Recommended reading list of early publications on atomic layer deposition-Outcome of the "Virtual Project on the History of ALD"

Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency. (C) 2016 Author(s).Peer reviewe

Connecting Planetary Composition with Formation

The rapid advances in observations of the different populations of exoplanets, the characterization of their host stars and the links to the properties of their planetary systems, the detailed studies of protoplanetary disks, and the experimental study of the interiors and composition of the massive planets in our solar system provide a firm basis for the next big question in planet formation theory. How do the elemental and chemical compositions of planets connect with their formation? The answer to this requires that the various pieces of planet formation theory be linked together in an end-to-end picture that is capable of addressing these large data sets. In this review, we discuss the critical elements of such a picture and how they affect the chemical and elemental make up of forming planets. Important issues here include the initial state of forming and evolving disks, chemical and dust processes within them, the migration of planets and the importance of planet traps, the nature of angular momentum transport processes involving turbulence and/or MHD disk winds, planet formation theory, and advanced treatments of disk astrochemistry. All of these issues affect, and are affected by the chemistry of disks which is driven by X-ray ionization of the host stars. We discuss how these processes lead to a coherent end-to-end model and how this may address the basic question.Comment: Invited review, accepted for publication in the 'Handbook of Exoplanets', eds. H.J. Deeg and J.A. Belmonte, Springer (2018). 46 pages, 10 figure

Beschichtung von Kohlenstofffaserbündeln und -geweben mittels Atomlagenabscheidung

In dieser Arbeit wird die Atomlagenabscheidung (ALD) zur Beschichtung von Kohlenstofffasern verwendet. Dabei werden zwei neuartige Titan-haltige Beschichtungen erzeugt und untersucht, sowie der Aluminiumoxid-ALD-Prozess auf Kohlenstofffasergewebe übertragen. Die erhaltenen Beschichtungen sollen in weiterführenden Arbeiten als mechanisch schwache Beschichtungen oder Oxidationsschutzschichten in faserverstärkten Keramiken eingesetzt werden. Im ersten Teil der Arbeit wird der TiO2-ALD-Prozess mit den Precursoren TiCl4 und H2O als Basis für die Herstellung von organisch-anorganischen Hybridmaterialsschichten verwendet. Dazu wird Furfurylalkohol in einer sequenziellen Pulsfolge entweder nur mit TiCl4 oder mit TiCl4 und H2O eingesetzt. Dabei entstehen dünne Schichten im Nanometerbereich deren Wachstum und chemische Zusammensetzung eingehend untersucht werden. Auf Grundlage der Ergebnisse wird ein möglicher Mechanismus für das Wachstum diskutiert. Die Beschichtungen werden weiterhin auf Polymerfolien aufgebracht und mechanischen Tests unterzogen. Diese zeigen, dass die Schichten leichter verformbar sind als reines Titanoxid. Des Weiteren wird ein neuartiger Prozess zur Herstellung von Titanphosphatbeschichtungen mittels der Atomlagenabscheidung vorgestellt. Dabei nimmt die Schichtdicke linear mit der Anzahl der Zyklen zu und die Reaktionen der Precursoren sind selbstlimitierend. Weiterhin wird die chemische Zusammensetzung der Beschichtung und deren Temperaturstabilität eingehend untersucht. Mittels thermogravimetrischer Analyse wird gezeigt, dass diese Schichten die Oxidationstemperatur von Kohlenstofffasern an Luft erhöhen. Im letzten Teil der Arbeit soll untersucht werden, ob der ALD-Prozess geeignet ist, geometrisch komplexe Kohlenstofffasergewebe gleichmäßig zu beschichten. Dazu wird Al2O3 auf Kohlenstofffasergeweben verschiedener Größen abgeschieden und die resultierende Schichtdicke an verschiedenen Stellen der Gewebe untersucht. Weiterhin wird mittels verschiedenen Mikroskopiemethoden überprüft, ob Defekte in der Beschichtung vorliegen

