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Wurtzite GaN(001)-films were implanted with 195 keV 57Fe ions with a fluence Φ = 4*1016 cm-2 at room temperature. No secondary phase was detected in as implanted state. In order to reduce the implantation damage and to investigate the formation of secondary phases the implanted samples were annealed at 1073 K in a reduced N2-atmosphere (0.5 bar) for several cycles in a minute range. The formation of secondary phases in Fe implanted GaN upon annealing was detected by means of in-situ x-ray diffraction and conversion electron Mössbauer spectroscopy (CEMS). In contrast to our previous experiments with the annealing in a N2-flow at 1.1 bar pressure [3] no α-Fe cluster were found, but Fe3N. The repeatable phase change from Fe3N at room temperature and Fe3-xN at 1023 K was observed by means of in-situ x-ray diffraction. The diffusion of Fe during the annealing process limits the availability of secondary phase and hence the repeatability. The annealing process is accompanied by a strong diffusion of Fe and dissolution of GaN. Oxygen contamination promotes the dissolution of GaN and the formation of β-Ga2O3. The oxidation is confirmed by CEMS. The ferromagnetism in the samples is related to the presence of Fe3-xN. No DMS related phenomena have been observed. The results demonstrate that by variation of pressure phase compositions, other than α-Fe, are possible. It is expected that by the proper choice of annealing conditions specific secondary phases can be created, leading to different electronic, magnetic and other properties.

We present spatially resolved X-ray diffraction pattern of individual GaAs nanorods grown catalyst-free throughout a pre-patterned amorphous SiNx mask onto germanium [111] surfaces. The experiment has been performed using synchrotron radiation using a micro-sized beam prepared by compound refractive lenses. Due to the non-polar character of the substrate the shapes of NR´s appear not uniform and vary between deformed hexagonal and trigonal in symmetry. Because the average diameter of NR´s equals the experimental resolution certain cuts through slightly inclined edges or corners of individual nanorods with lateral size of about 225 nm could be selected using spatially resolved reciprocal space mapping.

The beamline BM20 operated by the Forschungszentrum Dresden-Rossendorf is located at ESRF storage ring and divided into two experimental stations for spectroscopy and diffraction. A double crystal monochromator provides an energy range from 6 to 30 keV. A six-circle goniometer allows different scattering and diffraction methods like XRR, XRD, GID and GISAXS, additionally even in combination with X-ray spectroscopy. Different detector systems (point, one, two dimensional or energy dispersive) as well as an additional detector bank for large area detectors are available. A major part of ROBL-MRH experiments are performed as in-situ X-ray studies using a dual magnetron sputtering deposition chamber equipped optionally with an ion gun for ion beam bombardment and erosion. Using a hemispherical Beryllium dome scattering experiments can be carried out up to 1200°C under vacuum conditions. The focus of the beamline research is on thin film investigations and on new nanostructured materials. X-ray investigations are a very important tool to find the correlation between the functional and the corresponding structural properties that are generating this function and to explain the influence of different deposition conditions, substrate parameters etc. by the underlying physical processes making it possible to design thin films with specific properties. By the use of the deposition chamber for reactive magnetron sputtering thin films of Ti2AlN were for the first time synthesized. Different ways of synthesis, the thermal and phase behavior were investigated [1, 2]. A key element for the development of a new generation of solar cells are nanocrystalline materials. In-situ studies of the growth of SiO2/GeOx multilayers were carried out to create Ge nanocrystalls by subsequent thermal decomposition or directly by sputtering at elevated temperatures. [1] C. Höglund et al.; Appl. Phys. Lett., 90, 174106, (2007). [2] M. Beckers et al.; Appl. Phys. Lett., 89, 074101, (2006).

