W. Van Roy

Laser microprobe Fourier transform mass spectrometer with external ion source for organic and inorganic microanalysis

Abstract The earlier laser microprobe (LM) mass spectrometer with a time-of-flight (TOF) analyser showed that the irradiation of solids by a focused UV laser represents and interesting means of performing local analysis. However, the subsequent measurement of the generated ions is done under low-resolution conditions. The characterization of heterogenous samples and the occurence of poorly understood ion formation mechanisms motivated the development of an instrument with superior mass spectrometric performance. Specifically, Fourier transform (FT) mass spectrometry potentially provides the required high mass resolution and accurate mass determination in combination with adequate sensitivity. In this work an FT-LM mass spectrometer with an external source was developed. Analysis is performed in the reflection mode with a 5-μm spot from a Q-switched Nd:YAG laser. Transfer of ions from the external source into the cell is performed by static electrical fields. The resulting mass separation imposes limitations on the panoramic spectrum registration in the case of pulsed laser microbeam ionization of solids, producing ion bunches over not more than a few hundred microseconds. This paper addresses instrument design and performance with respect to sensitivity, spatial resolution and accuracy of m/z determination and the problem of panoramic registration. Attention is focused on the comparison of results from FT- and TOF-LM mass spectrometry in relation to the determination of the speciation of inorganic compounds and diagnostic analysis of organic molecules.

Magnetic/semiconductor heterostructures for spintronic devices

Summary form only given. We discuss materials options to build spintronic devices illustrated by our recent experimental findings in fabricating NiMnSb epitaxial magnetic contacts, ferromagnetic/insulator/semiconductor (FM/I/S) spin-LEDs and (Al,Ga)MnAs-based heterostructures. We use all the bandgap engineering tricks of advanced semiconductor devices to exploit and enhance spin-dependent effects.