Beschichtung von Kohlenstofffaserbündeln und -geweben mittels Atomlagenabscheidung

In dieser Arbeit wird die Atomlagenabscheidung (ALD) zur Beschichtung von Kohlenstofffasern verwendet. Dabei werden zwei neuartige Titan-haltige Beschichtungen erzeugt und untersucht, sowie der Aluminiumoxid-ALD-Prozess auf Kohlenstofffasergewebe übertragen. Die erhaltenen Beschichtungen sollen in weiterführenden Arbeiten als mechanisch schwache Beschichtungen oder Oxidationsschutzschichten in faserverstärkten Keramiken eingesetzt werden. Im ersten Teil der Arbeit wird der TiO2-ALD-Prozess mit den Precursoren TiCl4 und H2O als Basis für die Herstellung von organisch-anorganischen Hybridmaterialsschichten verwendet. Dazu wird Furfurylalkohol in einer sequenziellen Pulsfolge entweder nur mit TiCl4 oder mit TiCl4 und H2O eingesetzt. Dabei entstehen dünne Schichten im Nanometerbereich deren Wachstum und chemische Zusammensetzung eingehend untersucht werden. Auf Grundlage der Ergebnisse wird ein möglicher Mechanismus für das Wachstum diskutiert. Die Beschichtungen werden weiterhin auf Polymerfolien aufgebracht und mechanischen Tests unterzogen. Diese zeigen, dass die Schichten leichter verformbar sind als reines Titanoxid. Des Weiteren wird ein neuartiger Prozess zur Herstellung von Titanphosphatbeschichtungen mittels der Atomlagenabscheidung vorgestellt. Dabei nimmt die Schichtdicke linear mit der Anzahl der Zyklen zu und die Reaktionen der Precursoren sind selbstlimitierend. Weiterhin wird die chemische Zusammensetzung der Beschichtung und deren Temperaturstabilität eingehend untersucht. Mittels thermogravimetrischer Analyse wird gezeigt, dass diese Schichten die Oxidationstemperatur von Kohlenstofffasern an Luft erhöhen. Im letzten Teil der Arbeit soll untersucht werden, ob der ALD-Prozess geeignet ist, geometrisch komplexe Kohlenstofffasergewebe gleichmäßig zu beschichten. Dazu wird Al2O3 auf Kohlenstofffasergeweben verschiedener Größen abgeschieden und die resultierende Schichtdicke an verschiedenen Stellen der Gewebe untersucht. Weiterhin wird mittels verschiedenen Mikroskopiemethoden überprüft, ob Defekte in der Beschichtung vorliegen

Learning a Prior Model for Automatic Liver Lesion Segmentation in Follow-up CT Images

Liver tumors that are not surgically removed need to be closely monitored. A common procedure for their assessment involves acquiring CT images every few months and rating disease status based on the largest diameters of a subset of the lesions. The most prominent benefits of automatic lesion segmentation methods in this context are minimization of time consuming interaction and the possibility of volumetric measurements. While existing methods could be applied to each image individually, we propose to incorporate information gained from previous images of the same patient to enhance the segmentation. We learn a Probabilistic Boosting Tree that has an internal representation of tumor growth from a set of training images. Provided a baseline lesion segmentation, it can generate a patient specific lesion prior to guide the segmentation in a follow-up image. In this paper, we describe and compare different methods for building the growth model and integrating it into a segmentation system. The validity of the approach is shown in an experimental evaluation on a database of 14 patients. On the 17 pairs of baseline and follow-up images in this database, segmentation performance was measured once without and once with the proposed prior. When comparing the points of 90% sensitivity from each experiment, introducing the prior improved the precision of the segmentation from 82.7% to 91.9%. This corresponds to a reduction of the number of false positive voxels per true positive voxel by 57.8%

