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Realization of ion mass and energy selected hyperthermal ion-beam assisted deposition of thin, epitaxial nitride films: characterization and applicationSchumacher, Philipp 04 June 2019 (has links)
No description available.
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Diagnostika depozice tenkých vrstev připravovaných z dimethylphenylsilanu / Diagnostics of thin layer deposition using dimethylphenylsilane monomerProcházka, Michal January 2010 (has links)
The aim of this thesis is a study of processes during organosilicone thin film deposition via plasma polymerization. Recently, thin films are the most expanding way of surface modification of materials. They are used as protective coatings, functional layers, they can increase or decrease adhesion to different compounds (e.g. water), or just improve mechanical properties of bulk materials. Plasma polymers, which are not known so long, are a modern trend in evolution of thin film deposition. They have perfect adhesion to the substrate and they are highly resistant against most of chemical compounds. Their structure is quite different from the structure of classical polymers. Recently, organosilicon compounds are used as precursors for plasma polymers because silicon built in the structure of plasma polymer allows thin film deposition on glass substrate and the organic part of monomer gives us infinite possibilities of modification. In our case dimethylphenylsilane (DMPS) was used as a monomer. Various RF low pressure discharges were used during this study. Plasma diagnostic was performed by optical emission spectroscopy of inductive coupled plasma. This method allows us to determine plasma composition during the deposition process. Thus we can predict the composition of deposited thin film according to input parameters. From relative populations of fragments we are able to find out optimal conditions for deposition process. We can also calculate temperature of particles in plasma which gives us some information about particle energies. The first part of the study deals with the identification of particles (fragments) created by fragmentation of monomer in plasma environment. We successfully identified hydrogen atomic lines of Balmer’s series in the spectra. Many rotational lines of hydrogen molecule were also detected. Atomic carbon occurred only in small amount. Much more carbon was detected in the form of CH radical. We also found some weak lines connected to atomic silicon. When we used a mixture of DMPS and oxygen, OH radical and O2+ were present in spectra. Next, optimal settings of deposition were determined for particular fragments from relative intensities of these fragments in optical emission spectra. Using this information we are able to set up the process to deposit thin films of desired composition and properties. We calculated electron temperature from intensities of hydrogen lines in Balmer’s series. Rotational temperature was obtained from CH radical intensity. Unfortunately, there was no convenient radical from which intensity we would be able to calculate vibrational temperature. All results and information obtained during the research can be used in industrial plasma polymerization processes and development of new coatings and functional thin films. Other studies on DMPS or similar monomer may also be realized to get more knowledge about processes in plasma and this thesis could serve as a basis for further research. Moreover, this study is a part of an international project. The aim of this project is to study processes during plasma polymerization both theoretically and practically. Once finished, the project and its results will be presented in scientific literature and at international conferences.
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Uncovering Magnetic Order in Nanostructured Disordered Materials : A Study of Amorphous Magnetic Layered StructuresKorelis, Panagiotis January 2011 (has links)
The scope of this thesis is the study of the interplay between structure and magnetism in amorphous materials. The investigations focus on the growth of amorphous layers and the study of the influence of structural disorder and reduced physical extension on the magnetic properties of thin films and multilayers. The examined magnetic materials are FeZr alloys, as well as other amorphous transition metal alloys such as CoZr and FeCoZr. Thin films and multilayers of the studied materials were deposited using magnetron sputtering in ultra-high vacuum conditions. Their amorphous structure and layering quality was investigated using X-ray scattering techniques and in several cases with transmission electron microscopy. The chemical composition of the alloys was determined with Rutherford Backscattering Spectrometry. The magnetic properties were investigated using the magneto-optic Kerr effect and SQUID magnetometry, as well as polarized neutron reflectometry and X-ray magnetic circular dicroism measurements. For FeZr alloys deposited as multilayers with Al2O3 as spacer layer, it was found that Fe-rich nanocrystallites, formed at the metal/oxide interfaces, exert large influence on the magnetic properties. The use of AlZr alloys as buffer layers promotes the growth of highly amorphous FeZr layers. FeZr/AlZr multilayers with good layering quality can also be obtained. The influence of the reduced layer thickness on the magnetic moment, Curie temperature and magnetic dimensionality of the magnetic layers is addressed for FeZr/AlZr multilayers. Thin FeZr layers in these structures are found to belong to the 2D XY dimensionality class. The change of the magnetic moment and Curie temperature with reduced FeZr layer thickness is quantified. In addition, the induced magnetic moment in the alloy element Zr was investigated in FeZr and CoZr alloy films. The possibility to imprint a preferred magnetization direction during thin film preparation was demonstrated for FeCoZr layers. Lastly, AlZr alloy films were studied with respect to their oxidation stability at room and elevated temperatures, aiming towards development of materials with passivating properties.