Towards an increase of the magnetic recording density, materials with a high magnetic anisotropy are strongly recommended to overcome the physical limits due to superparamagnetism. For this reason, FePt alloys are widely studied because of the excellent magnetocrystalline anisotropy (KU ~ 5-8 x 10-7 erg/cm3) and large magnetic moments at 300K. [1] But, for perpendicular recording media, a (001) preferential orientation, perpendicular to the layer surface, is required. 10 and 15 nm Fe55Pt45 layers were deposited by dual magnetron sputtering on amorphous SiO2 / Si (001) substrate, varying the deposition methods, form co-deposition to monolayers sequence deposition, and working gas, from Ar to Xe, at 0.3 Pa. The Ar plasma is more energetic than the Xe one: it is characterized by sputtered atoms with a mean energy of about 12 eV and Ar reflected neutrals, reaching a mean energy of about 100 eV when backscattered from the Pt target. This energy budget that enhance the surface adatom mobility during deposition (few eV are required), and create vacancies (E > 40 eV), that decrease the phase transition temperature to 450°C for thin layers. [2] But, the impact of energetic atoms supports a vertical layers intermixing resulting in a randomly oriented FePt A1 structure at RT. Subsequent Rapid Thermal Annealing at 750°C is completely transforming the layer into the L10 phase, with a coercivity field HC = 1 T, but introducing a weak perpendicular magnetic anisotropy, not evidencing any difference between the deposition techniques. The reduction of the plasma energy, by using Xe as working gas, is not decreasing the layer magnetic properties (HC = 1 T) after annealing, but strongly enhance the (001) preferential orientation, with a dispersion of the (001) direction around the surface normal of 6°, already in the co-deposition experiment. The layer by layer technique, associated with Xe plasma, supports the (001) layer orientation after RTA at 750°C, underlining the importance to reduce the elements diffusion path to an atomistic scale. [3] [1] H. Kanazawa, G. Lanhoff, T. Suzuki, J. Appl. Phys. 87 (2000) 6143 [2] V. Cantelli, J. von Borany, A. Mücklich, Shengqiang Zhou, J. Grenzer, Nucl. Instr. and Meth. B, 257, 1-2 (2007) 406-410. [3] M. L. Yan, N. Powers, D. J. Sellmyer, J. Appl. Phys. 93, 8292 (2003)

The formation of surface-nanostructures with a characteristic size ranging from several nanometer up to microns has attracted significant interest in the last decades in the context of fabrication of novel opto-electronic and storage devices. One kind of those nanostructures are wave-like patterns (ripples) produced by an interplay between a roughening process caused by ion beam erosion (sputtering) of the surface and smoothening processes caused by surface diffusion. In this contribution we report on investigations of patterned Si (001) surfaces after irradiation with Xe-ions using ion-energies up to 70keV. During the sputtering, an amorphous surface-layer is formed followed by a rather sharp interface towards crystalline material, showing the same morphology as the surface. The structures of the amorphous layer and the amorphous-crystalline interface were studied by means of grazing incidence- small angle scattering (GISAXS) and diffraction (GID) using synchrotron-radiation. We found that the crystal structure at the interface is expanded along the ripples, caused by the creation of defects inside the surface region, whereas this expansion is strongly reduced across the ripples, which can be explained by an anisotropic defect distribution close to the amorphous-to-crystalline interface.

Unexpected ferromagnetism has been observed in carbon doped ZnO films grown by pulsed laser deposition [Phys. Rev. Lett. 99, 127201 (2007)]. In this letter, we introduce carbon into ZnO films by ion implantation. Room temperature ferromagnetism has been observed. Our analysis demonstrates that (1) C-doped ferromagnetic ZnO can be achieved by an alternative method, i.e. ion implantation, and (2) the chemical involvement of carbon in the ferromagnetism is indirectly proven.

Nanowires and chains of nanoparticles are of emerging interest in nano-electronics, nano-optics and plasmonics as well as for their monolithic integration into microelectronic devices; CoSi2 is a promising material due to its CMOS-compatibility in micro-electronics technology. It shows metallic behaviour with low resistivity and high thermal stability. It is well known that cobalt disilicide films can be formed in silicon by implanting Co in stoichiometric concentration and a subsequent annealing procedure. Ion beam synthesis allows the fabrication of epitaxial buried or surface CoSi2 layers on silicon. Sub-micron patterns with feature dimensions much smaller than 100nm can be directly produced by writing focused ion beam (FIB) cobalt implantation. We have studied the strain of the Si host lattice in the surrounding area of a single nanostructures depending on their crystallographic orientation using high resolution x-ray diffraction in combination with a highly focused (≈ 3µm) x-ray beam at the beam line ID1 at the ESRF. The pattern measured directly on the wire shows a small peak indicating tensile strain (approx. −1.4%). This feature can be only found if the beam focused on a nano wire whereas its intensity changes with the layer width.

The exchange coupling strength as a function of the buffer layer thickness is investigated for several carefully chosen seed materials. The crystal microstructure of the ferromagnetic(FM)-antiferromagnetic(AF) interface is directly related to the roughness and dimensionality of the buffer layer surface, which scales not only with such parameters as a texture and grain sizes but can be discussed as well in the frame of the wetting behavior of subsequent films. Particularly, it is shown that strong wetting between the substrate and the next layer can decrease the surface dimensionality and improve the growth conditions for the subsequent films. Thus, the smoothness of the FM-AF interface improves significantly which leads to a much stronger exchange coupling across the interface. In addition, it is demonstrated that the magnitude of the exchange bias is proportional to the grain sizes distribution, which is in good agreement with theoretical predictions.

