Boron and phosphorous implantation into (100) germanium : modeling and investigation of dopant annealing behavior

Germanium is increasingly being considered at this time for future silicon compatible optoelectronic and complementary metal oxide semiconductor (CMOS) device application. Germanium implantation will be a critical process for future device fabrication. However, critical properties like Pearson parameters and dopant activation temperatures are not well established. In this study, boron and phosphorus were implanted into (100) germanium with energies ranging from 20 to 320 keV and doses of 5 x 1013 to 5 x 1016 cm-2. The behavior of the boron and phosphorus before and after annealing for 3 hours at 400, 600 or 800°C in ultra high purity nitrogen were characterized using secondary ion mass spectrometry (SIMS), spreading resistance profiling (SRP) measurements, Hall Effect measurement, X-ray diffraction (XRD) measurement, and Rutherford backscattering spectrometry (RB S). A predictive model for the implanted dopant distribution\u27s dependence on energy was developed using the experimentally determined implant moments combined with Pearson distributions and the post-annealing electrical, structural and diffusion behavior was characterized. Results from numeric simulation and analytic calculations using Lindard-Scharff-Schiott (LSS) theory are presented to offer insight into the physics of the pre-annealed implanted dopant distributions

A modeling study of ion implantation in crystalline silicon involving Monte Carlo and molecular dynamics methods

Ph.DDOCTOR OF PHILOSOPH

Ion-Solid Interaction in Semiconductor Nanowires

Ionenstrahlimplantation ist eine nützliche und weit verbreitete Methode um Materialien zu dotieren. Nanostrukturen verhalten sich unter Ionenbestrahlung oft deutlich anders als das entsprechende Volumenmaterial; zum Beispiel unterscheiden sich die erzeugten Dotierprofile sowie die Erzeugung und das Ausheilen von Defekten. In der vorliegenden Arbeit wird dieses Unterschiedliche Verhalten unter Ionenbestrahlung von drei Gesichtspunkten aus untersucht: Im ersten Teil wird ein neu entwickeltes Computerprogramm zur Simulation der Ionenbestrahlung von Nanostrukturen vorgestellt und diskutiert. Ähnlich wie bei vergleichbaren Programmen wird dabei ein Monte-Carlo-Algorithmus in Kombination mit der Zweierstoß-Näherung verwendet. Im Gegensatz zu konventionellen Programmen wird das Target aber durch kleine Zellen und nicht durch Schichten repräsentiert, so dass sich beliebige Nanostrukturen dreidimensional abbilden lassen. Die erzielten Simulationsergebnisse stimmen gut mit experimentellen Befunden überein. Im zweiten Teil der Arbeit wird die ionenstrahlinduzierte Verbiegung von Nanodrähten untersucht. Je nach Energie der Ionen lassen sich die Nanodrähte in verschiedene Richtungen verbiegen und ausrichten. Als zugrundeliegender Mechanismus wird die inhomogene Verteilung verschiedener ionenstrahlinduzierter Defekte identifiziert. Der dritte Teil beschäftigt sich mit der Dotierung von GaAs-Nanodrähten mittels Mangan. Wegen der geringen Löslichkeit der Übergangsmetalle in III-V-Halbleitern kann das Mangan nicht beim Wachstum der Nanodrähte eingebracht werden. Es wird gezeigt, dass die Mangan-Dotierung von GaAs mittels Ionenstrahlimplantation möglich ist. Dabei ist eine erhöhte Implantationstemperatur erforderlich, um das in Nanodrähten ohnehin verstärkte dynamische Ausheilen noch weiter zu unterstützen und die Kristallinität der Nanodrähte zu erhalten. Alle drei Teile zeigen deutliche Unterschiede bei der Ionenbestrahlung von Nanodrähten im Vergleich zum Volumenmaterial

Samarium-Doped Fluorophosphate and Fluoroaluminate Glasses for High-Dose High-Resolution Dosimetry for Microbeam Radiation Therapy

Microbeam Radiation Therapy (MRT) is an important and developing radiotherapy technique that uses spatially fractionated doses, several orders of magnitude larger than that of the doses used in conventional radiation therapy. Healthy tissue displays remarkable resistance to damage caused from microscopically narrow, fractionated, planar beams of x-rays, while showing preferential damage towards cancerous growths, allowing for a high potential towards the treatment of often inoperable tumours. These synchrotron generated, spatially fractionated, planar beams are referred to as microbeams, and have a thickness of 20 – 50 µm and are separated by distances of 100 – 400 µm. The dose delivered at the center of the microbeam can be on the order of thousands of Grays (Gy), whereas the dose between each microbeam should be kept below tens of Gy. An important aspect of MRT is the spatial distribution of the dose delivered to the patient, which must be accurately measured. Ultimately, both high resolution and large dynamic range dosimetric measurements must be done simultaneously. The objective of this Ph.D. research involves the development and characterization of a dosimetric technique that fulfills the requirements of measuring dose distributions of microbeams. The proposed technique uses the indirect detection of x-rays, where the dose is recorded in a glass plate which can then be readout using a confocal microscopy system. The dose delivered is recorded by using trivalent samarium (Sm3+) doped fluoroaluminate and fluoro-phosphate glasses, where conversion from the trivalent form of samarium to the divalent form (Sm2+) occurs after exposure to x-rays. The extent of this conversion can be readout and digitized with high resolution using a confocal microscopy system that utilizes the easily distinguishable photoluminescent spectra of Sm3+ to Sm2+. The work carried out in this research involves the high resolution recording of microbeam profiles performed at the Canadian synchrotron, using samarium doped glass plates under a variety of irradiation parameters in order to determine their suitability for dosimetric applications. In particular, the dose rate and x-ray energy dependence of these materials is investigated, as well as the determination of the optimum Sm3+ dopant concentration. Further, the confocal measurement technique is investigated, as well as the suitability of ion implantation of samarium ions in order to improve the signal readout. Lastly, the change in dose distributions of microbeams is investigated by performing irradiations over a wide range of monochromatic x-rays, so that the potential effect of the selected energy on MRT treatment planning can be examined

Modelling and simulation of ion implantation induced damage

Ph.DDOCTOR OF PHILOSOPH