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Current-voltage characteristics were measured, electrically modeled, and calculated for gate oxides, which contain nanocrystals (NCs) in different distributions, sizes, and densities. Ge and Si NCs were synthesized embedded in separate thin SiO2 layers by ion implantation at different fluences and subsequent annealing. It was found that the currents through the NC containing thin gate oxides are strongly related to the NCs’ location and are not driven by ion implantation induced oxide defects. Charging of the NCs determines the internal electrical fields, which is confirmed by simultaneous current and capacitance measurements. Depending on the implanted fluence the Ge NCs were mainly detected in the oxide center or close to the Si/SiO2 interface. The Si NCs were fabricated in the oxide center sandwiched between two oxide regions denuded of NCs. The processes of Si NC formation, growth and dissolution are discussed by means of kinetic lattice Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

The write performance of a multidot-memory-like structure with respect to hole tunneling is investigated in metal-oxide-semiconductor (MOS) capacitors. The oxide of the MOS structure on p-type Si contains a layer of ion beam synthesized Ge nanocrystals (NC’s) very close to the Si/SiO2 interface. This structure is modeled in a floating gate-like approach, where the NC’s are considered as individual storage nodes and charged by direct tunneling of holes. Quantum confinement and Coulomb blockade effects of small Ge NC’s (1–6 nm) are discussed and found to be negligible for the present structure. A close agreement between the calculated write characteristics and experimental data clearly confirms the validity of the model. From the simulation results it is predicted that a flatband voltage shift of about ΔVFB=-1 V could be gathered with programming times tprog<1 μs. The write parameters (pulse voltage and duration) for a given ΔVFB value are mainly determined by the distance of the NC’s to the substrate. [ABSTRACT FROM AUTHOR]

We have observed a very inhomogeneous dissociation of stoichiometric and non-stoichiometric thin SiO2 layers (thermally grown on Si substrates) during high temperature annealing at a low partial pressure of oxygen. During this process some silicon of the (100)Si substrate and, in case of Si ion implantation, and additionally, excess Si is consumed. The SiO2 dissociation has been studied by electron microscopy and Rutherford backscattering spectrometry. Large holes (>1 μm) in non-implanted oxide layers have been observed which evolve probably from defects located at the Si/SiO2 interface. For Si implanted SiO2 additionally the formation of voids within the oxide during annealing has been observed preferably at the position of the implanted Si excess. Oxygen vacancies are possibly emitted from Si/SiO2 interfaces into the oxide and migrate through SiO2 with long-range distortions of the oxide network. In that way the hole and void formation in the oxide can be explained by oxygen-vacancy formation, migration and silicon-monoxide (SiO) emanation. As a driving force for growth of the large holes we identified oxygen diffusion from the Si/SiO2 interface to the bare Si surface. This surface is a sink of oxygen diffusion due to the emanation of volatile SiO, whereas the Si/SiO2 interface serves as an oxygen source. The predicted mechanism is consistent with the geometry of the holes in the SiO2 layer. [ABSTRACT FROM AUTHOR]

Boron ion implantation of thermochemically polished chemical vapor deposited diamond films with multienergies ranging between 24 and 150 keV and a total dose of about 2 × 10[sup 16] cm[sup -2] is used to get p-type conductivity, n-type conductivity is achieved by lithium ion implantation of the diamond films with a single energy of 50 keV and a dose of 2 × 10[sup 16] cm[sup -2]. The intrinsic areas separating the p- and n-doped regions form the active areas of the diodes into which charge carriers are simultaneously injected upon bias. Onset voltages of <10 V are due to the low concentration (∼10[sup 14]cm[sup -3]) of nitrogen related centers in the diamond films. The current-voltage (I-V) characteristics of the p-i-n diodes manifest trap filling, Frenkel-Poole emission, thermionic emission, and space charge limited current regimes. At 300 °C, currents as high as 12 mA are measured at a forward bias of 100 V. Rectification ratios of up to about four orders of magnitude are achieved. They increase with increasing width of the i region within the measured i region of 3-10 µm, as a result of the considerable decrease of the reverse bias current relative to the forward bias current. [ABSTRACT FROM AUTHOR]

The possibility to create a δ-like, interface-near Ge nanocluster band in a 20 nm thin SiO[sub 2] layer by ion-beam synthesis is demonstrated. The role of the post-implantation annealing conditions for the formation of Ge nanoclusters in the center of the layer, near the interface, or in both regions is discussed. The presence of hydrogen in the annealing atmosphere accelerates the redistribution of Ge in SiO[sub 2]. By applying a two-step annealing process, preannealing in hydrogen containing atmosphere at low temperature followed by a rapid thermal annealing at high temperature, the controlled fabrication of a single δ-like, interface-near Ge nanocluster band was achieved. In some clusters 〈100〉 lattice planes of Ge were observed. From this and the similar contrast situation for amorphous clusters it is concluded that the interface-near clusters consist of elementary germanium. [ABSTRACT FROM AUTHOR]

