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Research data of Millisecond Flash Lamp Curing for Porosity Generation in Thin Films

Flash lamp annealing (FLA) with millisecond pulse duration is reported as a novel curing method for pore precursors degradation in thin films. A case study on the curing of dielectric thin films is presented. FLA-cured films are being investigated by means of positron annihilation spectroscopy and Fourier-transform infrared (FTIR) spectroscopy in order to quantify the nm-scale porosity and post-treatment chemistry, respectively. Results from positron annihilation reveal the onset of formation of porous voids inside the samples at 6 ms flash treatment time. Moreover, parameter adjustment (flash duration and energy density) allows for identifying the optimum conditions of effective curing. Within such a systematic investigation, positron results indicate that FLA is able to decompose the porogen (pore precursors) and to generate interconnected (open porosity) or isolated pore networks with self-sealed pores in a controllable way. Furthermore, FTIR results demonstrate the structural evolution after FLA, that help for setting the optimal annealing conditions whereby only a residual amount of porogen remains and at the same time a well-densified matrix, and a hydrophobic porous structures are created. Raman spectroscopy suggests that the curing-induced self-sealing layer developed at the film surface is a graphene oxide-like layer, which could serve as the outside sealing of the pore network from intrusions.

Local crystallization of ferromagnetic layers is crucial in the successful realization of miniaturized tunneling magnetoresistance (TMR) devices. In the case of Co–Fe–B TMR devices, used most successfully so far in applications and devices, Co–Fe–B layers are initially deposited in an amorphous state and annealed post-deposition to induce crystallization in Co–Fe, thereby increasing the device performance. In this work, first direct proof of locally triggered crystallization of 10 nm thick Co–Fe–B films by laser irradiation is provided by means of X-ray diffraction (XRD) using synchrotron radiation. A comparison with furnace annealing is performed for benchmarking purposes, covering different annealing parameters, including temperature and duration in the case of furnace annealing, as well as laser intensity and scanning speed for the laser annealing. Films of Co–Fe–B with different stoichiometry sandwiched between a Ru and a Ta or MgO layer were systematically assessed by XRD and SQUID magnetometry in order to elucidate the crystallization mechanisms. The transformation of Co–Fe–B films from amorphous to crystalline is revealed by the presence of pronounced CoFe(110) and/or CoFe(200) reflexes in the XRD θ-2θ scans, depending on the capping layer. For a certain window of parameters, comparable crystallization yields are obtained with furnace and laser annealing. Samples with an MgO capping layer required a slightly lower laser intensity to achieve equivalent Co– Fe crystallization yields, highlighting the potential of laser annealing to locally enhance the TMR ratio.

Deionized water and glucose without yeast and with yeast (Saccharomyces cerevisiae) of optical density OD600 that ranges from 4 to 16 has been put in the ring electrode region of six different types of impedance biochips and impedance has been measured in dependence on the added volume (20, 21, 22, 23, 24, 25 &micro, L). The measured impedance of two out of the six types of biochips is strongly sensitive to the addition of both liquid without yeast and liquid with yeast and modelled impedance reveals a linear relationship between the impedance model parameters and yeast concentration. The presented biochips allow for continuous impedance measurements without interrupting the cultivation of the yeast. A multiparameter fit of the impedance model parameters allows for determining the concentration of yeast (cy) in the range from cy = 3.3 &times, 107 to cy = 17 &times, 107 cells/mL. This work shows that independent on the liquid, i.e., DI water or glucose, the impedance model parameters of the two most sensitive types of biochips with liquid without yeast and with liquid with yeast are clearly distinguishable for the two most sensitive types of biochips.

The adsorption of chiral molecules was recently shown to trigger a change in the magnetisation of mesoscopic magnetic domains in a ferromagnetic underlayer. In this work, we investigated the macroscopic (magneto-)optical response of chemisorbed α-helical polyalanine self-assembled monolayers (SAMs) on a gold and gold-capped-cobalt thin film on Au substrates using spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy and microscopy. The optical and magneto-optical spectra reveal selective chemisorption of the α-helical polyalanine molecules depending on the orientation of the substrate remanent magnetisation during the SAMs process. Moreover, a sign change of the magneto-optical response was observed in some of the magnetic substrates after the chiral SAMs formation.

