demonstrated that even in the case of Ga+, lower doses of the order of 1015 cm−2 can be sufficient to justify the optical patterning requirements of a-SiC for optical data storage (Figure 8a).

Figure 1. Crystalline-amorphous digital pattern obtainable by writing with a focused ion beam into a thin film of Si, SiC or C D [5].

Optical patterning of wide-bandgap amorphous materials

Focused ion beam (FIB) systems used for nanoscale patterning
Amorphous silicon carbide and tetrahedral amorphous carbon materials
FIB optical patterning of a-SiC and ta-C films

Thus, the change of absorption coefficient can reach ~2 orders of magnitude in the visible light range of the spectrum, even with the application of fairly moderate ion doses, which allows a choice of lower ion doses in view of a reduced cost. Possible applications of these results in the field of submicron lithography and high-density optical data archiving were suggested with respect to the most widespread focused microbeam systems based on Ga+ liquid metal ion sources. Beginning in the late 1970s, ion sources with the necessary properties began to appear, and one type that soon dominated was the liquid metal ion source (LMIS). With an extremely simple construction, high brightness and robust performance, the LMIS has become a central driver in the widespread adaptation of focused ion beam techniques in nanotechnology [20].

In the manufacturing process of LMIS, a tungsten needle with a tip diameter of 5–10 μm can be fabricated by electrochemical corrosion, and then a molten liquid metal is bonded to the tip of the tungsten needle. The electric field intensity of the Taylor cone can be as high as 1010 V/m, and the metal ions in the surface layer of the liquid metal would escape in the form of field evaporation, resulting in an ion beam. A gas injection system is also introduced into the sample chamber to improve the controllability and speed of nanofabrication.

An important feature that supports the environmental stability of the material is the relatively wide band gap, which can be tuned in the range of 1.8–3.0 eV. The high sp3 content in the films results in unique properties that include extreme stiffness (∼70 GPa), chemical inertness, high electrical resistivity, and wide optical bandgap. An increased breaking of the Si-C bond and formation of Si-Ga bonds is detected, implying that Ga replaces the C atom in the C-Si-H bond due to its lower electronegativity [31, 32].

The secondary ion images recorded immediately after the FIB implantation in the vacuum chamber are shown in the figure.

Near-field technique uses for reading nanoscale optical data

Atomic force microscopy characterization of FIB patterns
Scanning near-field optical microscopy (SNOM) of FIB patterns
Optimal optical contrast in FIB-patterned amorphous silicon carbide structures

Some further results of nanometer patterning experiments with Ga+ FIB a-SiC:H samples are shown in Figure 13 [36]. A typical diameter of the tip end of a chemically etched fiber is 100 nm and this determines the optical resolution. As a result of ion implantation, the optical density of the irradiated areas increases; therefore we see them as dark regions.

Topographic images of the irradiated areas were recorded with AFM before performing the SNOM experiments. As already mentioned in the previous section, SNOM can simultaneously provide an optical image of the corresponding topographic image. Compared to the unpatterned areas on the left side of the image, the ion beam irradiated areas are topographically lower while being optically more opaque.

The observed trend of the topographic features of the irradiated areas is the same as that observed by AFM (cf. Fig. 15), while the observed trend of the optical contrasts obtained by SNOM is qualitatively the same as that obtained by conventional optical microscopy (cf. Since the lowest optical contrast value of 0.2 obtained here is quite high, the inhomogeneous optical images of Fig. 17(C) can be attributed to the inhomogeneous optical properties of the material due to contamination or some interference effects, associated with the formation of two-dimensional periodic structures. The optical density of the ion-implanted regions is determined by two competing contributions, the mechanical thinning of the a–SiC:H film due to ion beam milling and the modification of the film properties (i.e., increased optical absorption) due to the ions implanted in the film.

When irradiating a film surface with a beam of accelerated ions, two main possible processes are involved: implantation of the ions into the film [1, 3] and ablation of the film [1, 44].

Figure 14. A schematic diagram of SNOM set-up. Photomultiplier tube (PMT); quartz tuning fork (T); piezoelectric stage for scanning (XY); piezoelectric actuator (Z) [ 42 ].

Conclusions

Subsequently, at higher irradiation doses, the ablation effect begins to dominate the implantation effect, leading to a slow decrease in optical contrast, while topographic thinning still increases. Local optical measurements such as in this work [43] are of particular interest in this regard as they provide a means of studying how sharp the optical contrast change is between the implant zones and nominally unaffected areas in between. It is also noted there for comparison that the change in the optical absorption in this case is slightly smaller than the order of magnitude change obtained in conventional far-field optical measurements in samples in which an unfocused, wide ion beam is implanted [17].

The large optical contrast in the case of far-field optical measurements arises mainly from amorphization changes in the host material, but these are less important here; instead, transmission changes are more strongly determined by the presence of Ga itself and the formation of nanoscale precipitates [33]. Furthermore, the increased surface temperature (including that of the Ga implant) splash from the ion beam irradiated regions will act to limit the achievable transmittance change. The support of the Bulgarian Academy of Sciences and the Maria Curie-Sklodowska University in Lublin, Poland, as well as the assistance of the staff of the Ion Beam Center at Helmholtz-Zentrum Dresden-Rossendorf e.V., a member of the Helmholtz Society imputation be, is gratefully acknowledged.

Fabrication of nanometer optical patterns in amorphous silicon carbide by focused ion beam writing.