Mikko Rossi

Energy loss measurement of protons in liquid water

The proton stopping power of liquid water was, for the first time, measured in the energy range 4.7-15.2 MeV. The proton energies were determined by the time-of-flight transmission technique with the microchannel plate detectors, which were especially developed for timing applications. The results are compared to the literature values (from ICRU Report 49 (1993) and Jannis tabulation (1982 At. Data Nucl. Data Tables 27 147-339)) which are based on Bethes formula and an agreement is found within the experimental uncertainty of 4.6%. Thus, earlier reported discrepancy between the experimental and literature stopping power values at lower energies was not observed at the energies considered in this experiment.

Semi-Empirical Model for SEGR Prediction

The underlying physical mechanisms in single event gate rupture (SEGR) are not known precisely. SEGR is expected to occur when the energy deposition due to a heavy ion strike exceeds a certain threshold simultaneously with sufficient electric field across the gate dielectric. Typically the energy deposition is described by using the linear energy transfer (LET) of the given ion. Previously the LET has been demonstrated not to describe the SEGR sufficiently. The work presented here introduces a semi-empirical model for the SEGR prediction based on statistical variations in the energy deposition which are described theoretically.

Low Energy Protons at RADEF - Application to Advanced eSRAMs

A low energy proton facility has been developed at RADEF, Jyv̈skyl̈, Finland. The proton energy selection, calibration and dosimetry are described. The first experiment with external users was performed using two memory test vehicles fabricated with 28 nm technology. Examples of single event upset measurements in the test vehicles embedded SRAMs (eSRAMs) as a function of proton energy are provided.

SEGR in SiO

This work presents experimental SEGR data for MOS-devices, where the gate dielectrics are are made of stacked SiO2–Si3N4 structures. Also a semi-empirical model for predicting the critical gate voltage in these structures under heavy-ion exposure is proposed. Then statistical interrelationship between SEGR cross-section data and simulated energy deposition probabilities in thin dielectric layers is discussed.

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This work presents experimental Single Event Gate Rupture (SEGR) data for Metal-Insulator-Semiconductor (MIS) devices, where the gate dielectrics are made of stacked SiO2-Si3N4 structures. A semi-empirical model for predicting the critical gate voltage in these structures under heavy-ion exposure is first proposed. Then interrelationship between SEGR cross-section and heavy-ion induced energy deposition probability in thin dielectric layers is discussed. Qualitively, a connection between the energy deposition in the dielectric and the SEGR is shown.

–Si

To minimize the dose applied to the specimens during imaging in a MeV ion microbeam we have investigated new concepts that allow collection of images with multi‐resolution support. To test the concept, a set of reference PIXE microbeam images with well‐characterised noise were segmented using both a direct down‐sampling technique and wavelet decomposition. The results show both techniques could be used to select fields of view with <2% of the fluence required to collect a normal image, however, there is no compelling reason to select one technique over the other.