Nanoscaled materials comprised of organic and inorganic components are becoming more and more important in nanotechnology due to the diversity of applications. The use of self-assembling organic systems as part of such a hybrid material, serving as template for the fabrication of arrays of inorganic nanoparticles, is an attractive approach for the development of new materials. Especially the proteinaceous bacterial surface layers (S-layers) that envelop bacterial cells are attractive for fabricating and patterning of nanostructures. These proteins are composed of protein monomers with the ability to self-assemble into two-dimensional arrays. The regular distributed pores of these paracrystalline arrays work as binding sites for various metals and offer ideal structures for the formation of regular distributed metallic nanoclusters of a defined size (15). Such arrays are very attractive for technical applications ranging from the development of novel catalysts to biomedical applications, development of innovative filter materials, the programmed assembly of nanometre scale electronic devices, and optical industry (7, 9). Another approach is the embedding of S-layer proteins into ceramics thus producing metal binding functionalized nanocomposites (12). Our current work focuses on the synthesis and characterization of different S-layer templated inorganic nanoclusters. Due to quantum size effects nanosized grains often exhibit changed physical and chemical properties in comparison to bulk material. We demonstrate the fabrication of catalytic active nanoparticles such as ZnO. The photocatalytic properties of ZnO-particles are interesting for their application as nanoscaled catalytic material, i.e. for the degradation of pharmaceutical residues that are released in environment.

The formation of surface-nanostructures with a characteristic size ranging from several nanometer up to microns has attracted significant interest in the last decades in the context of fabrication of novel opto-electronic and storage devices. One kind of those nanostructures are wave-like patterns (ripples) produced by an interplay between a roughening process caused by ion beam erosion (sputtering) of the surface and smoothening processes caused by surface diffusion. In this contribution we report on investigations of patterned Si (001) surfaces after irradiation with Xe+ -ions using ion-energies up to 40keV. During the sputtering, an amorphous surface-layer is formed followed by a rather sharp interface towards crystalline material, showing the same morphology as the surface. The structures of the amorphous layer and the amorphous-crystalline interface were studied by means of grazingincidence - small angle scattering (GISAXS) and diffraction (GID) using synchrotron-radiation. We found that the crystal structure at the interface is expanded along the ripples, caused by the creation of defects inside the surface region, whereas this expansion is strongly reduced across the ripples. This different relaxation may play a driving role in pattern formation at the interface.

Ion irradiation of Ni80Fe20/Ta multilayers induces an interfacial mixing of these two materials, which subsequently leads to a suppression of the ferromagnetic properties. In order to quantify the structural change grazing incidence x-ray reflectometry has been used. The ion irradiation induced intermixing has been studied by means of TRIDYN simulations. The broadening of the interfaces due to intermixing causes an enrichment of Ta in Ni80Fe20 and finally an amorphization of Ni80Fe20 above a Ta concentration of 10 to 20 percent [1]. Consequently the ferromagnetic properties are altered or even suppressed completely for high enough ion fluences. It is observed that the critical ion fluence for a complete suppression of the ferromagnetism depends sensitively on the number of interfaces. It is demonstrated that pure magnetic microstructures can be easily fabricated by local ion irradiation without changing the substrate topography. [1] J. Fassbender et al., Nucl. Instr. and Meth. in Phys. Res. B 248, 343 (2006).

A nonmagnetic to ferromagnetic transformation is observed when a Pt/C multilayer stack (total thickness ~ 60 nm, thickness of individual layers ~ 2 nm) with a small amount of Fe impurity, grown on a glass substrate, is irradiated with 2 MeV Au ions [1]. Using a subnanometer depth resolution technique it was found that ion beam induced preferential migration of Fe from C to Pt layers and the subsequent formation of FePt nanoparticles were responsible for the magnetic transformation [2]. Fe concentration in the C layers decreases exponentially with increasing ion fluence with simultaneous increase of the coercive field in the magnetic hysteresis loop. An example of ion beam induced opposite transformation, namely, ferromagnetic to nonmagnetic, is shown using a Si(5nm)/Ni(10 nm)/Si trilayer system, where ion-beam-induced atomic displacements across the Si/Ni interfaces form a mixed Ni1-xSix layer leading to a ferromagnetic to nonmagnetic transformation. In this case, with increasing ion (30 keV Ga) fluence the coercive field in the hysteresis loop decreases with increasing ion fluence and eventually magnetization is destroyed at a critical fluence. Having identified the critical fluence, a focused ion beam (FIB, 30 keV Ga) was used to fabricate a lateral multistrip pattern in this thin (10 nm) magnetic layer with alternate magnetic/nonmagnetic strips of nanometer dimensions. Magnetooptical Kerr effect microscopy reveals the anisotropy of the magnetic domain structure along and perpendicular to the FIB-patterned strips. In the light of the observed phenomena, future developments in the area of nanotechnology, such as ultrahigh density magnetic storage devices, single-electron spin-valve transistors etc. will be discussed. Some nanoscale structures that can be fabricated using FIB will offer the possibility of exploring new scientific aspects, such as magnons in ordered ferromagnetic spot arrays, in these structures. [1] B. N. Dev, S. Bera, B. Satpati, D. K. Goswami, K. Bhattacharjee, P. V. Satyam, K. Yamashita, O. M. Liedke, K. Potzger, J. Fassbender, F. Eichhorn and R. Groetzschel, Microelectronic Engineering 83, 172 (2006). [2] S. Bera, K. Bhattacharjee, G. Kuri and B. N. Dev Phys. Rev. Lett. 98, 196103 (2007).