Using synchrotron x-ray diffraction and reflectivity, we studied the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L10 phase of NiMn/Fe19Ni81 thin films deposited on a Si/SiO2 substrate as a function of the annealing temperature. The transformation to a dominating L10-ordered NiMn film takes place between 300 and 400 °C irrespective of the irradiation. This is also consistent with magnetization reversal measurements of the corresponding permalloy layers. The benefit of the ion irradiation is a reduction of the mosaicity for both the NiMn and the permalloy film, and a smoothening of internal interfaces. [ABSTRACT FROM AUTHOR]

Germanium nanocrystals in silicon dioxide were studied by atomic force microscopy (AFM) to reveal their size, density and distribution. The generation of the nanocrystals was accomplished by Ge+ ion implantation into a 100-nm silicon dioxide layer and subsequent annealing at high temperatures in an inert atmosphere. Rutherford backscattering spectroscopy was applied to reveal the Ge distribution after implantation and annealing, and the formation of the nanocrystals was proven by transmission electron microscopy. The oxide layer was gradually etched to uncover the nanocrystals located at different depth positions within the SiO2 layer. Subsequently, the unveiled surfaces were examined by AFM in order to determine the size and density of the exposed nanocrystals. A correlation between the nanocrystal properties and the Ge implantation dose was corroborated. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The formation of interface and border states in metal–oxide–semiconductor structures associated with the generation of embedded germanium nanocrystals in 20nm SiO2-layers by means of ion implantation and a subsequent annealing was examined. Deep level transient spectroscopy and related time-domain techniques were applied in order to study the charge trapping and emission at the Si–SiO2 interface. A significant dependence of the interface state density D it on the conditions of the cluster generation was found. Any Ge-implanted sample features a pronounced level at about 0.31eV above the valence band edge and a concentration above 1013 cm−2 eV−1, likely related to a Pb-center. A systematic variation of the filling pulse parameters was utilized in order to separate the response of fast and slow states, and to substantiate the existence of border traps located in the vicinity of the Si–SiO2 interface. The role of interface and border traps for the relaxation of the trapped charge in the nanocrystals is illustrated. [Copyright &y& Elsevier]

Abstract: The A1→L10 phase transition of Fe50Pt50 films, deposited at room-temperature on amorphous SiO2 by dc magnetron co-sputtering at 0.3Pa, was studied with in-situ X-ray diffraction. An almost complete transition characterized by a long-range order parameter S >0.8 is obtained already after a heat treatment at (320±20)°C. A post-deposition He ion irradiation (50keV, 1×1015 −3×1016 cm−2) does not further reduce the transition temperature. Theoretical calculations reveal that, due to the negligible thermalization of the sputtered atoms and reflected ions in the plasma, a considerable fraction of energetic ions and atoms meet the substrate surface. The low transition temperature is explained by the impact of energetic ions and atoms which provoke significant adatom mobility and a decrease of the activation energy for atomic reordering by vacancies. Consequently, using deposition parameters leading to a strong thermalized plasma, the FePt films showed an increase of the transition temperature up to 400°C, a lower S-value (S ≅0.6) and a reduced coercivity. [Copyright &y& Elsevier]

Abstract: The evolution of ion beam synthesized Co and Ge nanoclusters into a SiO2 matrix during annealing processes has been investigated by X-ray diffraction and transmission electron microscopy. Remarkable differences have been found between Ge and Co clusters behaviour. For Ge implanted SiO2 films, a clear influence of near-surface Ge oxidation and nanoclusters melting has been established. Annealing at temperatures around 1000°C leads to the formation of small (diameter ∼5nm) nanocrystals. Classical Ostwald ripening mainly drives the clusters thermodynamical growth. On the contrary, for Co-implanted SiO2 films, a jump-like transition in nanoclusters evolution has been established at about 800°C. A homogenous distribution of small (diameter ∼4nm) amorphous clusters is transformed into a bimodal clusters profile, characterised by large (diameter between 20 and 40nm) nanocrystals near the surface and a region of smaller clusters (diameter ∼7nm) in depth. During Co nanoclusters formation the influence of nanoclusters melting can be neglected. [Copyright &y& Elsevier]

