We have studied the effect of the dipolar magnetic coupling (also known as Néel coupling or "orange-peel" coupling) in tunneling magnetoresistive (TMR) elements. With an in situ scanning tunneling microscope we directly accessed the roughness of the films and found a close correspondence between the values for the coupling fields determined by the magneto-optical Kerr effect and the ones computed on the basis of the measured morphology parameters. We confirm an increase of the dipole coupling between magnetic layers with decreasing barrier thickness as predicted by the model. Deviations from the theoretical predictions are observed for the case of thinner soft magnetic layers, which can be explained by reduced magnetisation in very thin films. We demonstrate the importance of dipolar coupling for understanding the magnetic behaviour of TMR elements by comparing TMR curves for optimised and nonoptimised structures.

No description available.

<p>Over one million hip prostheses are implanted in patients worldwide each year and the need is increasing as the patient group of younger and more active patients is increasing. Many parameters affect the longevity of the implant, where aseptic loosening caused by wear debris is the most common reason for revision. To be able to monitor wear in vivo and also to predict the longevity of new materials for hip prostheses are therefore important issues in this interdisciplinary research area. This thesis comprise a true non-invasive 3D method for determination of acetabular cup wear using Computed Tomography (CT) intended for clinical routine use in order to plan for a revision. It also comprises investigations of the influence of surface roughness and sterilization method in wear testing of materials for hip prostheses. Mainly wear of ultra high molecular weight polyethylene (UHMWPE) was investigated since it is the most common soft bearing in hip prostheses. The 3D-CT method was found to be easy to use and showed an accuracy and repeatability at a clinical relevant level for acetabular cup wear. It should lend itself well to semi-automation. The influence of surface roughness was investigated with both a multidirectional pin-on-disk machine and with a hip simulator. A new low friction coating, Micronite, was also evaluated with the pin-on-disk machine. This coating showed potential for use in artificial joints, but further investigations are needed. In the hip simulator test, it was found that not only a rougher counter surface increased wear, but also sterilization by γ-irradiation increased wear of UHMWPE cups.</p>

<p>The appearance and design of a package are key properties to attract and to focus the attention of a customer. Print quality contributes to a great degree to achieve these requirements. Most critical perceived in terms of quality are print defects like mottling, gloss and stripiness, which all appear in the printing of corrugated board. Stripiness is especially critical because it is a defect directly caused by the corrugated board construction. A further cause can be generated by the production process of corrugated board. Pre-studies by Odeberg Glasenapp (2004) revealed a difference in surface micro-roughness between the regions on the peak line of the liner and the regions in the valley between two peaks of the corrugation. This knowledge was the basis for the work described in this thesis.</p><p>In a first stage, laboratory trials were conducted with sets of coated and uncoated samples of various grammages. The trial was set-up in order to simulate the conditions in the corrugator as closely as possible. In the evaluations, it was found out that the settings were too high. For that reason, the coated samples were influenced to a too high degree and needed to be excluded from further evaluations. With the uncoated samples, on the other hand, a change in micro surface roughness was detectable. The roughness is decreased on the peaks and the gloss appearance was the conclusion. The analysis of the printed samples focused on shifts in colour and print density. It is unclear if both are affected only surface roughness changes and/or by the typical corrugated board effect of washboarding.</p><p>A full-scale test was performed in order to confirm the results of the laboratory test. A test series was chosen with coated and uncoated outer liners. Contrary to the lab-test results, the uncoated grades showed no surface roughness changes. Instead, the coated samples were affected to a great extent. The changes in surface roughness and gloss appearance were similar to the lab-test. This confirms that the lab-test samples were exposed to heat, pressure and shear to a too high degree. The print analysis of the full-scale test did not agree with the laboratory test. Gloss lines were visually detectable, but they were difficult to measure. A reason could be that the ink is capable on forming an ink film layer on top of the surface of the paper. This would cover the micro roughness of the matt parts thereby creating an almost homogeneous glossy appearance.</p>

<p>The aim of this thesis is to investigate how material surfaces are affected by various surface treatments and how this relates to the adhesion of the coating. The materials that were studied were WC-Co and Cermets and the surface treatments used were polishing, grinding with coarser and finer abrasive grains, and finally wet blasting and dry blasting. Focus was on deformations and residual stresses in the surface, surface roughness and cracks. The test methods used for examining the samples included surface roughness measurements, residual stress measurements, adhesion tests using Rockwell indentation and SEM images of the surface and the cross section.<br /><br />The results concluded that polishing gives very good adhesion. Additionally, the adhesion for ground surfaces was good for WC-Co but very poor for Cermets. Furthermore, it was observed that finer abrasive grains did not result in better adhesion. In fact, the coarser grains gave slightly better results. Finally, it was concluded that wet blasting has a clear advantage over dry blasting and results in much better adhesion, especially for the Cermets. The results for the WC-Co were a bit inconsistent and so further research is required.</p>

