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The Rossendorf Beamline ROBL at the ESRF is operated since 1998 by the Institute of Resource Ecology and Ion Beam Physics and Materials Research of the HZDR. In 2011-2012 the optics of the beamline such as mirrors double crystal monochromator and diagnostic was modernized to meet future experimental demands. The Materials Research Station is focusing on in-situ investigations. These are in thin film synthesis by magnetron sputtering, in-operando measurements on lithium ion batteries, surface modification by ion implantation and high temperature investigations using reactive atmosphere like in chemical vapor deposition (CVD) processes. Iron nano-crystals are a common catalyst in the CVD growth reaction of carbon nano tubes. These crystals were formed by dewetting of the corresponding iron thin film at raised temperatures. Under reaction condition different iron phases such as Fe3C, alpha-Fe and gamma-Fe were detected. Their concentrations are strongly varying before, after and during the CVD process. This leads to the conclusion that besides Fe3C also metallic iron is catalytically active [1]. In graphene CVD nickel and copper are commonly used as catalyst. High resolution diffraction data were collected at reaction temperature. The lattice parameter was calculated using Lebail fit, corrected due to small shifts in sample surface temperature by the thermal expansion determined before. The results show a lattice expansion of nickel under different CVD atmospheres, indicating an uptake of hydrogen and carbon on interstitials in the metallic Ni. The carbon uptake is only partially reversible, but additional hydrogen can be assimilated .

AlxGa1xAs grown on GaAs is known to be almost perfectly lattice matched with a maximum lattice mismatch of 0.14% at room temperature and even less at temperatures of 700 C–800 C. However, as layer structures for edge-emitting diode lasers exhibit an increasing overall thickness of several microns of AlxGa1xAs, e.g., diode lasers comprising a super-large optical cavity, the accumulated elastic strain energy increases as well. Depending on the growth temperature the formation energy of dislocations can be reached, which is limiting the pseudomorphic growth. In this regard, the thermal expansion coefficient difference between layer and substrate is an important parameter. We utilize in situ curvature measurements during growth of AlxGa1xAs by metal-organic vapour phase epitaxy to determine the thermal expansion coefficient a. The curvature change with increasing layer thickness, as well as with wafer temperature at constant layer thickness is used to assess a. This is compared to ex situ temperature dependent X-ray diffraction measurements to obtain a. All determined values for α are in good agreement, yielding αAlAs = 4.1×10−6 K−1 for a given GaAs linear thermal expansion coefficient of αGaAs = 5.73×10−6 K−1.

Ion beam techniques are widely used in semiconductor and thin film industry for introducing dopant atoms into materials. Ion implantation is characterized by fast dynamic processes related to the formation and relaxation of collision cascades (100fs – 100ps), finally leading to the formation of different types of defects (vacancies, self-interstitials, clusters, etc.). The material undergoes also other strong modifications. For instance, implantation leads to a strained layer which expands in the direction normal to the substrate surface. This is due to the point that the bulk material prevents any lateral macroscopic expansion; and as a result the thin irradiated layer is subjected to an in-plane biaxial compressive stress due to the continuous accumulation of defects. Unfortunately, ion irradiation is a very fast process and it is almost impossible to monitor it in-situ with the present x-ray sources. However, the accumulation of damage and the diffusion of defects and implanted species are much slower process and can be observed in-situ using a time resolution in the order of seconds. An in-situ ion beam implantation experiment was set up at ROBL/MRH at ESRF. For this purpose an ion gas source with a maximal acceleration voltage of 5keV was mounted on a sputtering chamber. To realize sufficient volume damage the ion energy was further raised by increasing the electrostatic potential of the irradiated sample to 20keV using an additional power supply. Si and Al2O3 (001)-oriented substrates were irradiated using He+ at an ion flux of about 10^{13}ions/cm^{2}s at room temperature. Reciprocal space maps were measured to study the evolution of the implanted layer.

The radiation damage induced by neutrons and α-decay in YSZ (yttria-stabilized zirconia) was simulated using synchronized Zr+ & He+ dual ion beam implantation. [1] The measured damage profiles consist of two peaks which agree well with the calculated profiles of excess point defects generated by the collision cascade. The spatial separation of vacancy and interstitial defects is known as the “½Rp” effect describing the vacancy accumulation in the region at half of the projected ion range. This special implantation-related effect has to be considered carefully during the evaluation of experimental investigations which simulate isotropic irradiation effects caused by α-decay. Comparing the amount and type of radiation defects in single and dual beam implanted YSZ reveals that the implanted helium is released from the sample during simultaneous dual beam irradiation instead to be trapped by the created open volume defects at ½Rp region. According to first-principles total energy calculations, helium is mobilized and released via a vacancy-assisted trapping/detrapping mechanism induced by the simultaneous Zr+ ion implantation. The release of helium during room temperature dual beam irradiation demonstrates one of the suitable characteristics of YSZ that contributes to its excellent radiation hardness, since helium in YSZ can accumulate in undesirable helium bubbles and results in local surface swelling and lift-off. [1] Xin Ou et al. PHYSICAL REVIEW B 86, 224103 (2012)

Fission gas retention or release has a critical impact on the function of advanced nuclear materials. Helium trapping in, and release from, radiation defects induced by neutrons and by α decay in YSZ (yttria-stabilized zirconia) is experimentally simulated using synchronized Zr+ and He+ dual ion beam irradiation. The measured damage profiles consist of two peaks which agree well with the calculated profiles of implantation induced excess point defects. This special implantation related effect has to be carefully considered in the Evaluation of experimental investigations which simulate isotropic irradiation effects such as α decay. First-principles calculations show that helium is energetically favorable to be trapped by Zr vacancies in YSZ. Implanted helium alone in YSZ is accumulated in undesirable helium bubbles and results in local surface swelling and lift-off. However, under dual beam irradiation helium is released from vacancy defects and is out-diffused at room temperature. Helium is mobilized by a vacancy-assisted trapping/detrapping mechanism induced by the simultaneous Zr+ ion implantation. This behavior avoids the deleterious helium bubble formation and contributes to the suitable application characteristics of YSZ which result in its excellent radiation hardness.

