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The installation of a new 1.0 MV Tandetron accelerator and a recent upgrade of the 6.0 MV Tandem Van de Graaff accelerator increased the application possibilities of the Zagreb ion microbeam system. Several ion sources enable now the selection of a wide variety of ions. Most of them can be focused by the existing microprobe system. Sample positioning tools and new scanner control options are implemented in the new generation of SPECTOR data acquisition system. Details of the upgrades are presented.

The control of the carrier lifetime profile in semiconductor power devices is of fundamental importance to optimize device parameters. With respect to traditional technologies such as diffusion of metallic impurities, light ion irradiation at low doses provides precise spatial localization of defects acting as carrier traps and recombination centres. Hence, the generation of suitable lifetime profiles obtained by controlling ion fluence and energy allows the reduction of turn-off times and switching losses in power electronic devices. In order to characterise the effects of ion irradiation on carrier lifetime profiles, we have used the ion beam induced charge collection (IBIC) technique in lateral geometry to measure charge collection efficiency (CCE) profiles in silicon p+/n/n+ diodes under different applied bias conditions before and after a frontal 6.5 MeV He++ ion implantation at a total fluence of 2 × 10 12 ions/cm 2 . After the irradiation, the profile shows a clear drop of charge collection efficiency which occurs at the end of the ion range. The formalism based on Shockley–Ramo–Gunn’s theorem was applied to interpret the CCE profiles in both virgin and irradiated samples and to assess the free carrier lifetime profile modification following the radiation damage.

The Al–Cu–Fe system is interesting due to the existence of the quasicrystalline phase Al 62.5 Cu 25 Fe 12.5 as well as its approximant phases. A two-step procedure of thin film preparation is considered: deposition of a multilayer structure of individual elements and consequential annealing. To analyze the diffusion processes trilayers of individual elements were deposited by sputtering with a total thickness of about 400 nm. Afterwards, the samples were annealed in tube furnace in inert atmosphere. Rutherford backscattering spectrometry, Auger electron spectrometry and X-ray diffraction were used to quantify the depth profiles. The results point out to a three-stage process as a function of rising temperature: first Al and Cu form the γ-Al 4 Cu 9 compound layer; second the aluminium spreads throughout the film with copper and iron mainly divided. The β-Al(Cu,Fe) phase is observed. Complete homogenization is followed afterwards.

We have fabricated a position sensitive radiation detector by creating radiation damage regions in a Si photodiode. Radiation damage was created in layers at a depth of several mum by 7Li and 16O ion beams which had an energy between 2 and 4MeV. Ions were focused and scanned using a nuclear microprobe facility. The ion beam induced charge (IBIC) signals created in diodes during irradiation were simultaneously measured to monitor the exact ion beam fluence and analyzed to estimate the amount of defects created. By controlling the ion microbeam scanning system, graduated and position dependent radiation damage was produced in different micro-patterns. Such structures may be used as a simple position sensitive radiation sensor

The energy-dispersive x-ray fluorescence (EDXRF) technique has limitations in the quantitative analysis of light elements (low-Z analytes with Z < 10), for many reasons. This work, however, circumvents the problem through an a priori determination of low-Z analytes, representative of plant-based samples. The main purpose of this work was to characterize the major elements in the dark matrix of some plant-based samples (including biomonitors) using Rutherford backscattering spectrometry (RBS), and the results provided as a generalized input for EDXRF analysis. The derived stoichiometry and mass ratio for the moss, lichen, and cotton cellulose samples analyzed were found to be similar and close to C 7 H 10 O 5 , with an average matrix of C = 49.8%, H = 4.0% and O = 45.8%. Quantitative analysis of plant-based reference material IAEA-336 (lichen) was subsequently carried out. Use of the a priori determined dark matrix elements (from one-time RBS spectrometry) extended the scope of applicability of the EDXRF quantitative methods used, and improved accuracy in the elemental analysis of plant-based samples. The results obtained were in good agreement with the reference values.

In order to expand the application possibilities of ion beam induced charge (IBIC) technique to a wider range of semiconductor materials and devices, three novel modes of measurements have been developed. The fast beam deflector was used to produce ns pulses of single ions and the trigger signal provides a time scale for time resolved IBIC measurements. Longer pulses (>100 ns) containing tens or hundreds of ions were used to enhance IBIC signals in materials with poor charge transport properties. Continuous beam current (10 pA to 1 nA) of 3 MeV protons was used to measure ion beam induced voltage (IBIV) in thin amorphous silicon films. In these samples it was possible to correlate the charge collection properties with elemental distribution measured simultaneously with PIXE. Radiation damage was shown to be negligible for doses below 10^7 protons micro m-2.