Nanoscale, low-phase noise, tunable transmitter-receiver links are key for enabling the progress of wireless communi-cation. We demonstrate that vortex-based spin-torque nano-oscillators, which are intrinsically low-noise devices due to their topologically-protected magnetic structure, can achieve frequency tunability when submitted to local ion im-plantation. In the experiments presented here, the gyrotropic mode is excited with spin-polarized alternating currents and anisotropic magnetoresistance measurements yield discreet frequencies from a single device. Indeed, chromium-implanted regions of permalloy disks exhibit different saturation magnetisation than the surrounding, non-irradiated areas, and thus different resonance frequency, corresponding to the specific area where the core is gyrating. Our study proves that such devices can be fabricated without the need of further lithographical steps, suggesting ion irradiation can be a viable and cost-effective fabrication method for densely-packed networks of oscillators.

Comprehensive ex-situ and in-situ investigations of thermal curing processes in spin-on ultra-low-k thin films conducted by positron annihilation spectroscopy and Fourier transform infrared spectroscopies are presented. Positron annihilation lifetime spectroscopy of ex-situ cured samples reveals an onset of the curing process at about 200 °C, which advances with increasing curing temperature. Porogen agglomeration followed by diffusive migration to the surface during the curing process leads to the generation of narrow channels across the film thickness. The size of those channels is determined by a pore size distribution analysis of positron lifetime data. Defect kinetics during in-situ thermal curing has been investigated by means of Doppler broadening spectroscopy of the annihilation radiation, showing several distinct partially superposed and subsequent curing stages, i.e., moisture and residual organic solvents removal, SiOx network cross-linking, porogen decomposition, and finally creation of a stable porous structure containing micropore channels interconnecting larger mesopores formed likely due to micelle like interaction between porogen molecules, for curing temperatures not larger than 500 °C. Static (sequencing curing) states captured at specific temperature steps confirm the conclusions drawn during the dynamic (continuous curing) measurements. Moreover, the onset of pore inter-connectivity is precisely estimated as pore interconnectivity sets in at 380–400 °C.

CoFeB alloys are highly relevant materials for spintronic applications. In this work, the crystallization of CoFeB alloys triggered by thermal annealing was investigated by x-ray diffraction techniques and scanningelectron microscopy, as well as spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy forannealing temperatures ranging from 300 to 600◦C. The transformation of∼100-nm-thick CoxFe(80−x)B20filmsfrom amorphous to polycrystalline was revealed by the sharpening of spectral features observed in optical andmagneto-optical dielectric functions spectra. The influence of B on the dielectric function was assessed bothexperimentally and by optical modeling. By analyzing the Drude component of the optical dielectric function,a consistent trend between the charge-carrier scattering time/resistivity and the annealing temperature wasobserved, in agreement with the electrical investigations by means of the four-point-probe method.

Raw data of "A detailed EP and PAS study of porous structure of OSG films with various ratios of methyl terminal and ethylene bridging groups"- The positron part only.

Organosilicate-glass films with a varying ratio of terminal methyl and bridging ethylene groups are synthesized using BTMSE/MTMS mixtures and sol-gel technology. The films have been characterized by Fourier Transform Infrared spectroscopy, Ellipsometric Porosimetry and Positron Annihilation Spectroscopy. The hard bake at 400 ºC generates the final pore structure, which depends on the curing environment. It is shown that ethylene bridge is destructed during the hard bake in air via formation of peroxide radicals that form ΞSiOH during the further transformation. Continuous hard bake leads to condensation of silanol groups and form a structure similar to the ordinary silica. The pore size of highly porous materials (>30%) is larger in air cured films. Destruction of the ethylene bridge makes the films matrix soft and micropores collapse during the template evaporation due to the capillary forces. It leads to the film shrinkage, increases the size of internal voids. The air cured samples showed better mechanical properties than N 2 cured ones although in the last case ethylene bridging groups were preserved. The reason is that the collapse of micropores increases internal density and creates more favorable condition for condensation of silanol groups.