Equiatomic FeRh thin films with varying thickness have been prepared on MgO (100) substrates via molecular beam epitaxy (MBE). The optimization of the stoichiometry was monitored using XRD, RBS and AES while the magnetic properties were probed using SQUID magnetometry. XRD results evidence a well ordered CsCl-type crystal structure. By increasing the annealing temperature of the films, the structural quality of the films also increases. Moreover, the known first order phase transition at ~350 K from an antiferromagnetic (AF) to a ferromagnetic (FM) state slightly shifts towards higher temperatures. M-H loops of films annealed at 800 ∘C or 850 ∘C recorded at 300 K show an opening, which is likely related to the magnetic field-induced AFM-FM phase transition. Residual low-temperature ferromagnetic moments are of unknown origin, but likely related to strain or diffusion effects at the surface or interface.

In this article we show how to produce materials consisting of regularly ordered Ge quantum dots in amorphous alumina matrix with the controllable Ge quantum dot size, shape, spacing, crystalline structure and degree of regularity in the Ge quantum dot ordering. The production of such materials is achievable already at room temperature by magnetron sputtering deposition of a (Ge+Al2O3)/Al2O3 multilayer. The materials show large, size-dependent blueshift of the photoluminescence peak and enhancement in the oscillator strength caused by confinement effects. The materials also show advanced mechanical properties due to alumina matrix, and their internal structure is shown to be highly resistive to irradiation with energetic particles for a large range of the irradiation parameters. The reported materials have excellent potential for application in demanding environments for light harvesting.

Helmholtz-Beamline at XFEL

We report on an in-situ and ex-situ X-ray investigations of a self-assembled growth of Ge nanocrystals embedded in a dielectric matrix forming BCC- or FCC-like superstructures. Germanium quantum dots (QD’s) embedded in dielectric matrices like SiO2 [1] or Al2O3 [2] have numerous interesting properties e.g. a strong quantum confinement. They could be used in optoelectronic devices and memory systems. Such a material can be a key element for the development of a new generation of solar cells extending the spectral range for electrical energy generation, either for an up and/or down conversion of the incident photons or simply as one part of a multilayer stack arrangement.

YSZ (yttria-stabilized zirconia) with cubic phase is a promising nuclear material. YSZ has excellent radiation resistance and chemical stability and can be applied for the inter matrix layer of fuel cells or for the covering and storage of nuclear waste. The effect of irradiation on YSZ has been intensively investigated in recent years via single beam implantation.[1,2] Most of experimental works were performed to simulate the radiation damage from alpha particles by He+ implantation [2] or to simulate the neutron radiation damage and the damage introduced from alpha recoils by implantation of heavy ions. [1] In fact, the radiation damages created by the simultaneous dual beam implantation of Zr+ and He+ ions is much more adequate to reflect the real irradiation conditions. However this case is rarely reported in the literature due to the experimental restrictions. In this work the dual beam facility in Rossendorf is used for the investigation of the radiation damage in YSZ created either by simultaneous implantation of Zr+ & He+ or by separate single beam implantation. The samples were analyzed by a variety of methods such as Rutherford backscattering spectrometry in channeling mode, high resolution x-ray diffraction, positron annihilation spectroscopy, nanointendation and transmission electron microscopy. The results show that the excitation by the additional Zr+ implantation can activate and enhance the out diffusion of the simultaneously implanted He. The release of He.from YSZ substrate, instead to be trapped by implantation induced vacancies generated by the heavy Zr+ ions, avoids the formation and growth of He bubbles. Such bubbles make the material hard and brittle. In this way the ability of YSZ for the stable inclusion of nuclear waste in the long term is verified. Possible mechanisms are discussed. [1] S. Moll et al., Journal of Applied Physics 105, 023512 (1999). [2] G. Velisa et al., Journal of Nuclear Materials 402, 87 (2010).

We present ion beam erosion experiments on Si(001) with simultaneous sputter co-deposition of steel at 660 K. At this temperature the sample remains remains within the crystalline regime during ion exposure and pattern formation takes place by phase separation of Si and iron-silicide. After an ion fluence of F ≈ 5.9 × 1021 ions m−2 investigations by atomic force microscopy and scanning electron microscopy identify sponge, segmented wall and pillar patterns with high aspect ratios and heights of up to 200 nm. Grazing incidence X-ray diffraction and transmission electron microscopy reveal the structures to be composed of polycrystalline iron-silicide. The observed pattern formation is compared to the one in the range from 140 K to 440 K under otherwise identical conditions, where a thin amorphous layer forms due to the ion bombardment.

We present an investigation of ordering and PL properties of Ge QDs in an alumina matrix formed by magnetron-sputtering deposition of (Ge+Al2O3)/Al2O3 multilayers. The self-assembly process occurs during the deposition and results with the formation of three-dimensional quantum dots lattices. We investigate the dependencies of the size and ordering properties on the deposition temperature, rotation of the substrate holder and direction of the incoming flux of Ge during the deposition process. The results of the investigation show that tuning the deposition temperature enables manipulation with QD sizes and their mutual distances. We show that the ordering of QDs obtained by deposition on fixed substrate holder leads to the formation of a quantum dot crystal, while the rotation of substrate holder leads to randomly rotated domains with regular ordering. The observed phenomenon is explained by a combination of the surface morphology effect on the nucleation positions of Ge quantum dots with a lateral inhomogeneity of the ad-atom flux. In addition, we show that the resulting quantum-dot lattices have size-dependent PL properties.

We report on an in-situ X-ray investigation of a self-assembled growth of Ge nanocrystals embedded in a dielectrical matrix forming a BCC-like super structure. Such a material could be a key element for the development of a new generation of solar cells extending the spectral range for energy conversion. Using small angle scattering techniques and X-ray diffraction the formation of crystalline Ge nanoparticles during growth and annealing was studied in-situ at the BM20 beam line at that ESRF using a process chamber for magnetron sputter deposition and annealing that can be inserted into the goniometer. A single some 100nm thick Ge+Al2 O3 layer using magnetron sputtering was deposited at an elevated substrate temperature. The self-assembly during growth or subsequent annealing results in the formation of a well ordered three-dimensional BCC-like quantum dot lattice within the whole deposited volume. The formed nanocrystals are very small in size (< 4.0𝑛𝑚 with a very narrow size distribution and a large spatial density. The parameters of the formed super structure can be directly influenced by changing the deposition parameters. The self-ordering of the quantum dots is explained by diffusion mediated nucleation and surface morphology effects.