Under certain conditions ion beam bombardment on semiconductor surfaces leads to well-defined morphological structures in the nanoscale range caused by a self-organization process. Due to the ion impact as a start the surface-adjacent layer is amorphized before a periodical wave-like rippled structure on the surface as well as at the amorphous-crystalline interface is developed. So far we found that the ripple wavelength linearly scales with the ion energy in a range of 5 to 70 keV (50 to 300 nm). Furthermore, we try to evaluate the ripple patterns from the point of homogeneity and uniformity. Therefore, we defined a quality factor for the amplitude and a correlation length for the wavelength to characterize the structures over a larger scale. We used a routine to extract the ripple amplitude from the Atomic Force Microscopy (AFM) images. In order to determine the correlation length we prosecuted Grazing Incidence Small Angle X-Ray Scattering (GISAXS) measurements. Also, we asked for the mechanisms behind the formation of ripples. The investigation of the amorphous-crystalline interface gives a first hint. The subsurface structure has been identified by both Transmission Electron Microscopy (TEM) and Rutherford backscattering (RBS). Applying two different ion types for the formation of rippled patterns we could identify clear differences in the structure of the amorphous layer.

In thin film magnetism surface and interfacemorphologies are important sources of magnetic anisotropy. This can be either due to the reduced coordination of step edge atoms (intrinsic contribution) or due to magnetic stray fields emanating from the film corrugation (extrinsic contribution). Low energy ion erosion is perfectly suited to create a periodic surface modulation (so-called ripples) on the nanoscale. By changing the primary energy of the ions the ripple periodicities can be varied from 20 to 150 nm. Subsequently, thin magnetic films are deposited on these template systems in order to investigate the influence of the surface morphology on the induced magnetic anisotropies. For small ripple periodicities a strong uniaxial magnetic anisotropy is found which rapidly decrease for larger ripple periodicities. In the case of Permalloy (Ni81Fe19) the induced anisotropy can be more than a factor of 20 larger compared to the intrinsic anisotropy of flat Permalloy. The microscopic origin of this effect will be discussed.

ZnO(0001) single crystals annealed in high vacuum have been investigated with respect to their magnetic properties. Annealing at mild temperatures up to 773 K leads to ferromagnetic properties without any transition metal doping. Fe ion implantation at low temperatures leads to similar results. However, no evidence for the relevance of the Fe magnetic moment for the generation of ferromagnetism was observed. Nevertheless, the degradation of the magnetization with time is much less pronounced for the implanted crystals with respect to the purely annealed samples.

We measured the thermal expansion coefficient of a vertically stacked multi-quantum-well structure buried under a thick GaAs top layer before and after lateral patterning of the GaAs top layer. After patterning the thermal expansion coefficient of the whole multi-quantum-well structure differs from that of the planar structure by about 20%. Based on calculations in terms of methods of finite elements the effect is explained by the influence of the strain field originating from the bottom edges of the etched nanostructure. Due to the long range nature of this strain field the strain release within the individual quantum wells changes as a function from the distance from the valley.

Magnetic micro- and nanostructures are of great interest due to the fundamental physics involved if the dimension is shrunk as well as due to the application potential in storage, sensing and logic devices. For the creation of such structures typically lithography is used in combination with either etching or lift-off processes. In both cases the magnetic element is defined by isolated topographic structures. An alternative approach relies on the local ion irradiation of a magnetic multilayer structure. As a result of the ion irradiation an interfacial mixing between ferromagnetic layers and non-magnetic interlayers is achieved which consequently reduce and finally fully suppress the ferromagnetism. In order to demonstrate this behaviour Ni80Fe20/Ta multilayers with a different number of repetitions are used. The structural and magnetic properties are investigated by x-ray reflectivity and magneto-optic Kerr effect magnetometry as a function of noble gas irradiation fluence and number of multilayer repetitions. The experimental results are accompanied by TRIDYN simulations. In addition magnetic microstructures are created by means of large area ion irradiation through lithographically defined masks. By choosing the irradiation fluence the exchange coupling between the microstrucutres can be switching on and off. The magnetic domain configuration in these elements is imaged by means of Kerr microscopy and magnetic force microscopy. Thus the modified magnetization reversal curves can be interpreted on the basis of the micromagnetic domain structure.