Abstract: Superjunction devices (SJDs) are a novel class of power devices which break the physical limit of silicon with respect to the area-specific turn-on-resistance. SJDs consist of a modified vertical MOSFET structure which is characterized by additional deep pillar-like p-type regions formed inside the n(−) epi-layer below the transistor gate. In the present investigation ultra-high energy boron ion implantation of 2–25MeV was applied for forming the deep p-type regions laterally structured using Si stencil masks. For energies above 12MeV the incident ions exceed the Coulomb barrier for Si which leads (i) to a significant gamma and neutron emission during implantation and, (ii) an activation of the wafer and the mask material. However, the most relevant reaction for activation (11B+ 28Si→ 39K(nα)→ 34mCl(β,EC)→ 34S) has a half-life time of only 32min, hence the radiation level of the wafers drops below the critical limit within the processing time. Based on the described technology Infineon Technologies successfully prepared a set of prototype wafers with fully functional high-voltage transistors. Typical blocking capability was approx. 560V with an area-specific turn-on-state resistance of about 3.85Ωmm2. [Copyright &y& Elsevier]

Energies ranging between 24 and 50 keV, inclusively, are used for boron ion implantation of as-grown and thermochemically polished CVD diamond films at a total dose of 1016 cm−2 in order to achieve p-type conductivity. N-type conductivity is acquired by lithium ion implantation of the films by a single energy of 50 keV at a dose of 2×1016 cm−2. Current–voltage (I–V) characteristics reveal that leakage currents of diodes fabricated on as-grown films are approximately 2 orders of magnitude higher that those on polished films. Moreover, currents at higher voltages as less in the diodes of as-grown films in comparison to identical diodes on the polished films. The I–V characteristics of diodes on the polished films contain the trap filling, Frenkel-pole emission, thermionic emission and the space charge limited current regimes but those on the as-grown films manifest a quasi-linear behavior probably due to lateral penetration of implants in the i-regions. A reduction in current of approximately 2 orders of magnitude is observed on n–i–n structures after annealing the films at 300 °C. Onset voltages of <10 V are due to the low concentration (∼1014 cm−3) of nitrogen centers in the diamond films. [Copyright &y& Elsevier]

This paper describes a novel silicon detector with improved linearity characteristics for energetic electrons up to 50 keV. The modified pn-junction detector structure contains a buried implanted n(+) layer (N∼1–5×1015 cm−3) in the n-type Si substrate, which is attributed by a near-surface high-field region in the depletion zone. To enable a high-field region of several micrometers depth, high-energy ion implantation with 31P ions of 10–30 MeV was used. The corresponding electric field distribution of the novel detector is characterized by a constant electric field strength of 10–50 kV/cm from the surface down to the depth of the buried implanted layer. Detectors with considerable improved linearity up to electron current densities of 20 A/cm2 were been fabricated, which have been tested at the e-beam writer SB 350 of Leica Microsystems Lithography for electrons of 50 keV. [Copyright &y& Elsevier]

Charge storage properties of 20–30 nm gate oxides implanted with Si+ ions are investigated using MOS capacitors, single transistor structures and a non-volatile memory. The observed programming window can reach several volts for programming with electric fields of about 4–7 MV/cm. The structures exhibit good retention (250 °C, 280 h) and the endurance (>106 w/e-cycles) considerably exceeds the typical values of present EEPROM technologies. The capability of Si implanted SiO2 films as gate dielectrics for a real non-volatile memory is demonstrated for the first time by a 256 K-non-volatile static random access memory showing a programming window of larger than 1 V. [Copyright &y& Elsevier]

Strong blue and violet photoluminescence (PL) and electroluminescence (EL) at room temperature has been achieved from thin SiO2 layers implanted with group IV elements. Thermally grown SiO2 films with thicknesses between 130 and 500 nm were implanted with Si+, Ge+ or Sn+ ions followed by different annealing procedures. Based on PL and PL excitation spectra we tentatively interpret the blue–violet PL as due to a T1→S0 transition of an oxygen deficiency center. The strong EL is well visible with the naked eye and reaches a power efficiency of up to 5×10−3 for Ge. Whereas the EL intensity shows a linear dependence on the injection current for Ge-rich layers, the shape of the EL spectrum remains unchanged. It was found that the I–V characteristics shift to lower applied electric fields with increasing implantation fluence. Furthermore, it is assumed that the luminescence centers will be excited either by field ionization or by the scattering of hot electrons. Finally, the suitability of ion implanted silicon dioxide layers for optoelectronic applications is discussed. [Copyright &y& Elsevier]

Co nanoparticles fabricated by ion beam synthesis in SiO[sub 2] films were investigated with transmission electron microscopy and superconducting quantum interference device technique. Variation of the thermal treatment enables the formation of Co nanoclusters of different sizes ranging from 2 to 40 nm. Small nanoclusters of about 2–3 nm are amorphous, whereas clusters above 7 nm show the configuration of cubic Co nanocrystals. Measurements of magnetisation at temperatures between 2 K and 360 K reveal superparamagnetic behaviour for the small nanoclusters up to 3 nm and ferromagnetism for clusters above 7 nm. [ABSTRACT FROM AUTHOR]