We report on the fabrication of pseudomorphic wurtzite Gax Mnx N grown on GaN with Mn concentrations up to 10 % using molecular beam epitaxy. According to Rutherford backscattering the Mn ions are mainly at the Ga-substitutional positions, and they are homogeneously distributed according to depth-resolved Auger-electron spectroscopy and secondary-ion mass-spectroscopy measurements. A random Mn distribution is indicated by transmission electron microscopy, no Mn-rich clusters are present for optimized growth conditions. A linear increase of the c-lattice parameter with increasing Mn concentration is found using x-ray diffraction. The ferromagnetic behavior is confirmed by superconducting quantum-interference measurements showing saturation magnetizations of up to 150 emu/cm3 .

Nanowires and chains of nanoparticles are of emerging interest in nanoelectronics, nano-optics and plasmonics as well as for their monolithic integration into microelectronic devices. Epitaxial buried or surface CoSi2 layers in silicon can be formed by implanting Co in stoichiometric concentration and subsequent annealing. Ion beam synthesis allows the fabrication of submicron pattern, which can be formed either directly by a mass separated writing Co focused ion beam (FIB) or indirectly by a Ga FIB in combination with a thin Co film on the rear side of the Si wafer, providing the Co for the nanowire formation by diffusion. We have studied the strain of the Si host lattice around a single nanostructure depending on their crystallographic orientation using high-resolution x-ray diffraction and TEM. The X-ray experiment was carried out using a highly focused beam (~0.5µm) at the beam line ID01 at ESRF. Surrounding a wire a peak was found indicating a tensile strain of approx. -1.4%. The CoSi2 peak intensity is strongly modulated by moving from one wire to another. Moreover the diffuse scattered intensity around the Si bulk reflection is increased and is getting even more enhanced between the wires. A possible mechanism lying behind the CoSi2 structure formation is the lattice relaxation by stable dislocation loops. A zigzag like defect structure, characteristic for the formation of 311 defects, was identified by TEM at the grain boundary between the CoSi2 nanowires and the Si bulk.

Recently, there is a rise of interest in fabrication and investigation of nanometre sized magnetic objects. Magnetic properties can easily be manipulated by ion beam implantation. Focused-ion beam (FIB) techniques are one way to combine both nanopatterning and implantation. The main difference between standard ion implantation and FIB implantation is the beam current density, which could lead to differences in the structural and magnetic properties. The aim of this work is to compare both implantation techniques in terms of structural changes and to relate them to magnetic property changes. For our investigation we have used 50 nm thick non-ordered nano-crystalline permalloy (Ni81Fe19) films modified by a 30 keV Ga+ ion beam. The magnetic properties were characterised via magneto-optic Kerr effect measurements at room temperature. Both types of implantation demonstrate a degradation of saturation magnetisation with increasing ion fluence. For structural investigations we have applied several techniques. We have used the advantage of non-destructive X-ray techniques to study the structural changes. Besides X-ray diffraction, providing the long-range order information, EXAFS measurements to probe the local structure were performed. Both methods are statistical ones, whereas TEM imaging provides information on a local scale. Implantation leads to a crystallite growth from ~12 nm up to ~25 nm and further texturing of the material towards (111) direction at almost constant lattice parameter. In the case of FIB implanted samples the TEM images show crystallites growing through the entire film at high implantation fluences. The EXAFS analysis shows an almost perfect near-order coordination, corresponding to an fcc cell; only in the vicinity of the Ga atoms a small local deviation could be observed. In general FIB and standard implantation demonstrate similar behaviour with a shift in the fluence value. These results let us conclude that the simple presence of the Ga atoms is the dominating effect leading the degradation of saturation magnetisation.

For the development of nano-optical devices nano wires (NW) are of emerging interest. One of the most important steps in the fabrication of Si devices is doping using ion beam implantation. However, this may lead to a distortion of the NW’s crystalline structure or even to an amorphization. A subsequent annealing procedure is necessary to recover the crystalline structure. The advantage of implanted Si NW’s is that the electrical conductivities are significantly higher than MBE-grown in-situ doped ones [1]. NW’s of about 100nm in diameter and 100..400 nm in length, nominally undoped, were MBE grown on Si(111) using Au as a growth-initiator. We followed the structural changes of the NW’s caused by implantation and annealing. We used rapid thermal annealing up to a temperature of 1100∘ C of about 30 seconds to remove a possible damage induced by implantation. Diffraction experiments were carried out at the ID01 ESRF beamline using a microfocused X-ray beam in combination with a 2D detector to obtain 3D diffraction patterns. Our experiments have shown that defect structure and form of the investigated NW’s change after implantation and annealing.

The Rossendorf beamline (ROBL) BM20 at the European Synchrotron Radiation Facility in Grenoble is operated by Helmholtz Zentrum Dresden Rossendorf since 1999. ROBL belongs to Collaborative Research Group (CRG) of beamlines and provides two third parts of beamtime for users from HZDR, while the one third of beamtime is offered to external users selected by ESRF advisory committee. Two experimental stations are placed at the beamline: one is dedicated to materials research, while the second station is designed for spectroscopic investigations of actinides and other radionuclide’s. Material Research Hutch (MRH) is equipped with high precision heavy duty 6-circle diffractometer used for structural characterization of thin layers, nanoparticles, interfaces and analysis of other structural properties of solid state materials. Experimental installations allow users to perform different types of complex experiments including in-situ deposition, annealing in vacuum or gas environment, spectroscopic measurements, following (electro) chemical reactions or morphology transformations using available fast detectors and supplementary devices. Radiochemistry Hutch (RCH) possesses highly specialized safety system making possible investigations of alpha-emitting radionuclides by x-ray absorption spectroscopy (XAS) methods. (More information at www.hzdr.de). Extensive upgrade of beamline optics, which assets in gain of beam brilliance, homogeneity and accessible energy range is scheduled in 2011. According to our calculation, new monochromator combined with toroidal x-ray mirrors will increase beam intensity up to 3 orders of magnitude in respect to the present value. Energy tunable in the range from 6 up to 35 keV allows users to realize element sensitive spectroscopic measurements like XANES and EXAFS, as well as x-ray scattering investigations (XRD, XRR, GID or GISAX) in anomalous mode. MRH detector installations include novel 1D position sensitive and 2D image Dectris detectors, two modern energy dispersive detectors from KETEK and Bruker Axes, as well as traditional scintillator counters. Besides of that, experimental setup can be tailored with equipment loaned from ESRF instrument pool. Summarizing the overview of Rossendorf beamline, we would admit broad spectrum of research feasible at ROBL stations: all possible diffraction measurements combined with spectroscopic analysis can be performed during in-situ experiments involving film deposition, different types of annealing, chemical reactions etc. Upcoming modernization of x-ray optics will significantly improve brilliance of the beam, giving outstanding possibilities for researchers in their most challenging experiments.