Ion beam bombardment on semiconductor surfaces leads to welldefined morphological structures in the nanoscale range. Due to the impact of ions a self-organized wave-like surface structure develops. Ion bombardment causes an amorphization of a surface-adjacent layer of several nanometers and creates a periodical structure on the surface as well as at the amorphous-crystalline interface. We investigate the dependence of the periodicity on the crystallography of (100) silicon bombarded with Xe+ ions, the ion beam incidence and the azimutal angle of the sample surface. So far we found that the ripple wavelength scales with the ion energy in a range of 5 to 70 keV. In order to understand the initiation of the ripple formation we also ask the question which role the initial surface structure plays. Therefore we investigate the formation of ripples on pre-structured and rough surfaces such as wafers with an intentional miscut. Therefore, we not only introduce a certain initial roughness but also vary the orientation of the (100) lattice plane in respect to the surface. We try to distinguish between ion beam induced surface defects (sputter erosion) and the influence of the crystalline Si lattice (strain) on the ripple formation.

alpha,beta-dicyano substituted beta, beta*-dibutylquarterthiophene (DCNDButQT) was synthesized and fully characterized by 1H-NMR and 13C-NMR, elemental analysis, UV-visible spectroscopy, DSC, TGA and cyclic voltammetry. The band gap energy (deltaEg) calculated from cyclic voltammetry data was found to be 1.97 eV, which is in the range of semiconductor materials (deltaEg < 3.0 eV). DCNDButQT was deposited on different substrates (Al2O3, SiO2, TiO2) by vacuum deposition and solution-cast methods. The structure of the thin films analysed by AFM and XRD showed different morphology depending on cast method. The spin-coating and drop-casting films showed amorphous structure, whereas the vacuum-deposition films exhibit a fine crystalline structure. AFM of vacuum-deposition film revealed the formation of well-ordered terrace structures, the step between adjacent terraces is about 1.5 nm.

Two types of highly soluble oligothiophene based swivel cruciform are presented as semiconducting materials in OFETs. Transistor made from one of these oligomers exhibited mobilities of more than 0.01 cm^2/Vs and current on/off ratio of >105. This is among the highest values reported to date for wet processed OFETs utilizing oligothiophenes. In fact, the OFET-mobilities are comparable to values extracted from pulse-radiolysis time resolved microwave conductivity (PR-TRMC) experiment, indicating that carrier trapping is insignificant. In depth examination of the morphological, optical characteristics and thermal stability of the materials were carried to obtain information on the packing of the oligomers in the layer. Finally, the correlation between the transistor performance and the crystallinity of the layers is addressed.

The morphological evolution of surfaces during ion-beam irradiation has attracted a significant interest due to possibility of the development and the controlling of selforganization in nanostructures. Pattering and texture on nanometer length scale at metal and semiconductor surfaces has become a topic of intense research. In particular the surface and subsurface ripple formation under 40Ar+ ion-beam irradiation of Si (100) crystal has been studied recently. Strong ripple formation has been found for an irradiation energy of 60keV and incident angles around 60degree. During implantation a corrugated surface layer is formed, consisting of a strongly damaged, amorphous near-surface layer followed by a nearly sinusoidal shaped interface towards the crystalline material. In the present work, we investigate the onset and evolution of ripple-formation as function of implantation energy and incidence angle of the ion beam.

Ripple formation with a spatial periodicity in the sub-micrometer range on obliquely ion-bombarded solid surfaces has become a topic of intense research in the context of fabrication of nanoscale textured materials [1]. Ion-beam induced ripples are produced by the interplay between a roughening process caused by ion beam erosion (sputtering) of the surface and smoothening processes caused by thermally or ion-induced surface diffusion. Recently we have shown that Ar- ion irradiation of Si (001) surfaces under an angle of about 60° with respect to surface normal and using ion energies of about 60keV results in periodic crystalline ripple formation where the crystalline ripples are covered by a partially amorphous surface layer [2, 3]. In this contribution we report on investigations of patterned Si (001) surfaces after irradiation with Xe-ions using ion-energies between 5 and 40keV. Besides AFM measurements, the structure of the amorphous layer and the amorphous-crystalline interface were studied by means of grazing-incidence small-angle scattering (GISAXS) and grazing-incidence diffraction (GID) using synchrotron-radiation. The data reveal that both surface and crystalline ripples appear for all ion energies used. These ripples show asymmetric side-facets where the degree of asymmetry decreases for increasing ion-energy. They show short-range ordering; the ripple wavelength and thickness of the amorphous layer increase as a function of the ion-energy. Acknowledgement: One of the authors (A.B.) would like to thank the ESRF for financial support and the ID01 beamline-staff for providing beamtime and valuable help. [1] M.A. Makeev, R Cuerno and A.-L. Barabasi, Nuc. Inst. and Meth. in Phys. Res. B 197, 185 (2002). [2] S.Hazra, T.K. Chini, M.S. Sanyal, J. Grenzer U. Pietsch , Phys. Rev. B 70, 121307(R) (2004). [3] S. Grigorian, J. Grenzer, D. P. Datta, S. Hazra, T.K. Chini, M. K. Sanyal and U. Pietsch, Appl. Phys. Lett 89, 231915 (2006).

