Elongation mechanism of the ion shaping of embedded gold nanoparticles under swift heavy ion irradiation

The elongation process under swift heavy ion irradiation (74 MeV Kr ions) of gold NPs, with a diameter in the range 10-30 nm, and embedded in a silica matrix has been investigated by combining experiment and simulation techniques: three-dimensional thermal spike (3DTS), molecular dynamics (MD) and a phenomenological simulation code specially developed for this study. 3DTS simulations evidence the formation of a track in the host matrix and the melting of the NP after the passage of the impinging ion. MD simulations demonstrate that melted NPs have enough time to expand after each ion impact. Our phenomenological simulation relies on the expansion of the melted NP, which flows in the track in silica with modified (lower) density, followed by its recrystallization upon cooling. Finally, the elongation of the spherical NP into a cylindrical one, with a length proportional to its initial size and a width close to the diameter of the track, is the result of the superposition of the independent effects of each expansion/recrystallization process occurring for each ion impact. In agreement with experiment, the simulation shows the gradual elongation of spherical NPs in the ion-beam direction until their widths saturate in the steady state and reach a value close to the track diameter. Moreover, the simulations indicate that the expansion of the gold NP is incomplete at each ion impact.Peer reviewe

Determination of the energy standards by precision beta-spectroscopy methods

The technique allowing one to determine energy of transitions in atomic nuclei with high accuracy is developed. It is based on measurement of a difference of energy of internal conversion electron lines on high-resolution β- spectrometer π SQRT(2) with iron yoke and radius of an equilibrium orbit r = 50 cm at a constant magnetic spectrometer field. The accuracy of definition of γ-ray energies reaches from 0,2 up to 1 eV in the energy region from 100 up to 500 keV. That completely corresponds to the requirements to energy standards of 4-th order.Розроблено методику, яка дозволяє з високою точністю визначати енергії переходів в атомних ядрах. Методика основана на вимірах енергії електронів внутрішньої конверсії на β-спектрометрі високої роздільної здатності типу π SQRT(2) з залізним ярмом і радіусом рівноважної орбіти ρ = 50 см при постійному магнітному полі спектрометра. Точність визначення енергії переходів сягає від 0,2 до 1 еВ для області енергії від 100 до 500 кеВ, що повністю відповідає вимогам до енергетичних нормалей 4-го порядку.Разработана методика, позволяющая с высокой точностью определять энергии переходов в атомных ядрах. Методика основана на измерении разности энергии линий электронов внутренней конверсии на β- спектрометре высокого разрешения типа π SQRT(2) с железным ярмом и радиусом равновесной орбиты ρ = 50 см при постоянном магнитном поле спектрометра. Точность определения энергии переходов достигает от 0,2 до 1 эВ для области энергии от 100 до 500 кэВ, что полностью соответствует требованиям, предъявляемым к энергетическим нормалям 4-го порядка

Radiation Induced Point and Cluster-Related Defects with Strong Impact to Damage Properties of Silicon Detectors

This work focuses on the investigation of radiation induced defects responsible for the degradation of silicon detectors. Comparative studies of the defects induced by irradiation with 60Co- rays, 6 and 15 MeV electrons, 23 GeV protons and 1 MeV equivalent reactor neutrons revealed the existence of point defects and cluster related centers having a strong impact on damage properties of Si diodes. The detailed relation between the microscopic reasons as based on defect analysis and their macroscopic consequences for detector performance are presented. In particular, it is shown that the changes in the Si device properties after exposure to high levels of 60Co- doses can be completely understood by the formation of two point defects, both depending strongly on the Oxygen concentration in the silicon bulk. Specific for hadron irradiation are the annealing effects which decrease resp. increase the originally observed damage effects as seen by the changes of the depletion voltage. A group of three cluster related defects, revealed as deep hole traps, proved to be responsible specifically for the reverse annealing. Their formation is not affected by the Oxygen content or Si growth procedure suggesting that they are complexes of multi-vacancies located inside extended disordered regions.Comment: 14 pages, 15 figure

Performance studies of the CMS strip tracker before installation

Peer reviewe

CMS physics technical design report : Addendum on high density QCD with heavy ions

Peer reviewe

Electrical behaviour of MIS devices based on Si nanocrystal embedded in SiOxNy and SiOx films

International audienceWe analyse the electrical properties of multilayer made of silicon rich oxide (SRO) and silicon rich nitride (SRN) doped with Neodymium (Nd) layers integrated in MIS (Metal Insulator Semiconductor) device. The aim of such a study consists in fabricating thin layer for future electroluminescent devices doped with rare earth ions (Nd) which benefit from the efficient sensitizing effect of Si nanoclusters (Sinc) towards the Nd3+ ions. The deposition has been performed by reactive magnetron sputtering, consisting in the formation of alternating SRO/SRN films, with nominal thickness of 3 nm for each layer. The multilayer is then composed with 9 periods of SRO/SRN films, which was subsequently submitted to an optimized annealing treatment. The multilayer is deposited on p-type (111) oriented silicon substrate cm. Next, aluminum waswith resistivity in the range 0.001-0.005 thermally evaporated on active layer. Both aluminum and active layers were patterned by wet etching to define the geometry of the device. A second thermal evaporation of aluminum on the back surface was carried out to ensure the ohmic contact with the p-type crystalline silicon. Finally, the devices were annealed into forming gas (H2:N2, 10%) at 390°C to stabilize the electrical properties of the devices. The conduction mechanisms of the MIS structures were studied by analysing thermal and bias dependences of the carriers transport in relation with the silicon content (9, 11 and 15%) of the SRO layer

Ion-matter interaction: the three-dimensional version of the thermal spike model. Application to nanoparticle irradiation with swift heavy ions NA

International audienceIn the framework of swift heavy ion-matter interaction, the thermal spike has proved its worth for nearly two decades. This paper deals with the necessary refinement of the computation due to the kind of materials of interest, i.e. nanomaterials such as multilayered systems or composite films constituted of nanocylinders or nanospheres embedded in an insulating matrix. The three-dimensional computation of the thermal spike model is applied for the first time in the case of ions striking layers containing spherical nanoparticles embedded in a silica matrix. The temperature profiles calculated at each point (x, y, z) of the target for a total duration up to 10(-10) s and different values of ion impact parameter allow a possible explanation of the particle shape change under irradiation with swift heavy ions having an energy of several MeVamu(-1