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The Design And Production Of Interference Edge Filters With Plasma Ion Assisted Deposition Technique For A Space CameraBarutcu, Burcu 01 August 2012 (has links) (PDF)
Interference filters are multilayer thin film devices. They use interference effects between
the incident and reflected radiation waves at each layer interface to select wavelengths. The
production of interference filters depend on the precise deposition of thin material layers on
substrates which have suitable optical properties. In this thesis, the main target is to design
and produce two optical filters (short-pass filter and long-pass filter) for the CCDs that will
be used in the electronics of a space camera. By means of these filters, it is possible to take
image in different bands (RGB and NIR) by identical two CCDs. The filters will be fabricated
by plasma ion-assisted deposition technique.
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Nanoindentation of YSZ-alumina ceramic thin films grown by combustion chemical vapor depositionStollberg, David Walter 05 1900 (has links)
Combustion chemical vapor deposition (combustion CVD) is a thin film deposition process that uses a flame created by the ignition of an aerosol containing precursors dissolved in a flammable solvent. Combustion CVD is a relatively new technique for creating thin film oxide coatings. Combustion CVD has been successfully used to deposit high quality thin oxide films for potential applications such as thermal barrier coatings, dielectric thin films, composite interlayer coatings, etc. The present work involved developing the optimum parameters for deposition of thin films of yttria-stabilized zirconia (YSZ), alumina (Al₂O₃), and YSZ-alumina composites followed by a determination of the mechanical properties of the films (measured using nanoindentation) as a function of composition. The optimized parameters for deposition of YSZ, alumina, and YSZ-alumina composites onto single crystal a-plane alumina involved using an organic liquid as the flammable solvent and Y 2-ethylhexanoate, Zr 2-ethylhexanoate and Al acetylacetonate as the metal precursors at a 0.002 M concentration delivered at 4 ml/min at flame temperatures of 155 ℃ and substrate temperatures of 105 ℃. The resulting films were grown with deposition rates of ~ 1.5 μm/hr. Measurement of the mechanical properties (hardness, elastic modulus and fracture toughness) of the films was performed using a mechanical properties microprobe called the Nanoindenter®. In order to obtain valid results from nanoindentation, the combustion CVD films were optimized for minimum surface roughness and grown to a thickness of approximately 0.8 μm. With the penetration depth of the indenter at approximately 150 nm, the 800 nm thickness of the film made influences of the substrate on the measurements negligible. The hardnesses and elastic moduli of the YSZ-alumina films did not vary with the composition of the film. The fracture toughness, however, did show a dependence on the composition. It was found that second phase particles of alumina grown into a YSZ matrix increased the fracture toughness of the films (on average, 1.76 MPa• m⁰.⁵ for 100% YSZ to 2.49 MPa• m⁰.⁵ for 70 mol% YSZ/30 mol% alumina). Similarly, second phase particles of YSZ grown into an alumina matrix also increased the fracture toughness (on average, 2.20 MPa• m⁰.⁵ for 100% alumina to 2.45 MPa• m⁰.⁵ for 37.2 mol% YSZ/62.8 mol% alumina). Modeling of the fracture toughness of the YSZ-alumina films was successfully achieved by using the following toughening mechanisms: crack deflection from the second phase particles, grain bridging around the particles, and residual stress from the CTE mismatch between the film and the substrate and between the second phase particles and the matrix of the film.
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Semi Conducting Metal Oxide Gas Sensors: Development And Related InstrumentationAbhijith, N 06 1900 (has links)
A sensor is a technological device or biological organ that detects, or senses, a signal or physical condition and chemical compounds. Technological developments in the recent decades have brought along with it several environmental problems and human safety issues to the fore. In today's world, therefore, sensors, which detect toxic and inflammable chemicals quickly, are necessary. Gas sensors which form a subclass of chemical sensors have found extensive applications in process control industries and environmental monitoring.