We report unipolar resistive switching in polycrystalline, hexagonal yttrium manganite thin films grown on unpatterned Pt metal coated SiO2/Si substrates with circular Al top electrodes. Electroforming-free or electroforming-based resistive switching is observed, depending on the chemical composition (Y1Mn1O3, Y0.95Mn1.05O3, Y1Mn0.99Ti0.01O3, and Y0.94Mn1.05Ti0.01O3). The number of loading cycles measured at room temperature for samples with Y1Mn1O3 and Y0.95Mn1.05O3 composition is larger than 103. The dominant conduction mechanism of the metal-insulator-metal structures between 295 K and 373 K in the high resistance state is space charge limited conduction and in the low resistance state is ohmic conduction. Activation energies in Ohm's law region in the high resistance state are calculated from the Arrhenius equation and are evaluated to be 0.39 ± 0.01 eV (Y1Mn1O3), 0.43 ± 0.01 eV (Y0.95Mn1.05O3), 0.34 ± 0.01 eV (Y1Mn0.99Ti0.01O3), and 0.38 ± 0.02 eV (Y0.94Mn1.05Ti0.01O3).

This feature article covers the nano-analysis methods for four key material characteristics: electrical and electronic properties, optical, stress and strain, and chemical composition. With the downsizing of the geometrical dimensions of electronic, optoelectronic, and electromechanical devices from the micro to the nanoscale at the one hand and the increase of functionality density at the other, the previous generation of micro-analysis methods is no longer sufficient. Therefore, the metrology of materials’ properties with nanoscale resolution has become prerequisite in materials research and development. The article shortly reviews the standard analysis methods and focuses on advanced methods with a nanoscale spatial resolution based on atomic force microscopy (AFM): current-sensing AFM (CSAFM), Kelvin probe force microscopy (KPFM), and hybrid optical techniques coupled with AFM including tip-enhanced Raman spectroscopy (TERS), photothermal-induced resonance (PTIR) characterization methods (nano-Vis, nano-IR), photo-induced force microscopy (PIFM) and photothermal microspectroscopy (PTMS). The simultaneous acquisition of multiple parameters (topography, charge and conductivity, stress and strain, chemical composition) at the nanoscale is a key for exploring new research on structure-property relationships of nanostructured materials such as carbon nanotubes (CNTs) and nano/microelectromechanical systems (N/MEMS). Advanced nanocharacterization techniques foster the design and development of new functional materials for flexible hybrid and smart applications.

The fundamental oscillation mode of magnetic vortices in thin-film elements has recently been proposed for designing spin-torque-driven nano-oscillators [1]. Commercial applications require tuning of the output frequency by external parameters, such as applied fields or spin-polarized currents. However, the tunability of vortex-based devices is limited, since the gyrotropic frequency is specific to the individual sample design. Indeed, the fundamental frequency is known to be determined by the saturation magnetisation, M_s , as well as the geometrical confinement of the magnetisation, i.e. the diameter and height of the magnetic disk [2, 3]. Micromagnetic simulations [4] have shown that if regions with different saturation magnetisation can be induced in a magnetic disk, multiple precession frequencies can be generated. We show that ion implantation [5] is a novel route to fabricate such devices. Permalloy (Py) disks of various diameters and thicknesses were prepared using electron beam lithography followed by electron beam evaporation. Individual disks were contacted by gold leads to study the interaction of spin-polarized current with the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect (MOKE), X-ray magnetic circular dichroism (XMCD) and magnetotransport measurements. The magnetic field dependence of the vortex position can be tuned by the disk size as shown by XMCD (Figure 1 (a)). Higher magnetic stability due to larger annihilation fields can be achieved by smaller disk diameters, whereas larger field sensitivity is present in larger disks (Figure 1 (b)). Magnetotransport measurements on electrically contacted disks show the presence of anisotropic magnetoresistance (AMR) in different disks with varying thickness (Figure 1 (c)). Using a conventional lock-in technique, the resonance frequencies are measured for disks with different radii as shown in Figure 2 (a), with the inset showing the scanning electron microscope image of an electrically contacted disk. In order to modify the magnetisation within a single disk and to achieve two different oscillation frequencies, we implant chromium in different regions of the disk (inner and outer). Cr-implantation leads to a decrease in the Curie temperature and thus a reduction in the magnetic moment [6]. The reduction of M_s as a function of Cr fluence was optimised on extended Py films using a vibrating sample magnetometer – superconducting quantum interference device (VSM-SQUID), see figure 2 (b). A clear drop in M_s with increasing the chromium ion fluence is observed. Concentric donut-like structures were then implanted with Cr and the modification of dynamics as a function of magnetic field was investigated. An example of Cr implantation in a 3 µm radius disk at 30 keV with a fluence of 1.2×〖10〗^16 ions/cm^2 is shown in Figure 2 (c). The vortex core is shifted between the two different magnetisation regions by applying an external in-plane field. The vortex nucleates in the irradiated region at – 2.281 mT, leading to a resonance frequency of 30.2 MHz (shown in orange in Figure 2 (c)). Further increasing the external field pushes the vortex core to the non-irradiated region where the resonance frequency is 42.3 MHz (shown in green), corresponding to a field of + 1.597 mT. The results show that ion implantation is a novel way to obtain multiple frequencies from a single disk.