Abstract. The microstructural, optical and electrical properties of Si-, Ge- and Sn-implanted silicon dioxide layers were investigated. It was found, that these layers exhibit strong photoluminescence (PL) around 2.7 eV (Si) and between 3 and 3.2 eV (Ge, Sn) at room temperature (RT), which is accompanied by an UV emission around 4.3 eV. This PL is compared with that of Ar-implanted silicon dioxide and that of Si- and Ge-rich oxide made by rf magnetron sputtering. Based on PL and PL excitation (PLE) spectra we tentatively interpret the blue-violet PL as due to a T[sub 1] arrow right S[sub 0] transition of the neutral oxygen vacancy typical for Si-rich SiO[sub 2] and similar Ge- or Sn-related defects in Ge- and Sn-implanted silicon dioxide. The differences between Si, Ge and Sn will be explained by means of the heavy atom effect. For Geimplanted silicon dioxide layers a strong electroluminescence (EL) well visible with the naked eye and with a power efficiency up to 5 x 10[sup -4] was achieved. The EL spectrum correlates very well with the PL one. Whereas the EL intensity shows a linear dependence on the injection current over three orders of magnitude, the shape of the EL spectrum remains unchanged. The I - V dependence exhibiting the typical behavior of Fowler-Nordheim tunneling shows an increase of the breakdown voltage and the tunnel current in comparison to the unimplanted material. Finally, the suitability of Ge-implanted silicon dioxide layers for optoelectronic applications is briefly discussed. PACS: 78.60.F; 78.55; 61.72.T; 85.30.T;... [ABSTRACT FROM AUTHOR]

A Ge nanocrystal layer embedded in a thin gate oxide was prepared by ion beam synthesis in direct-tunneling distance to the Si substrate. The write performance was investigated in metal-oxide-semiconductor capacitors by means of capacitance measurements. With the experimental data and calculations using a floating-gate-like approach, the distribution of the tunneling oxide thickness dtox can be determined in high precision confirmed by high-angle annular dark-field scanning transmission electron microscopy imaging. The evolution of dtox during heat treatment is discussed in terms of Ostwald ripening; i.e., dtox increases with annealing time. [ABSTRACT FROM AUTHOR]

Examines the depth distribution of germanium (Ge) implanted into thermally grown SiO[sub 2] films. Discovery of the redistribution of the as-implanted Ge profile; Formation of the crystalline Ge nanoclusters; Discussion of the evolution of nanoclusters.

Investigates the photoluminescence and electroluminescence (EL) properties of germanium (Ge)-implanted silicon dioxide (SiO[sub 2]) layers thermally grown on a silicon substrate. Comparison of Ge-implanted SiO[sub 2] layers with Si-implanted SiO[sub 2] films; Analysis of the PL spectra as a function of annealing temperature; Magnitude of EL efficiency.

The motivation of this work is the tailored growth of Ge nanocrystals for photovoltaic applications. The use of superlattices provides a reliable method to control the Ge nanocrystal size after phase separation. In this paper, we report on the deposition of (GeOx–SiO2) superlattices via reactive dc magnetron sputtering and the self-ordered Ge nanocrystal formation during subsequent annealing. Attention is directed mainly to define proper deposition conditions for tuning the GeOx composition between elemental Ge (x=0) and GeO2 (x=2) by the variation in the deposition temperature and the oxygen partial pressure. A convenient process window has been found which allows sequential GeOx–SiO2 deposition without changing the oxygen partial pressure during deposition. The phase separation and Ge nanocrystal formation after subsequent annealing were investigated with in situ x-ray scattering, Raman spectroscopy, and electron microscopy. By these methods the existence of 2–5 nm Ge nanocrystals at annealing temperatures of 600–750 °C has been confirmed which is within the superlattice stability range. The technique used allows the fabrication of superlattice stacks with very smooth interfaces (roughness<1 nm); thus the Ge nanocrystal layers could be separated by very thin SiO2 films (d<3 nm) which offers interesting possibilities for charge transport via direct tunneling. [ABSTRACT FROM AUTHOR]

Au nanocrystals (NCs) were synthesized in a thin SiO2 layer by ion implantation and annealing in a tight distribution close to the Si/SiO2 interface. Between the NCs and the Si substrate a thin tunneling oxide forms self-organized during annealing totally depleted from Au NCs. Memory behavior is demonstrated by electron charging and discharging on metal–oxide–semiconductor capacitors. Lenticular liquid Au:Si droplets nucleate at the Si/SiO2 interface from silicon regions supersaturated by Au close to the oxide. Au NCs embedded in SiO2 above these droplets are stabilized during annealing due to a modified detailed balance of Au atom detachment and attachment. Capacitance-voltage and spreading resistance measurements reveal the impact of the Au contamination in the Si substrate. Structure and distribution of Au droplets and NCs are characterized by x-ray diffraction and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