Hydrogenated amorphous silicon solar cells were studied by the use of Rutherford backscattering and elastic recoil detection analysis. By the application of different ion types, energies and geometry, the layered structure of solar cells as well as their hydrogen content were determined. Results were correlated to optical and electrical properties of samples and the difference between the two types of solar cells, with “higher” and “lower efficiency”, is discussed.

Characteristics of Li ion batteries depend on resistance at interfaces of gel–polymer electrolyte with Li anode and with spinel cathode, respectively. Interfacial resistances are correlated to the spatial distribution of Li and other chemical species in vicinity of interfaces of gel–polymer with cathode or anode. Studies of gel–polymer interfaces in Li ion battery semicell samples (Li-anode/gel–polymer and spinel LiMn2O4 cathode/gel–polymer) have been performed by proton microbeam scans over the sample cross-section. PIGE spectroscopy has been used for Li and F detection and PIXE spectroscopy for detection of S, Mn and other elements of interest.

We have investigated powdered mixtures PbCO 3 ·2PbO+Ag 2 O and PbCO 3 ·PbO+Ag 2 O prefired in CO 2 and annealed in CO 2 +O 2 atmosphere. The samples exhibit resistive properties characteristic for superconductivity exceeding room temperature.

Area selective irradiation using MeV ions having different ranges has been performed in a nuclear microprobe to produce radiation damage microstructures in silicon photodiodes. IBIC (Ion Beam Induced Charge) technique has been used for on line monitoring of radiation damage produced by different fluences of He, Li and O ions of MeV energies. Three-dimensional patterning of radiation damage structures may be used for different applications. By creating a region of constant damage gradient in Si photodiode, position sensitive radiation detection has been demonstrated.

With intention to be used for the 3D analysis of hydrogen, a new ion-induced electron emission (IEE) ERDA system has been installed on the nuclear microprobe. A better depth resolution has been obtained with IEE particle identification system when compared to conventional ERDA systems that use stopping foil. Spectra of the forward scattered ions as well as the recoiled atoms are collected using the same particle detector. This simplifies normalization needed for quantitative analysis without the use of an additional detector. However, well defined but rather small solid angle of the IEE detector requires higher ion beam currents if sufficient sensitivity for H detection needs to be achieved. High beam currents focused to several micrometer spot size lead to rather high current densities and increased probability of H loss from the sample, which may limit the achievable sensitivity. By positioning IEE ERDA system at 45° instead of 30°, as well as by using heavier ions (O ions instead of He), two orders of magnitude better sensitivity can be obtained without a significant deterioration of depth resolution due to the increased recoil cross-section. In this work, several different sample types containing H have been studied. The capabilities of system for 3D imaging of H in samples have been demonstrated.

Bystroem-Evers compound Ag5 Pb2O6 has been annealed at 500-540 K under flow of electric current which results in a textured structure and anisotropic colossal electric conductivity (> 10^9 ohm-1cm-1) between 210-525 K. The related physical properties are primarly governed by dissociation of Ag from c-axis channels and lattice strains which in turn depend upon electric current., 13 pages, 7 figures

Thin tungsten films were prepared by sputtering of pure tungsten in a cylindrical magnetron device. The XRD-patterns of tungsten films deposited at 3.5 Pa argon pressure regularly exhibited only a very broad signal centered at 2θ≈40°—a distinctive mark of amorphous metals and alloys. The grain size of such amorphous-like tungsten material was estimated to be approximately 2 nm, while SAXS measurements yield a radius of gyration of 1.4 nm. Its thermal coefficient of the electric resistivity at room temperature was negative—a characteristic feature of amorphous metals and alloys. Thermal stability of the amorphous-like tungsten films was investigated by isochronal heating up to 720 °C in vacuum, with continuous monitoring of electric resistivity. The obtained results indicate that amorphous-like tungsten is thermally stable up to 450 °C.

Ion beam induced charge (IBIC) is already well established technique used for studying electronic properties of semiconductor materials and devices. Recently introduced Time Resolved IBIC (TRIBIC) method gives additional possibility to observe and analyse electric response of semiconductors (on a time scale) to the impact of a single high energy ion. In this work we present an attempt to extend the use of focused ion beams in characterising semiconductor materials and so enrich the information available from IBIC and TRIBIC experiments. High energy protons focused by a nuclear microprobe equipped with a controlled temperature stage were used to irradiate fully depleted samples and fill the trap levels at low temperatures. Thermally stimulated current (TSC) was then recorded during heating as a function of temperature. We observed difference in TSC spectra collected between 100 K and 300 K by selective irradiation of the samples close to either positive or negative electrode. The preliminary results indicate the usefulness of the method and justify the use of the focused ion beams to distinguish between the hole and electron traps present in materials.