The first results on in-situ investigations of pore formation in ultra low-k dielectrics during a curing process, i.e., a porogen removal by vacuum annealing will be presented. The main focus is to obtain insight into initial stages of pore networks formation up to their full development. The in-situ annealing and Doppler broadening positron annihilation spectroscopy measurements have been conducted on our Apparatus for In-situ Defect Analysis (AIDA) - the end-station of a slow positrons beamline at HZDR. In addition, positron lifetime spectroscopy has been utilized, where mono-energetic pulsed positron beam (MePS) serves as a probe to evaluate pore sizes, their concentration and distribution as a function of curing temperature and time. The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). The AIDA system was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox) and through the Helmholtz Energy Materials Characterization Platform (03ET7015)

The syntheses and characterization of the palladium complexes [Pd(accp)2] (7), [Pd(acch)2] (8), [Pd(η3-CH2CMeCH2)(accp)] (11), [Pd(η3-CH2CMeCH2)(acch)] (12), [Pd(η3-CH2CtBuCH2)(accp)] (13) and [Pd(η3-CH2CtBuCH2)(acch)] (14) (accp = 2-acetylcyclopentanoate; acch = 2-acetylcyclohexanoate) are reported. These complexes are available by the reaction of Haccp (2-acetylcyclopentanone) and Hacch (2-acetylcyclohexanone) with Na2[Pd2Cl6] forming 7 and 8 or with [(Pd(η3-CH2CRCH2)(μ-Cl))2] (9, R = Me; 10, R = tBu) forming 11–14. The molecular structures of 7, 8 and 14 are discussed. Complexes 7 and 8 consist of a square-planar coordinated Pd atom with two trans-positioned bidentate β-diketonate ligands. The asymmetric unit of 14 exhibits one molecule of the palladium complex and a half molecule of water. The thermal behavior of 7, 8 and 11–14 and their vapor pressure data were investigated to show, if the appropriate complexes are suited as CVD precursors for palladium layer formation. Thermogravimetric studies showed the evaporation of the complexes at atmospheric pressure upon heating. The vapor pressure of 7, 8 and 11–14 was measured by using thermogravimetric analysis, giving vapor pressure values ranging from 0.62 to 2.22 mbar at 80 °C. Chemical vapor deposition studies were carried out applying a vertical cold wall CVD reactor. Either oxygen or forming gas (N2/H2, ratio 90/10, v/v) was used as reactive gas. Substrate temperatures of 350 and 380 °C were utilized. With 11–14 dense and conformal as well as particulate palladium films were obtained, as directed by SEM studies, whereas 7 and 8 failed to give thin films, which is probably attributed to their high thermal stability in the gas phase. For all deposited layers, XPS measurements confirmed the partial oxidation of palladium to palladium(II) oxide at 380 °C, when oxygen was used as reactive gas. In contrast, thin layers of solely metallic palladium were obtained utilizing forming gas during the deposition experiments. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Positronium annihilation spectroscopy has become more and more important in microelectronics industry as one of the few methods to characterize engineered nanopores in next-generation (k < 2.4) interlayer dielectrics (ILD). With the addition of infrared spectroscopy a way is found to investigate the pore and network formation during the curing process. 1. Introduction Porous spin-on glasses are one great candidate for the integration as ultra low-k (ULK) dielectrics in Back-End of Line (BEOL) for advanced technology nodes. They offer the possibility of a structured pore network by using “Block Polymer Templated Inorganic Oxides” (USP 6,592,764) [1]. Therefore, it is possible to adjust the physical properties of these thin films [1] as well as pore size and porosity. However, these materials are also prone to dielectric damage [2,3] during the integration into back-end of Line. In addition, these material degradations will increase with porosity [3]. It follows, that beside the damage mechanism also the pore and network formation of ULK materials need to be investigated more in detail to comprehend integration damage from the very first time of appearance. This work will evaluated the formation of spin-on glasses during curing by positron annihilation spectroscopy to observe the pore formation and by Fourier Transform Infrared spectroscopy to study the network formation. 2. Experimental 2.1 Preparation of spin-on dielectrics For preparation of spin-on ULK material a solution from SBA Materials, Inc. was used. The ULK liquid precursor consists of an amphiphilic block copolymer with silicon alkoxide esters [1]. The final thickness is supposed to be 500 nm with an initial k-value of 2.2. The solution was spin-coated on 6-inch silicon wafers with 2000 rpm for 60 s. The spin-coated samples were soft baked for 120 s at 150 °C. The curing procedure was performed with the quartz glass oven PEO 603 from ATV technologies for different curing times at 450 °C under nitrogen atmosphere. The heat ramp of curing was chosen to be 7 °C/min. 2.2 Measurement techniques of pore and network structure Fourier Transform Infrared (FTIR) spectroscopy was used to determine the chemical and structural changes before and after different curing times. The measurements were performed in transmission mode in the mid-range from 400 to 4000 cm-1, using the Bruker Tensor 27 spectrometer. The optical response is given as absorbance and normalized to thickness as well as treated by a baseline subtraction. Thus a comparison of the different processes can be achieved. Furthermore, a deconvolution of the FTIR peaks at the oxide region (1300 cm-1 to 950 cm-1) was accomplished with the Peak-Fit Module of ORIGIN 8.5 software. As it is described in literature the oxide region is used to be deconvoluted into the following peaks: the suboxide-, network-, cage-peak [4,5] and the Si-O-C peak [6]. The area was normalized to the total area of the Si-O-Si area. The characterization of the nanopores were carried out at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) with positron annihilation spectroscopies (PAS). For determination of different pore components the Elbe Positron Source (EPOS) was used; a pulsed positron source with high repetition rate, high intensity and choosable energies for depth profile measurements [7,8]. Furthermore, by using the The Slow-Positron System of Rossendorf (SPONSOR) Doppler broadening spectroscopy