It will be reported about the effect of the sputtering gases, Ar and Xe, on FePt clusters formation by magnetron sputtering deposition at high working pressures. All layers, with bulk equivalent thicknesses between 3 to 5 nm, were realized at RT by a sequential layer by layer deposition or a co-deposition of Fe and Pt. After rapid thermal annealing at 500 °C, the highest L10 fraction was found using Xe as sputtering gas: Xe decreases the transformation activation energy and therefore, reduces the critical thickness necessary to obtain the high anistropic ferromagnetic phase. Ar assisted growths lead to FePt clusters in the L10 phase only if the sequential layer deposition is used, whereas for Xe no differences in the deposition techniques were observed. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) and PL excitation (PLE) properties of Sn-implanted SiO[sub 2] layers thermally grown on crystalline Si have been investigated and compared with those from Ge- and Si-implanted SiO[sub 2] layers. In detail, the violet PL of Sn-implanted SiO[sub 2] layers is approximately two and 20 times higher than those of Ge- and Si-implanted SiO[sub 2] layers, respectively. Based on PL, PLE, and decay time measurements, the violet PL is interpreted as due to a triplet-singlet transition of the neutral oxygen vacancy typical for Si-rich SiO[sub 2] and similar Ge- and Sn-related defects in Ge- and Sn-implanted SiO[sub 2] films. The enhancement of the blue-violet PL within the isoelectronic row of Si, Ge, and Sn is explained by means of the heavy atom effect. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Polycrystalline alumina samples ( α -Al 2 O 3 , purity: 99.8%) were irradiated with 63 Cu 5 + ions of 32 MeV kinetic energy (≈0.5 MeV/u) up to fluences of 10 14 ions/cm 2 at various temperatures ranging from 295 to 973 K. Ion beam induced luminescence and emission spectra were monitored at wavelengths from 320 to 800 nm. Optical absorption measurements were performed to deduce color center formation. Results were evaluated by the Birks model to determine the material’s radiation hardness. The applicability of alumina as scintillation screens for ion beam diagnostics could be extended by enhanced temperature operation. Analysis of the emission spectra shows a complex color center formation behavior as a function of fluence and temperature. [ABSTRACT FROM AUTHOR]

We present results of recent development of the color X-ray camera, type SLcam®, allowing detection of X-ray images with few microns resolution. Such spectral resolution is achieved with the use of high-quality polycapillary optics combined with sub-pixel resolution. Imaging of Siemens star resolution test chart reveals that the resolution limit of SLcam® can go down to nearly 5μm. Several real sample examples of measurements carried out at the laboratory, synchrotron, and particle-induced X-ray emission beamlines are shown. This is the first time SLcam® is used as particle-induced X-ray emission detector. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Experiments have been undertaken to explore the possibility of creating an oxygen barrier coating, which is effective in preventing oxidation and oxygen embrittlement of Ti and several low-Al content Ti-base alloys during exposure to oxidizing environments at elevated temperatures. The fabrication process has involved three steps, namely co-deposition of Ti and Al by magnetron sputtering onto a substrate material to be protected, followed by vacuum annealing and plasma immersion ion implantation of fluorine. The first two steps produce an overlay of γ-TiAl while the last step provides the necessary conditions for bringing about the halogen effect upon subsequent high-temperature oxidation. Analysis techniques such as cross-sectional transmission electron microscopy (XTEM) in conjunction with electron energy loss spectroscopy (EELS), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and elastic recoil detection (ERD) have been used to study the microstructure, phase formation and depth distribution of the elements in the coating material. Following oxidation in air at 600°C for 100h, specimens have been prepared for metallographic analysis, and their cross sections have been characterized by scanning electron microscopy (SEM) in combination with EDX, and electron probe microanalysis (EPMA). The results obtained show that during oxidation exposure the coating is capable of forming a protective alumina-containing scale which serves as an oxygen barrier, thereby preventing oxygen embrittlement. In addition, since the only constituents of the coating are Ti and Al, it exhibits excellent chemical substrate compatibility. [Copyright &y& Elsevier]

Abstract: Near equiatomic and Ti-rich Ni–Ti polycrystalline films have been deposited by magnetron co-sputtering using a chamber installed at a synchrotron radiation beamline. The in situ X-ray diffraction studies enabled the identification of different steps of the structural evolution during film processing. The depositions on a 140 nm amorphous SiO2 buffer layer heated at 520 °C (without applying bias voltage, Vb , to the substrate) led to a preferential growth of <100> oriented grains of the Ni–Ti B2 phase from the beginning of film growth until the end of the deposition. Films exhibiting a preferential growth of <110> oriented grains of the Ni–Ti B2 phase from the beginning of the deposition were obtained (without and with a Vb of −45 V) by using a TiN coating with a topmost layer formed by <111> oriented grains. Those trends have been observed for the growth of near equiatomic (≈50.0 at.% Ti–Ni) and Ti-rich (≈50.8 at.% Ti–Ni) Ni–Ti films. Additionally, an ion gun had been commissioned, which allows ion bombardment during sputter deposition or post-deposition ion irradiation. In this first series of experiments, a Ni–Ti film was irradiated with He ions after deposition (without exposing the film to the atmosphere, i.e., avoiding surface oxide formation), thus modifying deliberately the microstructure of the film locally. [Copyright &y& Elsevier]