The present thesis reports the attempt made in development of Zinc oxide thin film based gas sensors. ZnO is sensitive to many gases of interest like hydrocarbons, hydrogen, volatile organic compounds etc. They exhibit high sensitivity, satisfactory stability and rapid response. In the present work the developed sensors have been tested for their sensitivity for a typical volatile organic compound, acetone. An objective analysis of the various substrates namely borosilicate glass, sintered alumina and hard anodized alumina, has been performed as a part of this work. The substrates were evaluated for their electrical insulation and thermal diffusivity. The microstructure of the gas sensitive film on the above mentioned substrates was studied by SEM technique. The gas sensitive Zinc oxide film is deposited by D.C reactive magnetron sputtering technique with substrate bias arrangement. The characterization of the as-deposited film was performed by XRD, SEM and EDAX techniques to determine the variation of microstructure, crystallite size, orientation and chemical composition with substrate bias voltage. The thesis also describes the development of the gas sensor test setup, which has been used to measure the sensing characteristics of the sensor. It was observed that the ZnO sensors developed with higher bias voltages exhibited improved sensitivity to test gas of interest.
Gas sensors essentially measure the concentration of gas in its vicinity. In order to determine the distribution of gas concentration in a region, it is necessary to network sensors at remote locations to a host. The host acts as a gateway to the end user to determine the distribution of gas concentration in a region. However, wireless gas sensor networks have not found widespread use because of two inherent limitations:
Metal oxide gas sensors suffer from output drift over time; frequent recalibration of a
number of sensors is a laborious task.
The gas sensors have to be maintained at a high temperature to perform the task of gas
sensing. This is power intensive operation and is not well suited for wireless sensor
network.
This thesis reports an exploratory study carried out on the applicability of gas sensors in wireless gas sensor network. A simple prototype sensing node has been developed using discrete electronic components. A methodology to overcome the problem of frequent calibration of the sensing nodes, to tackle the sensor drift with ageing, is presented. Finally, a preliminary attempt to develop a strategy for using gas sensor network to localize the point of gas leak is given.
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Thin Films From Metalorganic Precursors : ALD Of VO2 And CVD Of (Al1-xGax)2O3Dagur, Pritesh 02 1900 (has links)
Thin films and coatings of oxides are used in various fields of science and technology, such as semiconductor and optoelectronic devices, gas sensors, protective and wear resistant coatings etc. Of late, there has been a tremendous interest in pure and doped vanadium dioxide as thermoelectric switch material. VO2 has been doped with hetero-atoms such as W, Mo, Nb, Ti etc. and effects of doping have been correlated with feasibility of being used as a smart window material. The oxide Al2O3 has been studied as an alternative gate dielectric. Ga2O3 is also a contender for replacing SiO2 as a dielectric material.
Atomic layer deposition (ALD) is a technique for the deposition of thin films of various materials and is found to be of considerable scientific and technological importance. In particular, using β-diketonate complexes as precursors is very useful in preparing thin films of oxides, as these precursors already contain a metal-oxygen bond. In this thesis, β-diketonate complexes have been used as precursors for deposition of thin films. The thesis has been divided into two parts: First part deals with deposition and characterization of thin films of VO2 on glass and fused quartz. The second part deals with synthesis and chemical and thermal characterization of bimetallic Al-Ga acetylacetonates along with thin film deposition using the same.
Chapter 1 presents a brief introduction to application of thin films of oxides in various fields of science and technology. A brief introduction to the ALD reactor used for the current work is also presented. The importance of thermal analysis of precursors for CVD is briefly reviewed. Chapter 2 deals with the instruments and methods used for the work done for this thesis. In Chapters 3 and 4 of the thesis, a detailed study of deposition of VO2 films on glass and fused quartz has been presented. The films deposited have been analyzed using a host of techniques, for their texture, microstructure and electrical properties. In spite of chemical similarities, considerable differences in structure and properties have been observed between the films deposited on the two substrates. These differences have been explained on the basis of the small chemical differences between the two substrates. Chapters 5, 6 and 7 deal with synthesis, thermal characterization and use of bimetallic Al-Ga precursors, respectively. The bimetallic acetylacetonates have been synthesized using ‘homogenization in solution’ approach. Chemical characterization of the precursors revealed that nominal percentages of Al and Ga are retained in the solid precursors. Single crystal structure confirmed the observation. Thermal analysis of the precursors showed that the precursors, which are solid solutions of Al and Ga acetylacetonates, show negative deviation from the Raoult’s Law. Films were deposited using these precursors and were found to near completely retain the composition of the precursors. Chapter 8 of the thesis presents the conclusions of the current work and proposes future directions.