was used to acquire also information about the atomic surrounding of the pores. Since the possibility of diffusing out of ortho-positronium (o-Ps) from film surface through open, interconnecting pores the ULK films were covered with a 20 nm thick carbon layer by evaporating using a pre-shaped carbon rod. 3. Results Fig. 1 shows the FTIR spectrum of the uncured and cured samples after 5 min, 30 min, 60 min and 90 min at 450 °C. The curing process at 450 °C for 90 min can be considered as complete cure. The uncured sample shows the –OH absorbance peak at 3400 cm-1 and the Si-OH peak at 914 cm-1 [9], which is characteristic for spin-on glasses in sol-gel science [10]. During the curing process the methylsilsesquioxane (MSQ) based Si-OH groups condensate and cross-linking occurs to form a 3D network [11]. Besides the Si-OH peak in the uncured sample the region from 3000 cm-1 to 2800 cm-1 is more pronounced compared to the cured samples. There are located the C-Hx vibration bands, which mostly correspond to porogen to form a porous network. The region from 900 cm-1 to 700 cm-1 is called the fingerprint region, where mostly the different Si-C vibration modes are dominate [9]. The absorbance peak at 1277 cm-1 belongs to the Si-CH3 vibration band. The two main mechanism during the curing of spin-on ULK are the cross-linking of the Si-OH groups to form a mechanically stable thin film and the porogen removal to form a porous network. The cross-linking of Si-OH to form the Si-O-Si linkage can be seen in Fig 1. in the range of 1250 cm-1 to 960 cm-1. Already after 5 min of curing the Si-O-Si region is formed almost completely and only little changes during further curing are observed. By taking a closer look at the Si-O-Si region, a shift from 1047 cm-1 to 1052 cm-1 can be observed. Within this region four peaks are overlapping: the suboxide-, network-, cage- [4,5] and the Si-O-C peak [6]. To distinguish between those peaks a deconvolution was done, where the results are shown in Fig. 2. With increasing curing time the network peak rises whereas the cage and the suboxide peak decreases. This behavior is likely due to the cross-linking of the network material and is less pronounced after 30 min of curing. The Si-O-C peak seams not to be affect by curing time. Fig. 3 and Fig. 4 show the results from the DBS and PALS measurements. From the DBS measurements two specific line parameters can be calculated: the S- and W-parameter. The S-parameter is a measurement of the open volume and the W-parameter is a measurement of the atomic environment of the annihilation site. The mean implantation depth for the positrons is given in nanometer scale at the upper x-axes based on the density of silica. The first 20 nm (until 1.2 keV) the S- and W-parameter corresponds to the carbon capping layer and retain unchanged for all treatments. The W-parameter for the uncured sample shows the highest values. Only for 20 nm Carbon layer the W-parameter is higher. Within the first minutes of curing, the porogen is almost removed and the W-parameter decreases. From 30 min to 90 min no change in W-parameter is visible anymore. Compared to the FTIR spectra (Fig. 1) in the region of 3000 cm-1 to 2800 cm-1 no change for all curing times are visible which shows the sensitive behavior of PAS measurements for nanopore evaluations. For the cross-linking behavior (Fig. 2) the dependence on curing time can still be observed in detail by FTIR. Therefore, it can be concluded that the porogen extraction at 450 °C with a slow heating ramp is completed within the first 30 min, whereas the cross-linking of the network takes places over the complete curing time. The calculated pore components from PALS measurements are shown in Fig. 4. Two different lifetime components were found. The upper diagrams show the diameter of the pores and the lower diagrams show the intensities of the pore components. The first pore component has a diameter of around 0.8 nm which does not change for all curing treatments and positron energies, whereas the intensities of the component 1 decrease from the uncured to the cured state. With regard to the FTIR results (Fig. 1 and Fig. 2), this pore component intensities shows the inverse behavior of the oxide region, where the network is formed. Therefore, this component is likely due to the unreacted Si-OH groups, which decreases during the curing. The second pore component arises from the pores itself and was not observed at the uncured sample. The mean diameter is about 3.4 nm, which lowers to 3 nm near the surface of the film. This can be due to the carbon capping layer deposition and needs further considerations. Also it can be seen that the pore diameter from 5 min to 30 min still increases and reaches a final value after 30 min. In addition, the intensity of the pore component 2 changes marginal. That confirms that the porogen extraction as well as the pore formation takes place within the first 30 min. 4. Summary In this work, the pore formation of spin-on ULK materials with an initial k-value of 2.2 was studied for a thermal curing process at 450 °C with a slow heat ramp for curing. After 5 min of curing most of the porogen is extracted and the network is formed almost completely, which can be seen by PAS and FTIR. The porogen extraction as well as the pore formation appear to be complete after 30 min, whereas the remaining time is needed to form the network. All the investigations are running right now for faster heat ramp of curing as well as for different curing temperatures to slow down the pore formation process and get a better understanding of the processes taking place inside the material during curing. References [1] P. Garrou, Solid State Technology, p. 10, Nov. 2010, Accessed 22 May 2017 [2] J.L. Shohet et al., ECS Transactions, 60 (1) p. 733-738 (2014) [3] M.R. Baklanov et al., Journal of Applied Physics 113, p. 041101, (2013) [4] L. Zhang et al., ECS Solid State Lett. 2 (2), p. N5 (2013) [5] A. Grill et al., J. Appl. Phys. 94 (10), p. 6697 (2003). [6] Y. Lin et al., J. Electrochem. Soc. 153 (7), p. F144 (2010) [7] A. Uedono et al. Applied Surface Science, Bd. 368, pp 272-276 (2016) [8] A. Wagner et al., Defect and Diffusion Forum, Bd. 331, pp. 25-40, (2012) [9] B. Xie et al., Microelectron. Eng, 76 (1-4) p. 52-59 (2004) [10] P. Eaton et al., J. Appl. Polym. Sci. 82 (8), p. 1097-4628 (2001) [11] A. Zenasni et al., J. Electrochem. Soc. 154 (1) p. G6 –G12 (2007)