Intersubband transitions in semiconductor quantum wells (QW) are crucial for mid-infrared lasers, detectors, and modulators. New compound materials such as lattice matched InGaAs/AlAsSb and strain compensated InGaAs/AlAs, both grown on InP, feature large conduction band discontinuities (>1eV) and allow the extension of the available wavelength range into the near infrared. Such short wavelengths require narrow QWs (

Ion-induced ripple structures on silicon, x-ray measurements and TEM The formation of periodic surface structures varying from several nanometers to a few micrometers caused by ion-beam sputter erosion processes on semiconductor surfaces has attracted significant interest for the fabrication of laterally structured materials on a nanoscale. We started systematic investigations of the rippled surface produced by Xe irradiation applying AFM. The subsurface structure has been identified by both TEM and depth resolved X-ray scattering methods such as GID. Furthermore the crystal structure of semiconductor surfaces should also kept clearly in mind. There is a strong evidence that the formation of ripples via ion beam erosion depends on preferred crystallographic directions of the silicon lattice.

Ion beam implantation is one of the major technologies in the semiconductor industry. Although there have been a lot of technological applications there is relatively little known about the structural changes of semiconductors after ion beam implantation. Of particular interest is the creation of lateral nanostructures using different methods of ion beam implantation. One method is to exploit the phenomenon of self-organization during the Ar+ implantation using an oblique ion beam bombarding the sample surface. This results in the growth of the periodic wavelike or ripple like morphology which is produced as a result of the interplay between a roughening process caused by the ion beam erosion (sputtering) of surface and a smoothening process caused by thermal or ion-beam-induced surface diffusion. At least the developing surface structures can be well described in terms of the Bradley-Harper model and respective extensions. Lot of investigations is going on to understand the formation of such nano-structures but mostly looking on the top surface. However, the ion energy dissipation takes place below the surface. Thus the investigation of the interface between the almost amorphous top layer and the underlying crystalline material is important for the understanding of pattern formation. Detailed studies on the ion induced ripple formation on Si have revealed that they appear only in a limited range of incident angles. The ripple wavelength appears to be linearly dependent on the ion energy and varies in between several nm and hundreds of nm when the ion energy changes from 0.5 to 100 keV. If the ion beam energy was increased up to the 100keV range one-dimensional ripple structures on Si (100) surfaces with wave lengths up to the micro meter range have been observed.Recent investigations using TEM and depth resolved X-ray diffraction methods discovered that the ripples at the surface are followed by a nearly sinusoidal shaped buried interface between the strongly damaged, not completely amorphous near-surface region and the crystalline material. Depending on the chosen energy and the irradiation dose the “amorphous” layer could be reach a thickness of 100nm and corresponds fairly well to the end of range distance of implanted ions.

L10 ordered, c-axis oriented FePt thin films belong to the most promising ferromagnetic materials for future magnetic storage media. The coercivity of such films can be significantly improved if changing from homogeneous to granular films or even to arrays of FePt nanoislands. This contribution describes the formation of self-assembled FePt nanoislands at single-crystalline Si(001) or amorphous SiO2/Si substrates after conventional DC magnetron sputtering. FePt is sputtered (0.5 Å/s) from an alloy target at a substrate temperature of approx. 300°C to an equivalent film thickness of 10 nm. The island formation and the low-temperatureL10 ordering are stimulated by an ultrathin Ag buffer layer. The well-separated FePt islands exhibit a quite regular size of typical 20 - 30 nm. X-ray diffraction investigations reveal the existence of L10 ordered FePt grains; a preferred orientation of the grains has been found for the islands deposited at the crystalline substrate. However, it is noteworthy that the island formation is obtained both for crystalline and amorphous substrate surfaces which is of significant practical relevance. The enhanced coercivity of patterned FePt films with respect to homogeneous FePt layers has been confirmed by SQUID measurements. The formation of the nanoisland structure is discussed in terms of the adatom surface mobility, the influence of energetic ions and the ratio of surface to stress-energy during thin film deposition.