Samoorganizacija Ge nanočestica u amorfnoj Al2O3 podlozi

We report on the evolution of wave-like nanopatterns induced by Xe+ ion irradiation at high fluences in an energy range between 5 keV and 70 keV. By means of atomic force microscopy a statistical analysis of the ripple amplitude and wavelength was carried out showing that the periodicity and the amplitude of the rippled structures follow a linear dependence on the energy. However, the evolution of the rippled patterns clearly differs for the lower and higher ion energies. For energies below 25 keV we observed almost no fluence dependence of the wavelength and amplitude in the investigated range of 1...8·1017 cm-2. But for energies above 25 keV and fluences above 1·1017 cm-2 coarsening was found. At energies larger than 50 keV Xe the ripple structures display a saturation regime for fluences higher than 5·1017 cm-2. Investigations with cross-sectional high resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed the appearance of Xe filled inclusions at ion energies above 25 keV. This result correlates with an almost stable ratio of the ripple wavelength to the ripple amplitude of about 30 occurring above a threshold fluence of 2·1017 cm-2 and above 25 keV. These results indicate that there is a certain threshold energy and fluence above which a stable form of the investigated wave-like structure is build up. This is possibly caused by the formation of noble gas inclusions at higher ion energies.

Nanocomposite materials become of ever increasing importance in numerous fields of science and technology such as tribology, plasmonics, spintronics, sensing, catalysis, including the strategic quest for renewable energies regarding photovoltaics, solar collectors or thermoelectrics. The macroscale properties of nanocomposite materials are strongly influenced by their nanoscale morphology. Therefore a control of this nanoscale morphology is of major importance. Here we present a GISAXS study of C:Ni nanocomposite thin films grown by ion beam assisted deposition (IBAD). IBAD combines Ar+ ion beam co-sputtering of a C-Ni target to produce film forming species with a simultaneous irradiation of the growing film with low energy (50-140 eV) Ar+ ions. Depending on the ion energy and metal content this leads to different 3D morphologies such as dispersed nanoparticles, tilted nanocolumns or spatially ordered compositional nanopatterns. These structures show their characteristic fingerprints in GISAXS patterns. A theoretical approach to reproduce such patterns will be presented. The results show that low energy ions provide a powerful means to induce the self-organizion leading to the formation of 3D compositional nanopatterns.

Focused ion beam irradiation is a versatile tool that can be used for magnetic nanostructuring. In this work we compare both FIB irradiation and a standard implantation taking into account their distinctive irradiation features. A 50nm thick permalloy layer (Ni80Fe20) irradiated with different Ga+ ion fluences was used for the investigations. The structure was studied via XRD and EXAFS measurements carried out on the ESRF ROBL and ID01 facilities. Additionally TEM and magneto-optic Kerr effect magnetometry were performed. Both types of irradiation demonstrate a similar behaviour: increasing the ion fluence causes a further material crystallization and a decrease of the magnetic moment. However FIB irradiation leads to a stronger crystallite growth due to the high current densities used.

We investigate the influence of ion beam parameters on the ripple formation on Si(001) surfaces after bombardment with Xe+ ions of 25 keV kinetic energy using a scanning ion beam system. By combining grazing incidence x-ray diffraction, small angle scattering and x-ray reflectivity, we show that during ion irradiation with 70◦ off-normal angle of incidence, changing the size of the irradiated area leads to an increased number of defects at the interface towards crystalline material. At 65◦ angle of incidence, the ripple amplitude grows.

Ion-beam eroded self-organized nanostructures on semiconductors offer new ways for the fabrication of high density memory and optoelectronic devices. It is known that wavelength and amplitude of noble gas ion-induced rippled structures tune with the ion energy and the fluence depending on the energy range, ion type and substrate. The linear theory by Makeev [1] predicts a linear dependence of the ion energy on the wavelength for low temperatures. For Ar+ and Xe+ it was observed by different groups [2] that the wavelength grows with increasing fluence after being constant up to an onset fluence and before saturation. In this coarsening regime power-law or exponential behavior of the wavelength with the fluence was monitored. So far, investigations for Xe ions on silicon surfaces mainly concentrated on energies below 1keV. We found a linear dependence of both the ion energy and the fluence on the wavelength and amplitude of rippled structures over a wide range of the Xe+ ion energy between 5 and 70keV. Moreover, we estimated the ratio of wavelength to amplitude to be constant meaning a shape stability when a threshold fluence of 2x1017cm−2 was exceeded.

Focused ion beam (FIB) techniques are one way to modify locally the properties of magnetic thin films. In previous works it was demonstrated that focused-ion-beam irradiation causes a considerable grain growth in magnetic thin films under certain conditions and therefore a change of their magnetic properties [1]. Although the grain growth can be already qualified by simple REM images a crystallographic tool is needed for a qualitative analysis. We used the advantage of nondestructive X-ray diffraction to study the grain growth. A magnetic thin film of 50nm thick permalloy film (Fe0.2Ni0.8) sputtered on Si was used for the investigations. We have analyzed two simple parameters such as the grain size and the microstrain depending on the ion dose and beam current. Due to the very small structures created by focused-ion-beam techniques (usually less then 0.4x0.4mm2 size) an optimized X-ray laboratory setup with a focused X-ray beam of 200µm was used. [1] C.M. Park and J.A. Bain, J. Appl. Phys. 91, 6830(2002).