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Studies On The Development Of Piezoelectric Thin Flm Based Impact SensorGokhale, Nikhil Suresh 12 1900 (has links)
Sensors is one of the major areas of current research. Thin film micro/nano sensors are gaining attention worldwide, as there is necessity of miniaturization. There are varieties of sensors available by utilizing different materials in bulk and thin film form for measuring parameters like temperature, pressure, flow, humidity etc. Apart from these, there are various sensors available to measure impact force.
Impact sensor offers potential application possibilities in robotics, aerospace, structural & mechanical engineering and related areas. Many physical principles have been explored for the realization of impact sensor. The present thesis reports the efforts made in developing impact sensor using piezoelectric thin film. The necessary brief background information on impact sensors is presented in Chapter 1. This includes the description of available literature on impact sensors and their probable applications. In Chapter 2, a review of the various techniques such as thin film deposition techniques, film thickness measurement techniques, thin film characterization techniques, used in our work are explained in detail. Chapter 3 explains the direct and indirect methods of characterization used for confirming the piezoelectric property of zinc oxide thin films. The detailed experimental work carried out in realizing the impact sensor using piezoelectric thin films is presented in chapter 4. This includes design of the sensor, calibration setup used & the procedure followed and results obtained.
Finally, we present the summary of the work carried out in the thesis, conclusions arrived at and the scope for carrying out further work in the direction of making the sensor more efficient.
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Μελέτη λεπτών μεταλλικών υμενίων σε μονοκρυσταλλικό οξείδιο του νικελίου με επιφανειακά ευαίσθητες τεχνικές και προσομοιώσεις μοριακής δυναμικήςΣυμιανάκης, Εμμανουήλ 14 September 2010 (has links)
Στην παρούσα εργασία μελετήθηκε η ανάπτυξη και η επακόλουθη συμπεριφορά κατά τη θέρμανση υμενίων μεταλλικού νικελίου και χρωμίου σε μονοκρυσταλλικό οξείδιο του νικελίου, NiO(100). Οι αποθέσεις έγιναν κοντά στη θερμοκρασία δωματίου σε περιβάλλον υπερυψηλού κενού 2 x 10-10 mbar χρησιμοποιώντας πηγές θερμικής εξάχνωσης, ενώ η χημική κατάσταση των επιφανειών προσδιορίστηκε με την χρήση φασματοσκοπίας φωτοηλεκτρονίων ακτίνων-Χ (XPS) και στην περίπτωση της απόθεσης Cr επιπλέον με φασματοσκοπία σκέδασης ιόντων (ISS). Οι φασματοσκοπικές μετρήσεις έγιναν με το υπόστρωμα σε θερμοκρασίες από 550 Κ έως 680 Κ, ώστε να αυξηθεί η αγωγιμότητα και να αποφευχθεί η διαφορική φόρτιση της επιφάνειας του κρυστάλλου.