Intersubband transitions in semiconductor quantum wells (QW) are crucial for mid-infrared lasers, detectors, and modulators. New compound materials such as lattice matched InGaAs/AlAsSb and strain compensated InGaAs/AlAs, both grown on InP, feature large conduction band discontinuities (>1eV) and allow the extension of the available wavelength range into the near infrared. Such short wavelengths require narrow QWs (

L10 ordered c-axis oriented FePt thin films belong to the most promising ferromagnetic materials for future magnetic storage media. The layer coercivity can be significantly improved if changing from a homogeneous to granular film morphology, or even to arrays of FePt nanoislands. This contribution describes the formation of self-assembled FePt nanoislands by conventional DC magnetron sputtering deposition on single-crystalline Si(001) or amorphous SiO2/Si substrates. The deposition was performed with substrate temperature of 320 °C and a working pressure of 0.4 Pa. In these conditions the deposition rate for FePt is about 0.4 Å/s, leading to an equivalent film thickness of 6 nm. An ultra thin Ag buffer layer, deposited in the same working conditions but with a deposition rate of about 1 Å/s, that, because of its nanoparticulate morphology, is supporting the islands formation. The well-separated FePt islands exhibit a quite regular size of typical 20 – 30 nm, for both employed substrates. X-ray diffraction analysis reveals the existence of L10 ordered FePt phase. However, it is noteworthy that the islands formation is obtained both for crystalline and amorphous substrate which is of significant practical relevance. The enhanced coercivity of patterned FePt films with respect to homogeneous FePt layers has been confirmed by SQUID measurements. The formation of the nanoisland structure is discussed in terms of the adatom surface mobility, the influence of energetic ions and the ratio of surface to stress-energy during thin film deposition.

We report on in-situ investigations of a recrystallization process of an ion beam-induced rip-pled silicon. The one dimensional ripple structure was created by 40Ar+ ion irradiation with dose of ~5x1017 ions/cm2 under an angle 60° with respect to the surface normal at an energy of 60 keV. At the surface the induced ripples have a period and an amplitude of about 915nm and 80nm, respectively. Structure and morphology of ripples were studied by two x-ray grazing in-cidence scattering methods, transmission electron microscopy and atomic force microscopy. X-ray grazing-incidence amorphous scattering pattern were recorded in-situ in a range from 250°C to 750°C. Up to about 500°C mainly we found a single broad scattering maximum cor-responding to the Si(111) inter-planar distances. At higher temperature these peaks becomes sharp and intense indicating the onset of a re-crystallization process in the amorphous top layer. Two processes were found, a formation of crystalline islands at the top of amorphous surface ripples and a growth of polycrystalline twins close to the former amorphous-crystalline inter-face.

Investigations of ripples morphology of Ar+ implanted silicon are presented. Particularly we have measured the degree of amorphization as a function of implantation dose by means of x-ray grazing amorphous scattering (GIAS). For perfect silicon crystals GIAS shows monotone decreasing background intensity versus the 2theta scattering angle. For implanted samples we find two broad peaks indicating short-range ordering of amorphous material changing with the penetration depth of probing x-ray. The appearance of embedded crystalline domains is indicated by additional sharp peaks on top of the amorphous scattering. 2theta- scans taken at different azimuthal angles of sample display strong anisotropy of amorphous scattering which only slightly changes with dose. Based on these results we suggest a model of dose-dependent amorphization. The strong damage of crystalline structure takes place along particular crystallographic directions and strongly reveal for low doses, before it becomes complete amorphous and mostly uniform at high doses of implantation. This mechanism can be used as a hint for the appearance of a ripples amorphous-crystalline interface found at these structures. We would like to thank S. Hazra and T.K. Chini for research collaborations. This work was supported by the DST-DAAD India-Germany

We report on the study of a two-dimensional dot lattice structures which was produced on GaAs and Si (001) substrates using a Ga+ focused ion beam in normal incidence with a spot size of about 50 nm, an energy of 25 keV and a dose of 1014 cm-2. The fabricated 2D-lattice structures consist of dots of almost circular shape with an area of about 2000 nm2 and a period of 250x250 nm2. The whole implanted area has a size of less than 0.2 mm2. We have investigated the interaction of the implanted ions with the host lattice as a function of the implantation conditions using grazing incidence diffraction at the ID10 and ID1 beam lines at the ESRF. The low-dose implantation creates interstitials and vacancies below the surface generating a weak displacement field resulting in a 2D periodical strain field in case of Si substrate. For the GaAs substrate we found a much more complex scattering pattern which depends on the in-plane orientation of the 2D dot lattice with respect to the crystallographic orientation of the crystal. A much stronger scattering contrast can be found if the 2D dot lattice misaligned by 14° degree. A simulation taking the interaction between the implanted ions and the host lattice into account shows an enhanced channelling of the ions into low-index crystallographic directions. Thus the dependence of the profile of implantation damage on the crystalline structure influences the scattering patterns.