Temperature dependence of the ion beam induced charge (IBIC) collection efficiency was studied in CdZnTe (CZT) in the range 166–330 K. A lateral surface between sputtered Au electrodes of the simple planar counter-grade CZT was irradiated by a focused 3 MeV proton microbeam. Measured charge collection efficiency profiles change with temperature. In order to understand better the charge collection mechanism at different temperatures time resolved ion beam induced charge (TRIBIC) technique was applied as well. Charge transients from the output of the preamplifier recorded by a fast storage oscilloscope showed that the electron transport is strongly influenced by temperature. Both IBIC and TRIBIC measurements showed negligible hole charge collection contribution in the studied detector.

Single crystals of cytosine monohydrate were used as a model for studying hole transfer in systems related to nucleic acids. Holes (and excess electrons) were induced by ionizing radiation at 15 K. Thiocytosine, imbedded in the cytosine lattice in variable amounts, served as a hole trap. The holes which are stabilized at thiocytosine give rise to an EPR signal well separated from the signals of other radicals present. The ratio of the amount of thiocytosine cations (i.e. trapped holes) to the amount of the remaining radicals is at least 10 times larger than the stochiometric thiocytosine/cytosine ratio, which displays significant hole transfer from cytosine to thiocytosine and subsequent trapping by the latter. The analysis of the hole transfer range in the lattice of cytosine monohydrate, composed of parallel sheets of cytosine bases, is rather complex. Unlike DNA, where each base in a  -stack is flanked by one base on each side, each cytosine base in the present system is surrounded by four other bases in a  -stacked structure. This results in a higher probability of finding a thiocytosine base in a closer proximity to the initially formed hole. Consequently, it seems that the net hole transfer is not larger than about 4 inter-base distances (~13 &Aring ; ; ) in the present system.

Several new technological applications of silicon carbide have attracted significant attention in recent years. As a wide gap semiconductor it has the capability to be used as a room temperature radiation detector. For most applications, material properties like homogeneity of charge transport, presence of defects, resistance to radiation damage, influence of light impurities (such as hydrogen) are of prime importance. Two different kinds of samples, crystalline (4H–SiC) and thin, amorphous (a-Si1−xCx:H) films, were studied using ion beam techniques. In the case of SiC single crystal radiation detectors, Li and proton beams with a wide range of energies were used to probe the charge collection efficiency at different device depths using the ion beam induced charge technique. Thin, amorphous and microcrystalline Si1−xCx:H films with a different stoichiometry and different degrees of structural ordering were examined using RBS and ERDA.

Some interesting results that could be eventually explained as coming from superconductivity (SC) in Pb 3 CO 5 -Ag 2 O (PACO) system are reported. Samples prepared at 340–350 °C in combined CO 2 -O 2 atmosphere exhibit low resistance states at room temperature (RT) with resistivity three orders of magnitude lower than that of silver. In addition, characteristic threshold current density dependence of electric resistance together with the DC susceptibility data obtained on balance support the idea of superconductivity in PACO system.

We have found that the doping of Pb3O4 with silver and its treatment in elevated oxygen pressure result in a number of novel metallic phases. The Pb1-xAgxO1+δ phases (0.4 < δ < 0.6; x ≈ 0.1-0.15) prepared at 260-330 °C exhibit electric and magnetic properties compatible with the indication of superconductivity (SC), which appears at Tc ≈ 285 K. SC can be attributed to Ag doped lead sesquioxide Pb2-xAgxO3-y (y ≈ ±0.2).

Deep trap levels in the semi-insulating SI CdZnTe detector material were characterized by simultaneous multiple peak analysis based on thermally stimulated current TSC measurements. In our TSCs that have been published previously electron hole pairs were created through the use of proton beam irradiation. Charge carriers were captured in deep traps and afterward released by thermal emission, which was recorded in the 90– 300 K range. We showed that the obtained TSC spectra could be well fitted with a unique set of 14 different deep traps, which were all simultaneously and completely characterized. The obtained trap data are in good accordance with earlier deep trap characterizations of the other authors obtained on similar SI CdZnTe materials using different methods.