Scanning capacitance microscopy (SCM) and -spectroscopy (SCS) were applied to study the charge trapping and the charge retention in silicondioxide layers with embedded Ge- or Si-nanoclusters. The nanoclusters were formed by ion beam synthesis. Applying a dc bias to the conductive nano-tip charge injection into the dielectric was achieved. While SCM images visualize the localized trapped charge in the oxide, the locally recorded dC/dV versus V curves allow to quantify the trap density. The evaluation of dC/dV shifts was used to compare the electronic properties of different oxide layers in dependence on the implantation parameters. In addition it is demonstrated, that combined SCM/SCS measurements are a suitable tool for the examination of the charge decay as well as of the reliability and degradation of oxide layers on a nanoscale. [Copyright &y& Elsevier]

Si-based light emitters will be a key element of future optoelectronics. One of the most promising approaches is Ge implantation into thin SiO[sub 2] films on crystalline Si. This system exhibits a strong violet electroluminescence with a power efficiency up to 0.5% [18], but the mechanism of electrical excitation is not yet fully understood. In this paper the electrical excitation of the luminescence centers is investigated by means of electrical and electroluminescence transient measurements. It is found that the most probable way to excite luminescence centers is the impact excitation by hot electrons. Whereas the injection is explained by trap-assisted tunneling of electrons from the substrate into the oxide, the electrons will be transported via traps or in the SiO[sub 2] conduction band. Furthermore, the electroluminescence rise and decay time is estimated to be of the order of 100 μs. [ABSTRACT FROM AUTHOR]

Rare earth oxides are promising candidates for future integration into nano-electronics. A key property of these oxides is their ability to form silicates in order to replace the interfacial layer in Si-based complementary metal-oxide field effect transistors. In this work a detailed study of lanthanum lutetium oxide based gate stacks is presented. Special attention is given to the silicate formation at temperatures typical for CMOS processing. The experimental analysis is based on hard x-ray photoemission spectroscopy complemented by standard laboratory experiments as Rutherford backscattering spectrometry and high-resolution transmission electron microscopy. Homogenously distributed La silicate and Lu silicate at the Si interface are proven to form already during gate oxide deposition. During the thermal treatment Si atoms diffuse through the oxide layer towards the TiN metal gate. This mechanism is identified to be promoted via Lu-O bonds, whereby the diffusion of La was found to be less important. [ABSTRACT FROM AUTHOR]

Nowadays ferromagnetism is often found in potential diluted magnetic semiconductor systems. However, many authors argue that the observed ferromagnetism stems from ferromagnetic precipitates or spinodal decomposition rather than from carrier-mediated magnetic impurities, as required for a diluted magnetic semiconductor. In the present article, we answer this question for Fe-implanted ZnO single crystals comprehensively. Different implantation fluences, temperatures, and post-implantation annealing temperatures have been chosen in order to evaluate the structural and magnetic properties over a wide range of parameters. Three different regimes with respect to Fe concentration and process temperature are found: (1) Disperse Fe2+ and Fe3+ at low Fe concentrations and low processing temperatures, (2) FeZn2O4 at very high processing temperatures, and (3) an intermediate regime with a coexistence of metallic Fe (Fe0) and ionic Fe (Fe2+ and Fe3+). Ferromagnetism is only observed in the latter two cases, where inverted spinel ZnFe2O4 and α-Fe nanocrystals are the origin of the observed ferromagnetic behavior, respectively. The ionic Fe in the last case could contribute to a carrier-mediated coupling. However, the separation between Fe ions is too large to couple ferromagnetically due to the lack of p-type carrier. For comparison, investigations of Fe-implanted epitaxial ZnO thin films are presented. [ABSTRACT FROM AUTHOR]

In the past decade, room temperature ferromagnetism was often observed in transition metal doped semiconductors, which were claimed as diluted magnetic semiconductors (DMS). Nowadays intensive activities are devoted to clarify weather the observed ferromagnetism stems from carrier mediated magnetic impurities, ferromagnetic precipitates, or spinodal decomposition. In this paper, we have correlated the structural and magnetic properties of transition metal doped ZnO, TiO2, and Si, prepared by ion implantation. Crystalline precipitates, i.e., transition metal (Co, Ni) and Mn-silicide nanocrystals, are responsible for the magnetism. Additionally due to their orientation nature with respect to the host, these nanocrystals in some cases are not detectable by conventional x-ray diffraction (XRD). This nature results in the pitfall of using XRD to exclude magnetic precipitates in DMS materials. [ABSTRACT FROM AUTHOR]