Η θέρμανση μέχρι 2 μονοστρώματα (ML) νικελίου αποτεθειμένου σε NiO(100) είχε πρόσφατα βρεθεί ότι οδηγεί σε σταδιακή εξαφάνιση του Ni0, φαινόμενο που αποδόθηκε σε οξείδωσή του με οξυγόνα από το υπόστρωμα. Καθώς η ποσότητα αυτή είναι σημαντικά μεγαλύτερη από τις τυχόν διαθέσιμες ποσότητες επιφανειακού οξυγόνου (π.χ. προσροφημένα υδροξύλια) και δεν υπάρχουν ενδείξεις για την παρουσία μη στοιχειομετρικού οξυγόνου στο εσωτερικό του μονοκρυστάλλου NiO(100), επιδιώχθηκε η διερεύνηση της προέλευσης των οξυγόνων που συμμετείχαν στην οξείδωση. Προς τούτο έγιναν διαδοχικές αποθέσεις Ni0 1,6 ML, 3,8 ML και 7,5 ML, ενώ μετά από κάθε απόθεση και πριν από την επόμενη το δείγμα θερμάνθηκε μέχρι τους 940 Κ, όπου στις δύο πρώτες περιπτώσεις επήλθε πλήρης οξείδωση του Ni0 ενώ στην τρίτη η οξείδωση δεν ολοκληρώθηκε στα χρονικά περιθώρια του πειράματος. Μια κατ’ αρχήν μοντελοποίηση της κινητικής της οξείδωσης υποδεικνύει προέλευση του διαθέσιμου οξυγόνου από πηγή σταθερής συγκέντρωσης στο εσωτερικό του κρυστάλλου. Η μοντελοποίηση των εντάσεων των φωτοκορυφών XPS με βάση σωματιδιακά υμένια νικελίου σταθερού μέσου πάχους που καλύπτουν κλάσμα της επιφάνειας, οδηγεί στο συμπέρασμα ότι η θέρμανση αρχικά οδηγεί σε γρήγορη συσσωμάτωση του νικελίου, ενώ στην συνέχεια τα μεγάλα σωματίδια Ni0 που σχηματίζονται καλύπτονται αρχικά από NiO και στην συνέχεια η οξείδωση προχωρά προς τον μεταλλικό τους πυρήνα. Καθώς από το πείραμα δεν προκύπτει άλλη πληροφορία για την προέλευση των οξυγόνων, διεξάχθηκαν προσομοιώσεις Μοριακής Δυναμικής προκειμένου να διερευνηθεί η δυνατότητα του τέλειου μονοκρυστάλλου να παρέχει πλεγματικά οξυγόνα στην επιφάνεια.
Οι προσομοιώσεις έγιναν στο ισόθερμο κανονικό στατιστικό σύνολο χρησιμοποιώντας τη μέθοδο του Nose πάνω σε μονοκρύσταλλο από 1728 ιόντα με εφαρμογή περιοδικών οριακών συνθηκών. Η ολοκλήρωση των εξισώσεων κίνησης έγινε με τον αλγόριθμο του Verlet, με χρονικό βήμα 2x10-15 s και χρησιμοποιήθηκε δυναμικό του τύπου σκληρών ιόντων, ενώ οι συνεισφορές Coulomb υπολογίστηκαν με την μέθοδο του Ewald. Πραγματοποιήθηκαν προσομοιώσεις για αποθέσεις με 8 ιόντα νικελίου (0,06ML), 16 ιόντα νικελίου (0,11ML) και 32 ιόντα νικελίου (0,22ML) σε θερμοκρασία 0,37Tm, με καταγραφή της συνάρτησης τοπικής πυκνότητας κατανομής των ιόντων οξυγόνου ανά 2000 βήματα. Οι προσομοιώσεις δείχνουν ότι ο τέλειος μονοκρύσταλλος μπορεί να σχηματίσει μεγάλο αριθμό οπών ιόντων οξυγόνου της τάξης του 10%, γεγονός που επιτρέπει την ερμηνεία του πειράματος, όπου περίπου 8ML Ni0 οξειδώθηκαν με οξυγόνα από το υπόστρωμα, χωρίς την ανάγκη υπόθεσης της παρουσίας άλλης πηγής μη στοιχειομετρικού οξυγόνου στο εσωτερικό του μονοκρυστάλλου.