To date only very few bistatic measurements (airborne or in controlled laboratories) have been reported. Therefore most of the current remote sensing methods are still focused on monostatic (backscatter) measurements. These methods, based on theoretical, empirical or semi-empirical models, enable the estimation of soil roughness and the soil humidity (dielectric constant). For the bistatic case only theoretical methods have been developed and tested with monostatic data. Hence, there still remains a vital need to gain of experience and knowledge about bistatic methods and data. The main purpose of this thesis is to estimate the soil moisture and the soil roughness by using full polarimetric bistatic measurements. In the experimental part, bistatic X-band measurements, which have been recorded in the Bistatic Measurement Facility (BMF) at the DLR Oberpfaffenhofen, Microwaves and Radar Institute, will be presented. The bistatic measurement sets are composed of soils with different statistical roughness and different moistures controlled by a TDR (Time Domain Reflectivity) system. The BMF has been calibrated using the Isolated Antenna Calibration Technique (IACT). The validation of the calibration was achieved by measuring the reflectivity of fresh water. In the second part, bistatic surface scattering analyses of the calibrated data set were discussed. Then, the specular algorithm was used to estimate the soil moisture of two surface roughnesses (rough and smooth) has been reported. A new technique using the coherent term of the Integral Equation Method (IEM) to estimate the soil roughness was presented. Also, the sensitivity of phase and reflectivity with regard to moisture variation in the specular direction was evaluated. Finally, the first results and validations of bistatic radar polarimetry for the specular case of surface scattering have been introduced. / Aktuell sind nur sehr wenige Messungen mit bistatischem Radar durchgeführt worden, sei es von Flugzeuggetragenen Systemen oder durch spezielle Aufbauten im Labor. Deshalb basieren die meisten der bekannten Methoden zur Fernerkundung mit Radar auf monostatis-chen Messungen der Rückstreuung des Radarsignals. Diese Methoden, die auf theoretischen, empirischen oder halb-empirischen Modellen basieren, ermöglichen die Schätzung der Oberfächenrauhigkeit und die Bodenfeuchtigkeit (Dielektrizitätskonstante). Im bistatischen Fall wurden bisher nur theoretische Modelle entworfen, die mittels monostatischer Messungen getestet wurden. Aus diesem Grund ist es von großer Bedeutung, Erfahrung und Wissen über die physikalischen Effekte in bistatischen Konfigurationen zu sammeln. Das Hauptziel der vorliegenden Dissertation ist es, anhand vollpolarimetrischer, bistatischer Radarmessungen die Oberfächenrauhigkeit und Bodenfeuchtigkeit zu bestimmen. Im experimentellen Teil der Arbeit werden die Ergebnisse bistatischer Messungen präsentiert, die in der Bistatic Measurement Facility (BMF) des DLR Oberpfaffenhofen aufgenommen wurden. Die Datensätze umfassen Messungen von Böden unterschiedlicher statistischer Rauhigkeit und Feuchtigkeit, die mittels eines Time Domain Reflectivity (TDR) Systems bestimmt werden. Zur Kalibration des BMF wurde die Isolated Antenna Calibration Technique (IACT) verwendet und anhand der Messung der Reflektivität von Wasser überprüft. Im zweiten Teil der vorliegenden Arbeit wird anhand der kalibrierten Daten eine Analyse der Oberflächenstreuung in bistatischen Konfigurationen vorgenommen. Im Anschluss daran wird mittels des Specular Algorithm eine Schätzung der Bodenfeuchte zweier Proben unter- schiedlicher Rauhigkeit (rau und fein) durchgeführt. Ein neues Verfahren zur Schätzung der Oberfächenrauhigkeit, das auf dem kohärenten Term der Integral Equation Method (IEM) basiert, wurde eingeführt. Daneben wird die Empfindlichkeit der Phase sowie der Reflektivität des vorwärtsgestreuten Signals gegenüber Veränderungen der Bodenfeuchtigkeit analysiert. Schließlich werden erste Ergebnisse und Validierungen bistatischer Radarpolarimetrie für den Fall der Vorwärtsstreuung präsentiert.