The structure control, especially at the nanoscale, is of the primary importance in the field of the materials science of thin films. Here, the hyperthermal ion induced self-organization caused by phase separation during the carbon-transition metal (Ni, Cu) thin film growth is reported. The films have been grown by ionized physical vapour deposition using filtered cathodic vacuum arc. Influence of the metal type, film composition, ion energy and incidence angle is studied. The film morphology has been determined by transmission electron microscopy and grazing incidence small angle x-ray scattering. At these growth conditions, atomic displacements are caused solely by impacting energetic ions, resulting in phase separation in an advancing surface layer. If the metal amount surpasses some critical value, this layer switches to an oscillatory mode and a nanoscale precipitation pattern emerges. The results show that for the perpendicular incoming depositing ion incidence the C:Ni film structure consists of alternating self-organized nickel carbide and carbon layer oriented parallel to the film surface. Moreover, the ion induced atomic mobility is not random, as it would be in the case of thermal diffusion, but conserves to a large extent the initial direction of the incoming ions, resulting in a tilting of the periodic precipitation structures for the oblique ion incidences. The metal nanopatterns no longer align with the advancing surface, but with the incoming ions. While both type of films show tilted structures, for C:Cu films the ‘tilted-lying’ transition is observed when increasing Cu content. We establish a dependence of the nanopattern morphology on the growth parameters and demonstrate a method for controlling the nanopatterning. The results are discussed on the basis of the interplay between thermodynamically driven phase separation and energetic ion induced ballistic effects. Application of this concept opens new ways for the bottom-up nanostructure control for composite materials.

Nano wires and chains of nano particles are of emerging interest in nanoelectronics, nano-optics and plasmonics as well as for their monolithic integration into microelectronic devices; CoSi2 is a promising material due to its CMOS-compatibility that shows metallic behavior 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. It has been shown that ion beam synthesis allows the fabrication of epitaxial buried or surface CoSi2 layers on silicon. Submicron patterns can be directly produced by a writing focused ion beam (FIB) cobalt implantation. The formation of continuous nano wire structures follows always the direction [1]. 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 (~1µm) X-ray beam at the beam line ID01 at the ESRF. The crystalline nano wire is embedded into the Si matrix and shows a tensile strain of about 1.4%. This feature can be only found if the beam focused on the nano wire itself. We will show that it is possible to investigate a single nano wire of a size of below 50 nm. The CoSi2 peak intensity is strongly modulated if we move from one wire to an other. Moreover the diffuse scattered intensity around the Si bulk reflection is increased and is getting even more enhanced between the wires (see Figure 1). A possible mechanism, the formation of stable dislocation loops, lying behind the formation of CoSi2 wires will be discussed. [1] Ch. Akhmadaliev, B. Schmidt and L. Bischoff, Appl. Phys. Lett. 89, 223129 (2006); Ch. Akhmadaliev, L. Bischoff and B. Schmidt; Mat. Sci. & Eng., C26, 818 (2006).

In recent years, the creation of surface-nanostructures due to ion-beam sputtering has gained much interest due to the possibility to pattern large surface areas with tunable morphologies in a short time. 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 strengthening processes caused by surface diffusion [1]. 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 an interface towards crystalline material, showing the same morphology as the surface. The structure and morphology of the amorphous layer and the amorphous-crystalline (a/c) interface were studied using synchrotron-radiation. Whereas the combination of grazing-incidence small angle scattering (GISAXS) and X-ray reflectivity can be used to study the surface morphology with large statistical sampling (Fig. 1), grazing incidence diffraction (GID) gives access to the buried crystalline material and probes both the morphology and the crystal structure of the a/c interface. We found that for non-optimal sputter conditions, defects are created at the a/c interface, leading to a net expansion of the crystal along the ripples [2]. This inclusion of defects can be reduced if optimal sputter conditions are chosen, leading to an increasing ripple amplitude rather than the formation of defects. Referenzen [1] M. A. Makeev et al., Nucl. Instrum. Methods Phys. Res., Sect. B 197, 185 (2002) [2] A. Biermanns et al., J. Appl. Phys. 104, 044312 (2008)

We report on an in-situ GISAXS study of the evolution of nanocomposite magnetic L10-FePt/Ag layers as a function of the Ag amount. Simultaneously, the formation of the hard ferromagnetic L10 phase has been detected by x-ray diffraction at grazing incidence. The methodology applied is a sequential magnetron sputtering deposition of FePt and Ag at 400°C on an a-SiO2 substrate: the deposition chamber is equipped with two Be windows to allow x-ray penetration and mounted on the six-circle goniometer of ROBL – BM 20 at the ESRF. [1] V. Cantelli, J. von Borany, N.M. Jeutter, J. Grenzer, Adv. Eng. Mat. 11, 478 (2009).

Ferromagnetic semiconductors with high Curie temperatures and large coercivity are very promising materials for spintronic applications. An approach to fabricate ferromagnetic GaMnAs is Mn ion implantation into GaAs followed by pulsed laser annealing (PLA) [1]. Magnetic Mn ions which occupy the Ga sublattice sites form acceptor centers and pro-vide free holes for the mediation of the parallel align-ment of the magnetic moments of the Mn ions. For a strong ferromagnetic interaction, activation of the Mn acceptor dopants over their thermodynamic equilib-rium solubility is necessary. Long time, rapid thermal, and also flash lamp annealing processes take too long to realize a large enough free hole concentration by activation of Mn acceptor dopants. From a thermody-namical point of view, the PLA process is beside the more expensive LT-MBE process the best route to fabricate oversaturated ferromagnetic GaMnAs. We investigated the influence of the implanted Mn concentration and PLA conditions on the structural and magnetic properties of GaMnAs thin films. We per-formed heatflow calculations to visualize the fast tem-peratue quenching during the PLA process [2]. Using SQUID magnetometry, we reveal a strong decrease of the saturation magnetization with increasing number of laser pulses during PLA (Fig. 1). However, the crystal-line quality is improved after several laser pulses. This has been verified by RBS (Fig. 2) and XRD measure-ments. The decrease of saturation magnetization after several laser pulses may be caused by the continuous Mn cluster formation during each PLA cycle. [1] M. A. Scarpulla. et al. APL 82 (2003) 1251 [2] D. Bürger et al. PRB 81 115202 (2010)

The formation of quantum dot crystals by multilayer deposition has been reported and explained satisfactorily only in crystalline materials, so far. Here we demonstrate a method for the growth of quantum dot crystals in amorphous matrices. The ordering of the positions of quantum dots is induced by the deposition of a multilayer on a periodically rippled substrate at an elevated substrate temperature. During the deposition, the quantum dots self-arrange following the morphology of the substrate. The result is a formation of well ordered lattice of Ge quantum dots in amorphous silica matrix. We have investigated the ordering of the dots by grazing-incidence small-angle X-ray scattering and we found that the distance of the dots in the multilayer interfaces close to the rippled surface indeed equals the ripple period. However, in more distant interfaces the dot-dot distance approaches the value for non-rippled substrate and the dot ordering is slightly less pronounced. This finding confirms the beneficial influence of the rippled substrate on the ordering of quantum dots in an amorphous matrix.