Για την μελέτη της αλληλεπίδρασης του Cr με το NiO(100), η οποία δεν είχε μελετηθεί συστηματικά μέχρι τώρα σε κλίμακα νανομετρικών υμενίων, έγιναν 4 πειράματα απόθεσης, που κατέληξαν σε 1,10 nm , 0,12 nm, 0,05 nm και 0,30 nm Cr0. Η απόθεση μεταλλικού χρωμίου σε θερμοκρασία δωματίου οδήγησε σε πλήρη κάλυψη της επιφάνειας του NiO(100), ενώ θέρμανση στους 550 Κ προκάλεσε συσσωμάτωση του χρωμίου και οξείδωσή του με παράλληλη αναγωγή του νικελίου του υποστρώματος. Περαιτέρω θερμάνσεις σε υψηλότερες θερμοκρασίες προκάλεσαν την εκ νέου οξείδωση του νικελίου. Η μοντελοποίηση των εντάσεων των φωτοκορυφών XPS με βάση σωματιδιακά υμένια χρωμίου και νικελίου δείχνει ότι το χρώμιο οξειδώνεται από κάτω προς τα πάνω και τελικά καλύπτει το μεταλλικό νικέλιο, χωρίς να αποκλείεται η ενδιάμεση ανάμειξη των δύο μετάλλων. Η μοντελοποίηση της οξείδωσης του ανηγμένου νικελίου σε μεγαλύτερη θερμοκρασία, δείχνει ότι ακολουθείται γενικά η ίδια πορεία , όπως και για απόθεση καθαρού Νi, με το οξείδιο του χρωμίου αρχικά να καλύπτει το σχηματιζόμενο NiO. Κατά την παρατεταμένη θέρμανση της διεπιφάνειας στους 940 Κ, η απόκλιση των πειραματικών σημείων από τις προβλέψεις του μοντέλου υποδεικνύει διεπιφανειακή ανάμειξη των υμενίων NiO και Cr2O3 και πιθανό σχηματισμό σπινελίου NiCr2O4, όπως αναφέρεται και στην βιβλιογραφία. Τα αποτελέσματα της φασματοσκοπίας ISS επιβεβαιώνουν σε ποιοτικό επίπεδο την ερμηνεία που αποδίδουν τα μοντέλα στις μετρήσεις XPS. / Deposition and annealing of Ni and Cr on a NiO(100) single crystal was studied using X-ray photoelectron spectroscopy (XPS) and Molecular Dynamics Simulations (MD) for the case of Ni and using XPS and Ion Scattering Spectroscopy (ISS) for the case of Cr. Depositions were carried out near room temperature in ultra high vacuum with base pressure of 2 x 10-10 mbar using Ni and Cr thermal evaporation sources . Both XP and IS spectra were taken while the sample was kept at an elevated temperature between 550K and 680K in order to avoid differential substrate charging.
Annealing of up to 2 monolayers (ML) Ni deposited on NiO(100) has been reported to result in the gradual elimination of metallic Ni, attributed to oxidation via the substrate. Since the necessary quantity of oxygen is far greater than any possibly available surface oxygen (e.g. adsorbed hydroxyl species) and there is no evidence of non stoichiometric oxygen within the NiO(100) single crystal, it was decided to investigate the origin of the oxygen species involved. To that purpose, three successive depositions of Ni0 on NiO(100) were conducted, 1.6 ML 3.8 ML and 7.5 ML. After each deposition and before the next one, the sample was annealed up to 940 K resulting in the complete oxidation of the deposited Nio , with the exception of the final deposition of 7.5 ML whereby the oxidation was not completed within the time frame of the experiment. Simple kinetic modelling of the oxidation is consistent with oxygen originating from a constant concentration source within the substrate.
Modelling of the XPS photoelectron intensities based on particulate films covering part of the substrate surface indicates that annealing leads initially to sintering and then to oxidation of the Ni0 particles, whereby they are covered by NiO as oxidation proceeds toward the metallic core. Since the experiment cannot provide any more information with respect to the origin of the oxygen, MD simulations where performed in order to investigate the ability of the perfect crystal to provide lattice oxygen to its surface.
The Molecular Dynamics simulations were carried out in the constant temperature canonical ensemble using the Nose scheme, with a slab geometry consisting of 1728 ions and applying periodic boundary conditions. The equations of motion were integrated by means of Verlet’s algorithm and with a time step of 2 x10-15 s, whereas a rigid ion potential was adopted for the atomic interactions and the Coulombic contributions were evaluated with the use of the Ewald summation. Results are presented for depositions of 8 Ni (0.06ML), 16 Ni (0.11ML) and 32 Ni (0.22ML) ad-cations. The evolution of these systems was followed for up to 300000 time steps at a temperature corresponding to 0.37Tm , while the oxygen ions local density distribution function was recorded every 2000 time steps during each simulation run. The simulations show that the perfect crystal can successively form up to 10% of oxygen vacancies in each layer, which can explain the experimental results whereby 8ML of Ni0 where oxidized, without affecting the equivalent concentration of the available oxygen in the substrate and without having to assume any non stoichiometric oxygen inside the NiO(100) single crystal.