Standard cells are fundamental circuit building blocks designed at very early design stages. Nanometer standard cells are prone to lithography proximity and process variations. How to design robust cells under variations plays a crucial role in the overall circuit performance and yield. This dissertation studies five related research topics in design and manufacturing co-optimization in nanometer standard cells. First, a comprehensive sensitivity metric, which seamlessly incorporates effects from device criticality, lithographic proximity, and process variations, is proposed. The dissertation develops first-order models to compute these sensitivities, and perform robust poly and active layout optimization by minimizing the total delay sensitivity to reduce the delay under the nominal process condition and by minimizing the performance gap between the fastest and the slowest delay corners. Second, a new equivalent source/drain (S/D) contact resistance model, which accurately calculates contact resistances from contact area, contact position, and contact shape, is proposed. Based on the impact of contact resistance on the saturation current, robust S/D contact layout optimization by minimizing the lithography variation as well as by maximizing the saturation current without any leakage penalty is performed. Third, this dissertation describes the first layout decomposition methods of spacer-type self-aligned double pattering (SADP) lithography for complex 2D layouts. The favored type of SADP for complex logic interconnects is a two-mask approach using a core mask and a trim mask. This dissertation describes methods for automatically choosing and optimizing the manufacturability of base core mask patterns, generating assist core patterns, and optimizing trim mask patterns to accomplish high quality layout decomposition in SADP process. Fourth, a new cell characterization methodology, which considers a random (line-edge roughness) LER variation to estimate the device performance of a sub-45nm design, is presented. The thesis systematically analyzes the random LER by taking the impact on circuit performance due to LER variation into consideration and suggests the maximum tolerance of LER to minimize the performance degradation. Finally, this dissertation proposes a design aware LER model which claims that LER is highly related to the lithographic aerial image fidelity and the neighboring geometric proximity. With a new LER model, robust LER aware poly layout optimization to minimize the leakage power is performed. / text

