J. von Borany

Ion beam synthesized nanoclusters for silicon-based light emission

Abstract Strong blue and violet photoluminescence (PL) and electroluminescence (EL) at room temperature has been achieved from thin SiO 2 layers implanted with group IV elements. Thermally grown SiO 2 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 T 1 →S 0 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.

Nanometer scale elemental analysis in the helium ion microscope using time of flight spectrometry.

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 ≤54nm and a time resolution of Δt≤17ns(Δt/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.

Physical aspects of precise spectrometry of α-particles with silicon pn-junction detectors

Abstract Investigations of energy and charge losses have been carried out for silicon planar α-particle detectors. The detectors were manufactured by an advanced technology, using ion implantation and various annealing temperatures. A detailed analysis of the recombination processes in α-particle tracks with a high electron-hole density and a measurement procedure for the main parameters of charge carrier loss have been developed. The procedure consists in the measurement of the pulse amplitude deficit as a function of the reverse bias voltage and the tilting angle as well as in a special treatment for the determination of carrier lifetimes, surface recombination velocities and dead layers. The experimental data show a reduction of the dead layer to 200 A, and of the energy resolution to 9–9.5 keV. The explanation implies possible changes of the doping profile due to acceptor diffusion under thermal treatment and the corresponding modification of the built-in field in the p + -layer. This effect suppresses the surface and Auger recombination of non-equilibrium carriers in tracks of α-particles.

Effect of Ge Content on the Formation of Ge Nanoclusters in Magnetron-Sputtered GeZrOx-Based Structures

Ge-rich ZrO2 films, fabricated by confocal RF magnetron sputtering of pure Ge and ZrO2 targets in Ar plasma, were studied by multi-angle laser ellipsometry, Raman scattering, Auger electron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction for varied deposition conditions and annealing treatments. It was found that as-deposited films are homogeneous for all Ge contents, thermal treatment stimulated a phase separation and a formation of crystalline Ge and ZrO2. The “start point” of this process is in the range of 640–700xa0°C depending on the Ge content. The higher the Ge content, the lower is the temperature necessary for phase separation, nucleation of Ge nanoclusters, and crystallization. Along with this, the crystallization temperature of the tetragonal ZrO2 exceeds that of the Ge phase, which results in the formation of Ge crystallites in an amorphous ZrO2 matrix. The mechanism of phase separation is discussed in detail.

Electrical effects of residual defects in Si after high energy implantation of Ge+ ions and annealing

Abstract This paper describes electrical effects of residual defects after a 12.5 MeV Ge + ion implantation in a dose range of 10 15 to 10 15 cm −2 into n-type Si and subsequent annealing at 1150°C. For analysis of the samples spreading resistance profiling and reverse current measurements of p + /n diodes were used. The results show in a peculiar manner a reduced charge carrier concentration in the depth range between the surface and the projected range of implanted ions. For a Ge dose of 10 15 cm −2 the reverse current of high energy implanted diodes is significantly reduced inside a depletion zone close to the p/n junction. But, for a dose greater than 10 15 cm −2 an increased reverse current is found. It is caused by generation centres located at both sides of the buried damage profile created by the Ge + ions. Therefore in this paper a method will be proposed to eliminate the undesired electrical effects of high energy implantation.

Influence of proton elastic scattering on soft error generation of SRAMs

It is known that protons usually do not deposit sufficient energy in a static random access memory (SRAM) cell to produce single-event-upsets (SEU) by direct ionization. In this work a model for the influence of elastically scattered protons is presented which explains the experimentally obtained SEU rate for protons at energies well below the Coulomb barrier threshold. A quantitative fit-parameter-free calculation of upsets is provided. Experimental results of low energy proton and helium irradiation of a 32 nm silicon-on-insulator (SOI) SRAM are presented to validate the model.