A Cost Constrained Boosting Algorithm for Fast Object Detection

Boosting methods are among the most widely used machine learning techniques in practice for various reasons. In many scenarios, however, their use is prevented by runtime constraints. In this paper we propose a novel technique for reducing the computational complexity of hierarchical classifiers based on AdaBoost, such as the probabilistic boosting tree, which are often used for object detection. We modify AdaBoost training so that the hypothesis generation is no longer based solely on the weak learner’s training error but also on a measure of hypothesis complexity. This is achieved by incorporating a cost function into the optimization process, effectively constraining feature selection, which leads to a reduced overall classifier complexity and thus shorter evaluation times. The validity of the approach is shown in an experimental valuation on real-world data. In a cross validation experiment with a system for automatic segmentation of liver tumors in CT images, the evaluation cost for classifying previously unseen samples could be reduced by up to 76% using the methods described here without losing classification accuracy

Conformal and superconformal chemical vapor deposition of silicon carbide coatings

The approaches to conformal and superconformal deposition developed by Abelson and Girolami for a low-temperature, low-pressure chemical vapor deposition (CVD) setting relevant for electronic materials in micrometer or submicrometer scale vias and trenches, are tested here in a high-temperature, moderate pressure CVD setting relevant for hard coatings in millimeter-scale trenches. Conformal and superconformal deposition of polycrystalline silicon carbide (SiC) can be accomplished at deposition temperatures between 950 and 1000 degrees C with precursor partial pressure higher than 20 Pa and an optional minor addition of HCl as a growth inhibitor. The conformal deposition at low temperatures is ascribed to slower kinetics of the precursor consumption along the trench depth, whereas the impact of high precursor partial pressure and addition of inhibitor is attributable to surface site blocking. With the slower kinetics and the site blocking from precursor saturation leading the growth to nearly conformal and the possibly preferential inhibition effect near the opening than at the depth, a superconformal SiC coating with 2.6 times higher thickness at the bottom compared to the top of a 1 mm trench was achieved. Published under an exclusive license by the AVS.Funding Agencies|SGL CARBON GmbH</p

Superconformal silicon carbide coatings via precursor pulsed chemical vapor deposition

In this work, silicon carbide coatings (SiC) were successfully grown by pulsed chemical vapor deposition (CVD). The precursors silicon tetrachloride (SiCl4) and ethylene (C2H4) were not supplied in a continuous flow, but were pulsed alternately into the growth chamber with H2 as a carrier and a purge gas. A typical pulsed CVD cycle was SiCl4 pulse – H2 purge – C2H4 pulse – H2 purge. This led to the growth of superconformal SiC coatings, which could not be obtained under similar process conditions using a constant flow CVD process. We propose a two-step mechanism for the SiC growth via pulsed CVD. During the SiCl4 pulse, a layer of Si is deposited. In the following C2H4 pulse, this Si layer is carburized, and SiC is formed. The high chlorine surface coverage after the SiCl4 pulse is believed to enable the superconformal growth via a growth inhibition mechanism

Superconformal silicon carbide coatings via precursor pulsed chemical vapor deposition

In this work, silicon carbide (SiC) coatings were successfully grown by pulsed chemical vapor deposition (CVD). The precursors silicon tetrachloride (SiCl4) and ethylene (C2H4) were not supplied in a continuous flow but were pulsed alternately into the growth chamber with H-2 as a carrier and a purge gas. A typical pulsed CVD cycle was SiCl4 pulse-H-2 purge-C2H4 pulse-H-2 purge. This led to growth of superconformal SiC coatings, which could not be obtained under similar process conditions using a constant flow CVD process. We propose a two-step framework for SiC growth via pulsed CVD. During the SiCl4 pulse, a layer of Si is deposited. In the following C2H4 pulse, this Si layer is carburized, and SiC is formed. The high chlorine surface coverage after the SiCl4 pulse is believed to enable superconformal growth via a growth inhibition effect.Funding Agencies|SGL CARBON GmbH</p