In order to study the interaction of Cr with NiO(100), which has not been studied systematically so far in the nanometric film thickness range, four quantities of Cr0 , 10 nm, 0,12nm, 0,05 nm and 0,30 nm , were deposited. Deposition at room temperature resulted in complete coverage of the NiO(100) surface, while annealing at 550 K caused sintering and oxidation of Cr as well as reduction of NiO to Ni0 while farther annealing at higher temperatures caused the re-oxidation of the reduced Ni. Modelling of the XPS photoelectron intensities based on particulate films, indicated that Cr0 particles are oxidized from the bottom and finally cover the Ni0 film produced by reduction of the NiO(100) substrate, however the possibility that metallic Cr mixes with metallic Ni forming surface alloy during the process cannot be excluded. The XPS-based modelling of the oxidation process of the reduced Ni at higher temperatures shows that these particles are initially covered by NiO while the oxidation proceeds toward the metallic core, just as in the case of pure deposited Ni.
Upon extensive annealing of the interface at 940 K, the deviation of the experimental results from the predictions of the model suggests that mixing of Cr2O3 and NiO occurs at the interface and possibly a NiCr2O4 spinel is formed, as reported in the literature. The ISS results qualitatively support the interpretation of the XPS results provided by the models.
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Etude et optimisation d'un procédé plasma basse puissance pour le dépôt de ZnO dopé et non dopé à propriétés photovoltaïques à partir d'une solution aqueuse / Study and optimization of a low power plasma reactor for the deposition of ZnO doped and undoped with photovoltaic properties from an aqueous solutionMa, Alexandre 10 December 2015 (has links)
Ce travail de thèse s'insère dans la Recherche et Développement du Photovoltaïque. L'objectif était d'étudier, développer et optimiser un nouveau procédé plasma de dépôt pour l'élaboration de couches minces d'oxyde de zinc (ZnO) pour l'application de couche fenêtre dans les cellules solaires de type Cu(In,Ga)Se2. La particularité de ce procédé est de réaliser rapidement des couches d'oxyde (≥ 0,6 nm/s) à partir d'une solution aqueuse de précurseurs non toxiques, interagissant, sous forme de gouttes, avec le plasma. La faisabilité du dépôt de ZnO par le réacteur plasma basse puissance (LPPR) a été vérifiée en obtenant des couches de ZnO homogènes, cristallines et transparentes grâce à l'optimisation des paramètres du réacteur. Le diagnostic du réacteur plasma et la modélisation/simulation du réacteur nous ont permis de constater que l'état physique et la taille des gouttes influent sur la qualité des couches d'oxyde. Des cellules solaires ont été réalisées permettant de valider la qualité des couches de ZnO obtenues via notre procédé plasma. Les meilleurs rendements sont d'environ 14 % ce qui est très prometteur pour les recherches futurs. L'étude du dopage de type N du ZnO a été abordé dans le but de réaliser une couche fenêtre complète par le réacteur LPPR. Cependant beaucoup d'améliorations et d'études restent à faire telles que la mise en place d'un système d'injection sophistiqué, ou encore l'investigation approfondie sur le dopage. Néanmoins une étude des coûts matières/énergie du procédé a été réalisée afin de pouvoir positionner le réacteur plasma parmi les autres techniques employées pour la réalisation de cellules CIGS. / This work is part of the Research and Development of Photovoltaic. The aim was to study, develop and optimize a new deposition plasma process for the elaboration of zinc oxide thin layers (ZnO) as the window layer in Cu(In,Ga)Se2 solar cells of. The particularity of this process is to quickly realize oxide layers (≥ 0.6 nm/s) from an aqueous solution of non-toxic precursors, interacting in the form of droplets, with the plasma. The feasibility of the ZnO deposition by the low power plasma reactor (LPPR) was checked by obtaining homogeneous, crystalline and transparent layers of ZnO thanks to the optimization of reactor parameters. The diagnostic and modeling / simulation of the plasma reactor allowed us to see that the physical state and droplet size affect the quality of the oxide layers. Solar cells were created to validate the quality of ZnO layers obtained via our plasma process. The best obtained efficiency is about 14% which is very promising for future research. The study of doping N type ZnO was addressed in order to achieve a complete window layer by LPPR reactor. However many improvements and studies are still needed, such as the establishment of a sophisticated injection system, or the thorough investigation on doping. Nevertheless a cost study about material/energy of the process was conducted in order to place the plasma reactor among other techniques used for the production of CIGS solar cells.
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