Željko Pastuović

New developments in IBIC for the study of charge transport properties of radiation detector materials

Abstract A study of charge transport properties in various radiation detector materials (Si, Si(Li), CdTe, GaAs, CVD and natural diamond) has become in recent years one of the major applications of the nuclear microprobe technique IBIC. In order to extend the capabilities of IBIC, further developments of the technique were considered. By changing the projectile type and energy, different sample layers in the range between one and several hundreds of microns can be imaged. A trigger signal from simultaneously detected secondary electrons or a transmitted ion enables time-resolved IBIC imaging to be carried out. Furthermore, simultaneous STIM imaging showing areal density distributions, can be essential for the interpretation of IBIC images.

Probability of divacancy trap production in silicon diodes exposed to focused ion beam irradiation

We present ion beam induced charge (IBIC) measurements of the critical displacement damage dose Dd values and modeling of the probability of divacancy trap production in p+−n−n+ silicon diodes exposed to megaelectron volt energy ion beam irradiation. The normalized induced charge (Q0/Q) measured by He ion probe in tested silicon diodes irradiated by focused He, Li, O, and Cl ion beams with energies of about 0.3 MeV/u increases linearly with Dd according to the modified radiation damage function and nonionizing energy loss (NIEL) theory. A simple IBIC model based on Gunn theorem showed clear dependence of the induced charge Q and corresponding equivalent damage factor Ked value on both a depth profile of charge created by ionizing particle (probe) and a depth distribution of stable defects created from primary defects produced by damaging ions. The average probability of the divacancy production (defined as the ratio of the final electrical active defect quantity and primary ion induced vacancy quantity fo...

Characterisation of SiC by IBIC and other IBA techniques

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.

Frontal IBICC study of the induced proton radiation damage in CdTe detectors

Abstract Within a continuous international effort in developing the non-cryogenic semiconductor detectors for gamma ray spectroscopy, various wide gap materials were considered. With a best performance achieved, CdTe- and CdZnTe-based detectors become today widely accepted and commercially available. In addition to possible future use of such detectors for particle-induced gamma-ray emission (PIGE), nuclear microprobes are in recent years applied more as their characterisation tool using the ion beam-induced charge collection (IBICC) technique. Several CdTe detectors of 2×2×1 mm 3 size were used in this study. On the basis of frontal IBICC measurements of the charge collection efficiency (CCE) distribution, the spectroscopy performance of detectors were measured. Further degradation of charge collection efficiency and the downward trend in peak position were studied by on-line irradiation of CdTe samples with 3 MeV protons up to 10 10 p/cm 2 radiation dose.

Defects in polycrystalline silicon studied by IBICC

In the research of semiconducting materials, ion beam-induced charge collection (IBICC) technique can provide interesting and straightforward information about the different electronic device characteristics. This nuclear microprobe technique was used for the qualitative analysis of charge collection efficiency spatial distribution in three different types of EFG silicon material. Using IBICC technique, we studied the influence of present light impurities (oxygen, carbon) on electrical activity of extended defects. It is shown that oxygen segregating close to structural defects influences their electrical activity, while for carbon we did not observe the same effect. We demonstrated that IBICC technique could be applied to provide spatial information about the position of electrically active defects, and/or their activation or deactivation during subsequent processing.

IBIC studies of structural defect activity in different polycrystalline silicon material

In the research of semiconducting materials, the ion beam induced charge collection (IBIC) technique can provide interesting and straightforward information about the different electronic device characteristics. This nuclear microprobe technique was used for the qualitative analysis of the spatial distribution of charge collection efficiency in several types of poly-Si material. We studied the influence of light impurities (oxygen, carbon) on electrical activity of extended defects. It is shown that oxygen segregating close to structural defects influences their electrical activity, while for carbon we did not observe the same effect. We demonstrated that IBIC can be applied to provide spatial information about the position of electrically active defects and its activation during subsequent processing.

IBIC study of charge collection properties in Si(Li) detectors

Abstract The nuclear microprobe technique ion beam induced charge (IBIC) has been used to probe the charge collection efficiency across the front surface of Si(Li) X-ray detectors. IBIC was performed using 2.667 MeV 6Li ions, avoiding the large penetration depth of the conventional proton-IBIC. The front surfaces of two Si(Li) detectors were scanned to image inhomogeneities of incomplete charge collection (ICC). The relationship between the X-ray peak shape of the tested detectors and the degree of incomplete charge collection is discussed.

ION BEAM TECHNIQUES FOR ANALYSIS OF CULTURAL HERITAGE OBJECTS: COLLABORATION BETWEEN THE RUÐER BOŠKOVIĆ INSTITUTE AND THE CROATIAN CONSERVATION INSTITUTE

Collaboration between the Croatian Conservation Institute (CCI) and the Laboratory for Ion Beam Interactions of the Ruđer Boskovic Institute (RBI) in the field of analysis of cultural heritage objects is reviewed. This collaboration is based on applications of ion beam analytical methods for characterization of inorganic pigments, alloys and other materials in paintings, statues and other objects of cultural value that are under restoration/conservation process by the CCI specialists. Elemental composition of samples is determined by using ion beam analysis techniques such as Particle Induced X-Ray Emission (PIXE) and Rutherford Backscattering Spectrometry (RBS). The work is performed at the ion microprobe and other end-stations installed with the RBI Tandem accelerator facility. The methodology of work will be shortly presented and illustrated by one example of recently performed work.