The fundamental oscillation mode of magnetic vortices in thin-film elements has recently been proposed for designing spin-torque-driven nano-oscillators [1]. Commercial applications require tuning of the output frequency by external parameters, such as applied fields or spin-polarized currents. However, the tunability of vortex-based devices is limited, since the gyrotropic frequency is specific to the individual sample design [2, 3]. Using micromagnetic simulations, [4] we show that if regions with different saturation magnetisation can be induced in a magnetic disk, multiple precession frequencies can be generated. Experimentally we employ ion implantation as a promising method to fabricate such devices [5]. Disks with different radii- 0.5 µm to 4 µm, thicknesses- 25 nm and 30 nm and lateral electrical contacts were prepared using electron beam lithography followed by electron beam evaporation to study the formation of magnetic vortices with respect to size and thickness. Magnetotransport measurements (Fig. 1(a)) show the presence of anisotropic magnetoresistance (AMR. The resonance frequencies measured using a lock-in technique on 25 nm thick permalloy disks are shown in Fig. 1(b). The disks were subsequently subjected to partial ion irradiation and the induced modification of the resonance frequency will be presented. The Nanofabrication Facilities Rossendorf at the IBC is gratefully acknowledged. Funding : Helmholtz Young Investigator Initiative Grant No. VH-N6-1048.