Highlights • Time of flight secondary ion mass spectrometry in a helium ion microscope. • Sub-8 nm lateral resolution in secondary ion imaging. • Cost effective and adaptable to existing devices. • Advanced ion optical simulation. Abstract A helium ion microscope, known for high resolution imaging and modification with helium or neon ions, has been equipped with a time-of-flight spectrometer for compositional analysis. Here we report on its design, implementation and show first results of this powerful add-on. Our design considerations were based on the results of detailed ion collision cascade simulations that focus on the physically achievable resolution for various detection limits. Different secondary ion extraction geometries and spectrometer types are considered and compared with respect to the demands and limitations of the microscope. As a result the development and evaluation of a secondary ion extraction optics and time-of-flight spectrometer that allows the parallel measurement of all secondary ion masses is reported. First experimental results demonstrate an excellent mass resolution as well as high-resolution secondary ion imaging capabilities with sub-8 nm lateral resolution. The combination of high resolution secondary electron images and mass-separated sputtered ion distributions have a high potential to answer open questions in microbiology, cell biology, earth sciences and materials research. [ABSTRACT FROM AUTHOR]

The recently installed and unique PIXE (particle-induced X-ray emission) set-up at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is mainly dedicated to applications for a detailed overview of elemental composition over large sample areas within a short time even at trace level. The so-called High-Speed-PIXE (HS-PIXE), a combination of a pnCCD-based pixel-detector with polycapillary X-ray optics, offers simultaneous imaging of sample areas up to 12 × 12 mm 2 with a lateral resolution better than 100 μm. Each of the 264 × 264 individual pixels detects X-ray photons in an energy range from 2 keV to 20 keV with an energy resolution of 152 eV (@Mn-K α ). A high precision sample manipulator offers the inspection of areas up to 250 × 250 mm 2 . During first experiments the determined resolution is (76 ± 23) μm using a sample of well-known sharp-edged chromium patterns. Trace element analysis has been performed using a geological sample, a tin ore, with an average Ta-concentration below 0.1 at.%. Fine-zoned structures became visible in the Ta-L α intensity map within only 45 min. The High-Speed-PIXE closes a gap in the analytical process flow chain especially for geoanalytical characterisations. It is a unique and fast detection system to identify areas of interest in comparably short time at large-area scale for further analysis. [ABSTRACT FROM AUTHOR]

Time of flight backscattering spectrometry (ToF-BS) was successfully implemented in a helium ion microscope (HIM). Its integration introduces the ability to perform laterally resolved elemental analysis as well as elemental depth profiling on the nm scale. A lateral resolution of ≤ 54 nm and a time resolution of Δ t ≤ 17 ns ( Δ t / t ≤ 5.4 % ) are achieved. By using the energy of the backscattered particles for contrast generation, we introduce a new imaging method to the HIM allowing direct elemental mapping as well as local spectrometry. In addition laterally resolved time of flight secondary ion mass spectrometry (ToF-SIMS) can be performed with the same setup. Time of flight is implemented by pulsing the primary ion beam. This is achieved in a cost effective and minimal invasive way that does not influence the high resolution capabilities of the microscope when operating in standard secondary electron (SE) imaging mode. This technique can thus be easily adapted to existing devices. The particular implementation of ToF-BS and ToF-SIMS techniques are described, results are presented and advantages, difficulties and limitations of this new techniques are discussed. [ABSTRACT FROM AUTHOR]

Ge-nanocrystals (NCs) were synthesized in amorphous TaZrOx by thermal annealing of co-sputtered Ge-TaZrOx layers. Formation of spherical shaped Ge-NCs with small variation of size, areal density, and depth distribution was confirmed by high-resolution transmission electron microscopy. The charge storage characteristics of the Ge-NCs were investigated by capacitance-voltage and constant-capacity measurements using metal-insulator-semiconductor structures. Samples with Ge-NCs exhibit a maximum memory window of 5 V by sweeping the bias voltage from --7 V to 7 V and back. Below this maximum, the width of the memory window can be controlled by the bias voltage. The fitted slope of the memory window versus bias voltage characteristics is very close to 1 for samples with one layer Ge-NCs. A second layer Ge-NCs does not result in a second flat stair in the memory window characteristics. Constant-capacity measurements indicate charge storage in trapping centers at the interfaces between the Ge-NCs and the surrounding materials (amorphous matrix/tunneling oxide). Charge loss occurs by thermal detrapping and subsequent band-to-band tunneling. Reference samples without Ge-NCs do not show any memory window. [ABSTRACT FROM AUTHOR]