We report on Xe+ induced ripple formation at medium-energy on single crystalline silicon surfaces of different orientation using substrates with an intentional miscut from the [001] direction and a [111] oriented wafer. The ion beam incidence angle in respect to the surface normal was kept fixed at 65° and the ion beam projection was parallel or perpendicular to the [110] direction. By a combination of atomic force microscopy, X-ray diffraction and high resolution transmission electron microscopy we found that the features of surface and the subsurface rippled structures such as ripple wavelength and amplitude and the degree of order do not depend on the surface orientation as assumed in recent models of pattern formation for semiconductor surfaces.

Self-organization at the nanoscale is a key issue in modern material science as it promises a potential route to commercially scalable production of functional nanomaterials. Here we present the growth-structure study of self-organized layered arrays of carbon encapsulated Ni nanoparticles grown by means of pulsed filtered cathodic vacuum arc deposition. Influence of the oblique ion incidence and Ni content on the film morphology is investigated. The film morphology has been determined by transmission electron microscopy (TEM) and grazing incidence small angle x-ray scattering (GISAXS) while C/Ni ratio was determined by means of nuclear reaction analysis. The C:Ni films with the Ni content in the range of ~6-50 at.% are considered. The results show that for the perpendicular incoming depositing ion incidence the C:Ni film structure consists of alternating self-organized nickel carbide and carbon layer oriented parallel to the film surface. However, for the oblique ion incidence the layered structure tilts in relation to the surface. The tilting angle and periodicity strongly depends on the deposition angle as well as on the Ni content. Combined TEM and GISAXS analysis shows that the film cross-sections can be described by two density modulation waves advancing with the growing film surface – one towards the incoming ions, another one with the weaker amplitude moving in roughly perpendicular direction. The results are discussed on the basis of the interplay between thermodynamically driven phase separation and energetic ion induced ballistic effects. Such structures show significant anisotropy which can be considered for tribological, optical, magnetic or magnetotransport applications.

The structure control, especially at the nanoscale, is of the utmost importance in the field of the materials science of thin films. Here, the hyperthermal ion induced self-organization caused by phase separation during the carbon-transition metal (Ni, Cu) thin film growth is reported. The films have been grown by ionized physical vapour deposition using filtered cathodic vacuum arc. Influence of the metal type, film composition, ion energy and incidence angle is studied. The film morphology has been determined by transmission electron microscopy and grazing incidence small angle x-ray scattering. At these growth conditions, atomic displacements are caused solely by impacting energetic ions, resulting in phase separation in an advancing surface layer. If the metal amount surpasses some critical value, this layer switches to an oscillatory mode and a nanoscale precipitation pattern emerges. We demonstrate that the ion induced atomic mobility is not random, as it would be in the case of thermal diffusion, but conserves to a large extent the initial direction of the incoming ions, resulting in a tilting of the periodic precipitation structures for the oblique ion incidences. The metal nanopatterns no longer align with the advancing surface, but with the incoming ions. We establish a dependence of the nanopattern morphology on the growth parameters and demonstrate a method for controlling the nanopatterning. Application of this concept opens new ways for the bottom-up nanostructure control for composite materials.

The properties of magnetic metals such as saturation magnetization and magnetic anisotropy can be modified in a controllable manner by energetic ions [1]. GaMnAs is a well known magnetic semiconductor. The ability to tune the magnetic properties of magnetic semiconductors is an important issue in future semiconductor devices. Here we tailored the magnetism of GaMnAs films by He+ ion irradiation. The GaxMn1-xAs films with a Mn concentration of 5% and the easy axis of magnetization lying in-plane have been grown on GaAs substrates by LT-MBE. He+ ions of 650 keV were used to place the peak of damage into the GaAs substrate, so that the GaMnAs epilayer lies in the relatively uniform part of the damage profile. We show that the coercivity can be increased (Fig.1) from 50 Oe to 165 Oe when the dose reaches 3×1014/cm2 ~ 6×1014/cm2. Meanwhile, the saturation magnetization at 5 K is only reduced slightly to 22 emu/cm3 compared to non-irradiated GaMnAs films with a saturation magnetization amounting to 27 emu/cm3. Magneto-transport results indicate that the sheet resistance is increased by about 4 times compared to the non-irradiated GaMnAs film with a sheet resistance of 103 Ω. The irradiated GaMnAs still has an in-plane easy axis of magnetization at 5 K, but the anisotropy energy is much decreased. When the dose increases to 1×1015/cm2, no M-H hysteresis has been probed. Our study demonstrates the tailoring of magnetism and magnetoresistance in GaMnAs films by He+ ion irradiation. [1] J. Fassbender and J. McCord, J. Magn. Magn. Mater. 320 (2008) 579–596

The last few years have seen an increasing interest in in-situ investigations on thin filmor nano structured systems. The advantages of these methods are clear: The (x-ray)investigations are done at the time of the phase or structure formation. Misleading results of ex-situ investigation due to altering or decomposition of the sample were avoided, metastable intermediate states were observed and additionally these experiments are less time consuming.The presented experiments were carried out at Material Research Station of the instrument BM20 at ESRF that is operated by the Forschungszentrum Dresden- Rossendorf. Our experimental station focuses on in-situ studies using different X-Ray diffraction and scattering methods in the energy range of 6 to 30 keV. The experiments can be combined with XRF and electrical resistivity measurements on demand. Two different topics of synthesis and processing are given. First, results on the formation of isolated Ge nano particles with well defined size by disproportion of germanium oxides in a silicondioxid matrix at higher temperatures of corresponding multilayer system were presented. Such materials are potential candidates for solar cells, extending the working spectral range for energy conversion. The size and ordering of the Ge nano crystallite can be controlled by the layer thicknesses as well as growth and annealing temperatures. Different in-situ growth techniques like reactive DC magentron sputtering of Si and RF- sputtering of SiO2 are compared. Secondly, the phase behavior of different metal catalyst onto different buffer layers for the carbon nanotube and graphene synthesis will be shown and discussed. Hereby diffraction experiments under controlled and reactive atmosphere were performed. As shown by in-situ investigations process were characterized on-line and structural as well as functional properties are correlated directly with each other. This increases the comprehension of synthesis and processing of functional materials.