Fully Depleted Silicon on Insulator transistors (FDSOI) are a promising approach for further scaling. The device features a fully depleted body which is isolated by an insulator box. This introduces better electrostatics, lower leakage current and thus better channel control. The device performance is heavily influenced by the orientation, confinement and strain in the ultra-thin body. In this work the electronic structure of ultra-thin silicon layers is investigated using Density Functional Theory (DFT). The simulation parameters for the model system were calibrated to reproduce the experimental band gap of bulk silicon. This ensures that the model describes the electronic structure of ultra-thin silicon layers accurately. Our study demonstrates the impact of confinement, orientation and strain on material dependent transport properties and their influence on the device performance. For this purpose our results will be used as an input for device simulations using Synopsys Sentaurus TCAD. We find that the band gap of the silicon layer increases with decreasing slab thickness which is a clear indication of quantum confinement. From the simulation, the band gap for the {100} confinement is found to be higher than {110} and {111} scenarios. Band gap is one of the factors which influence the intrinsic carrier in the semiconductor and thereby the transport. Another important factor for the transport is lattice strain. Strain is a useful method for modulating band structures. One good example is the transformation of direct band gap in {100} confined silicon slab to indirect band gap with 2 % biaxial compression. In our presentation we will discuss the influence of the effective mass as well. Furthermore, the strain dependence of the electronic structure and its impact on device properties is analyzed systematically.