Η εργασία αυτή περιγράφει αναλυτικά την κατασκευή και αξιολόγηση πειραματικής διάταξης ανακλαστικότητας ακτίνων-Χ, που πραγματοποιήθηκε στο Εργαστήριο Φυσικής Στερεάς Κατάστασης του τμήματος Φυσικής του Πανεπιστημίου Πατρών. Με τη βοήθεια αυτής της πειραματικής διάταξης θα είναι εύκολος ο καθορισμός των χαρακτηριστικών ιδιοτήτων επιφανειών καθώς επίσης και η μελέτη υμενίων τα οποία έχουν προσροφηθεί σε υποστρώματα. Στο πρώτο κεφάλαιο της εργασίας παρουσιάζονται οι βασικές σχέσεις υπολογισμού της ανακλαστικότητας καθώς και η μέθοδος ανάλυσης των πειραματικών αποτελεσμάτων. Στο επόμενο κεφάλαιο παρουσιάζονται αναλυτικά όλα τα βήματα που πραγματοποιήθηκαν για την κατασκευή της πειραματικής διάταξης. Στο κεφάλαιο αυτό περιγράφονται όλα τα μηχανικά μέρη του φασματόμετρου καθώς και οι απαιτούμενες ρυθμίσεις που πραγματοποιήθηκαν προκειμένου να εξασφαλιστεί η σωστή λειτουργία του. Με λήψη ενός φάσματος από ένα δείγμα πυριτίου και τον προσδιορισμό των γωνιών Bragg αποδείχθηκε η σωστή λειτουργία του γωνιομέτρου. Το επόμενο βήμα ήταν ο υπολογισμός της διακριτικής ικανότητας της συσκευής. Με υπολογιστικό πρόγραμμα [Ν. Κάτσενου Διπλωματική Εργασία] το οποίο λαμβάνει υπόψη του όλη την γεωμετρία της διάταξης υπολογίστηκε η διακριτική ικανότητα της συσκευής. Η τιμή της είναι 0.0120 και είναι σταθερή για τις γωνίες από 0.20 έως 1.60. Προκειμένου να βελτιωθεί η τιμή της διακριτικής ικανότητας είναι απαραίτητο να χρησιμοποιηθούν πολύ λεπτές σχισμές τόσο στη λυχνία όσο και στον απαριθμητή. Επιπροσθέτως κατασκευάστηκε ειδική διάταξη, “μαχαίρι”, το οποίο στηρίζεται στην βάση του δείγματος και όπως διαπιστώθηκε βελτιώνει την διακριτική ικανότητα της διάταξης και μειώνει το υπόστρωμα.. Ως τελευταίο βήμα ήταν ο υπολογισμός του υποστρώματος και η διόρθωσή του. Στο δεύτερο κεφάλαιο περιγράφεται αναλυτικά η διαδικασία διόρθωσης του υποστρώματος σε ένα φάσμα ανακλαστικότητας. Στην συνέχεια παρουσιάζονται πειραματικές μετρήσεις από διάφορα δείγματα. Σε όλα τα δείγματα χρησιμοποιήθηκε ως υπόστρωμα πυρίτιο. Στα περισσότερα από αυτά προσροφήθηκε, με την μέθοδο επίστρωσης με περιστροφή του υποστρώματος, πολυστηρένιο. Χρησιμοποιήθηκαν διάφορες συγκεντρώσεις διαλύματος πολυστηρενίου σε τολουόλιο προκειμένου να δημιουργηθούν δείγματα με διαφορετικά πάχη. Επίσης με την μέθοδο της εξάχνωσης εναποτέθηκε υμένιο αλουμινίου σε υπόστρωμα πυριτίου. Από τις πειραματικές μετρήσεις που προέκυψαν για την ανακλαστικότητα προκύπτει ότι η κρίσιμη γωνία ανάκλασης είναι 0.220 ενώ για γωνίες μεγαλύτερες από αυτή η ανακλαστικότητα αρχίζει και μειώνεται απότομα. Μέχρι την γωνία 2.00 η τιμή της ανακλαστικότητας μειώνεται περίπου έξι τάξεις μεγέθους. Χρησιμοποιώντας τις πειραματικές μετρήσεις που πήραμε μπορούμε να εξάγουμε πληροφορίες για το πάχος, την πυκνότητα και την τραχύτητα των επιφανειών που μελετάμε. Διαπιστώθηκε λοιπόν ότι η συσκευή λειτουργεί ικανοποιητικά. Βελτιώσεις που μπορούν να γίνουν αφορούν: α) Την κατασκευή θαλάμου κενού εντός του οποίου θα ευρίσκεται το δείγμα. Η βελτίωση αυτή θα επιτρέψει να λαμβάνονται φάσματα ανακλαστικότητας με πολύ χαμηλό υπόστρωμα. Με τον τρόπο αυτό θα βελτιωθεί η ποιότητα των φασμάτων για γωνίες ανάκλασης μεγαλύτερες από 1.20 γεγονός που θα δώσει πιο σαφής πληροφορίες για τη δομή πολύ λεπτών υμενίων. β) Μακροπρόθεσμα θα τοποθετηθεί στη συσκευή σύστημα παραλληλισμού της δέσμης το οποίο θα αυξήσει την ένταση της προσπίπτουσας ακτινοβολίας στο δείγμα. Με τον τρόπο αυτό θα ελαττωθεί ο χρόνος λήψης του συνολικού φάσματος ενώ ταυτόχρονα θα βελτιωθεί η στατιστική ιδιαίτερα στις μεγάλες γωνίες σκέδασης και θα καταστεί έτσι άνετη η μελέτη εξαιρετικά λεπτών υμενίων (μικρότερα των 20Å). / -

The aim of this thesis is to investigate how material surfaces are affected by various surface treatments and how this relates to the adhesion of the coating. The materials that were studied were WC-Co and Cermets and the surface treatments used were polishing, grinding with coarser and finer abrasive grains, and finally wet blasting and dry blasting. Focus was on deformations and residual stresses in the surface, surface roughness and cracks. The test methods used for examining the samples included surface roughness measurements, residual stress measurements, adhesion tests using Rockwell indentation and SEM images of the surface and the cross section.<br /><br />The results concluded that polishing gives very good adhesion. Additionally, the adhesion for ground surfaces was good for WC-Co but very poor for Cermets. Furthermore, it was observed that finer abrasive grains did not result in better adhesion. In fact, the coarser grains gave slightly better results. Finally, it was concluded that wet blasting has a clear advantage over dry blasting and results in much better adhesion, especially for the Cermets. The results for the WC-Co were a bit inconsistent and so further research is required.

It was investigated characteristics of surfaces of offset printing plates. A method of measurement of wetting angle was improved and there were investigated the wetting characteristics of hydrophilic surfaces of offset printing plates and their dependence on dampening solution and on printed run. Experimentally investigated 16 offset printing plates. Wetting angle increases with the run. Surface roughness was investigated using profilograph. Changes of surface roughness during printing were determined and it was found that during printing quantity of bigger over 1 µm irregularities increases.