Focused ion beam irradiation can be used as a tool for creation of magnetic nanos-tructures. Previous studies have shown that FIB irradiation of thin metallic films could induce significant grain growth and therefore modify magnetic properties [1-2]. In this work we compare X-ray diffraction studies with magnetic properties that were characterized by magneto-optic Kerr effect sensing both the in-plane and the out-of-plane components of the magnetization. A 50nm thick permalloy layer (Ni80Fe20) irradiated with different fluences of Ga+ ions was chosen for the investigations of grain size and microstrain. Due to the small irradiated areas produced by FIB irradiation XRD measurements were carried out on an optimized X-ray laboratory setup with a focused X-ray beam of 200µm as well as on the ESRF ID01 facility using a 1µm focused beam. Figure 1a shows rocking curves of the (111) permalloy reflection and demonstrates the material texturing with increase of ion fluence as there is a narrowing in FWHM and a rise of intensity. Low irradiation fluences up to 6.24*10E15 ions/cm2 modify the material and induce crystal-lite growth, whereas larger fluences completely destroy the crystalline structure. A further material crystallization should improve the magnetic properties. Due to the incorporation of Ga+ ions into the lattice additional softening of the permalloy film occurs and leads to the degradation of magnetic properties. In figure 1b a corre-sponding saturation Kerr rotation measurement is shown. It demonstrates a decrease of the magnetic moment with increasing ion fluence. [1] C.M. Park and J. A. Bain., J. of Appl. Phys. 91, 6830 (2002). [2] W.M. Kaminsky et al., Appl. Phys. Lett. 78, 1589 (2001).

We report on an in-situ study on the evolution of granular magnetic L10 -FePt/Ag layers deposited by magnetron sputtering on an amorphous SiO2 substrate. Using synchrotron radiation we investigated the nanostructure growth during deposition as function of the Ag thickness by the simultaneous detection of the cluster growth and of the formation of the hard ferromagnetic L10 -phase applying grazing incidence small-angle X-ray scattering (GISAXS) and X-ray diffraction, respectively. FePt/Ag nanoparticle were prepared using a dual magnetron deposition chamber, equipped with two Be windows to allow X-ray penetration, that was mounted on the six-circle goniometer of the Rossendorf beam line (ROBL BM20) at the ESRF (European Synchrotron Radiation Facility). The possibility to tune X-ray beam energy, to reduce air scattering and absorption, together with the high brilliance of the synchrotron source had made it possible to obtain a reliable GISAXS signal and to control the cluster morphology the initial stage [1]. [1] V. Cantelli, J. von Borany, N.M. Jeutter, J. Grenzer, Adv. Eng.Mat. 11, 478 (2009).

Dilute magnetic oxides are expected to play a key role in the development of electronics using the electron spin rather than its charge as information carrier. Indium oxide (IO), a transparent conductive material, is of potential interest for spintronics [1] due to its unique combination of magnetic, electrical, and optical properties. Highly oxygen deficient Cr:IO co-evaporated films revealed ferromagnetism [2]. In present work, we report the post-growth treatment effect on the structural, electrical, magnetic, and optical properties of Cr-implanted IO films. Cr is chosen as a dopant because of its large magnetic moment in the ionic state, and its antiferomagnetic nature in the bulk, ruling out the extrinsic origin of the ferromagnetism if Cr metal segregation occurs. It is non-trivial to form any ferromagnetic secondary phase of Cr oxide. Polycrystalline and amorphous, ca. 300 nm thick IO films were grown on SiO2/Si substrates using reactive pulsed magnetron sputtering and then implanted with Cr+ ions (1, 2, 3, 4 and 5 at% of Cr). The implantation energy was 120 keV. The magnetic-field dependence of magnetization of 2%Cr:IO showed a weak ferromagnetic behavior at 5K. A reasonable model for the Cr implanted IO films has been developed to extract optical constants from spectroscopic ellipsometry data below 3 eV. [1] C. Scarlat et al., Proceedings IBMM 2008, August 31- September 05, 2008, Dresden, Germany [2] J. Philip et al., Nature materials 5, 298 (2006).

The request for room-temperature diluted magnetic semiconductors resulted in a large interest in GaN containing transition metals. Recent investigations have shown that beside of the real dilute state spinodal decomposition as well as the formation of secondary phases may play an important role in the discussion of the origin of the ferromagnetism [1, 2]. In this study, the dynamics of formation of secondary phases is investigated on GaN epilayers deposited on sapphire and implanted with 57Fe+ ions (3, 8 and16 • 1016 cm−2) at room temperature. Samples were annealed at 750° – 1200° C in N2 and Ar flow for durations between some ms and some minutes. The formation of secondary phases in Fe implanted GaN upon annealing a N2-flow was detected ex-situ by means of x-ray diffraction and Mössbauer spectroscopy and supported by SQUID magnetometry. During annealing in reduced N2 atmosphere the reversal phase change from Fe3N at room temperature to Fe2.4N at 1023 K was observed by means of in-situ x-ray diffraction. Samples, annealed by a flash lamp in an Ar flow show the formation of different secondary phases depending on annealing time and temperature. [1] Bonanni et al., PRL 101, (2008) 135502 [2] Li et al., Journal of Crystal Growth 310, (2008) 3294–3298

The heteroepitaxial growth process of InAs nanowires (NW) on GaAs [(1) over bar(1) over bar(1) over bar](B) substrate was investigated by X-ray grazing-incidence diffraction using synchrotron radiation. For crystal growth we applied the vapor-liquid-solid (VLS) growth mechanism via gold seeds. The general sample structure was extracted from various electron microscopic and X-ray diffraction experiments. We found a closed GaxIn1-xAs graduated alloy layer at the substrate to NW interface which was formed in the initial stage of VLS growth with a Au-Ga-In liquid alloy. With ongoing growth time a transition from this VLS layer growth to the conventional VLS NW growth was observed. The structural properties of both VLS grown crystal types were examined. Furthermore, we discuss the VLS layer growth process.