The fundamental oscillation mode of magnetic vortices in thin-film elements has recently been proposed for designing spin-torque-driven nano-oscillators [1]. Commercial applications require tuning of the output frequency by external parameters, such as applied fields or spin-polarized currents. However, the tunability of vortex-based devices is limited, since the gyrotropic frequency is specific to the individual sample design. Indeed, the fundamental frequency is known to be determined by the saturation magnetisation, M_s , as well as the geometrical confinement of the magnetisation e.g. the diameter and height of a magnetic disk [2, 3]. Micromagnetic simulations [4] have shown that if regions with different saturation magnetisation can be induced in a magnetic disk, multiple precession frequencies can be generated. Ion implantation is a promising method to fabricate such devices [5]. To study the formation of magnetic vortices with respect to size and thickness, disks with different radii- 0.5 µm to 4 µm and thicknesses- 25 nm and 30 nm were prepared using electron beam lithography followed by electron beam evaporation. Moreover, to allow for electrical measurements, the single disks were contacted by gold leads to study the interaction of spin polarized current on the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect (MOKE), X-ray magnetic circular dichroism (XMCD) and magnetotransport measurements. The magnetic field dependence can be tuned by the disk size as shown by XMCD (Figure 1 (a)). Higher magnetic stability due to larger annihilation fields can be achieved by smaller disk diameters whereas larger field sensitivity is present in larger disks (Figure 1 (b)). Magnetotransport measurements on electrically contacted disks (Figure 2 (a)) show the presence of anisotropic magnetoresistance (AMR) in different disks with varying thickness (Figure 2 (b)). Additionally, to the shown static DC measurements, AC measurements are accessible by a lock-in technique and the resonance frequencies measured for 3 µm and 4 µm radii disks with 25 nm permalloy are 40.9 MHz and 29.5 MHz respectively. In order to alter the saturation magnetisation within defined volumes and to achieve two different oscillation frequencies, a concentric region is irradiated within the actual disk (Figure 2 (c)). After ion irradiation, modified magnetic vortex dynamics are investigated by ac-magnetotransport measurements and the results are supported by micromagnetic simulations. Acknowledgements: This work is supported by the Helmholtz Young Investigator Initiative Grant No. VH-N6-1048. Support of the Nanofabrication Facilities of Rossendorf at the Ion Beam Centre is gratefully acknowledged (Dr. Artur Erbe, Bernd Scheumann).

Porous spin-on glasses belong to ultra low-k (ULK) dielectrics and are promising candidates for integration in the semiconductor device fabrication technology. Their microstructure consists usually of interconnected pore networks distributed across the film rather than separated voids. The pore size and distribution are controllable to a large extent, however, the pore formation process itself is still not well understood. A dielectric damage during integration and material degradation of films with large porosity are still problematic issues. The first results on in-situ investigations of the pore formation during a curing process – a porogen removal by vacuum annealing will be presented. The main motivation is to obtain the insight into early stages of the pore formation and up to its full development. The in-situ annealing and Doppler Broadening – Positron Annihilation Spectroscopy (DB-PAS) measurements have been done on our Apparatus for In-situ Defect Analysis (AIDA) system [1], which is the end-station of the slow positrons beamline at HZDR. The comparison between preliminary ex-situ studies by means of DB-PAS [see Fig. 1], Positron Annihilation Lifetime Spectroscopy (PALS), and Fourier Transform Infrared Spectroscopy (FTIS) will be given. In Fig. 1(a) it is shown that o-Ps emission increases with t, thus can be a probe of films porosity as long as they are capped. The curing time of 5-30min. is sufficient to fully develop the pore network [Fig. 1(b)]. Porosity development and distribution will be discussed for annealing temperatures in the 100-400°C range and varied annealing time. [1] M.O. Liedke et al., Journal of Applied Physics 117, 163908 (2015).

The magnetic “vortex” is a potential candidate for future spintronic devices, like frequency sensors [S. Kasai, et al. PRL 97, 107204 (2006)] [R. Moriya, et al. Nat. Phys. 4:368 (2008)], spin torque oscillators [V. S. Pribiag, et al. Nat. Phys. 3:498 (2007)], and tunable magnonic crystals [J. Shibata, et al. PRB 67, 224404 (2003)]. The fundamental frequency is determined by the saturation magnetisation, as well as the geometrical confinement of the magnetisation i.e. the diameter and height of a magnetic disk. In this study, Permalloy disks (with diameters ranging from 1µm to 8µm) are patterned and contacted to study the interaction of spin polarized current on the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect, X-ray photoemission electron microscopy and magnetotransport measurements. The resonance frequency is measured using a lock-in technique based on the anisotropic magnetoresistance effect. Modification of the resonance frequency by ion irradiation will be presented.

Carbon nanotubes (CNTs) are a promising material for novel sensor and interconnect applications. In both cases, the device performance depends strongly on the electronic properties of the tubes. Methods for tuning the electronic structure and especially the band gap are highly desirable. A computational study of cobalt decorated CNTs, by means of density functional theory, reveals that very few cobalt atoms can have a significant impact on the electronic structure, turning semiconducting CNTs into the metallic state. This is further verified by quantum transport simulations. The influence of different amounts of cobalt is also investigated.