The morphological evolution of surfaces during ion-beam irradiation has attracted significant interest due to possibility of the evelopment and the controlling of self-organization in nanostructures. Pattering and texture on nanometer length scale at metal and semiconductor surfaces has become a topic of intense research. In particular the surface and subsurface ripple formation under 40Ar+ ion-beam irradiation of Si (100) crystal has been studied recently. Based on transmission electron microscopy (TEM), atomic force microscopy (AFM) and x-ray analysis a dramatic effect of the ripple formation was found at an irradiation energy of 60 keV. Apart from the crystalline part, the amorphization process is very important for understanding the amorphous-crystalline interface and the ripple formation mechanism. The dose of the ion beam was varied in the range from low 3e16 up to high 7e17 ions/cm^2 at an incident angle of 60° and an energy of 60 keV. Keeping the optimized irradiation parameters constant we have measured the degree of amorphization as a function of Ar+ dose by means of x-ray grazing incidence amorphous scattering (GIAS). For irradiated samples we found two broad peaks indicating a short-range ordering of amorphous material which does what with the penetration depth of probing x-ray. GIAS profiles probed at different azimuthal angles display a strong anisotropy of the amorphous scattering. The strong damage of the crystalline structure takes place along particular crystallographic directions. This is for the directional anisotropy: and strongly reveal for low doses, before it becomes completly amorphous and mostly uniform at high doses of implantation. Such behavior can be explained taking into account the anisotropy of the crystalline material and orientation of the ion beam with respect crystallographic orientation of the substrate material. This work was supported by the DST-DAAD India-Germany Collaborative Program. We are grateful to ID1 beamline staff for the support at ESRF.

A pentathiophene-based swivel cruciform, which allows rotation between the cruciform arms, was synthesized. Homogeneous microcrystalline films were processed from solution, and field-effect transistors utilizing this dimer gave hole mobilities up to 0.012 cm2/V·s.

The mechanism of ion-induced ripple-like structure formation at top-surface and at buried crystalline surface is being studied extensively by several techniques. Using the technique of grazing incidence x-ray scattering, we have measured the degree of amorphization in the region between buried-crystalline and top-surface ripples in silicon as a function of argon-ion dose. Two broad peaks of the amorphous scattering profiles were probed by varying the penetration depth of x-ray and revealed short-range ordering. Our results show that the strong damage of crystalline structure caused by ion bombardment takes place along particular crystallographic directions and displays ion dose dependent behavior.

Due to the high uniaxial anisotropy L10-ordered FePt is currently the most favored candidate for future high density storage applications. With respect to a feasible fabrication technology, it is necessary (i) to produce such films on amorphous substrates, and (ii) to enable a low processing temperature (T

Magnetron sputtered film stacks of 5nm Ta/50(15)nm NiMn/20nm Fe19Ni81 /5nm Ta deposited at Si/SiO2 substrates were subsequently irradiated with He+ ions (30 keV, 1e15 - 3e16 cm-2). Using synchrotron X-ray diffraction and reflectivity, the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L10 phase during annealing was studied. The transformation to a dominating L10 ordered NiMn film takes place between 300-400°C irrespective of the irradiation. Ion irradiation at low fluences offers beneficial effects with respect to a reduction of the mosaicity for both, the NiMn and the permalloy film, and a smoothening of internal interfaces.

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We report on the strain and defect analysis of lateral nanostructures created in Ga and Si substrates which was performed utilizing the method of X-ray grazing-incidence diffraction. The substrates were patterned by focused ion beam implantation technique using a Ga or AuGeSi liquid metal ion source.

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The spatial coherence of hard X-rays provided by a bending magnet of the storage ring BESSY II was investigated performing Young's interference experiment. The interference pattern was created by the diffraction of two 2 µm pinholes drilled into a thin tantalum foil by focused ion sputtering. Using an energy-dispersive detector with an energy resolution of 200 eV the interference pattern were detected simultaneously between 5 keV < E < 16 keV scanning a 5 µm pinhole through the detector window. The set-up is suitable to characterise the coherence properties of the beamline in a simple manner, i.e. to deduce parameters as the effective source size, the coherence length and the visibility. For the present case the visibility is near 100% at 5 keV and decreases to 20% at 16 keV.