The coupling effectiveness of the exchange spring effect can be influenced by the interface structure between hard and soft magnetic films. We have investigated the structural and magnetic properties of an Fe/Sm2Co7 exchange spring bilayer system after annealing and after low-energy ion irradiation. To study the interface properties X-ray reflectivity (XRR) measurements were carried out. From the XRR measurements it was shown that annealing influences the roughness of the layer surfaces causing an almost symmetrical broadening of the interfacial layers. Irradiation induces changes in the top three layers and the most pronounced effect upon irradiation is a change in electron density of the first two top layers and an interface broadening between Fe and Sm2Co7. In contrast annealing after irradiation triggers a material flow influencing the whole irradiated layers. The annealing afterwards therefore influences mainly the Fe layer by creating an Fe/Sm2Co7 intermixed region.

A systematic study of various, nominally undoped ZnO single crystals, either hydrothermally grown (HTG) or melt grown (MG), has been performed. The crystal quality has been assessed by x-ray diffraction, and a comprehensive estimation of the detailed impurity and hydrogen contents by inductively coupled plasma mass spectrometry and nuclear reaction analysis, respectively, has been made also. High precision positron lifetime experiments show that a single positron lifetime is observed in all crystals investigated, which clusters at 180–182 ps and 165–167 ps for HTG and MG crystals, respectively. Furthermore, hydrogen is detected in all crystals in a bound state with a high concentration (at least 0.3 at. %), whereas the concentrations of other impurities are very small. From ab initio calculations it is suggested that the existence of Zn-vacancy–hydrogen complexes is the most natural explanation for the given experimental facts at present. Furthermore, the distribution of H at a metal/ZnO interface of a MG crystal, and the H content of a HTG crystal upon annealing and time afterward has been monitored, as this is most probably related to the properties of electrical contacts made at ZnO and the instability in p-type conductivity observed at ZnO nanorods in literature. All experimental findings and presented theoretical considerations support the conclusion that various types of Zn-vacancy–hydrogen complexes exist in ZnO and need to be taken into account in future studies, especially for HTG materials.

We report on the formation of ion beam induced ripples in Si(001) wafers when bombarded with Ar+ ions at an energy of 60keV. A set of samples varying incidence and azimuthal angles of the ion beam with respect to the crystalline surface orientation was studied by two complementary near surface sensitive techniques, namely atomic force microscopy and depth-resolved X-ray grazing incidence diffraction. Additionally cross-section TEM investigations were carried out. The ripple-like structures are formed at the sample surface as well as at the buried amorphous-crystalline interface. Best quality of the ripple pattern was found when the irradiating ion beam was aligned parallel to the planes. The quality decreases rapidly if the direction of ion beam deviates from .

Magnetic semiconductors with high Curie temperatures are very promising materials for spintronic applications. An approach to fabricate GaMnAs is the Mn-implantation of GaAs followed by pulsed laser annealing (PLA) [1,2]. We investigated the influence of the Mn concentration and PLA conditions, e.g. number of laser pulses, on the structural and magnetic properties of (001)-oriented GaMnAs. Results from heatflow calculations helped us to understand the PLA process. Using SQUID magnetometry, we reveal a strong decrease of the saturation magnetization with increasing number of laser pulses. Zero field cooled/ field cooled measurements were performed to investigate the magnetization of the annealed GaMnAs layer. We found a spontaneous magnetization below the Tc and a large out-of- plane anisotropy. HR-XRD measurements revealed a lattice expansion normal to the surface after implantation. In dependence on the number of pulses, PLA decreases the strain (1 pulse) or overcompensates the strain (10 and 100 pulses). We conclude that Mn-implantation into GaAs followed by 1 laser pulse allows for the fabrication of strongly anisotropic, diluted magnetic GaMnAs. The drawback of the Mn-implantation is the loss of As from the GaAs surface as detected by means of Auger electron spectroscopy. Co-implantation with suitable elements is a possible approach to countervail the magnetic properties of annealed GaMnAs. [1] M. A. Scarpulla, O. D. Dubon, K. M. Yu, O. Monteiro, M. R. Pillai, M. J. Aziz, and M. C. Ridgway, Appl. Phys. Lett. 82, 1251 (2003). [2] M. A. Scarpulla, R. Farshchi, P. R. Stone, R. V. Chopdekar, K. M. Yu, Y. Suzuki, and O. D. Dubon, J. Appl. Phys. 103, 073913 (2008).

Magnetic semiconductors with high Curie temperatures and large coercivity are very promising materials for spintronic applications. An approach to fabricate GaMnAs is the Mn-implantation of GaAs followed by pulsed laser annealing (PLA). We investigated the influence of Mn concentration and PLA conditions, e.g. number of pulses, pulse length, and pulse energy, on the structural and magnetic properties of GaMnAs. Using SQUID magnetometry, we revealed a strong decrease of the saturation magnetization with increasing number of pulses. HRXRD-measurements revealed a lattice expansion normal to the surface after implantation. PLA leads either to a strain decrease (1 pulse) or even to a strain over compensation (10 pulses). We conclude that Mn implantation into GaAs followed by PLA is not sufficient for increasing the Curie temperature in GaMnAs. In addition, the drawback of the Mn implantation is the loss of As from the GaAs surface as detected by means of Auger electron spectroscopy. Heat transfer calculations and coimplantation with suitable elements are possible approaches to enhance the properties of GaMnAs.

We report on the influence of the initial roughness and crystallography of the substrate on the formation of self-organized ripple structures on semiconductors surfaces by noble gas ion bombardment. The Bradley-Harper theory predicts that an initial roughness is most important for starting the sputtering process which in the ends leads to the evolution of regular patterns. We produced regular patterns with intermediate Xe+ ion energies (5-70 keV) at different incidence and azimuthal angles which lead to the assumption that also crystallography plays a role at the beginning of ripple evolution. Most of the previous investigations started from the original roughness of a polished silicon wafer. We used (001) silicon wafers with a miscut angle of 1°, 5° and 10° towards [110]. We studied the ripple formation keeping the ion beam parallel to the [111], [-1-11] or [-111] direction, i.e. parallel, antiparallel or prependicular to the miscut direction [110]. The parallel and antiparallel case implies a variation of the incidence angle with increased roughness over the surface step terraces. The perpendicular orientation means almost no roughness. The results were compared to normal Si(001) and Si(111) wafers.