Wolfgang Pilz

From sponge to dot arrays on (100) Ge by increasing the energy of ion impacts

Ge surfaces of up to 780 K temperature have been irradiated at normal incidence with up to 1017 Bi+ ions cm−2 having kinetic energies from 10 to 30 keV. The resulting surface morphologies have been studied by scanning electron microscopy. While at room temperature the impacts of high-energy Bi+ ions result in porous networks, at elevated irradiation temperatures hexagonally ordered dot arrays are formed, whereas after a further temperature increase the surface becomes smooth. The comprehensive experimental studies have been summarized in a phase diagram of surface morphologies in the ion energy versus substrate temperature plane. In this phase diagram, the onset of dot formation with increasing substrate temperature has been consistently modeled by nanomelting of the collision cascade volume of ion impacts, thereby taking into account the thermodynamic parameters of amorphous Ge (melt temperature, heat of fusion, and heat capacity) as well as the energy density deposited in the cascade volume as predicted...

Temperature shift of neutron resonances

Temperature-induced shift of neutron resonances have been experimentally observed studying low-energy resonances of 103Rh, 109Ag, l61Dy and l63Dy with a time-of-flight spectrometer at the Dubna pulsed reactor The shifts are regarded as an analogue to the second-order Doppler effect in Mossbauer gamma-ray spectroscopy.

Polyatomic ions from a high current ion implanter driven by a liquid metal ion source

High current liquid metal ion sources are well known and found their first application as field emission electric propulsion thrusters in space technology. The aim of this work is the adaption of such kind of sources in broad ion beam technology. Surface patterning based on self-organized nano-structures on, e.g., semiconductor materials formed by heavy mono- or polyatomic ion irradiation from liquid metal (alloy) ion sources (LMAISs) is a very promising technique. LMAISs are nearly the only type of sources delivering polyatomic ions from about half of the periodic table elements. To overcome the lack of only very small treated areas by applying a focused ion beam equipped with such sources, the technology taken from space propulsion systems was transferred into a large single-end ion implanter. The main component is an ion beam injector based on high current LMAISs combined with suited ion optics allocating ion currents in the μA range in a nearly parallel beam of a few mm in diameter. Different types of LMAIS (needle, porous emitter, and capillary) are presented and characterized. The ion beam injector design is specified as well as the implementation of this module into a 200 kV high current ion implanter operating at the HZDR Ion Beam Center. Finally, the obtained results of large area surface modification of Ge using polyatomic Bi2+ ions at room temperature from a GaBi capillary LMAIS will be presented and discussed.

Temperature Dependence On The Emission Characteristics Of A AuGe Liquid Metal Alloy Ion Source

Focused ion beam systems employing liquid metal ion sources have become of increasing importance in the microelectronics industry. Maskless ion implantation as a modern patterning technique is one of the most attractive application of Focused Ion Beams. In spite of the fact that a great deal of research has been carried out on liquid metal ion sources, surprisingly few results exist on the temperature dependence of their emission characteristics. In this article we study a AuGe liquid metal alloy ion source. The unusual results are explained in terms of the abnormal behavior of the surface tension of the alloy with temperature.

Doppler broadenings of neutron resonances in crystal lattices compared with the gas-model approximation

Abstract Resonance-parameter uncertainties caused by the gas-model approximation for the description of the Doppler broadenings of the resonances in polycrystalline samples, are estimated for the low-energy resonances of U-238 and Pu-240.

Chemically Induced Shifts of Uranium Neutron Resonances

Transmission spectra were measured with a time-of-flight spectrometer at the Dubna pulsed reactor for several chemical compounds of uranium. The spectra were compared in the regions of low-energy resonances to observe chemically induced shifts which are interpreted as an effect of mean-square charge radius changes of the nuclei by neutron capture.