Achieving L2MS in a highly miniaturized instrument enables a powerful approach to the detection and characterization of aromatic organics in remote terrestrial and planetary applications. Tunable detection of molecular and fragment ions with high mass resolution, diagnostic of molecular structure, is possible on such a compact L2MS instrument. The selectivity of L2MS against low-mass inorganic salt interferences is a key advantage when working with unprocessed, natural samples, and a mechanism for the observed selectivity is proposed.

The principles of operation of a microelectromechanical (MEMS)-based magnetometer designed on the magnetoelastic effect are described. The active transduction element is a commercial (001) silicon microcantilever coated with an amorphous thin film of the giant magnetostrictive alloy Terfenol-D [(Dy0.7Te0.3)Fe2]. In addition to the magnetostrictive transducer, basic components of the magnetometer include: (a) mechanical resonance of the coated-microcantilever through coupling to an ac magnetic field; and (b) detection by optical beam deflection of the microcantilever motion utilizing a laser diode source and a position-sensitive detector. Currently, the sensitivity of this MEMS-based magnetostrictive magnetometer is ∼1μT.

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The MALDI (Matrix Assisted Laser Desorption/Ionization) technique, widely used to desorb and ionize large biomolecules, is applied here to small molecules having low vapor pressure, such as drugs and explosives. Furthermore, we report the coupling of the MALDI technique with a small, highly portable TinyTOF (Tim&Of-Flight) mass spectrometer developed in our laboratories. This mass spectrometer is a low voltage (-500V) coaxial reflectron design with a short (<20 cm) ffight tube that is specifically designed for low molecular weight substarces. The reflectron is designed to operate in two different modes that provide an extremely powerful pseudo-tandem mass spectrometry capability that is crucial for field applications. Using this system we have measured mass spectral signatures for cocaine, heroin, and the explosive RDX in the sub-nanogram range. Also reported here are continued developments on advanced MALDI sampling technologies, sensitivity and mass resolution enhancements of the Tmy-TOF, further decreases in system size and weight, and concepts for field operational systems.

An extensive investigation of InN overlayers on AlN-buffered (00.1) sapphire by reactive magnetron sputtering has been undertaken and the dependencies of several basic materials properties (film thickness, development and quality of heteroepitaxy, film morphology, and electrical transport) on such key deposition parameters such as the growth temperatures of the insulating AlN buffer layer and the InN overlayer and their thicknesses have been determined. Three prominent effects of the AlN buffer layer are (1) the stabilization of heteroepitaxial growth over a broad range of film and buffer layer growth temperatures; (2) the attainment of a higher Hall mobility (up to 60 cm2/V s) over much of the same range; and, (3) the retention of heteroepitaxial growth, higher Hall mobility, and pseudo-two-dimensional growth even in the limit of an InN layer of ∼40 Å. In the context of a structure-zone model, the AlN buffer layer is projected to effectively raise the growth temperature of the InN thin film. The increase in effective growth temperature is, however, insufficient to overcome low atomic and cluster mobility and to achieve single-crystal InN thin film growth.

A novel deposition technique, ultrahigh vacuum electron cyclotron resonance (ECR)-assisted reactive magnetron sputtering, has been developed for the preparation of group IIIA nitride thin films. In initial experiments, thin films of the semiconductor InN have been deposited on AlN-seeded (00.1) sapphire substrates, and the properties of these films studied as a function of growth temperature. Comparison to InN thin films grown by conventional reactive magnetron sputtering shows enhanced Hall mobilities (from about 50 to over 80 cm2/V s), a decreased carrier concentration (by about a factor of 2), an increased optical band gap, and an apparent reduction in homogeneous strain that is in part due to film relaxation induced by the ECR beam and in part to enhanced nitrogen content and more nearly stoichiometric films.

Two-step laser desorption mass spectrometry is a well suited technique to the analysis of high priority classes of organics, such as polycyclic aromatic hydrocarbons, present in complex samples. The use of decoupled desorption and ionization laser pulses allows for sensitive and selective detection of structurally intact organic species. We have recently demonstrated the implementation of this advancement in laser mass spectrometry in a compact, flight-compatible instrument that could feasibly be the centerpiece of an analytical science payload as part of a future spaceflight mission to a small body or icy moon.

Single-phase aluminum nitride films were deposited onto fused quartz and single-crystal sapphire by current-controlled, reactive, de magnetron sputtering from an aluminum metal target. Optical and structural properties were observed to correlate systematically with the composition of the sputter gas over a wide range of nitrogen partial pressures. A transition in the electrical conductivity of the deposited films occurred as a function of N2 partial pressure. This transition is driven by the condition of the target surface. When the N2 partial pressure was high and the target surface was substantially covered with AlNx, the deposited film was insulating, stoichiometric AlN. When the N2 partial pressure was low and the target surface was substantially Al°, the deposited film was conducting, substoichiometric AlNx.