Capabilities of Gossamer-1 derived small spacecraft solar sails carrying MASCOT-derived nanolanders for in-situ surveying of NEAs

Any effort which intends to physically interact with specific asteroids requires understanding at least of the composition and multi-scale structure of the surface layers, sometimes also of the interior. Therefore, it is necessary first to characterize each target object sufficiently by a precursor mission to design the mission which then interacts with the object. In small solar system body (SSSB) science missions, this trend towards landing and sample-return missions is most apparent. It also has led to much interest in MASCOT-like landing modules and instrument carriers. They integrate at the instrument level to their mothership and by their size are compatible even with small interplanetary missions. The DLR-ESTEC Gossamer Roadmap NEA Science Working Groups‘ studies identified Multiple NEA Rendezvous (MNR) as one of the space science missions only feasible with solar sail propulsion. Parallel studies of Solar Polar Orbiter (SPO) and Displaced L1 (DL1) space weather early warning missions studies outlined very lightweight sailcraft and the use of separable payload modules for operations close to Earth as well as the ability to access any inclination and a wide range of heliocentric distances. These and many other studies outline the unique capability of solar sails to provide access to all SSSB, at least within the orbit of Jupiter. Since the original MNR study, significant progress has been made to explore the performance envelope of near-term solar sails for multiple NEA rendezvous. However, although it is comparatively easy for solar sails to reach and rendezvous with objects in any inclination and in the complete range of semi-major axis and eccentricity relevant to NEOs and PHOs, it remains notoriously difficult for sailcraft to interact physically with a SSSB target object as e.g. the Hayabusa missions do. The German Aerospace Center, DLR, recently brought the Gossamer solar sail deployment technology to qualification status in the Gossamer-1 project. Development of closely related technologies is continued for very large deployable membrane-based photovoltaic arrays in the GoSolAr project. We expand the philosophy of the Gossamer solar sail concept of efficient multiple sub-spacecraft integration to also include landers for one-way in-situ investigations and sample-return missions. These are equally useful for planetary defence scenarios, SSSB science and NEO utilization. We outline the technological concept used to complete such missions and the synergetic integration and operation of sail and lander. We similarly extend the philosophy of MASCOT and use its characteristic features as well as the concept of Constraints-Driven Engineering for a wider range of operations

In-device spectroscopy at metal/organic semiconductor interfaces.

145 p.En esta tesis doctoral nos hemos basado en el estudio de las barreras energéticas presentes en lasinterfaces entre el nivel de Fermi de los metales y los niveles orbitales de semiconductores orgánicos.Este estudio se ha realizado mediante dispositivos electrónicos verticales de tres terminales y mediante lainyección y transporte de cargas eléctricas. De esta forma, hemos podido determinar cómo dichasbarreras energéticas afectan en el transporte eléctrico, lo cual influye directamente en el funcionamiento yeficiencia de dispositivos optoelectrónicos. La determinación de los niveles energéticos relativos devarios orbitales moleculares nos ha llevado a poder determinar directamente la banda de energíaprohibida de varios semiconductores orgánicos. El estudio se ha llevado a cabo con semiconductoresmoleculares y poliméricos tanto el ultra alto vacío como en condiciones ambientales respectivamente.Además de esto, hemos investigado cómo afecta la tensión mecánica en las barreras energéticas entremetales y semiconductores orgánicos. Para esto, hemos fabricado nuestros dispositivos en substratosflexibles y medidos doblados con distintos radios de torsión.En los dispositivos estudiados, las cargas se inyectan balísticamente en el semiconductor. Esta formaúnica de inyectar las cargas nos ha permitido observar en semiconductores orgánicos el Régimen deInversión Marcus. Como consecuencia de este régimen, hemos observado un diferencial de resistencianegativo en medida de corriente versus voltaje. Hemos podido manipular este último fenómeno mediantetemperatura, luz y campo eléctrico.CICnanoGUN

The development of sub-25 nm III-V High Electron Mobility Transistors

High Electron Mobility Transistors (HEMTs) are crucially important devices in microwave circuit applications. As the technology has matured, new applications have arisen, particularly at millimetre-wave and sub-millimetre wave frequencies. There now exists great demand for low-visibility, security and medical imaging in addition to telecommunications applications operating at frequencies well above 100 GHz. These new applications have driven demand for high frequency, low noise device operation; key areas in which HEMTs excel. As a consequence, there is growing incentive to explore the ultimate performance available from such devices. As with all FETs, the key to HEMT performance optimisation is the reduction of gate length, whilst optimally scaling the rest of the device and minimising parasitic extrinsic influences on device performance. Although HEMTs have been under development for many years, key performance metrics have latterly slowed in their evolution, largely due to the difficulty of fabricating devices at increasingly nanometric gate lengths and maintaining satisfactory scaling and device performance. At Glasgow, the world-leading 50 nm HEMT process developed in 2003 had not since been improved in the intervening five years. This work describes the fabrication of sub-25 nm HEMTs in a robust and repeatable manner by the use of advanced processing techniques: in particular, electron beam lithography and reactive ion etching. This thesis describes firstly the development of robust gate lithography for sub-25 nm patterning, and its incorporation into a complete device process flow. Secondly, processes and techniques for the optimisation of the complete device are described. This work has led to the successful fabrication of functional 22 nm HEMTs and the development of 10 nm scale gate pattern transfer: simultaneously some of the shortest gate length devices reported and amongst the smallest scale structures ever lithographically defined on III-V substrates. The first successful fabrication of implant-isolated planar high-indium HEMTs is also reported amongst other novel secondary processes