Abstract: Nickel–Titanium (Ni–Ti) thin film shape memory alloys (SMAs) have been widely projected as novel materials which can be utilized in microdevices. Characterization of their physical properties and its correlation with phase transformations has been a challenging issue. In the present study, X-ray beam diffraction has been utilized to obtain the structural information at different temperatures while cooling. Simultaneously, electrical resistivity (ER) was measured in the phase transformation temperature range. The variation of ER and integral area of the individual diffraction peaks of the different phases as a function of temperature have been compared. A mismatch between the conventional interpretation of ER variation and the results of the XRD data has been clearly identified. [Copyright &y& Elsevier]

Abstract: A special designed high-temperature vacuum chamber for in situ X-ray diffraction (XRD) measurements was used to study structural phase formation and transformation kinetics in molybdenum during oxygen ion implantation and post-annealing treatment. Oxygen ions with an energy of 1.5MeV were implanted in polycrystalline molybdenum up to a fluence of 3×1018/cm2 at different temperatures (160–700°C). Subsequently, implanted samples were annealed up to 700°C for in situ study during synthesis of buried oxide layers. Complementary, transmission electron microscopy (TEM) and sputter Auger electron spectroscopy (AES) were employed to obtain depth-dependent information concerning both the crystal structure and its elemental composition. The formation of different molybdenum oxides during oxygen implantation and post-implantation annealing process was observed by in situ X-ray analysis. The XRD spectra of samples implanted at 160°C show that MoO3 and/or Mo4O11 precipitates have been formed, whereas implantation in the temperature range 300–700°C preferably leads to the MoO2 phase formation. [Copyright &y& Elsevier]

Abstract: An in situ X-ray diffraction study was performed to characterize aspects of the kinetics of structural phase formations in transition metals during oxygen implantation. A specially designed high-temperature vacuum chamber for X-ray measurements was installed at the high-energy implantation beamline of the 3MV-Tandetron accelerator. Titanium and molybdenum sheets were implanted with oxygen ions with an energy of 1.5MeV up to a fluence of 1.6×1018O+-ions/cm2 without sample cooling. During implantation, the phase formation was continually investigated by in situ and real-time X-ray diffraction (XRD) with a position-sensitive proportional counter system. The phase formation was studied during annealing process by in situ XRD. The obtained results were compared with ex situ XRD measurements performed by different techniques at a standard diffractometer. The analysis of XRD patterns indicates the formation of a buried MoO2 layer in molybdenum. In the Ti samples no buried oxide is formed due to significant oxygen diffusion. [Copyright &y& Elsevier]

The electrical conduction mechanism of Ge-implanted SiO2 films exhibiting room-temperature blue electroluminescence with a power efficiency of up to 5×10−4 [Appl. Phys. Lett. 71 (1997) 2809] is investigated. In detail it will be shown that the current–voltage characteristic of Ge-implanted SiO2 layers for applied electric fields between 4.5 and 7 MV cm−1 can be modeled very well with the space charge limited (SCL) conduction mechanism in the trap-filled-limited (TFL) region. The current density j shows a power law dependence j∝Eα of the applied electric field E, and the temperature dependence of α exhibits the typical behavior of TFL injection currents. For applied electric fields above 7 MV cm−1 the charge transport mechanism is explained by SCL currents which are superimposed by effects of field emission, impact ionization, and electron–hole recombination. [Copyright &y& Elsevier]

The formation of Ti2AlN by solid state reaction between layers of wurtzite-AlN and α-Ti was characterized by in situ x-ray scattering. The sequential deposition of these layers by dual magnetron sputtering onto Al2O3(0001) at 200 °C yielded smooth, heteroepitaxial (0001) oriented films, with abrupt AlN/Ti interfaces as shown by x-ray reflectivity and Rutherford backscattering spectroscopy. Annealing at 400 °C led to AlN decomposition and diffusion of released Al and N into the Ti layers, with formation of Ti3AlN. Further annealing at 500 °C resulted in a phase transformation into Ti2AlN(0001) after only 5 min. [ABSTRACT FROM AUTHOR]

ZrO2/ZrGe2O3 superlattices were deposited on Si wafers and thermally treated at different temperatures to form Ge nanocrystals embedded in a ZrO2 matrix. The formation process of Ge nanocrystals has been investigated by means of methods like Raman spectroscopy, X-ray diffraction, and transmission electron microscopy. With increasing temperature, there is first a separation process leading to flat Ge clusters between amorphous ZrO2 layers and then at about 630 °C a crystallization process of both the Ge clusters and the ZrO2 layers starts simultaneously. An orientation relation of the Ge and ZrO2 nanocrystals could be proven by high-resolution transmission electron microscopy. [ABSTRACT FROM AUTHOR]

We report on the fabrication of pseudomorphic wurtzite Ga1-xMnxN 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, and 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. [ABSTRACT FROM AUTHOR]